S. Yamago et al., Thermal hetero [3+2] cycloaddition of dipolar trimethylenemethane to N-sulfonyl and N-acyl imines. Synthesis of gamma-amino acid derivatives, CHEM LETT, (9), 1999, pp. 879-880
Thermal hetero [3 + 2] cycloaddition reaction of a dipolar trimethylenemeth
ane 2 with an N-acyl or N-tosyl imine gives an alpha-methylene-gamma-pyrrol
idone acetal 4 in high yield, which upon hydrolysis affords a gamma-amino a
cid derivative.