Addition of trimethylsilyl azide and of “mixed anhydrides” to the N‐C(3) σ‐bond in 3‐substituted‐1‐azabicyclo[1.1.0]butanes

Trimethylsilyl azide adds smoothly to the highly strained N‐C(3) σ‐bond in 3‐ethyl‐1‐azabicyclo[1.1.0]‐butane ( 1 ) to afford an adduct, 2 , that reacts in situ with a variety of electrophilic reagents ( i.e ., ethyl chloroformate, p ‐toluenesulfonyl chloride, benzoyl chloride, acetyl chloride, and oxalyl chloride) to afford the corresponding N ‐substituted‐3‐azido‐3‐ethylazetidines 3–7 , respectively in 62–72% yield. Similarly, 1 reacts regiospecifically with “mixed anhydrides” ( i.e., p ‐toluenesulfonyl acetate, methanesulfonyl acetate, and benzoyl trifluoromethanesulfonate) to afford the corresponding adducts, 8–10 , respectively) in 38–68% yield. Reaction of p ‐toluenesulfonyl azide with 1‐aza‐3‐phenylbicyclo[1.1.0]butane ( 12 ) produces two products: N ‐( p ‐toluenesulfonyl‐3‐azido‐3‐phenylazetidine ( 13 , 15%) and a dimeric product, N ‐( N'‐p ‐toluenesulfonyl‐3′‐phenyl‐3′‐azetidinyl)‐3‐azido‐3‐phenylazetidine ( 14 , 28%). Ethyl chloroformate adds to the N ‐C(3) σ‐bond in 1‐aza‐3‐(bromomethyl)bicyclo[1.1.0]butane ( 15 ) to afford N ‐carboethoxy‐3‐(bromomethyl)‐3‐chloroazetidine ( 16 ) in 73% yield.