A new route to cross-conjugated Bis(enamines) and an unusual reaction with DDQ

A novel route to cross-conjugated bis(enamines) is discussed as is an unusual reaction with DDQ. The procedure is that used previously for thiazolidines from cysteine methyl ester to react with aldehyes with silver carbonate and DBU. The reactions gave transient 1-substituted methyl 2-azadiene-3-carboxylates that act as Diels-Alder dienes. When it is applied to other thiazolidines, products are isolable cross-conjugated bis(enamines).