SILYLATION OF CELLULOSE REGIOCONTROLLED BY BULKY REAGENTS AND DISPERSITY IN THE REACTION MEDIA

Reaction of cellulose (1) with the bulky thexyldimethylchlorosilane (T DMSCl) leads to regioselectively functionalized silyl celluloses with degree of substitution (DS) up to 2. Uniform 6-O-thexyldimethylsilyl c ellulose (2) was obtained in ammonia-saturated aprotic dipolar media, which was unexpected in a heterogeneous reaction. On the contrary, the 6-O-selectivity is low under homogeneous conditions in a N,N-dimethyl acetamide (DMA)/LiCl solution, and with an excess of TDMSCl 2,3-di-O-t hexyldimethylsilyl cellulose (3) can he synthesized. The polymer struc tures were characterized by two dimensional NMR spectroscopy after sub sequent methylation (polymers 4 and 5), desilylation (polymers 6 and 7 ) and acetylation (polymers 8 and 9) as well as by HPLC after chain de gradation of 4 and 5 to the complementary methyl glucoses.