Transition metal catalyzed radical cyclization: new preparative route to .gamma.-lactams from allylic alcohols via the [3.3]-sigmatropic rearrangement of allylic trichloroacetimidates and the subsequent ruthenium-catalyzed cyclization of N-allyltrichloroacetamides
摘要:
A sequence of reactions including [3.3]-sigmatropic rearrangement of allyl trichloroacetimidates (Overman rearrangement) followed by ruthenium-catalyzed cyclization of N-allyltrichloroacetamides provided a novel method for preparing trichlorinated gamma-lactams from allylic alcohols. No delta-lactam was formed as a byproduct. The cyclization of secondary N-allyltrichloroacetamides proceeded with good diastereoselectivity. Two types of tandem cyclizations to form bicyclic lactams took place in the cyclization of N-allyltrichloroacetamides from geraniol and linalool.
N-Tosylated α, β-unsaturatedamides and lactams undergo facile conjugate addition with R2CuLi or RMgX/CuI (cat.). Stereoselective synthesis of trans-β,γ-dialkyl-γ-lactams can be achieved by this procedure. The resulting N-tosylamide moiety is further transformed to alcohol and several carbonyl compounds by way of reduction or nucleophillic displacement.