Silicon heterocycles, literature

There were no reports in the literature between 1996 and 2006 on new syntheses of five-membered heterocycles containing three or more heteroatoms and at least one silicon atom that employ this particular synthetic methodology. 

This section considers both reduced or partially reduced metallaheterocycles, that is, with one or no double bonds. Most of the bibliographic data appropriate to this chapter deal with the preparation and characterization of the metallacycles and, accordingly, there have been little data on their reactions. The only examples found in the literature concerned silicon-containing heterocycles. 

All heterocycles of this class found in the literature have pure inorganic character, and contain phosphorus, boron, silicon, etc., as the fourth atom of the ring [see references included in (83IC2095)]. 

The reaction of N-heterocyclic chlorosilylene (LSiCl, L = PhC(NtBu)2) (5) with lithiumphosphide LiP(SiMe3)2 (6) leads to generation of the N-heterocyclic bis(trimethylsilyl)phosphino-silylene by virtue of phosphanylation of the chlorosilylene (Scheme 6.4.3.1) (7). The low-valent silicon functionality is retained and the phosphorus atom possesses labile TMS groups that can enable additional transformations. The starting materials, silylene chloride [LSiCl] (5) and lithium bis(trimethylsilyl) phosphate [LiP(SiIVIe3)2] (6) can be prepared according to the literature procedures. 

The N-heterocyclic cyclic silylene (CH)2 tBuN)2Si was previously synthesized by the reduction of the corresponding N-heterocyclic silicon dichloride with potassium (3). The new synthetic method employed (CH)2 tBuN)2SiHCl as the starting material, which could be reduced by 1,3-di-tert-butyl-imidazol-2-ylidene (IfBu) through dehydrohalogenation at room temperature. (CH)2 BuN)2SiHCl was prepared according to the literature method (5). 

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