1,2-trans-acetoxy alcohols

One pot conversion of alkenes into the corresponding trans-acetoxy alcohols was realized using Zr(Oi-Pr)4 catalyst with bis(trimethylsilyl) peroxide and trimethylsilyl acetate (Equation 44) [1, 50c]. The reaction is applicable for a series of cyclic alkenes to afford the corresponding 1,2-trans-acetoxy alcohols in high yields. NMR observation of the reaction mixture revealed the intermediacy of the corresponding... 

In the absence of added sensitizers, charge-transfer complexes between the aromatic substrate and molecular oxygen, which are revealed by a modification in the UV spectrum, "" may react. A weU-documented case is that of hexahelicene, which reacts under acidic conditions because protonation of the superoxide anion avoids reversion to the starting substrate in acetic acid, a vicinal trans-acetoxy alcohol is formed ... 

One-pot Synthesis of / -Cyanohydrins from Olefins, trans-/3-Cyanohydrins can be prepared efficiently by treating the corresponding olefins with bis(trimethylsilyl) peroxide and TMSCN in a reaction promoted by a bulky zirconium catalyst (eq 9). This reaction was much faster and cleaner in the presence of 20 mol % of PhsPO. A similar reaction performed in the presence of TMSOAc, albeit with a different catalyst Zr(0 Pr)4, resulted in the formation of trans-(i-acetoxy alcohols. Chlorohydrins can also be prepared if the corresponding olefins are treated with SnCLj and TMSCl in the presence of bis(trimethylsilyl) peroxide. ... 

Addition of l,3-bis(methylthio)allyllithium to aldehydes, ketones, and epoxides followed by mercuric ion-promoted hydrolysis furnishes hydroxyalkyl derivatives of acrolein5 that are otherwise available in lower yield by multistep procedures. For example, addition of 1,3-bis-(methylthio)allyllithium to acetone proceeds in 97% yield to give a tertiary alcohol that is hydrolyzed with mercuric chloride and calcium carbonate to saturated aldehyde.8 Similarly, addition of l,3-bis(methylthio)allyl-lithium to an epoxide, acetylation of the hydroxyl group, and hydrolysis with mercuric chloride and calcium carbonate provides a 5-acetoxy-a,/ -unsaturatcd aldehyde,6 as indicated in Table I. Cyclic cis-epoxides give aldehydes in which the acetoxy group is trans to the 3-oxopropenyl group. 

Pentan-2-one, 1-acetoxy Sd (roasted)" Pentan-3-one, A-acetoxy Sd (roasted)"" Pentane-2-3-dione Sd (roasted)" Pent-trans-2-en-4-one Sd (roasted)" Phenethyl alcohol Sd Hu" ... 

Diphenyl diselenide is an especially useful co-reagent with [bis(acetoxy)-iodo]benzene. For example, the BAIB/PhSeSePh (2 1) combination has been employed for trans, Markovnikov additions of PhSeOAc and PhSeOH to alkenes [35]. Such formal additions appear to be regulated by seleniranium intermediates, and were extended to intramolecular cyclizations of olefinic alcohols, carboxylic acids, and / -dicarbonyl compounds (Scheme 12). 

Inure et al94 reported the enzymatic resolution of trans-10-Azido-9-acetoxy-9,10-dihydrophenanthrene 111 in gram-scale using Candida cyclindracea lipase-catalyzed enantioselective hydrolysis in phosphate buffer. The substrate 111 (the ester) was obtained in 89 % yield and 83 % ee while the product 112 (the alcohol) was obtained in 90 % yield and 98 % ee. 

Isomerization of epoxides to allylic alcohols can be carried out under mild conditions using diethylaluminium dialkylamides (usually prepared in situ). A useful conversion of olefins into allylic acetates or ethers involves treatment of the olefin with phenyl selenyl bromide or chloride, addition of an alcohol or acid to give a P-substituted selenide (139), and selective oxidative elimination e.g. truns-cyclodode-cene gave 3-acetoxy-trans-cyclododecene in 85% yield. 

Oxymercuration, followed by reductive demercuration of methylenecyclohexanes, yielded tertiary alcohols, following axial solvent attack which takes place trans to a substituent in the 2-position except for acetoxy-derivatives. In the latter case, cis-alcohols are formed preferentially by intramolecular attack of the acetoxy-group or the mercurinium ion intermediate. 

Palladium-catalyzed intermolecular oxidations of dienes with carboxylic acids and alcohols as donors give 1,4-addition products. This chemistry has been studied extensively by Backvall. Early studies involved 1,4-additions of two acetoxy or alkoxy groups across a diene,More recently, intermolecular additions of two different nucleophiles have been developed. The ability to control the stereochemistry of the additions across cyclic dienes makes this procedure particularly valuable. As shown in Scheme 16.25, conditions for either cis or trans additions have been developed. Reactions conducted in the absence of added chloride form products from trans 1,4-addition, while reactions conducted in the presence of added chloride form products from cis 1,4-addition. 

The methanol can be replaced by other nucleophilic solvents such as ethanol, acetic acid, or water (in tetrahydrofuran as cosolvent) to give the corresponding ethoxy-, acetoxy-, or hydroxy-esters. Cyclic ethers (substituted tetrahydrofurans and tetrahydropyrans) are formed by intramolecular reaction when the unsaturated ester also contains an appropriately placed hydroxy-group, even in the presence of a reactive solvent. This has been developed into a procedure for the identification, analysis, and isolation of long-chain alcohols and acids having alkene unsaturation in positions 3 (trans only), 4 (cis or tram), or 5 (cis or trans) Such acids (or natural mixtures in which they are present) are reduced to alcohols and subjected to oxymercuration (in DMF as a non-participating solvent) and demercuration. Cyclic ethers are formed only when there is unsaturation at positions 3,4, or 5 other double bonds are unaffected. For example, methyl arachidonatc... 

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