Deprotections silver® nitrate

Deprotection. Silver nitrate is an effective catalyst for the protiodesilylation of TMS-protected alkynes. When a stoi-... 

All the reagents listed can be used to cleave trimethylsilyl groups from acetylenes fluoride, potassium carbonate under basic conditions in methanol, or silver nitrate/potassium cyanide.9 With the third method advantage can be taken of the fact that the later transition metals (e.g., copper or silvei) complex readily with acety-lides. Workup with concentrated potassium cyanide solution causes compound 32 to be cleaved tu alkyne 33. In this way silylated a -kynes can be deprotected in the presence of 0-silyl groups. 

Perhaps the most widely reported use of silver acetylides is in the deprotection of 1-trimethylsilyl-l-alkynes. Schmidt and Arens first reported the treatment of 1-trimethylsilyl-l-alkynes with silver nitrate to give the silver acetylide in situ, which, when treated with potassium cyanide, is converted to the free alkyne (Scheme 1.63).137 This very mild and selective, but toxic, means for the selective... 

Disubstituted 1,3-oxathianes 316, prepared from benzaldehyde and the corresponding 3-mercaptoalkanol, have been stereoselectively deprotonated at the equatorial position to yield, after reaction with electrophiles, 2,2-disubstituted products. t.S j-Benzoin was obtained in 75% ee in the case of using compound 316 (R = OTBS), after reaction with benzaldehyde and final deprotection of the major product 317 with NCS and silver nitrate (Scheme 83)490. 

Thiols react with dihydropyran in the presence of Bp3-Et20 (0°C, 0.5 h, 25 °C, 1 h) to yield (5)-2-tetrahydropyranyl hemithioacetals in satisfactory yields. In contrast to O-tetrahydropyranyl ethers, an 5-tetrahydropyranyl ether is stable to 4 N HCl-MeOH. Deprotection is conveniently accomplished with Silver(I) Nitrate (0°C, 10 min) or Hydrogen Bromide-Trifiuoroacetic Acid (90 min) in quantitative yields. Oxidation to disulfides can be carried out with lodine or Thiocyanogen ... 

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