Synthesis and X‐ray Crystal Structures of Silacalix[n]phosphinines: The First sp2‐Based Phosphorus Macrocycles

Several unique examples of phosphorus macrocycles, with PC double bonds, are obtained by a simple synthetic sequence that exploits the reactivity of 1,3,2-diazaphosphinines with silyl-substituted 1,4-diynes. In addition to the synthesis of calix[3] 1 and calix[4] 2, mixed macrocycles incorporating phosphinine, furan or thiophene units have also been prepared and structurally characterized.