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

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