Inter- and intramolecular isocarbon couplings of cobalt-complexed propargyl radicals: challenging the consensus

Intermolecular coupling reactions of Co2(CO)6-complexed, γ-ethyl propargyl radicals occurred with higher dl-diastereoselectivity than intramolecular cyclizations of isocarbon analogues (deinter−deintra≤52%). The observed phenomenon was interpreted in terms of a tandem action of two main determinants—sterics and CH/π coordination—with the latter being enabled by the methoxy groups located on the periphery of the aromatic nuclei (4-, 3,4-, 3,4,5-).