Slootweg, J. C.J. C.Slootwegde Kanter, FJJFJJde KanterSchakel, M.M.SchakelLutz, M.M.LutzSpek, A. L.A. L.SpekKozhushkov, Sergei I.Sergei I.Kozhushkovde Meijere, ArminArminde MeijereLammertsma, K.K.Lammertsma2018-11-072018-11-072005https://resolver.sub.uni-goettingen.de/purl?gro-2/49511Novel, highly stable, linear and branched mono- and diphospha[n]-triangulanes were synthesized in high yields by the CuCl-catalyzed phosphinidene addition to spirocyclopropanated methylenecyclopropanes and bicyclopropylidenes. The effect of spirofusion on the electronic properties of these esthetically attractive phosphacycles is apparent from X-ray single crystal structure analyses, which reveals a tightening of the phosphirane ring on additional spirocyclopropanation, and from the NMR features that show deshielded chemical shifts for the ring-phosphorus and -carbon atoms. Steric factors play a role in the addition reaction when the substrate alkene carries a second sphere of spirocyclopropane rings and causes the formation of 2-phosphabicyclo[3.2.0]heptenes in small amounts. These by-products most probably result from addition of the [PhP(Cl)W(CO),]-Cu-L (L=alkene or solvent) reagent to the spirocyclopropanated bicyclopropylidene to give an intermediate sigma-complex, which subsequently, facilitated by steric factors, undergoes a cyclopropylcarbinyl to cyclobutyl ring expansion followed by a [1,3]-sigmatropic shift.journal_article10.1002/chem.20050053816078293000233508800019