Acetylene-Substituted Phosphane Oxides: Building Blocks for Macrocycles

Phosphorus-based macrocycles with acetylenic scaffolds have been built from acetylene-substituted phosphane oxides that were formed from diisopropylphosphoramidic dibromide (3) and an acetylenic Grignard reagent. The fourand six-edged macrocycles 15 and 16, in which the iPr2NP(O) units are connected through 1,3-butadiyne rods, were obtained from the monosilylated derivative of iPr2NP(O)(C2H)2 (7) by multiple acetylene coupling reactions under oxidative Hay conditions. Reaction of iPr2NP(O)(Br)2 (3) with lithiated 1,2-diethynylbenzene gave a mixture of cis and trans monocyclic bis(phosphane oxide) 18. An X-ray crystal structure determination of the trans isomer shows the ring structure to adopt a puckered form.