Fert-Butyldimethylsilyl ether

This method is particularly effective with cyclic substrates, and the combined effects of intramolecular and intermolecular asymmetric induction give up to 76 1 (kf/ks) differentiation between enantiomers of a cyclic allylic alcohol. This kinetic resolution provides a practical method to resolve 4-hydroxy-2-cyclopentenone, a readily available but sensitive compound. Hydrogenation of the racemic compound at 4 atm H2 proceeds with kf/ks =11, and, at 68% conversion, gives the slow-reacting R enantiomer in 98% ee. The alcoholic product is readily convertible to its crystalline, enantiomerically pure fert-butyldimethylsilyl ether, an important building block in the three-component coupling synthesis of prostaglandins (67). 

The diphenylmethylene group provided an easy solution to the problem of selectively deprotecting the terminal 1.2-diol of a polyhydroxylated fragment of the antibiotic Roxaticin. Dissolving metal reduction of the diphenylmethylene group [Scheme 3.99] was accomplished in %% yield with lithium in liquid ammonia without harm to three isopropylidene groups and a fert-butyldimethylsilyl ether. 

AllylsUanes are reactive towards 1,3-dithienium tetrafluoroborate. The intermediate -silyl carbocation typically suffers elimination of the silyl cation to furnish a 2-allyl-1,3-dithiane (eq 5). This protocol was employed to homologate allylsilane 3 to produce dithiane 4, an intermediate in the synthesis of epiantillatoxin (eq 6). A fert-butyldimethylsilyl ether used as a protecting group was cleaved from 3 during this reaction. 

Methyl-/V-fert(butyldimethylsilyl)trifluoroacetam-ide (MTBSTFA, CAS 77377-52-7) is another common silylation reagent used for CWC-related chemicals. BSTFA silylates aminoalcohols such as triethanolamine (CAS 102-71-6) give higher recoveries than MTBSTFA, but the te/T-butyldimethylsilyl ethers formed when MTBSTFA is used are more stable than the trimethylsilyl ethers formed with BSTFA. 

The dependence of the acid-lability of trialkylsilyl and related ethers on the type of substitution at silicon is illustrated by the formation302 of l-0-(tert-butyldiphenylsilyl)-2,3 4,5-di-0-methylene-D-mannitol (47) in 96% yield on treatment of 6-0-(terf-butyldimethylsilyl)-l-0-(fert-butyldiphenylsilyl)-2,3 4,5-di-O-methylene-D-manni-tol (48) with 80% acetic acid. 

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