Trifluoromethane sulfonate hydrolysis

Another chemical method that liberates both O- and N-hnked ohgosaccharides from glycoproteins involves anhydrous trifluoromethane sulfonic acid or anhydrous hydrogen fluoride. Trifluoromethane sulfonate hydrolysis is performed at 0°C for 0.5-2h under nitrogen. The reaction mixture is cooled below -20°C in a dry ice-ethanol bath and slowly neutralized with 60% (v/v) aqueous pyridine (previously cooled to -20°C). 

Exclusion of Free Acid Impurities as the Initiating Species First, the NMR spectrum of trifluoromethanesulfonic acid in the 1,2-dichloroethane solvent used gave a singlet at 69.03, owever the spectrum of 1,1,2-tricyanoviny1-2-trifluoromethane-sulfonate 1 in the same solvent shows no peak downfield after 3 hours which indicates that the hydrolysis of the initiator to trifluoromethanesulfonic acid is not occurring during the polymer initiation step. 

Typically, the imidazolidinone catalyst is used with equimolar amounts of acid cocatalysts, such as HCl, HCIO4, trifluo-roacetic acid (TFA), trichloroacetic acid (TCAA), dichloroacetic acid (DCAA), 4-toluenesulfonic acid (PTSA), trifluoromethane-sulfonic acid (TfOH), 4-nitrobenzoic acid (PNBA), 2,4-dinitrobenzoic acid (DNBA), etc. The complex role of the acid cocatalysts is not totally elucidated. It may catalyze the initial addition of the amine to the aldehyde carbonyl group and also influence the overall selectivity of the process. Reactions are run typically in CH2CI2, or in THF in the presence of a protic cosolvent such as i-PrOH, or water. This protic additive has a considerable impact on the reaction rate without compromising the enantioselectivity, and, probably plays a role in the hydrolysis of the iminium intermediate. 

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