; this is very slow, but can be very selective. If excess reagent is used, the product will require flash chromatography to remove excess silanol and siloxane. For reproduction of material from all other RSC journals and books: For reproduction of material from all other RSC journals. do not need to formally request permission to reproduce material contained in this with the reproduced material. is available on our Permission Requests page. An excess of silyl chloride can be employed but is not necessary. Although many methods are available for forming silyl ethers, two common strategies for the silylation of alcohols are: reaction of the alcohol with a silyl chloride using an amine base at room temperature and reaction of the alcohol with a silyl triflate using a hindered amine base at low temperature. "Protection of hydroxyl groups as, Corey, E. J.; Cho, H.; Rücker C.; Hua, D. H. "Studies with trialkylsilyltriflates: new syntheses and applications.". The Crystallographic Structure of a Lewis Acid-Assisted Chiral Brønsted Acid as an Enantioselective Protonation Reagent for Silyl Enol Ethers. If the reaction were controlled solely by thermodynamics then, statistically, if the dianion is of similar reactivity to the monoanion, then a corresponding statistical mixture of 1:2:1 disilylated:monosilylated:unsilylated diol will result. If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. or in a thesis or dissertation provided that the correct acknowledgement is given 4:1:1 v/v/v AcOH:THF:water, room temp. This approach, catalyzed by Rh(III), is combined with the α-arylation of ketone-derived silyl enol ethers to achieve a direct cross-coupling event. If you already have an account, log in to access the content to which you are entitled. Following extraction, the product can be purified by flash chromatography. In cyclic voltammetry experiments the kinetics of the Si–O bond cleavage in the silyl enol ether cation radicals in dichloromethane and acetonitrile have been determined in the presence of various nucleophiles (methanol, 2-methylpropan-2-ol, pyridine and 2-bromopyridine) From the data, a nucleophile assisted Si–O bond cleavage mechanism has been inferred. The crystal structure of the enol silyl ether compound, C 28 H 33 NO 3 Si, 1, has been established by direct methods and refined to a final R value of 0.053 for 1825 observed reflections. Since R1R2R3 can be combinations of differing groups which can be varied in order to provide a number of silyl ethers, this group of chemical compounds provides a wide spectrum of selectivity for protecting group chemistry. formally request permission using Copyright Clearance Center. [6], Selective deprotection of silyl groups is possible in many instances. Common silyl ethers are: trimethylsilyl (TMS), tert-butyldiphenylsilyl (TBDPS), tert-butyldimethylsilyl (TBS/TBDMS) and triisopropylsilyl (TIPS). The general structure is R1R2R3Si−O−R4 where R4 is an alkyl group or an aryl group. 9, 10 In contrast to imines and N‐heterocycles, which can serve the role of the Lewis base within an FLP‐type system, 2 the lower basicity of silyl enol ethers necessitates an additional Lewis base for dihydrogen activation and subsequent hydrogenation. Purchase this article to get full access to it. Authors contributing to RSC publications (journal articles, books or book chapters) 2. Silyl ethers are a group of chemical compounds which contain a silicon atom covalently bonded to an alkoxy group.