%0 Journal Article %J Angewandte Chemie-International Edition %D 2016 %T Enantioselective synthesis of spirocyclohexadienones by NHC-catalyzed formal [3+3] annulation reaction of enals %A Yetra, Santhivardhana Reddy %A Mondal, Santigopal %A Mukherjee, Subrata %A Gonnade, Rajesh G. %A Biju, Akkattu T. %K annulation reactions %K asymmetric catalysis %K N-heterocyclic carbenes %K organocatalysis %K spiro compounds %X

The enantioselective synthesis of pyrazolone-fused spirocyclohexadienones was demonstrated by the reaction of alpha,beta-unsaturated aldehydes with alpha-arylidene pyrazolinones under oxidative N-heterocyclic carbene (NHC) catalysis. This atom-economic and formal [3+3] annulation reaction proceeds through a vinylogous Michael addition/spiroannulation/dehydrogenation cascade to afford spirocyclic compounds with an all-carbon quaternary stereocenter in moderate to good yields and excellent ee values. Key to the success of the reaction is the cooperative NHC-catalyzed generation of chiral alpha,beta-unsaturated acyl azoliums from enals, and base-mediated tandem generation of dienolate/enolate intermediates from pyrazolinones.

%B Angewandte Chemie-International Edition %I WILEY-V C H VERLAG GMBH %C POSTFACH 101161, 69451 WEINHEIM, GERMANY %V 55 %P 268-272 %8 JAN %G eng %N 1 %3

Foreign

%4 11.709 %R 10.1002/anie.201507802