O2‐Assisted Four‐Component Reaction of Vinyl Magnesium Bromide with Chiral N‐tert‐Butanesulfinyl Imines To Form syn‐1,3‐Amino Alcohols

An O2‐assisted, four‐component reaction has been developed to synthesize a wide range of syn‐1,3‐amino alcohols in one step. The reaction proceeds by oxygenation of vinyl magnesium bromide (component‐I) with O2 (component‐II) to give a magnesium enolate of acetaldehyde, which undergoes addition to a chiral N‐tert‐butanesulfinyl imine (component‐III) followed by a sequential addition with excess vinyl magnesium bromide (component‐IV). The approach allows diastereoselective synthesis of anti/syn‐ and syn/syn‐3‐amino‐1,5‐diols in good yields with high diastereoselectivity. The method was illustrated in an efficient, four‐step synthesis of piperidine alkaloid (−)‐2′‐epi‐ethylnorlobelol. Old reagent with a new use: Vinyl magnesium bromide, a widely used Grignard reagent, can be oxygenated with O2 to give a magnesium enolate intermediate. This enables a four‐component reaction that efficiently converts chiral N‐tert‐butanesulfinyl imine into a wide range of syn‐1,3‐amino alcohols in one step.