A metal-free and oxidant-free method for the one-pot preparation of quinazolin-4(3H)-ones enabled by electrochemical oxidation is described. Together with 2-aminobenzamides, a variety of aldehydes were successfully applied to an acid-catalyzed annulation and direct anodic oxidation cascade, affording structurally diverse quinazoline-4(3H)-ones in good to excellent yields. Additionally, certain alcohols can be directly applied instead of the corresponding aldehydes to achieve the same final products with the assistance of an electrolysis mediator (TEMPO). The reaction mechanism was carefully examined and the results strongly suggest that the direct and indirect oxidation go through different pathways. As an efficient and environmentally friendly access to a broad range of quinazolin-4(3H)-ones, the synthetic utility of this method was demonstrated by gram-scale operation, as well as the preparation of bioactive mackinazolinone and truncated erlotinib.

A formal [3 + 3] cycloaddition reaction between alkyl 2-aroyl-1-chlorocyclopropanecarboxylates 1 and common hydrazones 2 was developed. This process readily proceeded in diastereo-and regioselective fashion and gave alkyl 1,4,5,6tetrahydropyridazine-3-carboxylates in high yields under mild basic conditions. Treatment of the annulation products with DDQ leads to the formation of functionalized pyridazine-3-carboxylates, analogues of nicotinic acid ester.

Highly strained cyclopropenes are valuable functional building blocks in the construction of heterocyclic skeletons, which are highly appealing due to their wide and important applications in synthetic chemistry and medicinal...

We herein describe a novel TEMPO oxoammonium salt initiated Pictet–Spengler reaction of imines, generated in situ from carbonyl compounds and pyrrole- or indole-containing substrates, to afford 4,5-dihydropyrrolo[1,2-a]quinoxalines or 5,6-dihydroindolo[1,2-a]quin­oxalines in good to excellent yields. Moreover, a one-pot synthesis of a biologically important quinoxaline is achieved via a cyclization–dehydrogenation process using one equivalent of the oxoammonium salt.