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 deriv atives la-e (on C4 : H,H or H,CH3 or H,C6H5, both E and Z isomers), an d of the C4 unsubstituted 1-phenyl-1-ethoxy analogue 2, were studied w ith a number of electron-rich and electron-poor dienophiles, with resu lts showing that la-e give heterocycloadducts in Dlels-Alder reactions with electron-poor dienophiles. Michael adducts were obtained from th e EtAlCl(2) catalyzed reactions of these compounds with dimethyl acety lendicarboxylate. Compound 2 gave heterocyclic adducts as well but beh aved like a nucleophile, at least in the case of the reactions with di methyl acetylendicarboxylate and ethyl propynoate: these reactions aff orded 2-azatrienes as Michael adducts that gave pyridine derivatives u pon heating. The synthesis of the new 1-ethoxy-2-aza-1,3-butadiene 2 i s also reported.