Silicon heterocycles, reviews

The molecular structure of sila-heterocycles is reviewed <98MI649>. The Raman and infrared spectra of 1-chloro-l-methylsilabutane have been studied in detail <99MI399>. The first allenic coompoimds with both silicon and phosphorus doubly bonded (ArP C Si(Ph)Tip, Tip = 2,4,6-triisopropylphenyl) have been prepared and dimerised to give 38 and 39 in the ratio of 3 2 <99MI774>. 

Space precludes an extensive survey of silicon, germanium, tin and lead substituted derivatives of cyclopentadiene (the siloles and analogues). Until 1979, few plumboles were known (79RTC437), but now, with the siloles, germoles and stannoles, they represent one of the most extensively studied areas of Group IV substituted heterocyclic chemistry. The references prefacing Section 1.20.9 cover reviews for this section. 

Review articles on carbodiimides were published by Khorana in 1953, by Kurzer and Douraghi-Zadeh in 1967, byMikolajczykandKielbasinski in 1981 and by Williams and Ibrahim in 1981. Carbodiimides containing silicon, germanium, tin and lead substituents were reviewed by Gordetsov and coworkers in 1982, N-functionalized carbodiimides by Vovk and Samarai in 1992 and polycarbodiimides by Pankratov in 1993. A review on the synthesis of heterocycles by the aza-Wittig reaction appeared in 1991. ... 

Phosphorus can be partially replaced in cyclophosp-hazene rings by some heteroelements, for example, boron, silicon, arsenic, antimony, sulftir and the broad variety of such heterocycles cannot be discussed here in any detail, but their chemistry is well covered in several reviews. Examples include boracyclophosphazenes, numerous metal-containing heterocyclophosphazenes, and sulfur-containing heterocyclophosphazenes, to name only a few (Scheme 61). 

Silicon-containing heterocycles have been widely studied over the review period. Belzer et al. have studied nitrogen-containing silacycles <1996JOC3315> and within their research work, they described the photolysis of a trisilane 128... 

These two compounds 1 and 2 cannot always be considered as synthetic equivalents of diazomethane for example, they do not react with carboxylic acids to give esters. In fact, they play a very different role in synthesis, and it is demonstrated in this review that they are powerful synthetic building blocks. Since tin chemistry is often compared to that of silicon, a few results involving bis(trimethylstannyl)diazomethane 3 [4] will also be presented (Scheme 1). Juggling the relative steric bulk of the triisopropylsilyl versus the trimethylsilyl group, and the enhanced reactivity of tin-carbon compared to silicon-carbon bonds, the three diazomethane derivatives 1-3 are complementary synthons. Not only are they attractive precursors for the synthesis of stable compounds hitherto believed to be only transient intermediates, but also of new heterocycles or even of polymer crosslinking agents. 

For reviews on related topics, see a) Bourissou D, Bertrand G (1999) Acc Chem Res 32 561 b) Canac Y, Bourissou D, Gornitzka H, Schoeller WW, Baceiredo A, Bertrand G (1999) Phosphorus Sulfur Silicon 144-146 37 c) Etemad-Moghadam E, Koenig M (1996) Three-membered rings with two heteroatoms including phosphorus to bismuth. In Katritzky AR, Rees CW, Scriven EFV (eds) Comprehensive heterocyclic chemistry II. Pergamon, Oxford, vol 1 a, p 469... 

Mann, F. G., The Heterocyclic Derivatives of Phosphorus, Arsenic, Antimony, Bismuth, and Silicon, Interscience, New York, 1950 and F. G. Mann, Progress in Organic Chemistry, Butterworths, London, 1958, Chapt. 6. Contain reviews of the early work. 

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