REACTIONS OF 3-CARBOMETHOXY-2-AZA-1,3-BUTADIENE DERIVATIVES WITH DIENOPHILES

The reactions of 1,1-diphenyl-3-carbomethoxy-2-aza-1,3-butadiene derivatives la-e (on C4 : H,H or H,CH3 or H,C6H5, both E and Z isomers), and of the C4 unsubstituted 1-phenyl-1-ethoxy analogue 2, were studied with a number of electron-rich and electron-poor dienophiles, with results showing that la-e give heterocycloadducts in Dlels-Alder reactions with electron-poor dienophiles. Michael adducts were obtained from the EtAlCl(2) catalyzed reactions of these compounds with dimethyl acetylendicarboxylate. Compound 2 gave heterocyclic adducts as well but behaved like a nucleophile, at least in the case of the reactions with dimethyl acetylendicarboxylate and ethyl propynoate: these reactions afforded 2-azatrienes as Michael adducts that gave pyridine derivatives upon heating. The synthesis of the new 1-ethoxy-2-aza-1,3-butadiene 2 is also reported.