Copper-catalyzed domino reactions for the synthesis of Chromenes and Quinazolinones

Abstract

Copper has been widely used as a catalyst for bond formation, such as C(aryl)-C, C(aryl)-O, C(aryl)-N and C(aryl)-S due to their inexpensive, low toxicity and high natural abundance. Chromenes are one of the most important O-containing natural products with a wide range of biological activities. A various chromenes, having a functionality at the fourth carbon, were achieved from 2-bromobenzylidenemalonates and 1,3-diketones via Cu(I)-catalyzed domino reactions. The domino reactions consisted of Michael addition, a tautomerization and an intramolecular C(aryl)-O formation. Quinazolinones are important alkaloids showing a variety of biological and pharmalogical activities. The amine moiety quinazolinone derivatives were synthesized from N-(2-aminoethyl)-2-iodobenzamides and cyclic enaminones via Cu(l)-catalyzed domino reactions under mild reaction conditions. Interestingly, diamino moiety of 2-iodobenzamides operated as an internal ligand to assist the reaction process occurring smoothly. The domino processes underwent sequential a C(aryl)-N bond formation, an intramolecular Michael addition and retro-Mannich reaction.