Phosphaalkyne Cyclooligomers: From Dimers to Hexamers— First Steps on the Way to Phosphorus-Carbon Cage Compounds

摘要

The synthesis of 2,2-dimethylpropylidynephosphane 1 (tert-butylphosphaacetylene), the first phosphaalkyne stable at room temperature, by Becker et al. in 1981 marked the start of a remarkable development of this compound as a synthetic building blockin phosphorus heterocycle and complex chemistry. Initial milestones in the oligomerization of 1 were its cyclodimerization in the coordination sphere of cobalt to give the eta~4-l,3-diphosphacyclobutadiene complex 2 reported by Nixon et al.and Binger etal in 1986, and the thermal cy-clotetramerization of 1 to give the tetraphosphacubane 3 described by Regitz et al. in 1989 (Scheme 1). Except for these [2 + 2] cycloadditions of 1, only reactions with heteroalkenes and higher alkene homologues are knownto date.