Trimethylsilanol, reaction with

We also explored the direct conversion of S-b-tBM to S-b-MA.K. Hydrolysis under basic conditions (KOH in refluxing aqueous THF) was again resulted in unchanged S-b-tBM. The reaction with potassium trimethylsilanolate for 1 hr in refluxing toluene gave very little reaction. Only 10% of the expected amount of potassium was found by ICP, and the NMR and IR spectra were little changed from those of the starting copolymer. This difference in reactivity between S-b-MM and S-b-tBM parallels that observed for the reaction of alkyl methacrylate blocks with potassium superoxide (7-10). 

Analogous results were obtained for the enantioselective enzymatic esterifications of the related t-butyl-substituted alcohols 101 and 103 (carbon analogues of the silanes 95 and 97, respectively). Reaction with racemic 2-(4-chlorophenoxy)propanoic acid in water-saturated benzene yielded the corresponding t-butylalkyl (+)-2-(4-chlorophenoxy)propanoates 102 and 104, respectively76,77. The enantiomeric purity of the remaining (—)-2-(4-chlorophenoxy)propanoic acid was somewhat lower than that observed for the esterification of the analogous silicon compounds [91.1% ee (101), 71.6% ee (103)]. No esterification was observed for the Si/C analogues trimethylsilanol (MesSiOH) and t-butanol (MesCOH). 

Z)-(3-Silyloxyacrylonitriles 95 undergo cycloaddition reactions with a,P-unsaturated ketones to form a dihydro-pyran intermediate, which eliminates trimethylsilanol to furnish 3-cyano-4//-pyrans (Scheme 31) <1997S628>. 

IV), and nitriles (V) by reaction with f-butyl lithioacetate, (5, 371), lithio N,N-dimethylacetamide, and lithio acetonitrile, respectively, followed by elimination of trimethylsilanol (Peterson reaction). 

The observed reaction products of the reactions of 4 with sodium and potassium trimethylsilanolates show the course of several competitive reactions with splitting of Si-O as well as Si-H bonds. In contrast to (Me3SiO)3SiH (4) the siloxysilane (Et3SiO)3SiH (5) reacts with KOSiMe3 only under Si-0 bond splitting (Eq. 7), presumably due to steric reasons. 

Halogenated derivatives of isoquinoUne undergo SNAr reactions with displacement of the halide. This process tolerates a wide variety of nucleophiles, which include sodium hydroxide, alkoxides, trimethylsilanolate, ammonia, amides, ... 

Fluoride Ion Catalyzed Peterson-Type Reactions with Elimination of Trimethylsilanol... 

EWG = COgEt, CH=NBu, C(Me)=NBu R = Ph, PhCH=CH, 2-furyl, C7H15 Scheme 2.109. Fluoride ion catalyzed Peterson-type reaction with elimination of trimethylsilanol. 

Thus removal of water from classical rather inactive fluoride reagents such as tetrabutylammonium fluoride di- or trihydrate by silylation, e.g. in THF, is a prerequisite to the generation of such reactive benzyl, allyl, or trimethylsilyl anions. The complete or partial dehydration of tetrabutylammonium fluoride di- or trihydrate is especially simple in silylation-amination, silylation-cyanation, or analogous reactions in the presence of HMDS 2 or trimethylsilyl cyanide 18, which effect the simultaneous dehydration and activation of the employed hydrated fluoride reagent (cf, also, discussion of the dehydration of such fluoride salts in Section 13.1). For discussion and preparative applications of these and other anhydrous fluoride reagents, for example tetrabutylammonium triphenyldifluorosilicate or Zn(Bp4)2, see Section 12.4. Finally, the volatile trimethylsilyl fluoride 71 (b.p. 17 °C) will react with nucleophiles such as aqueous alkali to give trimethylsilanol 4, HMDSO 7, and alkali fluoride or with alkaline methanol to afford methoxytri-methylsilane 13 a and alkali fluoride. 

As already discussed in Section 2.2, crystalline dimethylsilanediol 53 can be prepared by hydrolysis from hexamethylcyclotrisilazane 51, from dimethoxydimethyl-silane [40], and from octamethylcyclotetrasilazane (OMCTS) 52. The most simple preparation of 53 is, however, controlled hydrolysis of dimethyldichlorosilane 48 in the presence of (NH4)2C03 or triethylamine [41]. Likewise, hydrolysis of hexam-ethylcyclotrisiloxane 54 and of octamethylcyclotetrasiloxane 55 eventually gives rise to dimethylsilanediol 53. In all these reactions the intermediacy of the very reactive dimethylsilanone 110 has been assumed, which can be generated by pyrolytic [42, 43] and chemical methods [44—46] and which cyclizes or polymerizes much more rapidly, e.g. in contact with traces of alkali from ordinary laboratory or even Pyrex glassware [40, 47] to 54, 55, and 56 than trimethylsilanol 4 polymerizes to hexamethyldisiloxane 7. Compound 111 is readily converted into dimethylsilanone 110 and MesSil 17 [46] (Scheme 3.6). 

With stirring and cooling triethylamine (25.3 g) is added dropwise to a solution of trimethylsilanol 4 (22.5 g) and 2-chloroacrylonitrile (22.0 g) in dry ether. The reaction mixture is then stirred for 7-8 h at 30-35 °C. The precipitated triethylammo-nium chloride is removed by filtration, the filtrate is concentrated, and the residue is distilled in vacuo (b.p. 85-86°C/6mm) to give 21.4 g (95%) 2-methoxyacryloni-trile 99 [32] (Scheme 3.15). 

Saponification of Esters or Lactones and Reaction of Persilylated Amides and Lactams with Aikaii Trimethylsilanolates. Conversion of Aromatic Esters into Nitriies by Use of Sodium-HMDS... 

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