Siloxymethylation

Methoxymethyl, 27 Methylthiomethyl, 33 (Phenyldimethylsilyl)methoxymethyl, 35 Benzyloxymethyl, 36 p-Methoxybenzyloxymethyl, 37 p-Nitrobenzyloxymethyl, 38 o-Nitrobenzyloxymethyl, 38 (4-Methoxyphenoxy)methyl, 38 Guaiacolmethyl, 39 /-Butoxymethyl, 39 4-Pentenyloxymethyl, 40 Siloxymethyl, 41... 

PHOTOINDUCED-ADDITION OF METHANOL TO (5S)-(5-0-tert-BUTYL-DIMETHYLSILOXYMETHYL)FURAN-2(5H)-ONE (4R,5S)-4-HYDROXY-METHYL-(5-0-tert-BUTYLDIMETHYL-SILOXYMETHYL)FURAN-2(5H)-ONE... 

The Peterson reaction was reported240 to give a quantitative yield of methyl [(R),(Z)-2-/m-butyldiphenylsiloxymethylcyclobutylidene]acetate on treatment of (5)-2-(ter -butyldiphenyl-siloxymethyl)cyclobutanone with methyl trimethylsilylacetate and lithium dicyclohexylamide. 

A solution of dicyclohexylamine (2.65 g, 14,6 mmol) in THF (20 mL) was treated with 1.66 M BuLi in hexane (8.8 mL, 14.6 mmol) at — 78 °C. The mixture was stirred for 30 min and a solution of methyl trimethylsilylacetate (2.14 g, 14.6 mmol) in THF (10 mL) was added dropwise, and the resulting solution was stirred for another 30 min. The mixture was kept at — 78 °C and a solution of (5)-2-(ferr-butyldiphenyl-siloxymethyl)cyclobutanone (2.42 g, 7.2 mmol) in THF (10 mL) was added dropwise. The reaction mixture was stirred for 1 h and then treated with a pH 7 phosphate buffer. Extraction with EtOAc, washing of the organic phase with brine and drying (Na2S04), followed by evaporation, left a crude material which was purified by column chromatography (silica gel, EtOAc/hexane 1 14) yield 2.82 g (100%). 

Siloxymethylation of cyclic ethers is accomplished using Co2(CO)8 under... 

The cobalt carbonyl complex is also an effective catalyst for the siloxy-methylation of aromatic aldehydes.110 Arylethane-l,2-diol disilylethers are obtained in good yields, resulting from incorporation of one molecule of CO and two molecules of HSiR3. Good selectivity for the siloxymethylation product is observed at 0°C in hexane. At 15°C, faster reaction rates are observed, but the selectivity for the CO-incorporated product is lower. In contrast, aliphatic aldehydes react under these conditions (1 atm CO, 0°C) to give only a small amount of CO-incorporated product, with a major product resulting from hydrosilylation. 

Co2(CO)8-catalyzed reactions of benzylic acetates with trimethylsilane and CO proceed under mild reaction conditions to give trimethylsilylethers of /3-phenethylalcohol in 43-76% yield. The highest yields are observed for benzyl acetates with electron-donating substituents.111 Secondary alkyl acetates are also good substrates in the reaction system, yielding enol silyl ethers.112 In addition, the cobalt complex is an effective catalyst for siloxymethylation of five-membered cyclic ortho esters, as shown in Eq. (41).113... 

The Rh-catalyzed reactions of lV,./V-aminals with HSiEt2Me and CO (50 atm) at 140 °C in benzene give unique siloxymethylation or ring-expansion products, e.g. 308-310 (equations 118-120)317. Incorporation of two CO molecules and rearrangement of the dimethylamino group take place in the reaction of N, N, N , N -tetramethylmethylenediamine (equation 119)317. 

The reaction of N,O-acetal 311 in the presence of NEt3 under the same conditions gives ring-opening siloxymethylation product 312 arising from exclusive C—O cleavage... 

The substrate range - scope and limitations The reaction can be performed efficiently with a broad variety of ketone donors and aldehydes. Enantioselectivity, however, depends on the enolate structure (Scheme 6.11) [60, 61]. In general, eno-lates bearing larger, branched alkyl groups or a phenyl group result in lower enantioselectivity. The best results were obtained with enolates bearing a methyl substituent (product (S)-16, 87% ee) or a siloxymethyl substituent (product (S)-17, 86% ee). 

Siloxymethylation.3 Glycosyl acetates undergo C-siloxymethylation on reaction with a hydrosilane and CO catalyzed by Co2(CO)8. Only the anomeric acetoxy group undergoes this reaction, which takes place from the side opposite to that of the acetoxy group at C3. The reactive reagent is probably a silylcobalt carbonyl, R3SiCo(CO)4. 

Substituted allylsilanes are subject to ene reaction with aldehydes and a,/3-unsaturated carbonyl compounds in the presence of a Lewis acid. The Et2AlCl-promoted reaction of /3-siloxymethyl-substituted allylsilane 27 with aldehydes gives more functionalized allylsilanes (Equation (37)).148 The use of TiCU instead of Et2AlCl leads to the Hosomi-Sakurai allylation. Catalytic enantioselective carbonyl-ene reactions of methallylsilanes have been achieved by using chiral Ti and A1 complexes.149,150... 

Photocatalyzed Addition of Methanol to (5S)-5-0-tert-Butyldimethyl-siloxymethyl-furan-2(5H)-one Synthesis of (4R,5S)-4-Hydroxy-methyl-5-0-tert-butyldimethylsiloxymethyl-furan-2(5H)-one. 

Stereospecific 1,4-addition of the carbanion (78) to (siloxymethyl)bicyclooctenone (84) yields mainly the corresponding l,4- y-adduct. In seven steps, this adduct is converted into the known b-lactol (85), from which pentalenolactone ( 0-methyl ester (86) may then be derived (Scheme 23)7 ... 

Methoxymethyl, 30 Methylthiomethyl, 38 (Phenyldimethylsilyl) methoxymethyl, 41 Benzyloxymethyl, 41 p-Methoxybenzyloxymethyl, 43 [(3,4-Dimethoxybenzyl)oxy] methyl, 43 p-Nitrobenzyloxymethyl, 44 o-Nitrobenzyloxymethyl, 44 [(i ) -1- (2-Nitrophenyl) ethoxy] methyl, 45 (4-Methoxyphenoxy)methyl, 45 Guaiacolmethyl, 46 [(p-Phenylphenyl)oxy]methyl, 47 f-Butoxymethyl, 47 4-Pentenyloxymethyl, 47 Siloxymethyl, 48 2-Methoxyethoxymethyl, 49 2-Cyanoethoxymethyl, 53 Bis(2-chloroethoxy)methyl, 53 2,2,2-Trichloroethoxymethyl, 53 2- (Trimethylsilyl) ethoxymethyl, 54 Menthoxymethyl, 58 0-Bis(2-acetoxyethoxy)methyl, 59 Tetrahydropyranyl, 59... 

Acetates can be used instead of alkenes. Cyclic ketones undergo ring expansion to give a-hydroxyketone precursors. Oxiranes ring-open with siloxymethylation at ambient temperature and CO pressure. ... 

Siloxymethyl alkenyl ketones 148, in which chirality is created by placing a methoxy substituent at an a-carbon of the silyl group, form complexes with Mg(OTf)2 to become chiral dienophiles. 2-(l-Methylimidazolyl) alkenyl ketones undergo enantioselective Diels-Alder reaction in water, in the presence of a DNA-based catalyst. 

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