18752-15-3Relevant articles and documents
B(C6F5)3-Catalyzed Silation of Alcohols: A Mild, General Method for Synthesis of Silyl Ethers
Blackwell, James M.,Foster, Katherine L.,Beck, Victoria H.,Piers, Warren E.
, p. 4887 - 4892 (1999)
The commercially available borane tris(pentafluorophenyl)borane, B(C6F5)3, is an effective catalyst for the dehydrogenative silation of alcohols using a variety of silanes, R3SiH, R2SiH2, and R2R′SiH. Generally, the reactions occur in a convenient time frame at room temperature using 2 mol % of the borane and are clean and high yielding, with dihydrogen as the only byproduct. Primary aliphatic alcohols are silated cleanly but slowly, with reaction times ranging from 20 to 144 h. Faster reaction times can be achieved by increasing the catalyst loading to 8 mol % or by heating the reaction to ～60°C. Secondary and tertiary alcohols react more rapidly, with most reactions being complete in 0.5-2 h. The reaction is tolerant of many functional groups including C=C, C=C, -Br, aliphatic ketones, C(O)OR, lactones, furans, OBn, OMe, and NO2; examples of each are given. Using the phenolic substrate 2,4,6-trimethylphenol, a number of different silanes were tested. Only the most bulky silanes (Bn3SiH and Pri3SiH) were not reactive under these conditions. The selectivity of the silation reactions are roughly governed by the relative basicity of the alcohols (and other functions in the molecule) with more basic groups being selectively silated. These observations are rationalized on the basis of a mechanism that invokes borane activation of the silane by hydride abstraction. The resulting intermediate silylium/hydridoborate ion pair then reacts with alcohols to give the observed silyl ether and dihydrogen products.
Unsuccessful attempts to add alcohols to transient 2-amino-2-siloxy- silenes-leading to a new benign route for base-free alcohol protection
Guliashvili, Tamaz,Tibbelin, Julius,Ryu, Jiyeon,Ottosson, Henrik
supporting information; experimental part, p. 9379 - 9385 (2011/01/07)
Thermolytic formation of transient 1,1-bis(trimethylsilyl)-2-dimethylamino- 2-trimethylsiloxysilene (2) from N,N-dimethyl(tris(trimethylsilyl)silyl) methaneamide (1) in presence of a series of alcohols was investigated. The products are, however, not the expected alcohol-silene addition adducts but silylethers formed in nearly quantitative yields. Thermolysis of 1 in the presence of both alcohols (MeOH or iPrOH) and 1,3-dienes (1,3-butadiene or 2,3-dimethyl-1,3-butadiene) gives alkyl-tris(trimethylsilyl)silylethers and the [4+2] cycloadducts between the silene and diene, which confirms the presence of 2 and that it is unreactive towards alcohols. The observed silylethers are substitution adducts where the amide group of the silylamide is replaced by an alkoxy group, and the reaction time is reflected in the steric bulk of the alcohol. Indeed, the formation of silylethers from the reaction of alcohols with silylamide represents a new base-free method for protection of alcohols. The protection reactions using 1 progresses at elevated temperatures, or alternatively, under acid catalysis at ambient temperature, and similar protections can be carried out with N-cyclohexyl(triphenylsilyl)methaneamide and N,N-dimethyl(trimethylsilyl)methaneamide. The latter silylamide can be used under neutral conditions at room temperature. The only by-products are formamides (N,N-dimethylformamide (DMF) or N-cyclohexylformamide), and the reactions can be performed without solvent. In addition to alcohols we also examined the method for protection of diols, thiols and carboxylic acids, and also these reactions proceeded in high yields and with good selectivities. The Royal Society of Chemistry.
An Efficient Catalyst for the Conversion of Hydrosilanes to Alkoxysilanes
Lorenz, Catrin,Schubert, Ulrich
, p. 1267 - 1270 (2007/10/03)
The copper(I) hydride 6 is an efficient catalyst for the alcoholysis of primary and secondary silanes.The reactions proceed at room temperature within a few hours and give the alkoxysilanes in high yields.Only with bulky alcohols or silanes are longer reaction times and/or increased temperatures required.The presence of air accelarates the reactions and gives rise to higher yields of alkoxysilanes, particularly with bulky alcohols.Diols react with PhRSiH2 (R = Me, Ph) to afford 1,3-dioxo-2-silacycloalkanes and with tertiary silanes to furnish the bissilylated diols.When unsaturated alcohols (2-propen-1-ol or 2-propyn-1-ol) are employed, the double or triple bond is retained. - Keywords: Catalytic silane alcoholysis; Alkoxysilanes
