Triisopropylsilyl chloride

Cycloaddition. A cobalt-catalyzed system has delivered highly efficient and regioselective Diels-Alder cycloadditions between trialkylsilylacetylenes and 1,3-dienes. TIPS-acetylene was equally effective as other silylacetylenes (TMS-, TES-, TPS-) for the Diels-Alder reaction with isoprene (eq 33).  

Ring-opening Reactions. In combination with a Lewis acid, lithium TIPS-acetylide reacts effectively with epoxides to form the desired adducts (eq 34).  

Sanghee Kim Seoul National University, Seoul, Korea 

Form Supplied in clear, colorless liquid commercially available (99% purity). 

A list of General Abbreviations appears on the front Endpapers 

Garcia Martinez, A. Herrera Fernandez, A. Moreno Jimenez, F. Garcia Fraile, A. Subramanian, L. R. Hanack, M. JOC 1992,57, 1627. 

(a) Garcia Martinez, A. Teso Vilar, E. Ldpez, J. C. Manrique Alonso, J. Hanack, M. Subramanian, L. R. S 1991, 353. (b) Garcia Martinez, A. Teso Vilar, E. Garcia Fraile, A. Ruano Franco, C. Soto Salvador, J. Subramanian, L. R. Hanack, M. S1987, 321. 

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Pyrroles and indoles can be protected with the r-butyldimethylsilyl group by treatment with TBDMSCl and n-BuLi or NaH. Triisopropylsilyl chloride (NaH, DMF, 0°-rt, 73% yield) has been used to protect the pyrrole nitrogen in order to direct electrophilic attack to the 3-position.It has also been used to protect an indole.This derivative can be prepared from the silyl chloride and The silyl protective group is cleaved with Bu4N F , THF, rt or with CF3COOH. 

A solution of p-bromophenol (23.1 mmol) dissolved in 40 ml CH2C12 was treated with triisopropylsilyl chloride (23.4 mmol), then cooled to 0°C, and further treated with imidazole (57.9 mmol) and stirred 30 minutes. The mixture was then warmed to ambient temperature and stirred an additional 12 hours. It was then diluted with diethyl ether, washed twice with 5M HC1, NaHC03 solution, water, brine, and dried. The crude product was purified by bulb-to-bulb distillation and the product isolated in 82% as a clear oil, BP = 149-150°C at 2.0mmHg. 

Triisopropylsilyl ethers are formed under essentially the same conditions as TBS ethers — i.e. primary or unhindered secondary alcohols are treated with triisopropylsilyl chloride (bp 198 °C/98.5 kPa) in dichloromethane or DMF in the presence of imidazole or DMAP [Scheme 4.85J.138 The TIPS group is too bulky to react with a tertiary alcohol and protection of hindered secondary alcohols can be very slow in which case triisopropylsilyl triflate in the presence of 2,6-lutidine is used.100 However, even with the triflate as the silylating reagent, the reaction can be slow as illustrated by the reaction in Scheme 4.86.61 Triisopropylsilyl triflate is commercially available and it can be easily prepared on a large scale from triisopropylsilane and triflic acid in 97% yield. 

During a monumental synthesis of Strychnine, the Overman group encountered difficulties with the simple selective protection of the primary alcohol function in diol 87,1 as its TIPS ether [Scheme 4.89].143 The best method involved treatment of diol 87.1 with 2 equivalents of triisopropylsilyl chloride and 2.2 equivalents of 1,1,3,3-tetramethylguanidine at 0 °C in N-methylpyrrolidinone until the diol could no longer be detected by thin layer chromatography. This treatment... 

Triisopropylsilyl chloride (TIPS-Cl) is an excellent reagent for the selective protection of a primary OH in the presence of a secondary OH group. ° A simple and efficient method for silylation of alcohols and phenols is using TIPS-Cl and imidazole under microwave irradiation. The TIPS group is stable under a wide range of reaction conditions, such as acid and basic hydrolysis, and toward powerful nucleophiles. 

Khalafi-Nezhad et al. [18] achieved silylation of the 5 -hydroxyl function of uridine by use of imidazole and triisopropylsilyl chloride in a microwave oven at 200 W for 60 s, obtaining 80% yield of silylated product. The same reaction in dime-thylformamide with conventional heating [19] gave a 76% yield of silylated product after 24 h. 

Triisopropylsilyl chloride. See Triisopropylchlorosilane Triisopropylsilyl trifluoromethane sulfonate CAS 80522-42-5 Synonyms TIPS triflate Trifluoromethanesulfonic acid triisopropylsilyl ester... 

Triethylsifyl Bntyldimethylsilyl Triisopropylsilyl chloride chloride chloride... 

Protection of the 3 - and 5 -Hydroxy Functions. The reagent design was based upon the fact that triisopropylsilyl chloride reacts 1000 times faster with primary alcohols than secondary alcohols. Thus in the case of 3, 5 -dihydroxy nucleosides the reagent initially silylates at the 5 -position. This is then followed by intramolecular reaction with the secondary alcohol at the 3 -position to give the doubly protected derivative (eq 1). ... 

Protection of Hydroxyl Groups. Triisopropylsilyl chloride (TIPSCl) continues to be widely used as the means of introducing the TIPS protecting groups onto alcohols. The steric bulk of the three isopropyl groups on the silicon atom provides considerable stability under acidic and basic conditions and allows selective removal of smaller, more labile silyl groups in the presence of TIPS ethers.i2.i3... 

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