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Preparative and 1 H NMR Investigation on Regioselective Silylation of Starch Dissolved in Dimethyl Sulfoxide
Author(s) -
Einfeldt Lars,
Petzold Katrin,
Günther Wolfgang,
Stein Armin,
Kussler Manfred,
Klemm Dieter
Publication year - 2001
Publication title -
macromolecular bioscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.924
H-Index - 105
eISSN - 1616-5195
pISSN - 1616-5187
DOI - 10.1002/1616-5195(20011101)1:8<341::aid-mabi341>3.0.co;2-9
Subject(s) - silylation , chemistry , regioselectivity , pyridine , dimethyl sulfoxide , polymer chemistry , organic chemistry , catalysis
Reaction of starch 1 dissolved in dimethyl sulfoxide (DMSO) with bulky thexyldimethylchlorosilane (TDSCl) in the presence of pyridine leads to regioselectively functionalized silyl ethers with a degree of substitution (DS) up to 1.8. The control of the DS Si , of the regioselectivity, and of the reaction pathway is described in detail. The reaction proceeds homogeneously up to DS Si of 0.6. With ongoing silylation the polymers form a separate phase incorporating the silylating agent to form TDS‐starches with DS Si values higher than 1.0. After peracetylation of the silyl starches, the substitution pattern has been characterized not only in the anhydroglucose repeating units (AGU) but also in the non‐reducing terminal end groups (TEG) by means of two‐dimensional 1 H NMR techniques. Up to DS Si 1.0, a very high regioselective functionalization of the primary 6‐OH groups in the AGU as well as in the TEG is detectable. With increasing silylation (DS Si > 1.0), the subsequent silylation takes place at the 2‐OH groups of the AGU and at the 3‐OH groups of the TEG. These results are compared with our own investigations on the silylation of starch in the reaction system N ‐methylpyrrolidone (NMP)/ammonia and on the silylation of cellulose in N,N ‐dimethylacetamide (DMA)/LiCl/pyridine solution.