SmI2-Promoted novel tandem elimination and coupling reactions of aliphatic imides with carbonyl compounds: application to the synthesis of dl-isoretronecanol

Treatment of α-hetero-substituted cyclic imides with carbonyl compounds mediated by samarium(II) diiodide in the presence of HMPA was found to undergo novel tandem elimination and reductive coupling reactions to generate α-hydroxyalkylated imides in good to high yields. Stereochemistry of the coupling products was researched and the result that increasing the steric bulkiness of the N-substituents leads to an increase of threo-selectivity was observed. The mechanistic origins of this stereoselectivity are also briefly documented and the reaction was further applied to the convenient synthesis of a simple pyrrolizidine alkaloid, isoretronecanol.