Synthetically Useful Aryl-Aryl Bond Formation via Grignard Generation and Trapping of Arynes. A One Step Synthesis of p-Terphenyl and Unsymmetric Biaryls

Article abstract of DOI:10.1021/jo00217a018

A one-pot route to p-terphenyls is described.Addition of 1,4-dibromo-2,5-diiodobenzene, 1, to excess aryl Grignard reagent gives the terphenyl di-Grignard 2 and the trihalo mono-Grignard 5.After aqueous quench, p-terphenyls are isolated in 30percent to 50percent yield (Table I).This yield can be improved to 70-80percent by adding potassium tert-butoxide or lithium tetramethylpiperidide to the reaction mixture prior to workup.Mechanisms involving organometallic aryne intermediates are proposed.With o-bromoiodoarenes in place of tetrahaloarenes the method can be adapted to prepare unsymmetric biaryls in good yield (Table II).