Initially, the feasibility of the idea was investigated on the δ-benzyloxy Weinreb amide 1 using n-BuLi as a nucleophile. Addition of n-BuLi (5 equiv) in THF at −78 °C to compound 1 led to the lithiated tetrahedral intermediate of type II, 3 which was added to a solution of lithium in liquid ammonia [Li (excess), NH 3 (l)] at −78 °C. After 5 min, the reaction was quenched with solid ammonium chloride and the hydroxy ketone 2 was isolated in 78% yield (Table 1, entry 1). The ...
