Polymer-bound diphenyl chlorosilane
(reagent used as an alcohol protecting group and linker for solid-phase organic synthesis)
Alternate Name: (diphenyl chlorosilane)polystyrene.
Physical Data: IR absorptions at 1430 and 1108 cm-1.1
Preparative Methods: lithiated polystyrene can be prepared via direct lithiation of cross-linked polystyrene with BuLi and TMEDA (1:1) at 65 °C in cyclohexane (1).1 Subsequent addition of diphenyl dichlorosilane in benzene followed by washing with excess benzene and drying in vacuo provides the desired functionalized polymer. Loading can be determined by hydrolysis and acid-base titration.1
Handling, Storage, and Precautions: reagent is water sensitive and cannot be stored for prolonged periods.
Alcohol Protecting Group
(Diphenylchlorosilyl)polystyrene can be used as a solid-phase silyl ether protecting group, and can be used to protect alcohols by addition of the reagent to an alcohol in the presence of a base such as pyridine or diisopropylethylamine (2). Cleavage of the alcohol from the resin can be effected cleanly with TBAF in methylene chloride or tetrahydrofuran.1 The steric bulk of the polymer allows selective installation at less sterically hindered alcohols.1
Silyl Linkers for Solid-Phase Organic Synthesis
Silyl ether linkers are advantageous for solid-phase organic synthesis due to their ease of formation and cleavage, provided that the synthetic strategy does not require other silyl protecting groups or strongly acidic conditions.2 Diphenylsilyl linkers have been used in solid-phase synthesis of oligosaccharides and glycoconjugates via the glycal assembly method (3); however, this linker is less stable than its diisopropyl counterparts (see polymer-bound diisopropyl chlorosilane).3-5
Polymer-bound diisopropyl chlorosilane;
trityl chloride resin;
- 1. Chan, T.-H.; Huang, W.-Q., J. Chem. Soc., Chem. Commun. 1985, 909.
- 2. Seeberger, P. H.; Haase, W.-C., Chem. Rev. 2000, 100, 4349.
- 3. Danishefsky, S. J.; McClure, K. F.; Randolph, J. T.; Ruggeri, R. B., Science 1993, 260, 1307.
- 4. Danishefsky, S. J.; Randolph, J. T.; Roberge, J. Y.; McClure, K. F.; Ruggeri, R. B., Polymer 1994, 35, 977.
- 5. Seeberger, P. H.; Danishefsky, S. J., Acc. Chem. Res. 1998, 31, 685.
Diana K. Hunt & Peter H. Seeberger
Massachusetts Institute of Technology, Cambridge, MA, USA
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