T-Butyldiphenylsilyl chloride

Methyl 2,3-di-O-benzyl-a-D-glucopyranoside t-Butyldiphenylsilyl chloride Tetrabutylammonium fluoride 2,2,6,6-Tetramethylpiperidine Potassium hydroxide Periodinane... 

HYDROXYL GROUPS f-ButyIdimethylsilane. t-Butyldiphenylsilyl chloride. Chloro-methyl methyl sulfide. lodomethyl methyl sulfide. 

The synthesis of the preceding vinyl amino sulfone offers a very good example of a stereospeciffc sulfide-directed epoxidation (Scheme 76). Oxidation of optically active sulffde alcohol (12 readily made from epoxycyciopentadiene and resolved) with MCPBA affords the corresponding sulfoxide, which is in equilibrium with the sulfenate ester. Treatment with pyridine hydrobromide and then phenyl disulfide and bromine gives the bromodiol (13), which is simply cyclized to the epoxide with aqueous sodium hydroxide solution (83% overall yield from the sulfoxide). Treatment of the P-epoxy sulfone widi DBU followed by in situ silylation with t-butyldiphenylsilyl chloride affords an 86% yield of vinyl sulfone (14). Mesylation of the alcohol moiety followed by immediate treatment with dimediylamine produces the amino vinyl sulfone via a syn Sn2 substitution. ... 

SOyl Ethers.—t-Butyldiphenylsilyl chloride reacts preferentially with the primary hydroxy-group of sugar derivatives (e.g. methyl a-D-glucopyranoside), although secondary hydroxy-groups also react if sufficient reagent is used. t-Butyl-... 

Azobisisobutyronitrile Cyclohexyl Methanesulfonyl Methanesulfonyl chloride Methyl fcrf-butyl ether t-Butyldiphenylsilyl t-Butyldiphenylsilyl chloride Trityl (triphenylmethyl) Tosyl... 

T,6,-tri-0-/t77 -butyldimethylsilyl ethers in yields of 10.5, 36.4, and 33.5%, respectively. Monosubstitution at C-6 and C-T under the conditions employed was not observed. When sucrose was treated with one molar equivalent of the more sterically hindered / -butyldiphenylsilyl chloride in pyridine, 6,-0-/t77 -butyldiphenylsilylsucrose was isolated in 49% yield (28). 6,6,-Di-0-/ -butyldiphenylsilylsucrose (78%) is obtained as the principal product when three molar equivalents of the silyl ating reagent are used. The 6,l,6,-tri-0-/ -butyldiphenylsilylsucrose is the principal product on treatment of sucrose with 4.6 molar equivalents of the silyl ating reagent. These results clearly show that HO-6 is the most reactive site toward silylation. 

The final steps in the preparation of the catharanthine fragment required that the last remaining protecting group (the t-butyldiphenylsilyl) be removed. This was accomplished with trifluoroacetic acid (TFA). The newly liberated primary alcohol was tosylated (toluensulfonyl chloride in the presence of tetramethylpropylenedi-amine), and the tertiary alcohol was protected as the trifluoroacetate derivative by treatment with trifluoroacetic anhydride in the presence of pyridine. 

Sterically hindered silyl ethers such as /t /7 -butyldimethylsilyl, / -butyldiphenylsilyl, and tricyclohexylsilyl have been proposed as alternatives to trityl ethers. Reaction of sucrose with 3.5 molar equivalents of / butyldimethylsilyl chloride produces the 6,l,6,-tri-0-silyl derivative in good yield (27). 

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