Rearrangement of 4-(1-Haloalkyl)- and 4-(2-Haloalkyl)-2-azetidinones into Methyl ω-Alkylaminopentenoates via Transient Aziridines and Azetidines
摘要:
The synthesis of 4-(1-haloalkyl)-2-azetidinones and 4-(2-haloalkyl)-2-azetidinones was investigated with use of the Staudinger reaction between in situ generated ketenes and alpha-haloimines or beta-haloimines. This new class of functionalized 2-azetidinones was further evaluated for its potential use as intermediates in the synthesis of highly functionalized compounds. The reaction of 4-(1-haloalkyl)-2-azetidinones and 4-(2-haloalkyl)-2-azetidinones with sodium methoxide in methanol yielded ring-opened products, i.e., methyl 2-alkoxy-4-(alkylamino)pentenoate and methyl 5-(alkylamino)pentenoate, respectively. Further attention was paid in detail to the reaction mechanism involved in this peculiar transformation. It was proven that these reactions proceeded via intermediate aziridines or azetidines.
Electrophile-Induced Ring Expansions of <i>β</i>-Lactams toward γ-Lactams
作者:Willem Van Brabandt、Norbert De Kimpe
DOI:10.1021/jo0509556
日期:2005.10.1
was developed from 4-(1-chloroalkyl)azetidin-2-ones. Starting from the latter β-lactams, a new synthesis of pyrrolidin-2-ones was achieved. When 4-isopropenylazetidin-2-ones were treated with bromine in dichloromethane, diastereoselective electrophile-induced ring expansions toward 5-bromopyrrolidin-2-ones were performed. Further oxidation of 3-benzyloxypyrrolidin-2-ones with bromine toward 3-bromopyrrolidin-2-ones