A New Reagent System for Efficient Silylation of Alcohols: Silyl Chloride-N-Methylimidazole-Iodine

Abstract

It was found that reactions of alcohols with silyl chlorides in the presence of N-methylimidazole were significantly accelerated by the added iodine, and on this basis a general, and high yielding method for efficient silylation of primary, secondary, and tertiary alcohols was developed.

Key words

silylation - silyl chlorides - iodine - N-methylimidazole

References and Notes

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11

General Procedure for the Preparative Silylation of Alcohols Listed in Table 1: An alcohol (1.0 mmol), N-methylimidazole (3.0 mmol) and iodine (2.0-3.0 mmol) were dissolved in an appropriate, anhyd solvent (3 mL, Table [1] ). A silyl chloride (TBDMSCl, TBDPSCl or TIPSCl; 1.1 mmol) was added and the reaction mixture was stirred at r.t. until the complete disappearance of the starting material (TLC analysis). The solvent was evaporated, the residue dissolved in EtOAc and washed with concd aq Na₂S₂O₃. The organic phase was dried over anhyd Na₂SO₄ and evaporated. The products were purified by silica gel column chromatography (CH₂Cl₂-MeOH, 100:0 → 95:5, Table [1] entries 1, 3 and 7; pentane-EtOAc, 10:0 → 9:1, Table [1] entries 2, 4-6, 8-10). The synthesized compounds were fully characterized with ¹H and ¹³C NMR and HRMS.