01701nas a2200253   4500008004100000022001400041245011600055210006900171260007500240300001200315490000700327520074400334653002501078653002501103653002801128653002001156653002001176100003301196700002301229700002301252700002401275700002201299856012601321       2016                        eng d  a1433-785100aEnantioselective synthesis of spirocyclohexadienones by NHC-catalyzed formal [3+3] annulation reaction of enals0 aEnantioselective synthesis of spirocyclohexadienones by NHCcatal  aPOSTFACH 101161, 69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcJAN  a268-2720 v553 a<p>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.</p>10aannulation reactions10aasymmetric catalysis10aN-heterocyclic carbenes10aorganocatalysis10aspiro compounds1 aYetra, Santhivardhana, Reddy1 aMondal, Santigopal1 aMukherjee, Subrata1 aGonnade, Rajesh, G.1 aBiju, Akkattu, T.  uhttps://library.ncl.res.in/content/enantioselective-synthesis-spirocyclohexadienones-nhc-catalyzed-formal-33-annulation-1