From <em>C</em>-phosphanylated thiazole-2-thiones to phosphaalkenes and tricyclic 1,4-diphosphinines

Abstract

The PhD Thesis “From C-phosphanylated thiazole-2-thiones to phosphaalkenes and tricyclic 1,4-diphosphinines” describes investigations on the synthesis of thiazolyl substituted phosphaalkenes, tricyclic 1,4-dihydro-1,4-diphosphinines and 1,4-diphosphinines. <br /> The synthesis of the starting material, i.e., (Et2N)2P- and Et2N(Cl)P-substituted thiazole-2-thiones is described in the first part. The latter was converted into a precursor for the synthesis of thiazolyl substituted phosphaalkene and its end-on tungsten(0) complex. Further studies upon deprotonation of the Et2N(Cl)P-substituted thiazole-2-thiones with LDA followed by cyclo-condensation to afford tricyclic 1,4-dihydro-1,4-diphosphinines are described. Furthermore, investigations on the reactivity of the tricyclic 1,4-dihydro-1,4-di-phosphinines towards oxidation, P-functionalization and towards electrophiles were conducted. The reduction of a 1,4-dichloro-1,4-dihydro-1,4-diphosphinine led to the synthesis and isolation of a stable, red-colored 1,4-diphosphinine, which was fully characterized via NMR MS, IR, UV/vis, CV and X-ray diffraction analysis, including also theoretical investigations (L.Nyulaszi). The reactivity of a thiazole-2-thione-derived 1,4-diphosphinine towards dienophiles revealed its dienic nature. Theoretical investigations (L.Nyulaszi) suggested that the LUMO of the 1,4-dphosphinine has larger coefficient at the phosphorus centers, which was experimentally verified using reactions with anionic nucleophiles, and even the very week KHMDS led to anionic phosphanido-related compounds which were isolated and could be quenched with electrophiles. The HOMO is largely concentrated on the thione sulfur centers, which explains why electrophiles such as MeOTf add to the S-centers thus affordinga bis(thiazolium) salt. Finally, first investigations on the reduction of the 1,4-diphosphinine leading to the isolable tricyclic system having two phosphanido-related centers is described.