1 -dimethylamino-4-methyl-1 -azadiene

Spanish researchers [32] also noted a considerable improvement upon sonica-tion of Diels-Alder reactions of l-dimethylamino-3-methyl-l-azadiene 44 with a variety of electron-deficient dienophiles by using diene as solvent or in acetonitrile (Scheme 4.9). Ultrasound irradiation which allows mild reaction conditions gave good to excellent yields. 

The pioneer work on this subject using simple 1-azadienes is due to Ghosez et al. (82TL3261 85JHC69) they succeeded in reacting 1-azadienes as 47r-electron components in Diels-Alder cycloadditions. Thus, l-dimethylamino-3-methyl-l-azabuta-l,3-diene (a,/3-unsaturated hydrazone) 54 did undergo [4 + 2] cycloaddition to typical electron-poor dienophiles, e.g., methyl acrylate, dimethyl fumarate, acrylonitrile, maleic anhydride, and naphthoquinone, producing pyridine derivatives 55-57 (Scheme 14). 

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