A new process for the regiocontrolled synthesis of substituted catechols and other 1,2-dioxygenated aromatics: Conjugate addition of vinyl-, aryl-, and heteroarylcopper reagents to cyclobutenediones followed by thermal rearrangement

Article abstract of DOI:10.1021/ja00067a027

A general method for the synthesis of substituted catechol derivatives has been developed utilizing the 1,4-addition of vinyl-, aryl-, and heteroarylcuprates to cyclobutenediones followed by thermal rearrangement. In situ protection with (methoxyethoxy)methyl chloride of the enolate derived from addition of the cuprate yields 2-alkoxy-4-R^unsat'd-2-cyclobutenones, which rearrange thermally to substituted catechols with differentiated hydroxy groups. Monosubstituted cyclobutenediones undergo highly regioselective 1,4-addition at the unsubstituted carbon; alternatively, regiocontrol can be exerted by addition to cyclobutenedione monoacetals. Differentially disubstituted cyclobutenedione monoacetals undergo regiospecific 1,4-addition to the unprotected enone moiety. Protection of the intermediate enolate and mild hydrolysis of the acetal yield 3,4-disubstituted 2-alkoxy-4-R^Unsat'd-2-cyclobutenones regiospecifically. Thermolysis of these products delivers substituted catechol monoethers regiospecifically.