Hydrazinium acetate

Scheme 6. Conditions (a) donor 271, TMSOTf cat., CH2CI2, 84% (b) complex 273 cat., CH2CI2, reflux, 94% (c) donor 275, TMSOTf cat., Et20, 0°C, 60% (d) hydrazinium acetate, DMF, — 10 0°C (e) H2, Pd/C, MeOH, 84% (over both steps)...

Several methods were described for the selective de-S-acetylation of 0-acetyl protected 1-thioglycoses. Sodium methoxide in methanol at low temperature (below -20 °C) was known to afford mainly the de-S-acetylated compound [16] or exclusively this compound when the reaction was quenched at low temperature by adding H-l- resin [17]. Demercuration of tetra-O-acetyl-l-phenylmercury(II)-thio- -D-glucopyranose (12) (Scheme 4) obtained by treatment of (8e) with phenylmercury(II)acetate afforded a convenient synthesis of tetra-0-acetyl-l-thio-/3-D-glucose (8a) [18]. This sequence applied to the a-anomer (10a) (Scheme 3) led to the expected de-S-acetylated compound (10b) [19]. Chemoselective deprotection of thioacetate at the anomeric position of peracetylated 1-thioglycoses was also achieved in good yield by action of cysteamine in acetonitrile or hydrazinium acetate in DMF [20,11]. 

Subsequently the already mentioned protocol of peracetylation of the free alcohol functionalities is performed. In step five you have to repeat the selective deprotection of the anomeric center with hydrazinium acetate with successive formation of the or-trichloroacetimidate in step six. 

Park WKC, Meunier SJ, Zanini D, Roy R (1994) Selective deprotection of thiolacetates with hydrazinium acetate. XVll International Carbohydrate Symposium (Ottawa) p 306 (1995) Carbohydr Lett 1 179... 

Chemoselective cleavage of anomeric thioacetates to the thioaldose in the presence of O-acetyl groups is possible under various conditions, e. g., methanolic sodium methoxide at low temperatures [121], phenylmercury acetate followed by demercuration [122], 2-aminoethanethi-ol [123], or hydrazinium acetate [124], and these methods have therefore often been used in the synthesis of thiooligosaccharides (O Sect. 3.2.1). As mentioned, glycosyl thioacetates can also be prepared from the 2-acetoxyglycal derivative (see Scheme 24). 

Homopropargylzinc chloride, 388 D-Homosteroids, 53 Htlnig s base, 151 Hydrazine hydrate, 230 Hydrazinium acetate, 207 Hydrazobenzene, 206 cis-Hydrindanes, 45 Hydriodic acid, 199-200 Hydroalumination, 131, 133, 237-238 Hydrodeamination, 412 Hydrogen bromide, 200-201 Hydrogen chloride-Titanium(IV) chloride, 201... 

T-O-Deacylation of ribonucleosides.1 This salt (1) is useful for regioselective 2 -O-deacylation of 2, 3, 5 -triacyl derivatives of ribonucleosides. Hydrazinium acetate is somewhat less effective. 

Hady, S.A., Nahringbauer, I. and Olovsson, L, Hydrogen bond studies. 38. The crystal structure of hydrazinium acetate, Acta Chem. Scand. 23, 2764-2772 (1969). 

Hydrazinium acetate is one of the few hydrazinium salts to decompose endothermically. The results of TG and DTA are complementary. 

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