Silanes and derivs

Research Focus Synthesis of poly(isobomyl methacrylate-coisobomyl acrylate)-b-methacryloxypropyl-tris(trimethylsiloxy)silane and derivatives as topical cosmetic components having high shine and gloss. 

The products obtained from ozonolysis of various silanes and derivatives are shown in Scheme 13. 

There are too many silanes and derivatives of silanes which sponty expld or ignite to be presented in total here (Refs 1 thru 12,14,15,17,... 

Silyiaminoboron Compounds. See under Silyi-amines in this Vol under Silanes and Derivatives ... 

TABLE 13. Measured bond dissociation energies for silanes and derived standard enthalpies of formation of associated radicals... 

TABLE 10.7. Silanes and Derivatives as nsed in Earlier Chapters... 

Hydrosilylation of I-vinyl-1-cyclohexene (77) proceeds stereoselectively to give the (Z)-l-ethylidene-2-silylcyclohexane 78, which is converted into (Z)-2-ethylidenecyclohe.xanol (79)[74]. Hydrosilylation of cyclopentadiene affords the 3-silylated 1-cyclopentene 80. which is an allylic silane and used for further transformations[75.75a]. Cyclization of the 1,3,8, lO-undecatetraene system in the di(2.4-pentadienyl)malonate 69 via hydrosilylation gives the cyclopentane derivative 81. which corresponds to 2.6-octadienylsilanc[l8,76]. 

The hexabutenylbenzene complex reacts with Br2 to give the dodecabromo-derivative, with bulky silanes and boranes to give regiospecific hydrosilylation and hydroboration (Scheme XII). 

As shown in Table XIV, the reactivity of (trichloromethyl)silanes varied depending upon the substituent on silicon. The reactivity and yields of (trichloromethyl)-methyldichlorosilanes were slightly higher than those of (trichloroinethyl)tri-chlorosilanes in the aluminum chloride-catalyzed alkylation as similarly observed in the alkylations with (ai-chloroalkyl)silanes and (dichloroalkyl)silanes. The electron-donating methyl group on the silicon facilitates the alkylation more than the electron-withdrawing chlorine. The minor products, (diphenylmethyl)chloro-silanes, were presumably derived from the decomposition of (triphenylmethyl)-chlorosilanes. 

Allylic derivatives are particularly important in the case of boranes, silanes, and stannanes. Allylic boranes effect nucleophilic addition to carbonyl groups via a cyclic TS that involves the Lewis acid character of the borane. 1,3-Allylic transposition occurs through the cyclic TS. 

The kinetic data for reactions of carbon-centered radicals with various silanes and the silanthrane derivatives 1-6 are numerous as shown in... 

In Table 3.1 are collected the rate constants with various silanes and silan-thrane derivatives 4-7 and the available Arrhenius parameters for some of them. 

The reduction of the trichloroacetamide derivative 56 with (TMS)3SiH afforded 57 in a 60% yield (Reaction 7.58) [68]. The final product is the result of cyclization and further removal of two chlorine atoms. In fact, 3.5equiv of silane and 1.1 equiv of AIBN are used. 

The combination of allylic amination, ring-closing metathesis, and a free radical cyclization provides a convenient approach to the dihydrobenzo[b]indoline skeleton, as illustrated in Scheme 10.10. The rhodium-catalyzed aUylic amination of 43 with the lithium anion of 2-iodo-(N-4-methoxybenzenesulfonyl)arrihne furnished the corresponding N-(arylsulfonyl)aniline 44. The diene 44 was then subjected to ring-closing metathesis and subsequently treated with tris(trimethylsilyl)silane and triethylborane to afford the dihydrobenzojhjindole derivative 46a in 85% yield [14, 43]. 

This methodology was applied to a two-step sequence for the preparation of enantio-merically enriched dihydrobenzo[h]furans (Scheme 10.11) [46]. Rhodium-catalyzed allylic etherification of (S)-47 (>99% ee), with the sodium anion of 2-iodo-6-methyl-phenol, furnished the corresponding aryl allyl ethers (S)-48/49 as a 28 1 mixture of regioisomers favoring (S)-48 (92% cee). Treatment of the aryl iodide (S)-48 with tris(trimethylsilyl)silane and triethylborane furnished the dihydrobenzo[h]furan derivatives 50a/50b as a 29 1 mixture of diastereomers [43]. 

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