@article { ISI:000368065300033,
	title = {Enantioselective synthesis of spirocyclohexadienones by NHC-catalyzed formal [3+3] annulation reaction of enals},
	journal = {Angewandte Chemie-International Edition},
	volume = {55},
	number = {1},
	year = {2016},
	month = {JAN},
	pages = {268-272},
	publisher = {WILEY-V C H VERLAG GMBH},
	address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY},
	abstract = {<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>},
	keywords = {annulation reactions, asymmetric catalysis, N-heterocyclic carbenes, organocatalysis, spiro compounds},
	issn = {1433-7851},
	doi = {10.1002/anie.201507802},
	author = {Yetra, Santhivardhana Reddy and Mondal, Santigopal and Mukherjee, Subrata and Gonnade, Rajesh G. and Biju, Akkattu T.}
}
@article {45733,
	title = {Unified approach to fused and spirocyclic oxindoles through lewis-acid-promoted opening of spiroepoxyoxindoles with allylsilanes: application to the formal synthesis of (+/-)-physovenine},
	journal = {European Journal of Organic Chemistry},
	year = {2017},
	month = {MAY },
	pages = {2603-2609},
	type = {Article},
	abstract = {<p>A protocol for the construction of oxindoles containing all-carbon quaternary centres in a highly regioselective manner has been developed. The reaction involves opening of spiroepoxyoxindoles with allylsilanes to give Hosomi-Sakurai-type products as well as new silicon-containing spirocyclic oxindoles. A formal synthesis of (+/-)-physovenine was accomplished in five steps using this protocol.</p>},
	keywords = {alkaloids, Allylation, annulation, Lewis acids, spiro compounds},
	issn = {1434-193X},
	doi = {10.1002/ejoc.201700259},
	author = {Sharma, Brijesh M. and Yadav, Mahesh and Gonnade, Rajesh G. and Kumar, Pradeep}
}
