Alcohol allylic primary alcohols

A -Bromoacetamide is successfully applied to the oxidation of secondary alcohols in preference to allylic primary alcohols [743]. 

The reagent reacts with vitamin Ai, a sensitive allylic primary alcohol, in methylene chloride-pyridine to give a crystalline ester useful for isolation of the vitamin... 

On the other hand, Alexakis et al. have developed a sequential reaction exploiting the compatibility between a cationic iridium catalyst and chiral diphenylprolinol trimethylsilyl ether. The role of the iridium complex was proposed to isomerise the starting allylic primary alcohols into the corresponding aldehydes in the presence of H2, while the chiral amine catalyst promoted the a-functionalisation of these aldehydes through reaction with vinyl sulfone to give the corresponding Michael adducts as a mixture of syn-and (Z h -diastereomers obtained in moderate yields, moderate to excellent... 

Bu SnH stereospecifically replaces one halide group of (110) by H the group replaced is determined by the reactivity order Fselective oxidant for secondary and allylic or benzylic alcohols, other primary alcohols remaining unaffected. It can be used to convert diols such as (111) into a>-hydroxyketones e.g. 112). 

Smooth oxidation of alcohols under mild, neutral conditions can be achieved via Tt-allylpalladium intermediates. The reaction of aliphatic allyl carbonate 98 with a palladium(O) catalyst generates palladium alkoxide species 99, which subsequently undergoes (3-hydride elimination to give carbonyl compound 100. This reaction is very clean since the by-products are CO2 and propylene (101). The reaction can readily be applied to secondary alcohols, allylic primary and secondary alcohols and benzylic alcohols. The oxidation of primary alcohols is prohibitively slow. 

The synthetic utility of the [WZnMn"2(H20)2][(ZnW9034)2] polyoxometalate as catalyst for hydrogen peroxide activation, was then extended to additional substrate classes having various functional units [57]. Thus, allylic primary alcohols were oxidized selectively to the corresponding epoxides in high yields and >90% selectivity. Allylic secondary alcohols were oxidized to a mixture of aP-unsaturated ketones (the major product) and epoxides (the minor product). Secondary alcohols were oxidized... 

The slow oxidation of primary alcohols, particularly MeOH, is utilized for the oxidation of allylic or secondary alcohols with allyl methyl carbonate without forming carbonates of the alcohols to be oxidized. Allyl methyl carbonate (564) forms 7r-allylpalladium methoxide, then exchange of the methoxide with a secondary or allylic alcohol 563 present in the reaction medium takes place to form the 7r-allylpalladium alkoxide 565, which undergoes elimination of j3-hydrogen to give the ketone or aldehyde 566. The lactol 567 was oxidized selectively with diallyl carbonate to the lactone 568 without attacking the secondary alcohol in the synthesis of echinosporin[360]. 

Nickel peroxide is a solid, insoluble oxidant prepared by reaction of nickel (II) salts with hypochlorite or ozone in aqueous alkaline solution. This reagent when used in nonpolar medium is similar to, but more reactive than, activated manganese dioxide in selectively oxidizing allylic or acetylenic alcohols. It also reacts rapidly with amines, phenols, hydrazones and sulfides so that selective oxidation of allylic alcohols in the presence of these functionalities may not be possible. In basic media the oxidizing power of nickel peroxide is increased and saturated primary alcohols can be oxidized directly to carboxylic acids. In the presence of ammonia at —20°, primary allylic alcohols give amides while at elevated temperatures nitriles are formed. At elevated temperatures efficient cleavage of a-glycols, a-ketols... 

BzCl or BZ2O, Pyr, 0°. Benzoyl chloride is the most common reagent for the introduction of the benzoate group. Reaction conditions vary, depending on the nature of the alcohol to be protected. Cosolvents such as CH2CI2 are often used with pyridine. Benzoylation in a polyhydroxylated system is much more selective than acetylation. A primary alcohol is selectively protected over a secondary allylic alcohol, and an equatorial alcohol can... 

The AE reaction has been applied to a large number of diverse allylic alcohols. Illustration of the synthetic utility of substrates with a primary alcohol is presented by substitution pattern on the olefin and will follow the format used in previous reviews by Sharpless but with more current examples. Epoxidation of substrates bearing a chiral secondary alcohol is presented in the context of a kinetic resolution or a match versus mismatch with the chiral ligand. Epoxidation of substrates bearing a tertiary alcohol is not presented, as this class of substrate reacts extremely slowly. 

Unsymmetric allylstannanes in which the tin substituent is at the more substituted end of the allyl fragment have been obtained by oxidative elimination of primary alkyl aryl selenides which are available from the corresponding primary alcohols. This procedure was satisfactory for allylstannanes unsubstituted at the 3-position, but elimination of secondary aryl selenides gave mixtures of regioisomers33. 

Dipyridiue-chromium(VI) oxide2 was introduced as an oxidant for the conversion of acid-sensitive alcohols to carbonyl compounds by Poos, Arth, Beyler, and Sarett.3 The complex, dispersed in pyridine, smoothly converts secondary alcohols to ketones, but oxidations of primary alcohols to aldehydes are capricious.4 In 1968, Collins, Hess, and Frank found that anhydrous dipyridine-chromium(VI) oxide is moderately soluble in chlorinated hydrocarbons and chose dichloro-methane as the solvent.5 By this modification, primary and secondary alcohols were oxidized to aldehydes and ketones in yields of 87-98%. Subsequently Dauben, Lorber, and Fullerton showed that dichloro-methane solutions of the complex are also useful for accomplishing allylic oxidations.6... 

DKR requires two catalysts one for resolution and one for racemization. We and others have developed a novel strategy using enzyme as the resolution catalyst and metal as the racemization catalyst as shown in Scheme 1. The R-selecfive DKR can be achieved by combining a R-selective enzyme with a proper metal catalyst and its counterpart by the combination of the metal catalyst with a -selective enzyme. This strategy has been demonstrated to be applicable to the DKR of secondary alcohols, allylic esters, and primary amines. Among them, the DKR of secondary alcohols has been the most successful. 

The synthesis in Scheme 13.21 starts with a lactone that is available in enantiomer-ically pure form. It was first subjected to an enolate alkylation that was stereocontrolled by the convex shape of the cis ring junction (Step A). A stereospecific Pd-mediated allylic substitution followed by LiAlH4 reduction generated the first key intermediate (Step B). This compound was oxidized with NaI04, converted to the methyl ester, and subjected to a base-catalyzed conjugation. After oxidation of the primary alcohol to an aldehyde, a Wittig-Horner olefination completed the side chain. 

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