Search

A novel hypervalent iodine mediated cascade transformation of anilines and aldehydes to benzimidazoles was developed.

A novel catalyst-free hypervalent iodine(iii)-promoted tandem nucleophilic addition/aromatic nucleophilic substitution reaction of o-fluoroanilines with formamides toward 2-aminobenzoxazoles.

Palladium-catalyzed oxidative formal [4+1] annulation of pyridine-substituted acrylonitriles toward divergent fused N-heterocycles synthesis is reported. The heterodifunctionalization reaction with Cu(OAc)2 and urea as the nitrogen source accesses to nitrile-substituted pyrazolo[1,5-a]pyridines in moderate to good yields, while the homodifunctionalization reaction with FeBr3 leads to synthesis of nitrile-substituted indolizines in excellent yields.

Three-membered unsaturated rings have been widely utilized in organic synthesis due to their inherent highly strained structures. Although much research has been applied to ring-expansion reactions...

An efficient nano-Cu2O-catalyzed cascade multicomponent reaction of 2-halobenzoic acids and trimethylsilyl cyanide with diverse amines was developed using water as a solvent, affording versatile N-substituted phthalimide derivatives in moderate to excellent yields. This novel strategy features carbon monoxide gas-free, environmentally benign, one-pot multistep transformation, commercially available reagents, a cheap catalyst without any additives, wide functional group tolerance, and operational convenience.

A novel catalyst-free radical oxidative C-H annulation reaction of arylamines with α-keto acids toward benzoxazin-2-ones synthesis under mild conditions was developed. This hypervalent iodine(III)-promoted process eliminated the use of a metal catalyst or additive with high levels of functional group tolerance. Hypervalent iodine(III) was both an oxidant and a radical initiator for this reaction. The synthetic utility of this method was confirmed by the synthesis of the natural product cephalandole A.

A metal-free three-component annulation reaction for the synthesis of indolizine thiones via tandem C-C/C-N/C-S bond formation was developed. Various 2-alkylpyridines with aromatic ynals and elemental sulfur proceeded smoothly under catalyst-free conditions, and the desired products were obtained in moderate to excellent yields.

A Lewis acid-catalyzed three-component annulation reaction of 2-aminopyridines and ynals with elemental sulfur was established. A series of imidazo[1,2-a]pyridine thiones was obtained in moderate to excellent yields. The merits of this transformation include easily available starting materials, multiple C-heteroatom bond formation in one pot, good functional group tolerance, elemental sulfur as S source, operational simplicity, etc.

An efficient one-pot Sonogashira coupling and annulation reaction affording 4H-quinolizin-4-ones in moderate to excellent yields is described. A variety of substituted iodoarenes and 2-alkylazaarenes were well tolerated, and especially the unsaturated double and triple bonds were compatible under the standard conditions.

An efficient nano-Cu2O-catalyzed cascade multicomponent reaction of 2-halobenzoic acids and trimethylsilyl cyanide with diverse amines was developed using water as a solvent, affording versatile N-substituted phthalimide derivatives in moderate to excellent yields. This novel strategy features carbon monoxide gas-free, environmentally benign, one-pot multistep transformation, commercially available reagents, a cheap catalyst without any additives, wide functional group tolerance, and operational convenience.

Cu-catalyzed domino decyanation and cyanation reaction of acyl cyanides with amines or alcohols have been developed. The cyano sources were generated in situ via C-CN cleavage yielding the corresponding cyano substituted amides or esters in moderate to excellent yields. This approach features a cheap copper catalyst, domino decyanation and cyanation reaction, readily available starting materials, broad substrate scope, operational simplicity, and the potential for further transformation of the cyano group.

Metallacycloallenes are metallacyclic derivatives of cyclic allenes, in which a CH2 (type A) or CH (type B) segment is formally replaced by an isolobal transition-metal fragment. In constrast to the well-developed chemistry of metallacycloallenes of type A, the synthesis of metallacycloallenes with the structural features of type B has met with limited success. In this study, we present the reaction of η2-alkynol-coordinated osmacycle 1 with 2-aminopyridine in the presence of hypervalent iodine reagent, leading to the formation of imidazopyridinium-fused 4-osmacyclohexa-2,3,5-trienone 2 and 4-osmacyclohexa-2,5-dienone 3. Two key intermediates, η2-ethynyl ketone coordinated osmacycle 4 and 4-osmacyclohexa-2,5-dienone 5, were isolated and fully characterized, which suggest the hypervalent iodine reagent plays an important role in the formation of the fused metallacycloallene 2.

A Lewis acid-catalyzed three-component annulation reaction of 2-aminopyridines and ynals with elemental sulfur was established. A series of imidazo[1,2

η2-Iminoketenyl species have often been postulated as the intermediates in nucleophile-induced carbyne–isocyanide C–C coupling processes. However, such species are elusive. Here we report direct formation of η2-iminoketenyl complexes from reactions of metallapentalyne with isocyanides. Our studies show that steric effects of N-substituents of the isocyanides play an important role in the stability of the three-membered metallacycles of the η2-iminoketenyl complexes. Sterically bulky isocyanides, such as tert-butyl or 1-adamantyl isocyanides, inhibit bending at the isocyanide nitrogen atoms, a requirement for formation of η2-iminoketenyl structures. Reactions of metallapentalyne with excess isocyanide allow the metal-bridged metallaindene derivativesto be isolated as a result of the isocyanide insertion into the M–Cα σ bond of metallapentalyne.

Alkali-resistant osmabenzene [(SCN)2(PPh3)2Os{CHC(PPh3)CHCICH}] (2) can undergo nucleophilic aromatic substitution with MeOH or EtOH to give cine-substitution products [(SCN)2(PPh3)2Os{CHC(PPh3)CHCHCR}] (R=OMe (3), OEt(4)) in the presence of strong alkali. However, the reactions of compound 2 with various amines, such as n-butylamine and aniline, afford five-membered ring species, [(SCN)2(PPh3)2Os{CH=C(PPh3)CH=C(CH=NHR')}] (R'=nBu(8), Ph(9)), in addition to the desired cine-substitution products, [(SCN)2(PPh3)2Os{CHC(PPh3)CHCHC(NHR')}] (R'=nBu(6), Ph(7)), under similar reaction conditions. The mechanisms of these reactions have been investigated in detail with the aid of isotopic labeling experiments and density functional theory (DFT) calculations. The results reveal that the cine-substitution reactions occur through nucleophilic addition, dissociation of the leaving group, protonation, and deprotonation steps, which resemble the classical "addition-of-nucleophile, ring-opening, ring-closure" (ANRORC) mechanism. DFT calculations suggest that, in the reaction with MeOH, the formation of a five-membered metallacycle species is both kinetically and thermodynamically less favorable, which is consistent with the experimental results that only the cine-substitution product is observed. For the analogous reaction with n-butylamine, the pathway for the formation of the cine-substitution product is kinetically less favorable than the pathway for the formation of a five-membered ring species, but is much more thermodynamically favorable, again consistent with the experimental conversion of compound 8 into compound 6, which is observed in an in situ NMR experiment with an isolated pure sample of 8.

973 Program [2012CB821600]; National Natural Science Foundation of China [20925208, 21174115, 21272193]; Research Grants Council of Hong Kong [HKUST603711]; program for Changjiang Scholars and Innovative Research Team in University