Siloles synthesis

In 1993, Ikenaga et al. reported efficient silole synthesis using readily prepared (trialkylstannyl)hydrosilanes as a silylene source [30]. Silanes 75 reacted with various terminal alkynes 74 at room temperature to afford 3,4-disubstituted siloles 76 as a major regioisomer (Scheme 6.22). 

J. Chen, Z. Xie, J.W.Y. Chen, C.C.W. Law, and B.Z. Tang, Silole-containing polyacetylenes. Synthesis, thermal stability, light-emission, nanodimensional aggregation and restricted intramolecular rotation, Macromolecules, 36 1108-1117, 2003. 

The l,l-bis(diethylamino) silols 304 and 305 are excellent precursors for the synthesis of other 1,1-difunctionalized silols (Scheme 43).374 The reaction of 304 and 305 with EtOH/AlCl3 and HC1 produces the silols 306 and 307 containing ethoxy groups or chlorine atoms attached to the silicon. The 1,1-dichloro silols 308 and 309 have been converted into the corresponding 1,1-difluoro silols 310 and 311 with ZnF2. Hydrolysis of 309 and 311 yields the fluorosilanol 312 and the silanediol 313, respectively (Scheme 43). 

After a fairly large number of unfruitful attempts between 1960 and 19803, the synthesis of the first C-unsubstituted silole, 1-methylsilole (3), was described by Barton and Burns5 (equation 1). 

The mechanistic study of this reaction has also shown that in the case of a substituted allyl group an exocyclic [l,3]-silatropic rearrangement is in competition (.Ea = 173-176 kJmol-1) with the endocyclic retroene reaction6. Thus the yield of silole reaches at most about 40%. However, this method can be used for the synthesis of C-methylated siloles having a Si—H bond (see Section II.B.2.e). 

Siloles 39 and 40 have been prepared in this way by Tamao and coworkers54 in 64 and 40% yield, respectively, the 2,5-dithienylsilole 40 being a useful monomer unit for the synthesis of thiophene-silole copolymers (see Section IV.B). 

A significant contribution by Tilley and coworkers, in addition to material cited earlier187 192, describes the synthesis, structure and electronic properties of various silole... 

Studies in the chemistry of group 14 metalloles over the past few years have been numerous. Mention should be made of the synthesis of the C-unsubstituted l//-silole the structures of the product itself, as well as of its tautomeric forms and dimer, have been established. Progress has also been made in developing new synthetic routes. By way of a transmetallation reaction from zirconacyclopentadiene, the synthesis of group 14 hete-rocyclopentadiene derivatives was considerably facilitated. On the other hand, though the method is limited to 3,4-diphenylsiloles, a further noticeable contribution was a general and versatile synthesis of the corresponding 2,5-difunctional derivatives. 

The incorporation of siloles in polymers is of interest and importance in chemistry and functionalities. Some optoelectronic properties, impossible to obtain in silole small molecules, may be realized with silole-containing polymers (SCPs). The first synthesis of SCPs was reported in 1992.21 Since then, different types of SCPs, such as main chain type 7r-conjugated SCPs catenated through the aromatic carbon of a silole, main chain type cr-conjugated SCPs catenated through the silicon atom of a silole, SCPs with silole pendants, and hyperbranched or dendritic SCPs (Fig. 2), have been synthesized.10 In this chapter, the functionalities of SCPs, such as band gap, photoluminescence, electroluminescence, bulk-heterojunction solar cells, field effect transistors, aggregation-induced emission, chemosensors, conductivity, and optical limiting, are summarized. 

Silole (silacyclopentadiene) is a silicon-containing five-membered cyclic diene, that is, a silicon analog of cyclopentadiene. Since the first synthesis of a silole, 1,1,2,3,4, 5-hexaphenylsilole, by Braye and Hubei in 19591, the chemistry of siloles has been... 

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