Genuine heterocycles from the acid-induced cyclization of (silylamino)(imino)(chalcogeno)phosphoranes and as a result of chloride ion abstraction from bis[bis(trimethylsilyl)amino]thiophosphoryl chloride
作者:Neil Burford、Simon Mason、Rupert E. H. Spence、J. Marc Whalen、John F. Richardson、Robin D. Rogers
DOI:10.1021/om00042a045
日期:1992.6
The thio and seleno derivatives of the tricoordinate phosphorane P[NtBu(SiMe3)](NtBu)E 1 (E = S, Se) undergo a novel cyclization upon reaction with Lewis acids. A number of derivatives of the NSiEP framework have been isolated and characterized, including X-ray crystal structures of three derivatives, the neutral complexes NtBuSiMe2SP(Me)NtBu.AlCl3 (2a) and NtBuSiMe2SeP(Me)NtBu-GaCl3 (3), and the triflate salt of the protonated complex [NtBuSiMe2SP(Me)NtBu.H+] (2c). The new compounds are rare examples of ring systems which contain only one atom of each element in the heterocyclic framework, systems for which we introduce the terminology "genuine heterocycles". A similar cyclization process is observed for the new thiophosphoryl chloride P[N(SiMe3)2]2(S)Cl (4) in the presence of chloride ion acceptors to give salts of the cation [N(SiMe3)SiMe2SP(Me)N(SiMe3)2]+ (5), a direct analog of genuine heterocycles 2. Two salts of 5 have been structurally characterized. Both cyclization reactions have been examined by variable-temperature P-31 and H-1 NMR spectroscopy, and speculations are made as to the nature of the observed intermediates. The NSiSP(N) genuine heterocyclic unit is shown to be thermodynamically unstable with respect to the isomeric NSiNP(S) 1,3-diazasilaphosphetidine framework 6. The isomerization process is initiated by reaction with a base and can also be promoted thermally for salts of 5.