A series of monodentate ferrocenylphosphines, Fc3P (1a), Fc2PhP (1b), and Fc2ArP (1c; Fc = ferrocenyl, Ar = 3,4-methylenedioxyphenyl), were prepared, and their electronic and steric properties were quantitatively determined. By the IR measurements of their respective Ni(CO)3(phosphine) complexes, the electronic properties of the ferrocenyl group in organophosphines were estimated to be similar to those of primary alkyl groups. The ferrocenyl group is a better electron donor than a methyl group and a poorer donor than an ethyl group. The gold(I) chloride complexes of 1a-c were prepared and their X-ray crystal structures were determined. The %V bur parameters for 1a-c were calculated using the X-ray structural data, and their â³Tolman cone anglesâ³ were estimated. The steric influence of the ferrocenyl group in organophosphines was clarified to be larger than those of cyclohexyl, tert-butyl, and o-tolyl groups and is comparable to that of a mesityl group.
Copper-catalyzed regioselective aminothiolation of terminal and internal alkenes with N-fluorobenzenesulfonimide and thiols has been developed. The three-component reaction is promoted by the addition of dimethyl sulfide. In addition to aromatic alkenes, aliphatic alkenes are subjected to the reaction, affording various aminothiolation adducts as single regioisomers. The radical process is proposed by preliminary mechanistic studies, involving radical trap and radical clock experiments.
Homocoupling of stannyl- and alkyl-substituted alkynes with Cp2TiBu2 gave unsymmetrical titanacyclopentadienes (αß isomers) with >95% regioselectivities, whereas the coupling with Cp2ZrBu2 provided symmetrical zirconacyclopentadienes (αα isomers) with >93% selectivities. This is the first example of metal-dependent regioselective homocoupling of unsymmetrical alkynes on group 4 elements.
Dibromodihydropentacene compound 1 was palladated and then lithiated to give a lithiated-palladated intermediate. Both of the lithium moiety and the palladium complex moiety on dihydropentacene unexpectedly survived in the solution. The Li and Pd moieties reacted with electrophiles and nucleophiles respectively to give the substituted dihydropentacene products. Aromatization of these dihydropentacenes gave substituted pentacene derivatives.
The treatment of titanacyclopentadienes with bismuth(iii) chloride gave spiro compounds in moderate yields. Two carbon atoms of the diene moiety of the titanacyclopentadiene were connected to one carbon atom of the Cp ligand. This is in sharp contrast to the formation of dihydroindene derivatives, where two carbon-carbon bonds were formed between the diene moiety and the adjacent two carbon atoms of the Cp ligand.
The C2-symmetric tetralin-fused 1,4-diiodo-1,3-butadiene derivatives, (Z,Z)-2,3-di(1-iodoalkylidene)tetralin 1a-c, are atropisomeric and can be resolved into the two persistent axially chiral enantiomers by HPLC on a chiral stationary phase. The enantiomerically pure compounds can serve as chiral organocatalysts for dearomatizing spirolactonization to show good performance in up to 73% ee.
Nickel-catalyzed direct selenation of benzamides bearing an 8-quinolyl auxiliary with elemental selenium provides benzoisoselenazolones in good yield via carbon-selenium and nitrogen-selenium bond formation under aerobic conditions. In addition to aryl C-H bonds, the method can also be applied to alkenyl C-H bonds, constructing an isoselenazolone skeleton. Simple mechanistic analysis shows that the reaction proceeds through a rate-determining C-H bond cleavage. The obtained benzoisoselenazolones are transformed into various organoselenium compounds and utilized as the catalyst for bromolactonization of alkenoic acids.
The highly selective synthesis of triene derivatives was achieved by a zirconocene-mediated three-component coupling reaction, and the trienes were efficiently subjected to 7-endo mode cyclization. The reaction of unsymmetrical zirconacyclopentadienes prepared from two different alkynes with N-bromosuccinimide (NBS) followed by treatment with allyl halides in the presence of CuCl afforded the corresponding heptatrienes in good yields. When the trienes reacted with an organolithium reagent, 7-endo mode cyclization occurred smoothly to give the corresponding cycloheptadiene.
Stereoselective construction of spiro-fused tricyclic compounds from enynes having a tethered imine with diazoalkenes was achieved by Rh(I)- and Rh(II)-catalyzed sequential reactions. This method consists of three reactions, i.e., Rh(I)-catalyzed cyclization of enynes with a tethered imine, Rh(II)-catalyzed cyclopropanation with diazoalkenes, and Cope rearrangement. Notably, the sequential reactions can be operated in one pot, in which Rh(I) and Rh(II) catalysts work in relay without any serious catalyst deactivation to afford the spirocycles in a stereoselective manner.
Palladium-catalyzed carbothiolation of terminal alkynes with azolyl sulfides affords various 2-(azolyl)alkenyl sulfides with perfect regio- and stereoselectivities. The present addition reaction proceeded through a direct cleavage of carbon-sulfur bonds in azolyl sulfides. The resulting adducts that are useful intermediates in organic synthesis are further transformed to multisubstituted olefins containing azolyl moieties.
A reaction of [PdCl2(cod)] (cod = 1,5-cyclooctadiene) and an E/Z mixture of quinoline-2-carbaldehyde (pyridine-2-carbonyl)hydrazone (HL) gave two kinds of Pd(II) mononuclear complexes, [PdCl(Z-L-κ(3)N,N',N'')] (1) and [PdCl2(E-HL'-κ(2)N,N')] (2), where L(-) is the deprotonated hydrazonate anion and HL' is the quinolinium-hydrazonate zwitterionic form of HL. Complex 2 is gradually converted to 1 in solution, and complex 1 is a good precursor to prepare a Pd(II)/Ru(II) heterodinuclear complex bridged by hydrazonate, trans(Cl,Cl)-[RuCl2(PPh3)2(µ-L)PdCl] (3).
We prepared hydrazone-palladium(II) complexes of [PdCl2(HL(n))] and [PdCl(L(n))] (n = 1-3) by the reaction of [PdCl2(cod)] or [PdCl2(PhCN)2] and the hydrazone ligands of HL(n) {N'-(pyridin-2-ylmethylene)picolinohydrazide (HL(1)), N'-[1-(pyridin-2-yl)ethylidene]picolinohydrazide (HL(2)), and N'-[(6-methylpyridin-2-yl)methylene]picolinohydrazide (HL(3))}. The structures of the complexes were determined by X-ray analysis. The hydrazone ligands had κN(py1),κN(imine) and κN(amidate),κN(py2) bidentate coordination modes in [PdCl2(HL(n))] (1, n = 1; 2, n = 2) and in [PdCl2(HL(3))] (3), respectively. In contrast, tridentate coordination modes of κN(py1),κN(imine),κN(py2) and κN(py1),κN(amidate),κN(py2) were observed in [PdCl(L(n))] (4, n = 1; 5, n = 2) and in [PdCl(L(n))] (6, n = 1; 7, n = 2; 8, n = 3). Thermal conversion of complexes 1-3 to complexes 6-8 proceeded in acetonitrile. Complexes 4 and 5 were obtained from complexes 1 and 2, respectively, in a basic acetonitrile solution under dark conditions. Complex 4 reverted immediately to complex 1 in an acidic acetonitrile solution that included hydrochloric acid. However, under room light, in the basic acetonitrile solution that included trimethylamine, complex 4 converted photochemically to complex 6. The thermochromic or vapochromic structure conversion of these complexes also occurred in the solid state. On heating at 180 °C, the color of the crystals of complexes 1, 2, and 3 changed from yellow to orange in the solid state. (1)H NMR and/or UV-vis absorption spectroscopy confirmed that the orange complexes 6-8 were produced. The reddish-orange crystals of complexes 4 and 5 were exposed to hydrogen chloride vapor to yield the yellow products of complexes 1 and 2, respectively.
The title compound, [Ru(C10H8N2)2(C16H12N4O)](BF4)2·3CH2Cl2, crystallizes with one complex dication, two BF4 (-) counter-anions and three di-chloro-methane solvent mol-ecules in the asymmetric unit. The central Ru(II) atom adopts a distorted octa-hedral coordination sphere with two 2,2'-bi-pyridine (bpy) and one quinoline-2-carbaldehyde (pyridine-2-carbon-yl)hydrazone (HL) ligand. The hydrazone ligand has a Z form and coordinates to the Ru(II) atom via the amide-O and imine-N atoms, affording a planar five-membered chelate ring, while its pyridine-N and quinoline-N donor atoms in the substituents are non-coordinating. The hydrazone N-H group forms an intra-molecular hydrogen bond with the quinoline-N atom. In the crystal, the quinoline moiety of HL shows the shortest π-π stacking inter-action with the pyridine substituent of HL in a neighbouring complex, the centroid-to-centroid distance being 3.793â (3)â Å.
A palladium-catalyzed and picolinamide-directed C-H thiolation of naphthylamine derivatives with diaryl disulfides has been developed to provide a convenient route to 8-sulfenyl-1-naphthylamines. The reaction proceeds via a 5-membered palladacycle intermediates to afford the peri-thiolated products exclusively, in contrast to the conventional ortho-functionalization. Moreover, the related direct selenation was also achieved with diaryl diselenides, giving the corresponding selenated products with perfect site-selectivity.
1-Naphthylamine/chemistry , Chalcogens/chemistry , Disulfides/chemistry , Palladium/chemistry , Picolinic Acids/chemistry , Selenium Compounds/chemistry , Amides/chemistry , Catalysis , Molecular Structure
The radical addition of the Cl-S σ-bond in sulfenyl chlorides to various C-C triple bonds has been achieved with excellent regio- and stereoselectivity in the presence of a catalytic amount of a common iron salt. The reaction is compatible with a variety of functional groups and can be scaled up to the gram-scale with no loss in yield. As well as terminal alkynes, internal alkynes underwent stereodefined chlorothiolation to provide tetrasubstituted alkynes. Preliminary mechanistic investigations revealed a plausible radical process involving a sulfur-centered radical intermediate via iron-mediated homolysis of the Cl-S bond. The resulting chlorothiolation adducts can be readily transformed to the structurally complex alkenyl sulfides by cross-coupling reactions. The present reaction can also be applied to the complementary synthesis of the potentially useful bis-sulfoxide ligands for transition-metal-catalyzed reactions.
A direct selenation of inert C-H bonds of benzamide derivatives and their related compounds with diselenides has been achieved with the palladium catalyst. The reaction was compatible with a variety of functional groups, including a bromo group. Primitive mechanistic insights revealed that the reaction proceeded through a C-H bond cleavage and the sequential oxidative addition of diselenides. The present synthetic method can be applied to the facile synthesis of selenoxanthone which can be regarded as promising heterocyclic materials.
Titanacyclopentadienes, prepared from [Cp2TiBu2] and either two equivalents of an alkyne or a diyne, were treated with PMe3 (3â equiv) at 50 °C for 3â h and then with azobenzene at room temperature for 12â h to give 4,5,6-trisubstituted indene derivatives with the loss of one substituent in good yields. This reaction contrasts sharply with our previously reported reaction for the formation of 4,5,6,7-tetrasubstituted indene derivatives without the loss of substituents by the treatment of titanacyclopentadienes with azobenzene without PMe3. (13)Câ NMR spectroscopy of the product derived from a (13)C-enriched complex revealed that the five carbon atoms originating from a Cp ligand were arranged linearly in the trisubstituted indene derivatives, in contrast to the 4,5,6,7-tetrasubsituted indene derivatives, in which the corresponding five carbon atoms are arranged in a ring.
Cyclopentanes/chemistry , Titanium/chemistry , Carbon-13 Magnetic Resonance Spectroscopy , Ligands , Molecular Structure
A series of picenes having methoxy groups was synthesized through Pd-catalyzed Suzuki-Miyaura couplings or Wittig reaction/intramolecular cyclization sequences, and their physicochemical properties and single-crystal structures were evaluated. The substitution position effects between the outer 1,12-, 2,11-, and 4,9-position and the inner 3,10-position are quite different; the former showed the same electronic structure as that of picene, but the latter results in a HOMO geometry different from those of picene and other methoxy picenes. In addition, crystal structures of four types of methoxy-substituted picenes 4a-c,e strongly depend on their substitution position and number of methoxy groups, which dramatically changes the structures from the fully anisotropic 1D π-stacked structure to a unique 3D herringbone structure due to steric hindrance of methoxy groups. The calculations of transfer integrals based on their single-crystal structures reveal that the methoxy picenes have intermolecular overlaps less effective than that of the parent nonsubstituted picene. These results are attributed not only to the packing structure but also to electronic structures such as the HOMO distribution. The preliminary OFET of the representative 4c,e showed hole mobilities significantly lower than that of picene due to their less effective intermolecular overlaps, as predicted by the calculated transfer integrals.
Photoreactivities of Ni(II)- and Pt(II)-hydrazone complexes, [NiCl(L)] (Ni1) and [PtCl(L)] (Pt1), respectively [HL = 2-(diphenylphosphino)benzaldehyde-2-pyridylhydrazone], were investigated in detail via UV-vis absorption, (1)H nuclear magnetic resonance (NMR) spectroscopy, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry; the two photoproducts obtained from the photoreaction of Pt1 were also successfully identified via X-ray analysis. The absorption bands of the Ni1 and Pt1 complexes were very similar, centered around 530 nm, and were assigned as an intraligand charge transfer transition of the hydrazone moiety. The absorption spectrum of Pt1 in a CH3CN solution changed drastically upon photoirradiation (λ = 530 nm), whereas no change was observed for Ni1. (1)H NMR and ESI-TOF mass spectra under various conditions suggested that the photoexcited Pt1* reacts with dissolved dioxygen to form a reactive intermediate, and the ensuing dark reactions afforded two different products without any decomposition. In contrast to the simple photo-oxidation of HL to form a phosphine oxide HL(PâO), the X-ray crystallographic analyses of the photoproducts clearly indicate the formation of a mononuclear Pt complex with the oxygenated hydrazone ligand (Pt1O) and a dinuclear Pt complex with the oxygenated and dimerized hydrazone ligand (Pt2). The photosensitized reaction in the presence of an (1)O2-generating photosensitizer, methylene blue (MB), also produced Pt1O and Pt2, indicating that the reaction between (1)O2 and ground-state Pt1 is the important step. In a highly viscous dimethyl sulfoxide solution, Pt1 was slowly, but quantitatively, converted to the mononuclear form, Pt1O, without the formation of the dinuclear product, Pt2, upon photoirradiation (and in the reaction photosensitized by MB), suggesting that this photoreaction of Pt1 involves at least one diffusion-controlled reaction. On the other hand, the same complexes Pt1O and Pt2 were also produced in the degassed solution, probably because of the reaction of the photoexcited Pt1* with the biradical character and H2O.
Chlorothiolation of terminal alkynes with sulfenyl chlorides yields anti-adducts without transition-metal catalysts. In sharp contrast, transition-metal-catalyzed chlorothiolation has not been developed to date, possibly because organosulfur compounds can poison catalyst. Herein, the regio- and stereoselective palladium-catalyzed chlorothiolation of terminal alkynes with sulfenyl chlorides is described. syn-Chlorothiolation offers a complementary synthetic route to chloroalkenyl sulfides. 2-Chloroalkenyl sulfides can easily be transformed into various sulfur-containing products, most of which are often found in natural products and pharmaceuticals.
