ol7b02061_si_002.pdf (9.35 MB)
Nazarov Cyclization and Tandem [4 + 2]-Cycloaddition Reactions of Donor–Acceptor Cyclopropanes
journal contribution
posted on 2017-08-17, 21:08 authored by Gangarajula Sudhakar, S. K. Mahesh, S. Phani Babu Vemulapalli, Jagadeesh Babu NanuboluThe development of aryl vinyl/divinyl
donor–acceptor cyclopropanes
(DACs) as novel Nazarov cyclization (NC) precursors is described.
The 1,3-zwitterion, generated from DACs embedded in the divinyl framework,
acts as a pentadienyl cation, a requisite for Nazarov cyclization.
A cyclic allyl cation in the course of NC was trapped with external
nucleophiles to provide an interrupted NC product. Indeed, an allyl
cation in this reaction is analogous to a 1,4-zwitterion that on reaction
with dipolarophiles provided an easy access to substituted pyrans
with excellent yield and diastereoselectivity via NC followed by a
formal [4 + 2] cycloaddition.