Thermal Hetero [3 + 2] Cycloaddition of Dipolar Trimethylenemethane to N-Sulfonyl and N-Acyl Imines. Synthesis of γ-Amino Acid Derivatives

Thermal hetero [3 + 2] cycloaddition reaction of a dipolar trimethylenemethane 2 with an N-acyl or N-tosyl imine gives an α-methylene-γ-pyrrolidone acetal 4 in high yield, which upon hydrolysis affords a γ-amino acid derivative.