2-aryl-N-tosylazetidines as formal 1,4-dipoles for [4 + 2] cycloaddition reactions with nitriles: an easy access to the tetrahydropyrimidine derivatives

[reaction: see text] A new synthetic route to 2-aryl-N-tosyl azetidines has been developed starting from N-tosylarylaldimines in two steps in an overall yield of 63-70%. A formal [4 + 2] cycloaddition of these 2-aryl-N-tosylazetidines with nitriles in the presence of BF3.OEt2 has been described for the synthesis of substituted tetrahydropyrimidines. It is proposed that the reaction proceeds in Ritter fashion.