Dual behavior of 2-azetidinone-tethered arylimines as azadienophiles or azadienes. Application to the asymmetric synthesis of indolizidine-type systems

The first methodology to prepare indolizidine systems directly from beta -l actams has been developed. This process involves the amide bond cleavage of the beta -lactam ring in the aza Diels-Alder cycloadducts with concomitant cyclization. Indolizidinone precursors arise from normal, as well as inver se electron-demand condensation involving the C=N moiety of 2-azetidinone-t ethered imines as the dienophile or the heterodiene contributor.