RESUMEN
The functionalization of etheric C-O bonds via C-O bond cleavage is an attractive strategy for the construction of C-C and C-X bonds in organic synthesis. However, these reactions mainly involve C(sp3)-O bond cleavage, and a catalyst-controlled highly enantioselective version is extremely challenging. Here, we report a copper-catalyzed asymmetric cascade cyclization via C(sp2)-O bond cleavage, allowing the divergent and atom-economic synthesis of a range of chromeno[3,4-c]pyrroles bearing a triaryl oxa-quaternary carbon stereocenter in high yields and enantioselectivities. Importantly, this protocol not only represents the first [1,2]-Stevens-type rearrangement via C(sp2)-O bond cleavage, but also constitutes the first example of [1,2]-aryl migration reactions via vinyl cations.
RESUMEN
Medium-sized N,S-heterocycles have received tremendous interest due to their biological activities and potential medical applications. However, asymmetric synthesis of these compounds are extremely rare. Described herein is a catalyst-dependent [3,3]-sigmatropic rearrangement of sulfoxide-ynamides, enabling divergent and atom-economic synthesis of a series of valuable medium-sized N,S-heterocycles in moderate to good yields with broad substrate scope. Importantly, excellent enantioselectivities have been achieved via an unprecedented chirality-transfer. Moreover, theoretical calculations are employed to elucidate the origins of the catalyst-dependent stereospecific [3,3]-rearrangement.