@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 {43910,
	title = {Enantioselective synthesis of functionalized β-lactones by NHC-catalyzed aldol lactonization of ketoacids},
	journal = {Journal of Organic Chemistry},
	volume = {82},
	year = {2017},
	month = {AUG},
	type = {Article},
	abstract = {N-Heterocyclic carbene (NHC)-catalyzed intramolecular aldol lactonization of readily available ketoacids leading to the enantioselective synthesis of cyclopentane-fused β-lactones is presented. The reaction proceeds via the generation of NHC-bound enolate intermediates formed from the ketoacids in the presence of the peptide coupling reagent HATU and NHC generated from the chiral triazolium salt. The functionalized β-lactones are formed under mild conditions in high yields and enantioselectivities.},
	doi = {10.1021/acs.joc.7b01526},
	author = {Mondal, Santigopal and Mukherjee, Subrata and Das, Tamal Kanti and Gonnade, Rajesh G. and Biju, Akkattu T.}
}
@article {43351,
	title = {Enantioselective synthesis of spiro γ-butyrolactones by N-heterocyclic carbene (NHC)-catalyzed formal [3+2] annulation of enals with 3-hydroxy oxindoles},
	journal = {Organic \& Biomolecular Chemistry },
	volume = {16},
	year = {2017},
	month = {FEB},
	pages = {2013 - 2019},
	abstract = {The N-heterocyclic carbene (NHC)-catalyzed enantioselective formal [3 + 2] annulation of α,β-unsaturated aldehydes with 3-hydroxy oxindoles is presented. Under oxidative conditions using the bisquinone oxidant, the reaction resulted in the synthesis of spiro γ-butyrolactones in moderate to good yields, enantioselectivity and diastereoselectivity. The reaction likely proceeds via the generation of the NHC-bound α,β-unsaturated acylazolium intermediate from enals, which was intercepted by the dioxindoles in a formal [3 + 2] pathway to form the spirocyclic compounds. However, a deeper mechanistic investigation revealed that the reaction can also proceed via the homoenolate intermediate. In this case, the dioxindole was oxidized to the corresponding isatin derivative using traces of air under basic conditions, and was intercepted with the NHC-bound homoenolate intermediate in a formal [3 + 2] pathway to afford the spiro compound.},
	doi = {10.1039/C7OB00148G},
	author = {Mukherjee, Subrata and Joseph, Sumi and Bhunia, Anup and Gonnade, Rajesh Ghanshyam and Reddy, Santhi Vardhan and Biju, Akkattu T.}
}
@article {45481,
	title = {Enantioselective N-heterocyclic carbene-catalyzed cascade reaction for the synthesis of pyrroloquinolines via N-H functionalization of indoles},
	journal = {Organic letters },
	volume = {20},
	year = {2018},
	month = {NOV},
	pages = {6998-7002},
	type = {Article },
	abstract = {Functionalization of the indole N-H bond for enantioselective synthesis of biologically important pyrroloquinoline derivatives has been reported under oxidative N-heterocyclic carbene catalysis conditions. The interception of catalytically generated chiral alpha,beta-unsaturated acylazoliums with the indole derivatives proceeds in an aza-Michael/Michael/lactonization sequence to deliver the pyrroloquinoline derivatives in good yields, diastereoselectivities, and enantioselectivities. The simultaneous enhancement of reactivity and selectivity observed in polar aprotic solvents is noteworthy.},
	issn = {1523-7060},
	doi = { 10.1021/acs.orglett.8b02820},
	author = {Mukherjee, Subrata and Shee, Sayan and Poisson, Thomas and Besset, Tatiana and Biju, Akkattu T.}
}
@article {46782,
	title = {Enantioselective synthesis of tricyclic beta-lactones by NHC-catalyzed desymmetrization of cyclic 1,3-diketones},
	journal = {Organic Letters},
	volume = {22},
	year = {2020},
	month = {JUL},
	pages = {5407-5411},
	type = {Article},
	abstract = {<p>The NHC-catalyzed desymmetrization of cyclic-1,3-diketones allowing the enantioselective construction of tricyclic beta-lactones with five contiguous stereocenters, including two quaternary stereocenters, has been developed. The mild and operationally simple addition of a-bromoenals to cyclopentane-1,3-diketone derivatives proceeds via the initial formation of chiral alpha,beta-unsaturated acylazolium intermediates and culminates in a cascade reaction, following the Michael-aldol-Iactonization pathway to deliver the beta-lactone derivatives in moderate to good yields and excellent selectivity.</p>
},
	issn = {1523-7060},
	doi = {10.1021/acs.orglett.0c01756},
	author = {Shee, Sayan and Mukherjee, Subrata and Gonnade, Rajesh G. and Biju, Akkattu T.}
}
