A Catalyst and Solvent Free Route for the Synthesis of N-Substituted Pyrrolidones from Levulinic Acid.

An efficient, metal-free, catalyst-free and solvent-free methodology for the reductive amination of levulinic acid with different anilines has been developed using HBpin as the reducing reagent. This protocol offers an excellent method to avoid solvents and added catalysts on the synthesis of different kinds of N-substituted pyrrolidones under metal free conditions. It is also the first report for the synthesis of different pyrrolidones by solvent-free as well as catalyst-free methods. The proposed mechanism for the formation of pyrrolidone has been supported by DFT calculations and control experiments.

Aerobic Oxidation of Primary Amines to Imines in Water using a Cobalt Complex as Recyclable Catalyst under Mild Conditions.

Oxidative coupling of primary amines to imines has been achieved by using a water soluble cobalt complex as catalyst and air as the oxidant at near ambient conditions. Aromatic, heteroaromatic and aliphatic amines were successfully converted to the corresponding imines with yields of up to 96 %. A 20 gram scale reaction for the synthesis of imine from benzylamine in good yield is also demonstrated with this method. The catalyst has been found to be reusable with up to five cycles. It is highly efficient, gives a turnover number (TON) of up to 128, and shows chemoselectivity with the only byproducts being water and ammonia. Control experiments and mechanistic studies indicate that the CoII /CoIII catalytic cycle is responsible for these oxidative transformations. Some of the reactive intermediates of this reaction have also been isolated and structurally characterized.

Reactions of alkyne- and butadiyne-derived fluorinated cyclophosphazenes with diiron and dimolybdenum carbonyls.

The reaction of (ß-phenylethynyl)pentafluorocyclotriphosphazene, [(PhC≡C)(F)PN](PNF2)2, with Fe2(CO)9 in refluxing hexane resulted in five new compounds, namely, [Fe(CO)2{η(2):η(2)-2,4-(P3N3F5)2Ph2C4Fe(CO)3}-µ-CO] (1), [Fe(CO)2{η(2):η(2)-2,5-(P3N3F5)2Ph2C4Fe(CO)3}-µ-CO] (2), [Fe(CO)2{η(5)-2,5-(P3N3F5)2Ph2C4CO}C(Ph)═C(P3N3F5)](3), [Fe(CO)3{η(2):η(2)-2,4-(P3N3F5)2Ph2C4CO] (4), and [Fe(CO)3{η(2):η(2)-2,5-(P3N3F5)2Ph2C4CO] (5). While compounds 1, 2, 4, and 5 have five-membered ferracyclopentadiene or cyclopentadienone rings coordinated to the Fe(CO)3 unit in the η(2):η(2) mode, compound 3 has a 2,5-cyclopentadienone ring attached to an Fe(CO)2(P3N3F5)C═C(Ph) unit, where Fe is η(5)-bonded to the cyclopentadienone ring, and the carbon that is α to the phenyl unit of the Fe(CO)2(P3N3F5)C═C(Ph) group is σ-bonded to the oxygen atom of the cyclopentadienone ring. Formation of five-membered cyclic compounds having two fluorophosphazene units on the vicinal carbon atoms of C4R2R'2Y rings was not observed in this reaction. No examples of Fe(CO)3-bound cyclobutadiene complexes were also isolated from this reaction. A similar reaction in the presence of trimethylamine N-oxide, NMe3O, was found to proceed at -20 °C with the formation of compounds 4 and 5 only. In contrast to the Fe2(CO)9 reaction, a reaction of alkyne-derived pentafluorocyclotriphosphazenes, [(RC≡C)(F)PN](PNF2)2 [R = Ph, Fe(C5H5)2] with the molybdenum complex Cp(CO)3Mo-Mo(CO)3Cp (Cp = cyclopentadienyl) in refluxing toluene resulted in the simple tetrahedral clusters Cp(CO)2Mo(P3N3F5)C-C(Ph)Mo(CO)2Cp (6) and Cp(CO)2Mo(P3N3F5)C-C(Fc)Mo(CO)2Cp (7) (Fc = ferrocenyl). A similar reaction of Cp(CO)3Mo-Mo(CO)3Cp with butadiyne-derived fluorophosphazenes, [(RC≡C-C≡C)(F)PN](PNF2)2 [R = Ph, Fe(C5H5)2], yielded the tetrahedral clusters Cp(CO)2Mo(P3N3F5)C-C(C≡CPh)Mo(CO)2Cp (8) and Cp(CO)2Mo(P3N3F5)C-C(C≡CFc)Mo(CO)2Cp (9) with the tetrahedral Mo2C2 unit forming exclusively with the alkyne unit of the butadiyne group bound to the cyclophosphazene ring. The crystal structures and infrared spectral data of these molybdenum clusters showed the presence of a semibridging carbonyl on one of the molybdenum units. All new compounds were characterized by IR, NMR [(1)H, (13)C{(1)H}, (31)P{(1)H}, and (19)F{(1)H}] and high-resolution mass spectrometry studies. Compounds 2, 3, 5, and 7-9 were also structurally characterized using single-crystal X-ray diffraction studies.

Synthesis, spectral, and structural studies of porphyrins having sterically hindered [η(5)-CpCo(η(4)-C4Ph4)] cobalt sandwich units at the meso positions.

Synthesis, spectral, and structural studies of the first examples of porphyrins substituted at the meso positions with sterically hindered η(5)-CpCo(η(4)-C4Ph4) cobalt sandwich units are described. The novel dipyrromethane derived cobalt sandwich compound {η(5)-[(C4H4N)2CH]C5H4}Co(η(4)-C4Ph4) 1, as well as its parent aldehyde, η(5)-[C5H4(CHO)]Co(η(4)-C4Ph4), were used in the synthesis of porphyrins having one or two η(5)-CpCo(η(4)-C4Ph4) groups at their meso positions. 1,9-Diformyldipyrromethane derived η(5)-CpCo(η(4)-C4Ph4) 2 was synthesized using dipyrromethane 1 under Vilsmeier conditions. A reaction of 2 with unsubstituted dipyrromethane under basic conditions in the presence of Pd(C6H5CN)2Cl2 yielded an A-type palladium coordinated porphyrin 3 [where A = η(5)-CpCo(η(4)-C4Ph4)]. A similar reaction of 2 with meso aryl and ferrocenyl-substituted dipyrromethanes yielded trans-AB type palladium coordinated porphyrins 4-6 [where A = η(5)-CpCo(η(4)-C4Ph4) and B = 4-tert-butylphenyl 4, ferrocenyl 5, and pentafluorophenyl 6]. Reactions of 2 with 5-ferrocenyl dipyrromethane under the same reaction conditions in the presence of Ni(acac)2 and Zn(OAc)2 gave the trimetallic nickel(II) and zinc(II) complexed trans-AB type porphyrins 7 and 8 having both cobalt and iron sandwich units at the meso positions. Crystal structure of the Pd(II) porphyrin 5 and nickel(II) porphyrin 7 showed nonplanar structures having distinct ruffle type distortion of the porphyrin ring. Demetalation of the zinc(II) trans-AB type porphyrin 8 in the presence of trifluoroacetic acid gave the metal free base porphyrin 9. Reactions of the cobalt sandwich aldehyde [(η(5)-C5H4(CHO)]Co(η(4)-C4Ph4) with sterically hindered dipyrromethane derivatives under acid-catalyzed condensation reactions gave trans-A2B2 type porphyrins [where A = η(5)-CpCo(η(4)-C4Ph4) and B = pentafluorophenyl, 10 mesityl 11]. In contrast, reactions of [η(5)-C5H4(CHO)]Co(η(4)-C4Ph4) with sterically unhindered meso-4-tert-butylphenyl dipyrromethane resulted in both AB3 12 and cis-A2B2 13 type porphyrins [where A = η(5)-CpCo(η(4)-C4Ph4) and B = (4-tert-butylphenyl] as a result of scrambling. The new porphyrin derivatives have been structurally characterized, and their spectral and electrochemical features were determined.

C-H Bond Functionalization of Aryl Acids and Amines by 'On-water' Reaction: Bi-dentate Directing Group Enabled Synthesis of Biaryl and m-Teraryl Carboxamides.

Herein, we report a palladium-catalyzed 'on-water' methodology for the synthesis of biaryl and m-teraryl derivatives of aryl carboxamides by selective mono and bis C-H bond functionalization. 8-aminoquinoline and 2-thiomethylaniline were used as directing groups for C-H bond functionalization of aryl carboxamides with various aryl and alkyl iodides using 3.0-4.0 mol% of Pd(OAc)2 as catalyst and water as the solvent resulting in 45-97% isolated yields of the mono and bis C-H bond functionalized products. Using an 8-aminoquinoline carboxamide core, C-H bond functionalization of indole-3-carboxylic acid and a late-stage functionalization of aspirin molecule have also been carried out. Reactions of benzyl/naphthyl picolinamides with aryl iodides gave 60-96% yield of the arylated products using the picolinamide directing group. Moreover, the insoluble nature of products in an aqueous medium enabled us to explore the reusability of the solvent, i. e., water and the catalyst. Control experiments and structural studies were carried out which confirmed the in situ formation of unique palladacycles during the reaction. Removal of the directing groups has been carried out to convert the functionalized products into amines and fluorenone compounds useful in industrial and pharmaceutical applications.

A Bench-stable 8-Aminoquinoline Derived Phosphine-free Manganese (I)-Catalyst for Environmentally Benign C(α)-Alkylation of Oxindoles with Secondary and Primary Alcohols.

Herein, we report a new air-stable phosphine-free 8-AQ (8-aminoquinoline) based Mn(I) carbonyl complex as the catalyst for the C(α)-alkylation of oxindoles with alcohols. The Mn complex [(8-AQ)Mn(CO)3 Br] works effectively as a catalyst for the α-alkylation of oxindoles by both secondary as well as primary alcohols. The procedure has been used for the synthesis of pharmaceutically important recently developed oxindoles such as 3-(4-methoxybenzyl)indolin-2-one, 3-(4-(dimethylamino)benzyl)indolin-2-one, 3-(4-(dimethylamino)phenyl)-5-fluoroindolin-2-one and 3-(benzo[d][1,3]dioxol-5-ylmethyl)indolin-2-one, which are found to be effective in preventing specific types of cell death in neurodegenerative disorders. Control experiments have been carried out to investigate the reaction mechanism and the crucial role of metal-ligand cooperation via -NH2 moiety during catalysis.

Reduction of esters to alcohols and iodides using aminodiborane (µ-NH2B2H5): scope and mechanistic investigations.

Herein, we report an efficient methodology for the reduction of esters, carbonates, and anhydrides to alcohols using in situ generated aminodiborane from iodine and ammonia borane. This methodology also finds use for the transformation of esters to iodides by varying the stoichiometry of reagents. The protocol has broad substrate scope for transformation of esters to alcohols and iodides with excellent yields. The method is also useful for synthesizing pharmaceutically and industrially important compounds such as a Cinacalcet precursor, a Streptoindole analogue, and 1,4-pentanediol. Control studies and DFT calculations carried out to study the reduction mechanism of esters using aminodiborane indicate that a dioxaborinamine intermediate is formed during the reaction.

Acceptorless Dehydrogenation of Alcohols and Transfer Hydrogenation of Aldehydes in Water Using a Single Bifunctional, Bistate, Water-soluble Ruthenium Catalyst.

A water-soluble bifunctional, bistate ruthenium catalyst has been developed using the 8-aminoquinoline ligand which responds to an acid-base stimuli and is catalytically active for two complementary reactions. The "Ru-amino state" is highly active for catalytic transfer hydrogenation of various aldehydes using formic acid as the hydrogen source resulting in a range of primary alcohols. On the other hand, the "Ru-amido state" is active for the acceptorless dehydrogenation of alcohols to yield carboxylate salts or ketones. The reactions can be carried out in air without an inert atmosphere and the products can be purified by simple extraction without the use of any chromatographic techniques. A range of functional groups which include electron-rich and deficient (hetero)arenes and alkenes, alkynes, halides, esters, cyano, and nitro groups, are all well tolerated, indicating excellent chemoselectivity for transfer hydrogenation.

Ring-closing metathesis reactions of terminal alkene-derived cyclic phosphazenes.

The first examples of ring-closing metathesis (RCM) reactions of a series of terminal alkene-derived cyclic phosphazenes have been carried out. The tetrakis-, hexakis-, and octakis(allyloxy)cyclophosphazenes (NPPh(2))(NP(OCH(2)CH=CH(2))(2))(2) (1), N(3)P(3)(OCH(2)CH=CH(2))(6) (2), and N(4)P(4)(OCH(2)CH=CH(2))(8) (3) and the tetrakis(allyloxy)-S-phenylthionylphosphazene (NS(O)Ph)[NP(OCH(2)CH=CH(2))(2)](2) (4) were prepared by the reactions of CH(2)=CHCH(2)ONa with the cyclophosphazenes (NPPh(2))(NPCl(2))(2), N(3)P(3)Cl(6), and N(4)P(4)Cl(8) and the S-phenylthionylphosphazene (NS(O)Ph)(NPCl(2))(2). The reactions of 1-4 with Grubbs first-generation olefin metathesis catalyst Cl(2)Ru=CHPh(PCy(3))(2) resulted in the selective formation of seven-membered di-, tri-, and tetraspirocyclic phosphazene compounds (NPPh(2))[NP(OCH(2)CH=CHCH(2)O)](2) (5), N(3)P(3)(OCH(2)CH=CHCH(2)O)(3) (6), and N(4)P(4)(OCH(2)CH=CHCH(2)O)(4) (7) and the dispirocyclic S-phenylthionylphosphazene compound (NS(O)Ph)[NP(OCH(2)CH=CHCH(2)O)](2) (8). X-ray structural studies of 5-8 indicated that the double bond of the spiro-substituted cycloalkene units is in the cis orientation in these compounds. In contrast to the reactions of 1-4, RCM reactions of the homoallyloxy-derived cyclophosphazene and thionylphosphazene (NPPh(2))[NP(OCH(2)CH(2)CH=CH(2))(2)](2) (9) and (NS(O)Ph)[NP(OCH(2)CH(2)CH=CH(2))(2)](2) (10) with the same catalyst resulted in the formation of 11-membered diansa compounds NPPh(2)[NP(OCH(2)CH(2)CH=CHCH(2)CH(2)O)](2) (11) and (NS(O)Ph)[NP(OCH(2)CH(2)CH=CHCH(2)CH(2)O)](2) (13) and the intermolecular doubly bridged ansa-dibino-ansa compounds 12 and 14. The X-ray structural studies of compounds 11 and 13 indicated that the double bonds of the ansa-substituted cycloalkene units are in the trans orientation in these compounds. The geminal bis(homoallyloxy)tetraphenylcyclotriphosphazene [NPPh(2)](2)[NP(OCH(2)CH(2)CH=CH(2))(2)] (15) upon RCM with Grubbs first- and second-generation catalysts gave the spirocyclic product [NPPh(2)](2)[NP(OCH(2)CH(2)CH=CHCH(2)CH(2)O)] (16) along with the geminal dibino-substituted dimeric compound [NPPh(2)](2)[NP(OCH(2)CH(2)CH=CHCH(2)CH(2)O)(2)PN][NPPh(2)](2) (17) as the major product. The dibino compound 17, upon reaction with the Grubbs second-generation catalyst, was found to undergo a unique ring-opening metathesis reaction, opening up the bino bridges and partially converting to the spirocyclic compound 16.

Synthesis and reactions of ethynylferrocene-derived fluoro- and chlorocyclotriphosphazenes.

The reactions of lithiated ethynylferrocene, FcC[triple bond]CLi (Fc = ferrocenyl), with fluoro- and chlorocyclotriphosphazenes, N(3)P(3)X(6) (X = F, Cl), resulted in the formation of stable mono-FcC[triple bond]CP(3)N(3)X(5) [X = F (1), Cl (2)] and geminal bis[(FcC[triple bond]C)(2)PN](X(2)PN)(2) [X = F (3), Cl (4)], ethynylferrocene-substituted cyclophosphazenes. The reactions of 1 and 2 with CpCo(COD) were found to differ in the nature of the sandwich compounds (eta(5)-Cp)Co{eta(4)-C(4)[Fc(2)(N(3)P(3)X(5))(2)]} formed. While the fluorophosphazene-derived compound 1 yielded both cis and trans isomers of the cyclobutadiene complexes 5 and 6, the chlorophosphazene-derived compound 2 was found to give only the trans-cyclophosphazene-disubstituted cyclobutadiene compound 7. The reaction of 3 with CpCo(COD) was found to give the compound (eta(5)-Cp)Co{eta(4)-C(4)-1,3-(Fc)(2)-2,4-[NP(C[triple bond]CFc)(NPF(2))(2)](2)} (8) having one of the alkyne units of the cyclophosphazene moiety of 3 remaining unreacted even after reaction with an excess of CpCo(COD). The first click reactions of ethynylferrocene-derived cyclophosphazenes have been carried out by reacting 1 and 4 with benzyl azide, resulting in novel mono- and disubstituted cyclophosphazene-derived 1,2,3-triazoles. The reaction of 1 with benzyl azide yielded two positional isomers of the 1,2,3-triazole, (1-PhCH(2), 4-Fc, 5-P(3)N(3)F(5))C(2)N(3) (9), and (1-PhCH(2), 4-P(3)N(3)F(5), 5-Fc)C(2)N(3) (10), with the latter having a benzyl group in the vicinity of the ferrocene unit as the major product. A similar reaction of 4 with benzyl azide was found to yield five triazole-based products, with two, [(1-PhCH(2)-4-FcC(2)N(3))(C[triple bond]CFc)PN](PNCl(2))(2) (11) and [(1-PhCH(2)-5-Fc-C(2)N(3))(C[triple bond]CFc)PN](PNCl(2))(2) (12), having one unreacted alkyne unit in the molecule. Among the bis-triazole-derived chlorophosphazenes [(1-PhCH(2)-4-Fc-C(2)N(3))(2)PN](PNCl(2))(2) (13), [(1-PhCH(2)-4-Fc-C(2)N(3))(1-PhCH(2)-5-Fc-C(2)N(3))PN](PNCl(2))(2)] (14), and [(1-PhCH(2)-5-Fc-C(2)N(3))(2)PN](PNCl(2))(2) (15), the unsymmetrically disubstituted bis-triazole compound 14 was found to be the major product. The fluorophosphazene-derived triazole 10 was found to readily form a disubstituted square-planar complex trans-[(1-PhCH(2)-4-P(3)N(3)F(5)-5-Fc)C(2)N(3)](2)PdCl(2) (16) with PdCl(2)(PhCN)(2). All of the new ferrocene- and cyclophosphazene-derived compounds except 8 and 12 have also been structurally characterized.

Catalytic Oxidation of Alcohols and Amines to Value-Added Chemicals using Water as the Solvent.

Designing reactions in aqueous media has been one of the major challenges in modern organic synthesis, especially to avoid the use of large amounts of organic solvents whose disposal is a matter of grave concern from an environmental perspective. The oxidation of alcohols and amines is an essential and important step in the synthesis of many valuable products including polymers and pharmaceuticals. In recent times, there has been a surge in the use of water as a solvent in many organic reactions. This review focuses specifically on the oxidation reactions of alcohols and amines carried out in water media using transition metal catalysts, metal-free catalysts and photocatalysts.

NaCl as Catalyst and Water as Solvent: Highly E-Selective Olefination of Methyl Substituted N-Heteroarenes with Benzyl Amines and Alcohols.

Oxidative coupling of benzylamines and alcohols with methyl substituted N-heteroarenes such as quinolines and quinoxalines has been achieved using chloride, a sea abundant anion as the catalyst for practical synthesis of a wide range of E-disubstituted olefins in aqueous medium. Detailed mechanistic studies and control experiments were carried out to deduce the reaction mechanism which indicated that in situ formed ClO2- is the active form of the catalyst. We have successfully carried out a 1 g scale reaction using this methodology, and five pharmaceutically relevant conjugated olefins were also synthesized by this method in moderate to good yields.

Oxidative Coupling of Benzylamines with Indoles in Aqueous Medium to Realize Bis-(Indolyl)Methanes Using a Water-Soluble Cobalt Catalyst and Air as the Oxidant.

Oxidative coupling of benzylamines with indoles to bis-(indolyl)methanes (BIMs) was achieved using an inexpensive water-soluble cobalt complex, Co(bpb). The catalyst was found to be quite effective when air was used as the oxidant and water as solvent under mild reaction conditions. Aromatic amines were successfully converted to the corresponding BIMs with yields up to 85 %. We have successfully carried out a 1 gram scale reaction, and few pharmaceutically relevant compounds were also synthesised by this method in good yields. Control experiments have also been carried out to understand the possible reaction mechanism.

Synthesis of unsymmetrical multi-aroyl derivatives of ferrocene using palladium catalysed oxidative C-H aroylation.

A palladium catalysed methodology for mono-selective oxidative aroylation of ferrocene has been achieved. 10 mol% of Pd(OAc)2 was used as the catalyst for this radical aroylation reaction using O-methyl-oxime as the directing group. tert-Butyl hydroperoxide was used as an oxidant and both aldehydes and alcohols were used as acyl-equivalents. The protocol has been extended to aryl, heteroaryl and sterically hindered aroylating agents. Acidic-hydrolysis with 6(N) HCl of the directing group resulted in unsymmetrically substituted ketone derivatives of ferrocene, which have not been achieved otherwise.

Selective Reactivity of the Phosphorus-Chlorine and Carbon-Chlorine Bonds in Cyclic Chlorocarbaphosphazenes: An Unusual Activation of a Carbon-Nitrogen Bond in Trialkylamines.

Acyclic tertiary amines such as triethylamine and tri-n-propylamine used as HCl scavengers in nucleophilic substitution reactions of cyclic chlorocarbaphosphazenes [N(3)PC(2)Cl(4) (I) and N(3)P(2)CCl(5) (II)] with (CF(2))(n)()(CF(2)CH(2)OH)(2) [n = 0 (III) or 1 (IV)] are found to undergo a facile C-N bond cleavage with the regiospecific substitution of the dialkylamino groups on the ring carbon atoms of the carbaphosphazene. In the case of cyclic amines such as 1-methylpiperidine and 4-methylmorpholine, the cleavage was found to occur regiospecifically at the N-CH(3) bond, resulting in the ring substitution of the cyclic secondary amino group on the dicarbaphosphazene ring carbon atoms. The polyfluoro diol III forms a spirocyclic ring exclusively at the phosphorus site in compounds [CF(2)CH(2)O](2)PN(3)C(2)[N(C(2)H(5))(2)](2) (1), [CF(2)CH(2)O](2)PN(3)C(2)[N(C(3)H(7))(2)](2) (2), [CF(2)CH(2)O](2)PN(3)C(2)[NCH(2)(CH(2))(3)CH(2)](2) (3), and [CF(2)CH(2)O](2)PN(3)C(2)[N(CH(2))(2)O(CH(2))(2)](2) (5) along with the formation of carbon-substituted carbaphosphazenes, Cl(2)PN(3)C(2)[NCH(2)(CH(2))(3)CH(2)](2) (4) and Cl(2)PN(3)C(2)[N(CH(2))(2)O(CH(2))(2)](2) (6). Reaction of II with III in the presence of triethylamine affords the dispiro product [CF(2)CH(2)O)(2)](2)P(2)N(3)C[N(C(2)H(5))(2)] (7), which crystallizes in a polar orthorhombic space group, Cmc2(1). Upon refluxing of I or II with R(3)N (R = C(2)H(5), n-C(3)H(7)) in toluene, the amino-substituted carbaphosphazenes, Cl(2)PN(3)C(2)[N(C(2)H(5))(2)](2) (8), Cl(4)P(2)N(3)C[N(C(2)H(5))(2)] (9), and Cl(4)P(2)N(3)C[N(n-C(3)H(7))(2)] (10) are obtained in good yields. Hydrolysis of 8 leads to the formation of Cl(O)PN(H)N(2)C(2)[N(C(2)H(5))(2)](2) (11). When lithium salts of the fluoro diols III and IV are reacted with I or II in diethyl ether, the P-Cl bond is selectively substituted, yielding the spirocyclic [CF(2)CH(2)O](2)PN(3)C(2)Cl(2) (12), [CF(2)(CF(2)CH(2)O)(2)]PN(3)C(2)Cl(2) (13), [CF(2)CH(2)O](2)P(2)N(3)CCl(3) (14), and [(CF(2)CH(2)O)(2)](2)P(2)N(3)CCl (15). The C-Cl bonds in 12 and 14 were easily substituted by their reaction with 4-FC(6)H(4)XNa (X = O or S) to form [CF(2)CH(2)O](2)PN(3)C(2)[4-FC(6)H(4)O](2) (16) and [CF(2)CH(2)O](2)PN(3)C(2)[4-FC(6)H(4)S](2) (17). Reactions of 12 and 13 with (CH(3))(3)SiN(CH(3))(2) under mild conditions result in the elimination of (CH(3))(3)SiCl along with the formation of [CF(2)CH(2)O](2)PN(3)C(2)[N(CH(3))(2)](2) (18). The X-ray analyses of 13 and 18 represent the first examples of eight-membered spirocyclic phosphazenes. The thermal behavior of II, 9, 10, 14, and15 has also been investigated at 120 degrees C. Single-crystal X-ray diffraction studies were carried out for 1, 2, 7, 9-14, and 16-19, and these compounds are also characterized using IR, (1)H, (13)C, (19)F and (31)P NMR spectroscopy, MS, and elemental analysis.

Chiral multidentate oxazoline ligands based on cyclophosphazene cores: synthesis, characterization and complexation studies.

Chiral oxazoline based bi and hexadentate ligands built on cyclophosphazene cores have been synthesized and characterized. (NPPh2)2[NP(m-OC6H4C(O)OCH3)2] (1) was prepared by the reaction of gem-(NPPh2)2(NPCl2) with methyl-3-hydroxy benzoate in the presence of Cs2CO3. Compound 1 was converted to the dicarboxylic acid (NPPh2)2[NP(m-OC6H4C(O)OH)2] (2) by base promoted hydrolysis with KO(t-Bu). The dicarboxylic acid 2 on reaction with oxalyl chloride followed by (S)-(+)-2-amino-3-methyl-1-butanol, triethylamine and mesyl chloride was converted to the C2-symmetric phosphazene based chiral bisoxazoline ligand (NPPh2)2[NP{m-OC6H4(4-iPr-2-Ox)}2] (3) (Ox = oxazolinyl). A similar C2-symmetric bisoxazoline derivative having an oxazoline group attached to the para position of the phenyl ring was also synthesized starting from (NPPh2)2[NP(p-OC6H4C(O)OCH3)2] (4) which was first converted to the dicarboxylic acid (NPPh2)2[NP(p-OC6H4C(O)OH)2] (5) and finally to (NPPh2)2[NP{p-OC6H4(4-iPr-2-Ox)}2] (6) and (NPPh2)2[NP{p-OC6H4(4-Ph-2-Ox)}2] (7) under similar reaction conditions. Reaction of 6 with Pd(OAc)2 in acetic acid at room temperature and with PdCl2(C6H5CN)2 in refluxing benzene resulted in chiral palladium complexes Pd(OAc)2(NPPh2)2[NP{p-OC6H4(4-iPr-2-Ox)}2] (8) and PdCl2(NPPh2)2[NP{p-OC6H4(4-iPr-2-Ox)}2] (9), respectively. The utility of these palladium complexes as chiral catalysts for the asymmetric rearrangement of trichloroacetimidates to trichloroacetamides has been explored. The hexa(methylbenzoate) derivative of cyclophosphazene [PN(OC6H4COOCH3)2]3 (10) on treatment with KO(t-Bu) and H2O gave the hexacarboxylic acid derivative [PN(OC6H4COOH)2]3 (11), which on treatment with oxalyl chloride followed by (S)-(+)-2-amino-3-methyl-1-butanol/(S)-(+)-2-phenylglycinol, triethylamine and mesyl chloride was converted to the C3-symmetric cyclophosphazene based chiral hexaoxazoline ligands [PN{OC6H4(4-iPr-2-Ox)}2]3 (12) and [PN{OC6H4(4-Ph-2-Ox)}2]3 (13). The bis(phebox) derivative of the cyclophosphazene was prepared starting from (NPPh2)2[NP{OC6H3(COOCH3)2}2] (14), by the reaction of gem-Ph4P3N3Cl2 with dimethyl 5-hydroxyisophthalate in the presence of Cs2CO3. Compound 14 was converted to the tetracarboxylic acid (NPPh2)2[NP{OC6H3(COOH)2}2] (15) by base promoted hydrolysis with KO(t-Bu). The tetracarboxylic acid 15 on reaction with oxalyl chloride followed by (S)-(+)-2-amino-3-methyl-1-butanol/(S)-(+)-2-phenylglycinol, triethylamine and mesyl chloride was converted to the bis(phebox) substituted tetraphenylcyclophosphazene derivatives (NPPh2)2[NP{OC6H3(4-iPr-2-Ox)2}2] (16)/(NPPh2)2[NP{OC6H3(4-Ph-2-Ox)2}2] (17). A similar tetra(phebox) derivative was synthesized from (NPPh2)[NP{OC6H3(COOCH3)2}2]2 (18) which was first converted to (NPPh2)[NP{OC6H3(COOH)2}2]2 (19) and further converted to the tetra(phebox) derivative (NPPh2) [NP{OC6H3(4-Ph-2-Ox)2}2]2 (20). All new compounds were characterized by IR, NMR [(1)H, (13)C{(1)H} and (31)P{(1)H}] and HRMS studies. Compounds 1, 2, 4, 5, 7, 14 and 18 have also been structurally characterized.

Palladacycles of novel bisoxazoline chelating ligands based on the dimeric cyclobutadiene linked cobalt sandwich compound [(η5-Cp)Co(η4-C4Ph3)]2.

The reaction of 1,4-diphenylbutadiyne along with diphenylacetylene, when carried out with η(5)-[MeOC(O)Cp]Co(PPh(3))(2) resulted in the cyclobutadiene linked dimeric cobalt sandwich compound {[η(5)-MeOC(O)Cp]Co(η(4)-C(4)Ph(3))}(2) (1) along with the known monomeric compound η(5)-[MeOC(O)Cp]Co(η(4)-C(4)Ph(4)). Compound 1, on treatment with KOH gave the dicarboxylic acid {η(5)-[HOC(O)Cp]Co(η(4)-C(4)Ph(3))}(2) (2) which on reaction with oxalyl chloride followed by (S)-2-amino-3-methyl-1-butanol, triethylamine and mesylchloride was converted to the bis(cobalt oxazoline) based chiral ligand {[η(5)-(4-iPr-2-Ox)Cp]Co(η(4)-C(4)Ph(3))}(2) (3) (Ox = Oxazolinyl). Compound 3 on reaction with palladium acetate gave an NCN bound bis(cobalt-oxazolinyl) palladacycle {[η(5)-(4-iPr-2-Ox)Cp]Co(η(4)-C(4)Ph(3))}(2)PdOAc (4) having both the oxazolinyl groups bound to the palladium in a chelate mode and one of the Cp rings forming a five membered [C,N] palladacycle. Reaction of 4 with aq. NaCl resulted in the chloro analogue of 4, {[η(5)-(4-iPr-2-Ox)Cp]Co(η(4)-C(4)Ph(3))}(2)PdCl (5). A nonchiral bidentate bis cobalt oxazoline ligand {[η(5)-(Ox)Cp]Co(η(4)-C(4)Ph(3))}(2) (6) was also prepared by replacing (S)-2-amino-3-methyl-1-butanol with 2-amino-1-ethanol in the procedure used for the preparation of 3. A reaction of 1,4-diphenylbutadiyne, diphenylacetylene and (η(5)-Cp)Co(PPh(3))(2) resulted in the dimer [(η(5)-Cp)Co(η(4)-C(4)Ph(3))](2) (7) and small amounts of a trimer [(η(5)-Cp)Co(η(4)-C(4)Ph(3))](2)[(η(5)-Cp)Co(η(4)-C(4)Ph(2))] (8) having no substituents on the Cp rings. All the compounds except 2 were structurally characterized. Structural studies on palladacycles 4 and 5 showed interesting anagostic C-H···Pd interactions between the ortho hydrogen of one of the Cp rings and the palladium centre. Preliminary studies carried out on the palladacycles showed promising catalytic activity in the asymmetric rearrangement of trichloroacetimidates.

Synthesis and selectivity in the formation of cyclophosphazene-derived 1,3-cyclohexadienes from reactions of RCpCo(COD) [R = MeOC(O)] with alkynes and alkenes.

The first examples of mono and bisfluorophosphazene derived [eta (5)-cyclopentadienyl] [eta (4)-1,3-cyclohexadiene] cobalt complexes have been prepared along with the sandwich compound [eta (5)-carbomethoxycyclopentadienyl] [eta (4)-1,3-bis(pentafluorocyclotriphosphazenyl)-2,4-diphenylcyclobutadiene] cobalt and acetylene trimerized products from the reactions of [eta (5)-MeOC(O)C 5H 4]Co[COD], PhCCP 3N 3F 5 and phenylacetylene in the presence or absence of an additional cycloalkene or indene. Formation of these mono and bis fluorophosphazene derived cobalt cyclohexadiene complexes provide experimental evidence for a metallacyclopentadiene pathway for cyclohexadiene formation in CpCo catalyzed reactions. Selectivity is also observed in the formation of bisfluorophosphazene derived cyclohexadienes which stems from the fact that two P 3N 3F 5 units cannot be accommodated on vicinal carbon atoms of a carbacycle or metallacycle. Interestingly, reactions of (beta-phenylethynyl)pentafluorobenzene with [eta (5)-MeOC(O)C 5H 4]Co[COD] in the presence and absence of external cycloalkene under identical reaction conditions yielded only the cis and trans isomers of the metallocene [eta (5)-MeOC(O)C 5H 4]Co[eta (4)-C 4Ph 2(C 6F 5) 2] along with alkyne trimerized product indicating that the selectivity in cyclohexadiene formation is governed more by steric than electronic factors. All the new compounds were characterized by (1)H, (13)C, (31)P, and (19)F NMR as well as mass spectrometry and elemental analysis. Mono and bispentafluorocyclotriphosphazene derived [eta (5)-cyclopentadienyl] [eta (4)-1,3-cyclohexadiene] cobalt complexes and [eta (5)-carbomethoxycyclopentadienyl] [eta (4)-bis(1,3-pentafluorophenyl)-2,4-diphenylcyclobutadiene] cobalt have also been structurally characterized by single crystal X-ray analysis.

Synthesis and characterization of novel fluorophosphazene-derived cobaltacyclopentadienyl metallacycles: reagents for assembly of aryl-bridged fluorophosphazenes.

Reaction of (beta-phenylethynyl)pentafluorocyclotriphosphazene, F5P3N3C identical with CPh, with in situ generated eta5-(MeOC(O)C5H4)Co(PPh3)2 resulted in the formation of two isomers of cobaltacyclopentadienylmetallacycles, (eta(5)-carbomethoxycyclopentadienyl)(triphenylphosphine)-2,5-bis(pentafluorocyclotriphosphazenyl)-3,4-diphenyl cobaltacyclopentadiene (1) and (eta5-carbomethoxycyclopentadienyl)(triphenylphosphine)-2,4-bis(pentafluorocyclotriphosphazenyl)-3,5-diphenyl cobaltacyclopentadiene (2), along with the sandwich compound [eta5-carbomethoxycyclopentadienyl]-[eta4-1,3-bis(pentafluorocyclotriphosphazenyl)-2,4-diphenylcyclobutadiene]cobalt (3). Formation of cobaltacyclopentadienylmetallacycles or cyclobutadienylmetallocene having two fluorophosphazene units on vicinal carbon atoms of the rings was not observed in this reaction. Reaction of 1 with diphenylacetylene resulted in the formation of a novel aryl-bridged fluorophosphazene, 1,4-bis(pentafluorocyclotriphosphazenyl)-2,3,5,6-tetraphenyl benzene (4), and the conversion of cobaltametallacycle to the sandwich compound, [eta5-(MeOC(O)C5H4]Co(eta4-C4Ph4) (5). Reaction of 1 with phenylacetylene resulted in the formation of aryl-bridged fluorophosphazene, 1,4-bis(pentafluorophosphazenyl)-2,3,5,-triphenyl benzene (6). New compounds 1-4 were structurally characterized. In compound 1, the two fluorophosphazene units were oriented in gauche form with respect to each other. However, in compounds 2 and 3, they were eclipsed to each other, and in compound 4, they were oriented anti to each other.

Preparation of the first examples of ansa-spiro substituted fluorophosphazenes and their structural studies: analysis of C-H...F-P weak interactions in substituted fluorophosphazenes.

The reactions of fluorophosphazenes, endo ansa FcCH(2)P(S)(CH(2)O)(2)[P(F)N](2)(F(2)PN) (1) (Fc = ferrocenyl) and spiro [RCH(2)P(S)(CH(2)O)(2)PN](F(2)PN)(2) (R = Fc (2), C(6)H(5) (3)], with dilithiated diols have been explored. The study resulted in the formation of the first examples of ansa-spiro substituted fluorinated cyclophosphazenes as well as a bisansa substituted fluorophosphazene. The bisansa compound [1,3-[FcCH(2)P(S)(CH(2)O)(2)]][1,5-[CH(2)(CH(2)O)(2)]]N(3)P(3)F(2) (4) was found to be nongeminaly substituted with both the ansa rings in cis configuration, which is in stark contrast to the observations on cyclic chlorophosphazenes where geminal bisansa formation has been observed. The ansa-spiro compounds (5-7) underwent the ansa to spiro transformation leading to dispiro compounds in the presence of catalytic amounts of CsF at room temperature. Two of the ansa-spiro compounds, endo-[3,5-[FcCH(2)P(S)(CH(2)O)(2)]][1,1-[CH(2)(CH(2)O)(2)]]N(3)P(3)F(2) (5) and endo-[3,5-[FcCH(2)P(S)(CH(2)O)(2)]][1,1-[FcCH(2)P(S)(CH(2)O)(2)]]N(3)P(3)F(2) (6), were structurally characterized, and the crystal structures indicate boat-chair conformation as well as crown conformation for the eight-membered ansa rings. Weak C-H.F-P interactions observed in the crystal structures of the ansa-spiro substituted fluorophosphazene derivatives have been analyzed and compared with C-H.F-P interactions of other fluorinated phosphazenes and thionyl phosphazenes.