Silicon-containing heterocycles

Silicon-containing heterocycles such as sUoles or silines have received much attention in materials sciences because of their unique electronic properties, arising mainly from their low-lying LUMO [45]. Particular interest has been focused on the application of it-conjugated sUoles to light-emitting materials [46]. Consequently, much effort has been devoted to the development of new methods for their efficient and selective synthesis. 

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The synthesis of silicon-containing heterocycles was reported employing Si-C bond-forming <01JOM160> or aldehyde allylation <01TL581> reactions to prepare the metathesis substrates (Scheme 54). 

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... 

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. 

Of the ring systems which come under this silicon-containing heterocycles section, the most widely studied from 1995 to 2005 were those containing nitrogen and called l-aza-3-silacyclopentanes. 

For example, dichlorodimethylsilane reacted with (l,4-diphenyl-2-butene-I,4-diyl) magnesium at — 78 C to give c/s-1,1-dimethyl-2,5-diphenylsilacyclopent-3-ene in 66% isolated yield (Table 5, entry 1). Asymmetrically substituted silicon-containing heterocycles can also be prepared in this fashion (see Table 5, entries 3-5). 

Table 5 Preparation of Silicon-Containing Heterocycles and Spiro Compounds from Asymmetric (2-Butene-l,4-diyl)magnesium...

Scheme 5 Preparation of silicon-containing heterocycles and spiro compounds.

Functionally-substituted disilanes are useful starting materials for silylenes, silicon containing heterocycles or for polymeric silicon-containing materials. The classical method to prepare functionalized disilanes is the cleavage of aryl groups by HCI/AICI3 [1] or by triflic acid [2]. An easier method is the introduction of chloro- or alkoxygroups by replacement of amino substituents. 

Carbene reactions are of virtually no synthetic importance for silicon-containing heterocycles, mostly because of the poor selectivity of the carbene insertion processes involved. Thus cyclization of carbene 475 may be effected via Caikyi Si, Caryi" Si and C—H bond insertions as well as via... 

Ball milling of stoichiometric amounts of two solid reagents, Diels-Alder partners led to synthesis of silicon-containing heterocyclic product. Cyclic diene 1,1-dimethyl-2,3,4,5-tetraphenylsilole 1 reacts with iV-methyl maleimide in solid-state milling to afford the enrfo-Diels-Alder cycloadduct 3 stereospeciflcally (Scheme 5.1) [1]. Notably, transfer of reaction conditions from solution chemistry to solvent-free procedure does not have any effect on stereochemical outcome [2]. 

A palladium-catalyzed arylation of TBDPS-protected 2-bromophenols and 2-bromoanilines via C-H activation vras reported in 2009. Moderate to good yields of the desired six-membered silicon-containing heterocyclic compounds were produced (Scheme 3.18). After deprotection with F , the corresponding 2-phenyl phenols or 2-phenyl anilines were formed. 

A new class of tellurium-silicon containing heterocycles, 4,4-diorganyl-l,l,3,6-tetrachloro-l,4-tellura(IV)silafulvenes, has been characterized spectroscopically by Amosova et for compounds with Z configuration... 

Amine 17 was prepared from4 by reaction with aniline at 80 °C. Treatment of 17 with mercury(II) acetate followed by borohydride reduction gave the azasilacycle (18) in modest yield (eq 9). This result is in accord with the 8-carbocation stabilizing effect of a silicon atom. Synthon 4 is thus a useful building block for the preparation of silicon-containing heterocycles. 

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