Selectivity in the acylation of partially silylated hydroxy polymers - a study with trimethylsilyl cellulose and model compounds

Abstract

Acylation of partially trimethylsilylated cellulose, glycerol (1), 1,3‐bis(trimethylsiloxy)‐2‐propanol (2), methyl‐2,3,4,6‐tetrakis‐O‐trimethylsilyl‐α‐D‐glucopyranoside (10) and methyl‐2,3,4‐tris‐O‐trimethylsilyl‐α‐D‐glucopyranoside (11) either with acyl chlorides/triethylamine at room temperature or with acyl chlorides at elevated temperature in the absence of an acid scavenger has been studied. Selective acylation of free hydroxy groups has been found with acyl chloride/amine, though complete conversion of free hydroxy groups of cellulose could not be achieved under these conditions. High temperature acylation, however, results in an unselective reaction of free hydroxy groups and trimethylsilyloxy groups. Trans‐silylation takes place and chlorination is found in the reaction of 1 and 2. Carbohydrates were not chlorinated under these conditions, silyl cellulose, however, is strongly depolymerized.

Diol-Ritter Reaction: Regio- and Stereoselective Synthesis of Protected Vicinal Aminoalcohols and Mechanistic Aspects of Diol Monoester Disproportionation

“…All epoxides or diols used were commercially available and used without further purification. Monoesters ( rac )- 1a/ ( rac )- b and ( rac )- 13a as well as reported diester impurities ( rac )- 5 , ( rac )- 7 , ( rac )- 9 , ( rac )- 11 , ( rac )- 13e , ( rac )- 15 , and ( rac )- 17 were characterized by NMR comparison with commercial or synthesized standards (see the Supporting Information). Acetonitrile was distilled from P 4 O 10 and stored over 4 Å sieves in a drybox.…”