A Versatile Preparation of Geländer-type P-terphenyls from a Readily Available Diacetylenic Precursor

A series of doubly bridged p-terphenyls (4) have been synthesized utilizing a facile three-step synthesis starting from the readily available diacetylenic precursor (1) in excellent overall yields, and their structures were confirmed by 1H/13C NMR spectroscopy as well as by X-ray crystallography. The racemization barrier between the meso and chiral atropisomers of one of the derivatives of 4 was found to be approximately 12 kcal/mol by variable-temperature NMR spectroscopy. The versatility of the protocol developed herein was further demonstrated by the preparation of a quadruply bridged penta-p-phenylene derivative.