A Catalyst-Free Approach to Construct 3-(Cyclopentenone)oxindoles Through a Phosphine-Ylide-Initiated Triple Domino Sequence

Switchable C2/C3 positional selectivity of thioisatins in a three-component domino reaction: combined computational and experimental studies

The nucleophile-induced domino reaction is a featured reactivity mode of thioisatin, but the C2/C3 positional selectivity towards a nucleophile has not been understood in-depth. In this work, a domino reaction of thioisatin with bromoacetophenone and tryptamine hydrochloride to produce a benzothiophene-fused eight-membered N-heterocycle was described, showing that the Brønsted acid-base form of the amine partner was crucial for the selectivity, because using tryptamine instead of tryptamine hydrochloride gave a different product. Control experiments and density functional calculations revealed that the domino reaction using tryptamine or tryptamine hydrochloride was triggered by a condensation reaction at the C2 or C3 position of thioisatin, respectively. A delicate balance between local electrophilicity and polarization effect may be responsible for the observed selectivity.

Multicomponent benzannulation of allylic P-ylides with isocyanates or aldehydes for construction of anilines and biaryls

The reactivity of allylic phosphorus ylides generated in situ from alkoxycarbonylmethylenephosphoranes and propiolates is investigated toward isocyanates and aromatic aldehydes, which leads to one-pot multicomponent benzannulations for efficient synthesis of polysubstituted anilines and biaryls, respectively. The mechanism may involve a tandem [2+2] cycloaddition/fragmentation/Wittig/cyclization/elimination/aromatization sequence.

Darzens reaction of thioisatins and sulfonium salts: approach to the synthesis of thiochromenone derivatives with anticancer potency

A new Darzens reaction of thioisatins and sulfonium salts has, for the first time, been reported. This reaction allows efficient access to thiochromenone derivatives in good to excellent yields under mild reaction conditions. The substrate scope includes both electron-withdrawing and electron-donating groups on both the thioisatins and sulfonium salts. Moreover, some of the synthesized thiochromenone derivatives have been found to show potent anticancer activities against six different cancer cell lines using the methylthiazoltetrazolium (MTT) assay.

Phosphine-catalyzed [4 + 2] annulation of γ-benzyl allenoates: facile synthesis of benzothieno[3,2-b]pyran derivatives

An efficient tris(4-methoxyphenyl)phosphane catalyzed domino reaction between γ-benzyl allenoate and ethyl (Z)-2-(3-oxobenzo[b]thiophen-2(3H)-ylidene)acetate has been developed, which produces a series of 2H-benzo[4,5]thieno[3,2-b]pyran derivatives in high yields.

Direct N–H/α,α,β,β-C(sp3)–H functionalization of piperidine via an azomethine ylide route: synthesis of spirooxindoles bearing 3-substituted oxindoles

A protocol for the direct functionalization of N–H/α,α,β,β-C(sp³)–H of piperidine without any metal or external oxidants is reported.

NaH promoted [4+3] annulation of crotonate-derived sulfur ylides with thioaurones: synthesis of 2,5-dihydrobenzo[4,5]thieno[3,2-b]oxepines

The [4+3] annulation reaction of crotonic acid derivative sulfur ylides with thioaurones has, for the first time, been reported using NaH as the base. A diverse array of 2,5-dihydrobenzo[4,5]thieno[3,2-b]oxepines is obtained in good to excellent yields. The proposed mechanism is investigated and supported by DFT calculations.

DABCO-catalyzed unusual [4 + 2] cycloaddition reaction: non-substituted allenoate acts as a four-carbon synthon and facile synthesis of spirooxindoles

The first example of a non-substituted allenoate to act as a four-carbon synthon in a DABCO-catalyzed domino reaction is reported.