@article {48040,
	title = {Dynamic kinetic resolution of gamma,gamma-disubstituted indole 2-carboxaldehydes via NHC-Lewis acid cooperative catalysis for the synthesis of tetracyclic epsilon-lactones},
	volume = {13},
	year = {2022},
	month = {OCT},
	pages = {11513-11518},
	type = {Article},
	abstract = {<p>
	The ubiquity of epsilon-lactones in various biologically active compounds inspired the development of efficient and enantioselective routes to these target compounds. Described herein is the enantioselective synthesis of indole-fused epsilon-lactones by the N-heterocyclic carbene (NHC)-Lewis acid cooperative catalyzed dynamic kinetic resolution (DKR) of in situ generated gamma,gamma-disubstituted indole 2-carboxaldehydes. The Bi(OTf)(3)-catalyzed Friedel-Crafts reaction of indole-2-carboxaldehyde with 2-hydroxy phenyl p-quinone methides generates gamma,gamma-disubstituted indole 2-carboxaldehydes, which in the presence of NHC and Bi(OTf)(3) afforded the desired tetracyclic epsilon-lactones in up to 93\% yield and \&gt;99 : 1 er. Moreover, preliminary studies on the mechanism of this formal [4 + 3] annulation are also provided.</p>
},
	issn = {2041-6520},
	doi = {10.1039/d2sc03745a},
	author = {Balanna, Kuruva and Barik, Soumen and Shee, Sayan and Gonnade, Rajesh G. and Biju, Akkattu T.}
}
