Epoxides, alcoholysis formation

Next to iodine there is also another class of neutral Lewis acids known. Tetracyanoethylene, dicyanoketene acetals and derivatives can catalyse reaction due to their tt-Lewis acid properties. They promoted the alcoholysis of epoxides [238], tetrahydropyranylation of alcohols [239], monothioacetahzation of acetals [240], and carbon-carbon bond formation of acetals [241,242] and imines [243] with silylated carbon nucleophiles. 

H3PW12O40 shows a higher activity for the alcoholysis of epoxides [Eq. (15)] than H2SO4, PTS, or HCIO4 (9, 124, 175). While rapid deactivation is observed with H2S04, which is probably due to the formation of an alkyl sulfate, H3PW12O40 maintains its high catalytic activity. 

In the polyurethane industry, the polymeric glycols are prepared by anionic polymerization of epoxides such as ethylene oxide and propylene oxide. Poly(tetra-methylene glycol), which was prepared by polymerization of tetrahydrofuran, was subjected to chain extension by reaction with diisocyanate (polyurethane formation) and with dimethyl terephthalate (polyester by alcoholysis). 

Amino-6-chloromethyl- (248) gave 3-amino-6-butoxymethyl-2-pyrazinecar-bonitrile (249) (BuOH, reflux, 12 days 77% or likewise, 2 days 58%).612 Also other examples 53,391,871,957 1059,1139 for examples of intramolecular alcoholysis (epoxide formation) see end of this section. 

When an unsymmetrical secondary alcohol is formed, depending on which carbon-oxygen bond is cleaved. With propylene oxide, for example, a base-catalyzed reaction favors the formation of the secondary alcohol almost exclusively, whereas, a non-catalytic or acid-catalyzed alcoholysis yields a mixture of the isomeric ethers. However, the reactions of other a-epoxides, such as 3,4-epoxy-l-butene, 3,4-epoxy-l-chloropropane (epichlorohydrin), 3,4-epoxy-l-propanol (glycidol), and styrene oxide, are more complicated with respect to which isomer is favored. ... 

Rubber Seed Oil Rubber seed oil (RSO), which has a high C18 3, n-3 content (6), has a lower alcoholysis rate than linseed oil, but a higher alcoholysis rate than soybean oil and melon seed oil (165). Studies on the epoxidation of RSO by peroxyacetic acid generated in situ have shown that increase in the process temperature increases the rate of epoxide formation (166). The optimum alcoholysis temperature for RSO is 245 2°C. 

Using route II [1], the desired silanes are accessible in a two-step synthesis The ft)-epoxyalkenes are obtained by partial epoxidation of the corresponding a,dienes with w-chloroperbenzoic acid. The lower product yields (47-50 %) compared to the direct epoxidation of side-reaction. The subsequent hydrosilylation requires the ethoxysilane HSi(OEt)3 as educt in order to exclude ring opening during the otherwise nescessary alcoholysis step. The lower reactivity of HSi(OEt)3 compared to chlorosilanes significantly reduces the formation of isomers but, on the other hand, considerably decreases the product yields (31-70 %). 

Nucleophilic reactions. Chiral epoxides are converted into 2,2-dimethyl-l,3-dioxolanes with inversion of configuration by reaction with acetone. An efficient procedure for imine formation from ketones and amines specifies TiCU as promoter. Hydrolysis (or alcoholysis) of RCONH2 is achieved in the presence of TiCU in acidic media. 

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