An Efficient Intramolecular 1,3-Dipolar Cycloaddition Involving 2-(1,2-Dichlorovinyloxy)aryldiazomethanes: A One-Pot Synthesis of Benzofuropyrazoles from Salicylaldehydes

摘要

A novel intramolecular 1,3-dipolar cycloaddition strategy for a rapid entry into benzofuropyrazoles is described. In it three-step sequence, (E)-2-(1,2-dichlorovinyloxy)aryldiazomethanes were generated in situ from the corresponding salicylaldehydes. Intramolecular cycloaddition followed by dehydrohalogenation garnered 3-chlorobenzofuropyrazoles in excellent yields. By careful choice of solvent, base, and reaction conditions, the entire sequence call be carried Out in a one-pot procedure.