Diastereoselective nickel-catalyzed reductive Aldol cyclizations using diethylzinc as the stoichiometric reductant: Scope and mechanistic insight

Article abstract of DOI:10.1021/ja0775624

In the presence of diethylzinc as a stoichiometric reductant, Ni(acac) ₂ functions as an efficient precatalyst for the reductive aldol cyclization of α,β-unsaturated carbonyl compounds tethered to a ketone electrophile through an amide or an ester linkage. The reactions are tolerant of a wide range of substitution at both α,β-unsaturated carbonyl and ketone components and proceed smoothly to furnish β-hydroxylactams and β-hydroxylactones with generally high diastereoselectivities. A series of experiments, including deuterium-labeling studies, was carried out in an attempt to gain some insight into the possible reaction mechanisms that might be operative.