Diversity-oriented synthesis of chromenopyrrolidines from azomethine ylides and 2-hydroxybenzylidene indandiones via base-controlled regiodivergent (3+2) cycloaddition.

An organobase-directed, regiodivergent 1,3-dipolar cycloaddition of azomethine ylides and 2-hydoxybenzylidene indandiones is reported. The scarcely explored reversal of the nucleophilic site in azomethine ylides has been exploited for their regiodivergent (3+2) cycloaddition, which subsequently resulted in two different cascade processes to generate functionally distinct chromenopyrrolidines in a diversity oriented manner.

Four-Component Synthesis of Phosphonium Salts: Application Toward an Alternative Approach to Cross-Coupling for the Synthesis of Bis-Heteroarenes.

A series of stable phosphonium salts have been synthesized via a novel four-component reaction of an arene nucleophile, 2-heteroatom substituted aryl aldehyde, and phosphine in presence of an acid. The phosphonium salts thus obtained were utilized for the synthesis of a variety of bis-heteroarenes, providing an efficient alternative method to the classical cross-coupling strategies.

Diastereoselective Synthesis of Rauhut-Currier-Type Adducts via an Unexpected α-Addition of α,ß-Unsaturated γ-Butyrolactams to Coumarin Derivatives.

A novel, base-catalyzed and highly diastereoselective direct Michael addition-isomerization sequence is presented for the efficient synthesis of Rauhut-Currier-type adducts. An unexpected α-addition of γ-butyrolactam onto the 3-acyl coumarin derivatives was observed rather than the γ-addition, which is more common. The adducts could further undergo hydrolysis/decarboxylation to generate the products which are equivalent to those obtained by α-addition of γ-butyrolactam onto the corresponding chalcones.

Synthesis of Functionalized Furans via Chemoselective Reduction/Wittig Reaction Using Catalytic Triethylamine and Phosphine.

An efficient protocol for the synthesis of highly functionalized furans via intramolecular Wittig reaction has been developed using catalytic amounts of phosphine and triethylamine. Silyl chloride served as the initial promoter to activate the phosphine oxide. Reduction of the activated phosphine oxide by hydrosilane resulted in generation of phosphine, while decomposition of Et3N·HCl resulted in regeneration of base, which mediated formation of phosphorus ylide. Remarkably, the in situ generated byproduct, Et3N·HCl, also catalyzes reduction of phosphine oxide.