Elimination of trimethylsilanol

Methyl 4-nitrobutyrate 1099, on treatment with Me3SiBr 16/NEt3, affords the unsaturated O-trimethylsilylated oxime 1101, in 71% yield, via the O-trimethylsilyl nitronate 1100 and elimination of trimethylsilanol 7 [107, 131] whereas the nitro compound 1102 is converted by TCS 14/NEt3, via 1103, into the / -chlorooxime 1104, in 39% yield [107] (Scheme 7.45). 

Base-catalyzed, Add-catalyzed and Thermal Eliminations of Trimethylsilanol. Peterson Reactions... 

Because of the large number of publications in this field, this chapter wiU be limited to giving an idea of developments in this area. Because the Peterson reaction can be viewed as a special case of base-catalyzed reaction, this reaction will be discussed in Section 10.2 after general base-catalyzed eliminations of trimethylsilanol... 

Pyrolysis of bis(trimethylsilyl)phenyl methanol 1668 at 500 °C leads, via elimination of trimethylsilanol 4, to the carbene intermediate 1669, which rearranges, via the carbene intermediate 1670, to give l,2-dimethyl-2,3-benzo-l-silacyclopent-2-ene 1671, in 25% yield, or rearranges via olefin 1672 and adds 4 to give the siloxane 1673 in 29% yield and smaller amounts of benzyltrimethylsilane 83 and styrene [43, 44]. Pyrolysis of l,l-bis(trimethylsilyl) cyclohexylalcohol 1674 furnishes, via the carbene intermediate 1675, 90% of olefin 1676 [43, 44] (Scheme 10.20). 

In this approach, the SENA skeleton is assembled from nitroalkene (42) and nucleophile 56.With the exception of two examples (entries 1 and 2 in Table 3.2), the reaction does not stop at SENA 51, which either undergoes intramolecular cyclization through [3 + 2]-cycloaddition to give fused heterocycles (as a rule after elimination of trimethylsilanol) (198-200) or is involved in [3+ 2]-cycloaddition with specially added methyl vinyl ketone or methyl acrylate to form (after elimination of silanol) substituted isoxazolines in rather high yields (201). 

Thermal elimination of trimethylsilanol from A,-trimethylsiloxy isoxazolidines was also documented (175, 185). Presumably, this process is accelerated by the resulting trimethylsilanol. 

In Sections 3.5.3. and 3.5.4, it was demonstrated that silylation of AN sometimes afford conjugated nitrosoalkenes as unstable intermediates with various reactivities (503). The generation of scarcely known a-nitroso alkenes, containing EWG groups in the p position, by elimination of trimethylsilanol from the corresponding SENAs is of particular interest (see Scheme 3.224). 

The reactions of AN without electron-withdrawing groups at the j3-C atom proceed through the pathway 1. In this case, trimethylsilanol is eliminated from intermediate BENA to give silyl derivatives (566), which can easily be transformed into oximes (567) (504, 545). Evidently, the presence of bases would accelerate elimination of trimethylsilanol. 

From a secondary amide, formation of a nitrile ylid because of plausible elimination of trimethylsilanol prior to cyclization might be expected. However, it is possible that this elimination occurs after cyclization. Thus, the true 1,3-dipole would be the imidate methylide. In any case, the final product will be a A -pyrroline.458... 

The Peterson olefination is a connective alkene synthesis and represents a useful alternative to the Wittig reaction. The precursors for the Peterson olefination are 3-hydroxy-alkyltrimethylsilanes which undergo P-elimination of trimethylsilanol under basic or acidic conditions to furnish stereodefined alkenes. This olefination method is especially valuable for the preparation of terminal and exo-cyc ic double bonds and for the methylenation of hindered ketones where the Wittig reaction is problematic. Also, the... 

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). 

There is one more way for conversion of ort/to-nitroarylacetonitriles into indoles. Alkylation of such nitriles with allyl or benzyl halides followed by treatment of the compounds obtained with basic agents results in a multistep transformation, which is likely to proceed via intermediate nitrosoarenes, to produce 1-hydroxyindoles. For instance, alkylation of ort/io-nitroarylacetonitriles with 3-phenylallyl bromide gives the compounds that in the presence of chlorotri-methylsilane and triethylamine undergo cyclization into 3-cyano-l-hydroxy-2-vinylindoles (Scheme 70) [188]. Presumably, this reaction proceeds via 0-silylation of the nitronate anion and 1,5-elimination of trimethylsilanol from the intermediate trimethylsilyl nitronate, followed by cyclization and a hydrogen shift. 

The films of the silylated precursors of polyamic acid convert directly by heat treatment to yellow, transparent, and tough films of aromatic polyimides with the elimination of trimethylsilanol. ... 

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. 

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