Diversity-Oriented Synthesis of Furo[3,2-c]coumarins and Benzofuranyl Chromenones through Chemoselective Acylation/Wittig Reaction.

A highly efficient and chemoselective one-pot protocol for the diversity-oriented synthesis of two types of coumarin-based formal cross-coupling adducts, furo[3,2-c]coumarins and 3-benzofuranyl chromenones, is described. Key attributes of the methodology are an initial chemoselective acylation of functionalized phosphorus zwitterions and a subsequent chemoselective intramolecular Wittig reaction that preferentially resulted in one of the two coumarin derivatives in high yield, depending on relative reactivities and the addition sequence of the acylating agents.

Chemo- and Diastereoselective Michael-Michael-Acetalization Cascade for the Synthesis of 1,3-Indandione-Fused Spiro[4.5]decan Scaffolds.

A novel, organobase-catalyzed and highly chemoselective Michael-Michael-acetalization cascade is presented for the efficient synthesis of spiro-indandione skeletons. Following this very simple protocol, a broad range of products was obtained in good yields with excellent diastereocontrol. The role of steric factors in the acetalization step was evaluated.

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.

An enantioselective cascade for simultaneous generation of five quaternary stereocenters from fully substituted enones.

A highly enantioselective cascade reaction for the generation of five quaternary stereocenters in one-pot operation is reported for the first time in the history of organic synthesis. Cinchona-alkaloid derived hydrogen-bonding catalyst furnished structurally complex cascade products from simple substrates in excellent yields and stereoselectivities.