[2+2] Cycloaddition of electron-poor acetylenes to (E)-3-dimethylamino-1-heteroaryl-prop-2-en-1-ones: synthesis of highly functionalized 1-heteroaroyl-1,3-butadienes
Microwave-assisted [2+2] cycloaddition of (E)-3-dimethylamino-1-heteroaryl-prop-2-en-1-ones to dimethyl acetylenedicarboxylates gives (2E,3E)-dimethyl-2-[(dimethylamino)methylene]-3-(substituted)succinates in 8–91% yield. In the case of a 4,5-dihydrothiazoline derivative, cycloaddition also took place at the endocyclic CN double bond.
2-aryl-, and 2-heteroaryl-substituted pyridine 3,4-dicarboxylates and their N-oxides from the corresponding methyl ketones in good to excellent yield, demonstrated with 22 examples in each case, is described. The method complements the current coupling reactions of 2-heterocyclic organometallicreagents.