Regioselective Synthetic Approach to Higher Alkenes from Lower Alkenes with Sulfoxides in the Fe3+/H2O2 System via Direct Alkylation or Arylation of the Csp2-H Bond on the C═C Bond of Alkenes.

The regioselective synthetic approach to higher alkenes from lower alkenes by using sulfoxides as alkyl or aryl reagents in the Fe3+/H2O2 system has been developed. This reaction realized direct alkylation or arylation of alkenes. In this reaction, sulfoxides afforded one Csp3 or Csp2 atom to the C═C bond of alkenes; one new Csp2-Csp3 bond or Csp2-Csp2 bond was formed. Nearly 40 products including di-, tri-, and tetra-substituted products were regioselectively synthesized. Both aliphatic and aromatic alkenes could participate in this reaction. Moreover, not only dimethyl sulfoxide but also three other sulfoxides can be applied to this reaction, including diethyl, dibenzyl, and diphenyl sulfoxide. The mechanism studies showed that this reaction may experience a coupling process via radical addition-elimination and the Fe3+/H2O2 system made the sulfoxides offered one alkyl or aryl radical to the C═C bond of alkenes.

[3+1+1+1] Annulation to the Pyridine Structure in Quinoline Molecules Based on DMSO as a Nonadjacent Dual-Methine Synthon: Simple Synthesis of 3-Arylquinolines from Arylaldehydes, Arylamines, and DMSO.

A [3+1+1+1] annulation of arylamines, arylaldehydes, and dimethyl sulfoxide (DMSO) to the pyridine structure in quinolines using DMSO as a nonadjacent dual-methine (═CH-) synthon is disclosed. In this annulation, arylamines provide two carbon atoms and one nitrogen atom, arylaldehydes furnish one carbon atom, and DMSO provides two nonadjacent methines (═CH-) to the pyridine ring in quinoline molecules. This annulation provides a simple approach for the synthesis of 3-arylquinolines from readily available substrates in useful yields. On the basis of the control experiments and the literature, a plausible mechanism is proposed.

Unexpected Annulation between 2-Aminobenzyl Alcohols and Benzaldehydes in the Presence of DMSO: Regioselective Synthesis of Substituted Quinolines.

An unexpected annulation among 2-aminobenzyl alcohols, benzaldehydes, and DMSO to quinolines has been disclosed. For the reported annulation between 2-aminobenzyl alcohols and benzaldehydes, the change of the solvent from toluene to DMSO led to the change of the product from the diheteroatomic cyclic benzoxazines to monoheteroatomic cyclic quinolines. This annulation can be used to synthesize regioselectively different substituted quinolines by the choice of different 2-amino alcohols, aldehydes, and sulfoxides as substrates. Interestingly, introducing substituent groups to the α-position of sulfoxides resulted in the interchange of the positions between benzaldehydes and sulfoxides in the product quinolines. On the basis of the control experiments and literatures, a plausible mechanism for this annulation was proposed.

Two C═C Bond Participation in Annulation to Pyridines Based on DMF as the Nonadjacent N and C Atom Donors.

Two C═C bond participation in annulation to pyridines using N,N-dimethylformamide (DMF) as the N1 and C4 synthons has been carried out. In this reaction, DMF contributed one N atom and one C atom to two disconnected positions of pyridine ring, with no need for an additional nitrogen source. Two C═C bonds in two molecules of substituted styrenes offered four carbon atoms in the presence of iodine and persulfate. With the optimized conditions in hand, both symmetric and unsymmetric diaryl-substituted pyridines were obtained in useful yields. On the basis of relevant literature and a series of control experimental results, a possible mechanism was proposed in this work, which may demonstrate how DMF provides both N1 and C4 sources.

Metal-Free-Catalyzed Synthesis of Allyl Nitriles via Csp2-Csp3 Coupling between Olefins and Azobis (Alkyl-carbonitrile).

The metal-free-catalyzed synthesis of allyl nitriles from Csp2-Csp3 coupling between olefins and azobis was carried out. Key on this work was that the synthesis of allyl nitriles directly using olefin as a starting material was considered to be more efficient and economical than the alkyne, alkynyl carboxylic acid, or cinnamic acid used in previous works. Moreover, in this reaction, iodine served as the sole promoter, azobis served as a cyanation reagent, and N2 was the only nontoxic byproduct that could avoid the utilization of metal catalysts and virulent nitrile reagents and generation of toxic wastes. With an optimum condition in hand, more than 30 examples of desired products including aromatic and aliphatic nitriles have been synthesized in good to excellent yields. Based on control experiments and literature data, a plausible mechanism of cyanation was proposed.

Transition Metal-Free α-Csp3-H Methylenation of Ketones to Form C═C Bond Using Dimethyl Sulfoxide as Carbon Source.

A direct α-Csp3-H methylenation of arylketones to form C═C bond using dimethyl sulfoxide as one-carbon source is achieved under transition metal-free reaction condition. Various aryl ketone derivatives react readily with DMSO, producing the α,ß-unsaturated carbonyl compounds in yields of 42 to 90%. This method features a transition metal-free reaction condition, wide substrate scope and using DMSO as novel one-carbon source to form C═C bond, thus providing an efficient and expeditious approach to an important class of α,ß-unsaturated carbonyl compounds. Based on the preliminary experiments, a plausible mechanism of this transformation is disclosed.

Transition-Metal-Free Oxidative Decarboxylative Cross Coupling of α,ß-Unsaturated Carboxylic Acids with Cyclic Ethers under Air Conditions: Mild Synthesis of α-Oxyalkyl Ketones.

A novel K2S2O8-promoted decarboxylative cross coupling of α,ß-unsaturated carboxylic acids with cyclic ethers was developed under aerobic conditions. The present protocol, which includes C-C and C═O bond formation in one step through addition, oxidation, and decarboxylation processes, leads to the desired ketone products in moderate to excellent yields. In addition, mechanism studies showed that the transformation process undergoes a radical pathway via a direct activation of the α-sp3 C-H bond of oxygen of the cyclic ether.

Transition-Metal-Free TBAI-Facilitated Addition-Cyclization of N-Methyl-N-arylacrylamides with Arylaldehydes or Benzenesulfonohydrazides: Access to Carbonyl- and Sulfone-Containing N-Methyloxindoles.

A highly efficient addition-cyclization of N-methyl-N-arylacrylamides with arylaldehydes or benzenesulfonohydrazides was developed using a catalytic amount of the quaternary ammonium salt (TBAI) under metal-free conditions, leading to the carbonyl- and sulfone-containing oxindoles. Compared to previous methods, which require excessive amounts of explosive organic peroxides and precious or toxic metal reagents, the present protocol, which gave access to 3,3-disubstituted oxindoles, is a safe and green approach, resulting in the formation of various useful carbonyl- and sulfone-containing oxindoles in yields of 40-94%.

Transition-Metal-Free Synthesis of Carbonyl-Containing Oxindoles from N-Arylacrylamides and α-Diketones via TBHP- or Oxone-Mediated Oxidative Cleavage of C(sp(2))-C(sp(2)) Bonds.

Carbonyl-containing oxindoles can be prepared from N-arylacrylamides and α-diketones by TBHP- or oxone (KHSO5)-mediated C(sp(2))-C(sp(2)) bond cleavage and new C(sp(2))-C(sp(3)) bond formation. This methodology is characterized by its simple and transition-metal-free conditions and good functional group compatibility utilizing inexpensive and readily available reagents, thus providing a practical and efficient approach to an important class of 3-(2-oxoethyl)indolin-2-ones which are highly valued synthetic intermediates of biologically active molecules. In this transformation, alkylcarbonyl-containing oxindoles were obtained in majority when N-arylacrylamides reacted with asymmetric aliphatic/aromatic α-diketones. On the basis of the preliminary experiments, a plausible mechanism of this transformation is disclosed.

Iron-facilitated oxidative radical decarboxylative cross-coupling between α-oxocarboxylic acids and acrylic acids: an approach to α,ß-unsaturated carbonyls.

The first Fe-facilitated decarboxylative cross-coupling reaction between α-oxocarboxylic acids and acrylic acids in aqueous solution has been developed. This transformation is characterized by its wide substrate scope and good functional group compatibility utilizing inexpensive and easily accessible reagents, thus providing an efficient and expeditious approach to an important class of α,ß-unsaturated carbonyls frequently found in bioactive compounds. The synthetic potential of the coupled products is also demonstrated in subsequent functionalization reactions. Preliminary mechanism studies suggest that a free radical pathway is involved in this process: the generation of an acyl radical from α-oxocarboxylic acid via the excision of carbon dioxide followed by the addition of an acyl radical to the α-position of the double bond in acrylic acid then delivers the α,ß-unsaturated carbonyl adduct through the extrusion of another carbon dioxide.

Metal-free synthesis of oxindoles via (NH4)2S2O8-mediated halocarbocyclization of alkenes in water.

A metal-free synthesis of oxindoles was achieved through the (NH4)2S2O8-mediated halocarbocyclization of alkenes. This protocol provides a practical and environmentally benign method for the construction of halo-containing oxindoles in water. The advantages of this reaction are its good functional group tolerance and mild reaction conditions. On the basis of experimental observations, a plausible reaction mechanism is proposed.

Copper-catalyzed aerobic decarboxylative sulfonylation of cinnamic acids with sodium sulfinates: stereospecific synthesis of (E)-alkenyl sulfones.

A copper-catalyzed aerobic decarboxylative sulfonylation of alkenyl carboxylic acids with sodium sulfinates is developed. This study offers a new and expedient strategy for stereoselective synthesis of (E)-alkenyl sulfones that are widely present in biologically active natural products and therapeutic agents. Moreover, the transformation is proposed to proceed via a radical process and exhibits a broad substrate scope and good functional group tolerance.

Phenyliodonium diacetate mediated direct synthesis of benzonitriles from styrenes through oxidative cleavage of C═C bonds.

A metal-free PhI(OAc)2 mediated nitrogenation of alkenes through C═C bond cleavage using inorganic ammonia salt as nitrogen source under mild conditions was developed, affording nitriles in moderate to good yields. The advantages of this reaction are mild reaction conditions, operational simplicity, and use of an ammonium salt as nitrogen source. Based upon experimental observations, a plausible reaction mechanism is proposed.

Oxidative rearrangement of internal alkynes to give one-carbon-shorter ketones via manganese porphyrins catalysis.

Oxidative rearrangement of internal alkynes catalyzed by manganese(III) porphyrin is described, which opens a new access to one-carbon-shorter ketones using molecular oxygen. Under the standard conditions, a variety of alkynes including diarylalkynes and arylalkylalkynes rearranged smoothly to the corresponding ketones in high yields. Based upon experimental observations, a plausible reaction mechanism is proposed.

Pd-catalyzed decarboxylative arylation of thiazole, benzoxazole, and polyfluorobenzene with substituted benzoic acids.

A Pd-catalyzed decarboxylative coupling of thiazoles and benzoxazole with various substituted benzoic acids is developed. The reaction is compatible with both electron-rich and electron-poor benzoic acids. It can also be extended to the synthesis of polyfluoro-substituted biaryls using polyfluorobenzenes as the starting materials.

Novel phosphoramidates with porphine and nitrogenous drug: one-pot synthesis and orientation to cancer cells.

One-pot synthesis of novel phosphoramidates with porphine and nitrogenous drug was accomplished. In the absence of light, MTT test showed that they killed the BEL-7402 liver cancer cells effectively in vitro. The cell viability studied on normal liver and cancer cells showed that porphine phosphoramidates selectively kill the cancer cells, which was in sharp contrast with the non-porphine containing compound 4-formylphenyl N,N-bis(2-chloroethyl)-phosphoramidate. These results, coupled with the cell uptake test showing that they could differentiate the tumor cells from the normal cells by their selective accumulation in cancer cells, gave strong support to the notion that the introduction of porphine moiety in these molecules was responsible for the effectiveness and cell differentiability of these porphine phosphoramidates.

One-step preparation of xanthones via Pd-catalyzed annulation of 1,2-dibromoarenes and salicylaldehydes.

A one-step preparation of xanthones via Pd-catalyzed annulation of 1,2-dibromoarenes and salicylaldehydes was developed.

Unprecedented degradation of nickel(II) 2,3,12,13-tetrabromo-5,10,15,20-tetraarylporphyrins by the anion of E-benzaldoxime: a novel approach to nickel(II) chlorophins and bacteriophins.

A novel and convenient approach to chlorophins and bacteriophins has been developed through a degradation of nickel(II) 2,3,12,13-tetrabromo-5,10,15,20-tetraarylporphyrins by the anion of E-benzaldoxime. The UV-vis spectra of these chlorophins and bacteriophins are similar to those of metalated chlorin and bacteriochlorin systems but with more intense and bathochromically shifted Q-bands.

Regioselective syntheses of 2- and 4-formylpyrido[2,1-b]benzoxazoles.

o-Acetaminophenols (2) reacted with Vilsmeier reagent under Meth-Cohn conditions to yield 2-formylpyrido[2,1-b]benzoxazoles (5) unexpectedly besides the known compounds 2-(benzoxazol-2'-yl)-3-dimethylaminoacroleins (4). Refluxing 4 in acetic anhydride gave 4-formylpyrido[2,1-b]benzoxazoles (6), an isomer of 5. Both 5a and 6a were structurally characterized by X-ray crystallography. A mechanism for the formation of 5 involving sequential chlorination, dimerization, intramolecular elimination of HCl to form the oxazole ring, formylation twice, and regioselective intramolecular nucleophilic cyclization to construct the pyridone ring is proposed.

An efficient copper-catalyzed oxidative Mannich reaction between tertiary amines and methyl ketones.

An efficient oxidative Mannich reaction between tertiary amines and unmodified methyl ketones has been developed, using copper salts as the catalyst and O(2) as the oxidant.