Base-catalyzed efficient tandem [3 + 3] and [3 + 2 + 1] annulation-aerobic oxidative benzannulations.

An efficient synthesis of substituted benzenes via a base-catalyzed [3 + 3] aerobic oxidative aromatization of α,β-unsaturated carbonyl compounds with dimethyl glutaconate was reported. All the reactions were carried out under mild, metal-free conditions to afford the products in high to excellent yields with molecular oxygen as the sole oxidant and water as the sole byproduct. Furthermore, a more convenient tandem [3 + 2 + 1] aerobic oxidative aromatization reaction was developed through the in situ generation of the α,β-unsaturated carbonyl compounds from aldehydes and ketones.

Synthesis of acridines and persubstituted phenols from cyclobutenones and active methylene ketones.

A new benzannulation strategy that proceeds via a regiospecific [4 + 2] cycloaddition of readily available cyclobutenones and active methylene ketones has been developed. On the basis of this strategy, persubstituted phenols/anilines with up to six different functional groups on the benzene ring were synthesized in a single step. In addition, a series of acridine derivatives were prepared in excellent yield from persubstituted phenols/anilines.

Tandem [5+1] annulation-isocyanide cyclization: efficient synthesis of hydroindolones.

A new strategy for the rapid construction of functionalized reduced indoles starting from activated methylene isocyanides and 1,5-dielectrophilic 5-oxohepta-2,6-dienoates (and their equivalents) through a [5+1] annulation-isocyanide cyclization cascade under basic conditions has been developed. This strategy allows the synthesis of polysubstituted dihydroindolones and tetrahydroindolones in high to excellent yields under extremely mild conditions in a single step.

Highly efficient access to bi- and tricyclic ketals through gold-catalyzed tandem reactions of 4-acyl-1,6-diynes.

Single step: Fused bicyclic and bridged tricyclic ketals were synthesized in a single step from the reactions of easily available 4-acyl-1,6-diynes with H(2)O and alkanols (see scheme). The highly efficient AuCl(3)-catalyzed multicomponent domino reactions, involving five C-O bond formations, can proceed in a highly regio- and diastereoselective manner at room temperature under air and lead to structures of high molecular complexity from simple starting materials in an atom economic way.