Amines protection, trifluoromethanesulfonic acid

The C-4 acids (183 and 184) have also been subjected to borane reduction conditions to afford alcohol 195 in 23-50% yield or 64% yield as the C-8 epimeric mixture (195 and 196, Scheme 29) [34, 49, 64]. The C-8 alcohol epimers 195 and 196 have been treated separately as a common intermediate for a number of C-4 derivatives including esters, ethers, and amines [34, 49, 64], Alcohols 195 and 196 was subjected to DCC, DMAP, and desired acid chloride or carboxylic acid in CH2CI2 affording ester analogs in 50-92% yield [64], Esters prepared include alkyl, aryl, and fluorenylmethyloxycarbonyl (Fmoc) protected amino acid derivatives (197 and 198) [64]. Ethers were prepared with various alkyl halides and Ag20 in CH3CN at 40 °C. Alkyl, allyl, and benzyl ethers were prepared in 45-80% yield (199 and 200) [34,64]. Alcohols 195 and 196 were then activated to the triflates and displaced by a variety of amines by treatment with trifluoromethanesulfonic anhydride and desired amine in 22% - quantitative yield over two steps (201 and 202)... 

Aniline allowed to react at -78° with trifluoromethanesulfonic acid anhydride and triethylamine in methylene diloride -> N-phenyltriflamide. Y 97%. - The protective group can be removed by reduction. F. e. and triflating agent, also Gabriel-type synthesis of prim, amines from halides via triflamides, s. J. B. Hendrickson and R. Bergeron, Tetrah. Let. 1973, 3839. 

Protection of alcohols.1 Dimethylthexylsilyl ethers are prepared from primary or secondary alcohols by reaction with 1 and either imidazole or N(C2H5)3 in DMF. The ethers of tertiary alcohols are prepared by reaction with dimethylthexylsilyl trifluoromethanesulfonate in the presence of lutidine or N(C2H5)3. Silylation of amines, amides, mercaptans, and acids is conducted under similar conditions. 

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