citral (3)] with cysteine gave 1:2 adducts of a novel structuraltype, namely hexahydro-1,4-thiazepines. To the best of our knowledge, the spontaneous formation of a seven-membered heterocycle from the addition of cysteine to alpha,beta-unsaturated aldehydes is unprecedented. The adduct 6 obtained from citral, under acidic conditions, reacted further to give the newbicyclic compound 8.