Development of a new sterically protecting auxiliary of the metacyclophane type and application to unsymmetrical diphosphene, 1,3-diphosphaallene, and 1,4-diphosphabutatrieneElectronic supplementary information (ESI) available: Physical data. See http://www.rsc.org/suppdata/cc/b2/b209666h/

Abstract

A new bulky bromobenzene of the metacyclophane type was converted to an unsymmetrically substituted 1,4-diphos-phabutatriene whose spin-spin coupling constant (3Jpp) turned out to be larger, for the first time, than the 2Jpp value of the corresponding 1,3-diphosphaallene.