Allyl alcohol epoxidation

The application of the AE reaction to kinetic resolution of racemic allylic alcohols has been extensively used for the preparation of enantiomerically enriched alcohols and allyl epoxides. Allylic alcohol 48 was obtained via kinetic resolution of the racemic secondary alcohol and utilized in the synthesis of rhozoxin D. Epoxy alcohol 49 was obtained via kinetic resolution of the enantioenriched secondary allylic alcohol (93% ee). The product epoxy alcohol was a key intermediate in the synthesis of (-)-mitralactonine. Allylic alcohol 50 was prepared via kinetic resolution of the secondary alcohol and the product utilized in the synthesis of (+)-manoalide. The mono-tosylated 3-butene-1,2-diol is a useful C4 building block and was obtained in 45% yield and in 95% ee via kinetic resolution of the racemic starting material. 

Allylic alcohols can be converted to epoxy-alcohols with tert-butylhydroperoxide on molecular sieves, or with peroxy acids. Epoxidation of allylic alcohols can also be done with high enantioselectivity. In the Sharpless asymmetric epoxidation,allylic alcohols are converted to optically active epoxides in better than 90% ee, by treatment with r-BuOOH, titanium tetraisopropoxide and optically active diethyl tartrate. The Ti(OCHMe2)4 and diethyl tartrate can be present in catalytic amounts (15-lOmol %) if molecular sieves are present. Polymer-supported catalysts have also been reported. Since both (-t-) and ( —) diethyl tartrate are readily available, and the reaction is stereospecific, either enantiomer of the product can be prepared. The method has been successful for a wide range of primary allylic alcohols, where the double bond is mono-, di-, tri-, and tetrasubstituted. This procedure, in which an optically active catalyst is used to induce asymmetry, has proved to be one of the most important methods of asymmetric synthesis, and has been used to prepare a large number of optically active natural products and other compounds. The mechanism of the Sharpless epoxidation is believed to involve attack on the substrate by a compound formed from the titanium alkoxide and the diethyl tartrate to produce a complex that also contains the substrate and the r-BuOOH. ... 

Key words Olefin epoxidation, allylic alcohol epoxidation, insertion, direct oxygen... 

Semen, reactive oxygen species, 612 Sensorial quaUty appreciation, oxidation stabihty, 664 Semm protein oxidative damage, 614 see also Human seram Sesquiterpenes, stractural chemistry, 133-6 SET see Single electron transfer Sharpless epoxidation, allylic alcohols, 789 Shelf durability, peroxide value, 656 Ship-in-the-bottle strategy, chiral dioxetane synthesis, 1176-7... 

Oxidations. The reagent 1 oxidizes primary and secondary alcohols to carbonyl compounds in fair to good yield. It is not useful for epoxidation of simple alkenes, but it epoxidizes allylic alcohols to form a,/ -epoxy alcohols in 60-70% yield, In general, this epoxidation is more stcreospccific than that observed with r-butyl hydroperoxide in combination with Mo(CO)6 (9, 81-82). 

A novel approach to the asymmetric synthesis of epoxides, allylic alcohols, a-amino ketones, and a-amino aldehydes from carbonyl compounds through a,/i-epoxy sulfoxides using the optically active p-tolylsulfmyl group to induce chirality./. Org. Chem. 1989, 54, 3130-3136. 

Reduction of a,fi-unsaturated epoxides. Allylic alcohols can be prepared by-reduction of a,/3-unsaturated epoxides. Although yields are only moderate (40-h.S"/o), the method is stereoselective in that the (Z)-isomer is formed. The reaction is believed to involve conjugate reduction. ... 

TBA4(Cr0)PWu039 Alkene Epoxide, allylic alcohol, allylic ketone... 

THA4(Cr0)PWu039 THA,5(Cr0)SiW11039 Alkene Alkene Allylic alcohol Triphenylphosphine Epoxide, allylic alcohol, allylic ketone Epoxide, allylic alcohol, allylic ketone Allylic ketone Triphenylphosphine oxide MeCN or C6H6 MeCN or C6H6 MeCN c6h6 ... 

Epoxidation. Allylic alcohols un analogous to that of peracid, but contrarx u... 

SCHEME 4.12 The catalysts 18 and 19 for epoxidation allylic alcohols. (Adapted with permission from Ref. [64], Copyright 2(X)1 Elsevier.)... 

The molybdenum peroxo-complex (3) oxidizes primary and secondary alcohols, but epoxidizes allylic alcohols. Chlorosulphonyl isocyanate is a further electrophile which may be used to activate DMSO in the oxidation of alcohols. In the presence of triethylamine, a wide variety of alcohols may be oxidized at -78 °C, in high isolated yield. 

Allylic Alcohols. Full details have appeared of the conversion of epoxides into allylic alcohols, mediated by trimethylsilyl trifluoromethanesulphonate (Scheme 4) (see 6,163 4,145), and this sequence is mentioned in a review of trialkylsilyl perfluoroalkanesulphonates as reagents opening of an epoxide ring occurs at the more substituted centre. The use of trimethylsilyl iodide for the epoxide-allyl alcohol transformation (5, 158) is discussed in a review of the preparation and applications of this reagent. ... 

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