Ring opening of donor-acceptor-type cyclopropene unveils electrophilic ketene with vinylogous [4 C + n] periselective cyclization mode.

ABSTRACT: Since its advent 120 years ago, the [2+n] coupling cyclization of ketene has been prevalently used for the synthesis of N- and O-heterocycles. In contrast, its vinylogous version, i.e., use of alkenyl ketene as 4 C synthon, remain elusive. We report herein that in the rare S_N1-type ring-opening of electron-deficient cyclopropene, the initially formed sp²-carbocation-containing zwitterionic intermediate undergoes facile 1,4-alkoxy migration to generate a functionalized alkenyl ketene. This electrophilic intermediate not only allows for challenging N-nucleophiles to be engaged in the conventional ketene [2+n] reactions (n = 1 ~ 3), also unveiled the vinylogous [4+n] cyclization mode, as exemplified by the [4 + 1] and formal [4 + 4] cyclization to construct pyrrolidinone

SUBMITTER: Huang J 

PROVIDER: S-EPMC12041596 | biostudies-literature | 2025 Apr

REPOSITORIES: biostudies-literature