Divergent Reactivity in Tandem Reduction-Michael Ring Closures of Five- and Six-Membered Cyclic Enones

摘要

In this study, methyl(+/-)-1-(2-nitrobenzyl)-4-oxo-2-cyclohexene-1-carboxylate and methyl (+/-)-(2-nitrobenzyl)-4-oxo-2-cyclopentene-1-carboxylate were prepared and subjected to reductive cyclization under dissolving metal conditions. The two reactants showed divergent behavior with the six-ring substrate reacting at the ester carbonyl and the five-ring substrate closing on the enone double bond. The C, difference in reactivity is attributed to the conformational flexibility, relative reactivity, and steric environment of C4-substituted six- and five-membered cyclic enones.