Polar-Radical Cyclization Cascades with Magnesiated Nitriles
作者:Stephen Bolgunas、Ehecatl Paleo、Embarek Alwedi、Yunjing Wei、Taylor M. Keller、Fraser F. Fleming
DOI:10.1021/acs.orglett.3c01094
日期:2023.5.19
via a polar-radical addition–cyclization cascade. One-electron oxidation of magnesiated nitriles generates nitrile-stabilized radicals that cyclize onto a pendant olefin and then rebound onto the nitrile through a reduction–cyclization sequence; subsequent hydrolysis affords a diverse array of bicyclo[3.2.0]heptan-6-ones. Combining the polar-radical cascade with a 1,2:1,4-carbonyl-conjugate addition
Here we describe the realization of a one-pot protocol for the β-C–H halogenation of cyclic enones via umpolung of the β-carbon. The developed method includes hydrazone formation and selective β-halogenation (bromination, chlorination) with N-bromosuccinimide and Palau’chlor (2-chloro-1,3-bis(methoxycarbonyl)guanidine) followed by hydrolysis of the hydrazone moiety. Using the optimized conditions,
Enzymatic resolution of 3-bromo-cyclohept-2-enol: application to the determination of the absolute configuration of diethyl (3-hydroxy-cyclohept-1-enyl)phosphonate
Enzymaticresolution of racemic 3-bromo-cyclohept-2-enol 2 with lipozyme affords enantiomerically pure (S)-(−)-2 whose absolute configuration was determined by chemical correlation, and further allowed an enantioselective synthesis of (S)-(+)-diethyl (3-hydroxy-cyclohept-1-enyl)phosphonate 1.