Tris silane oxidation

The combination of PhSiH3 with a catalytic amount of bis(tri-n-butyltin) oxide reduces azides to primary amines in excellent yields (Eq. 3 33).556 The reducing agent is (n-Bu)3SnH formed in situ by the silane. Azides are converted into Boc-protected primary amines with the PMHS/Pd/C reagent (Eq. 3 34).557,558... 

In order to assess the synthetic potential of enzymatic oxidations for organosilicon chemistry, the (hydroxyalkyl)silanes 95, 97 and 99 have been studied for their oxidation (dehydrogenation) with horse liver alcohol dehydrogenase (HLADH E.C. l.l.l.l)79. For this purpose, these compounds were incubated with HLADH in a TRIS-HC1 buffer/THF system in the presence of NAD+. As monitored spectrophotometrically (increase of absorbance of the NADH formed), the (2-hydroxyethyl)silane 97 and the (3-hydroxypropyl)silane 99 were better substrates for HLADH than ethanol, whereas the related (hydroxymethyl)silane 95 was not a substrate under the experimental conditions used. Interestingly, the corresponding carbon analogue 101 was found to be accepted by HLADH. On the other hand, the (2-hydroxyethyl)silane 97 was found to be a better... 

Sodium borohydride-Palladium chloride. Sodium borohydride-Rhodium(lII) chloride. Sodium borohydride-Tin(II) chloride. Sodium cyanoborohydride. Sodium 9-cyano-9-hydrido-9-borabicyclo[3.3.1]nonane. Sodium dithionite. Sodium hydride-Sodium t-amyl oxide-Zinc chloride. Sodium trimethoxyborohydride. Tetra-/i-butylammonium borohydride. Tetra-n-butylammonium cyanoborohydride. Tetra-n-butylammonium octahydrotriborate. Tri-n-butyltin hydride. Triethoxy silane. Triisobutylaluminum-Bis(N-methyl-salicyclaldimine)nickel. Zinc borohydride. REDUCTIVE CYCLIZATION Cobaloximc(I). 

The trimethylsilylated ylides (1), easily generated from trimethyl chlorosilane and ylides, react with aldehydes 2 to form vi-nylsilanes 3 (2,3). The vinylphosphonium silanolates 4 are also formed. Compounds 3 are versatile reagents for further reactions (4). The ylide J (with R1 =H) reacts with aldehydes 2 to give the dienes j). The oxidation of with the adduct 6, from triphenyl-phosphite and ozone, gives access to a generaT synthesis of acyl-silanes (trimethylsilylketones) (2). The silylated ylides react to form phosphonium salts 7 with halogen compounds. The salts 7.can be desilylated by fluorine ions. The disubstituted ylides JO Tormed can be converted in statu nascendi with aldehydes V[ into the tris-substituted olefin J2 (2,3). In the case of R3-I, vinyl... 

Generation of 3-indolylacyl radicals from the selenoesters 149, using either /j-Bu3SnH or tris(trimethylsilyl)silane (TTMSS) followed by reaction with various alkenes, offers a route to 3-acylindoles 150. On the other hand, the use of n-Bu Sn2 under irradiation gave cyclopent[6]indole derivatives such as 151 via a cascade involving initial addition of the acyl radical to the alkene, and a subsequent oxidative cyclization at the indole C-2 <02JOC6268>. 

In contrast to the oxidative generation of radicals described above, redactions of alkyl iodides nsing tris(trimethylsilyl)silane also produces alkyl radicals under conditions suitable for Minisci-type substitution. Carboxylic acids (a-keto acids) are also useful precursors for alkyC° and/or acyC radicals via silver-catalysed peroxide oxidation, or from their l-hydroxypyridine-2-thione derivatives, the latter in non-aqueous conditions. 

Chlorosulphanes will also react with sodium salts of silane thiols to give polysulphides. Thus bis(chlorodisulphanyl)alkanes yield bis-silyl trisulphanyl alkanes (equation 45)40, and the tris-p-tolyl and methyldiphenyl silane thiol salts can be oxidized by iodine to crystalline disulphides, and coupled with dichlorosulphanes to give bis-silyl polysulphides. The polysulphides (MePh2Si)2Sn (n = 3—5) can be cleanly hydrolysed with H20 or D20 to give the pure H2S or D2S (equation 46)41. 

Alkylation of the Uthium salt of TMSCHN2 (TMSC(Li)N2) gives a -trimethylsLlyl diazoalkanes which are useful for the preparation of vinylsilanes and acylsilanes. Decomposition of a-tri-methylsilyl diazoalkanes in the presence of a catalytic amount of Copper(I) Chloride gives mainly ( )-vinylsilanes (eq 12), while replacement of CuCl with rhodium(II) pivalate affords (Z)-vinylsilanes as the major products (eq 12). Oxidation of a-trimethylsilyl diazoalkanes with m-Chloroperbenzoic Acid in a two-phase system of benzene and phosphate buffer (pH 7.6) affords acylsilanes (a-keto silanes) (eq 12). ... 

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