Alcohol allylic secondary alcohols

Li et al.2S9 Nishikawa et al. described how an organomanganese compound could ring-open an allylic tetrahydropyran to give allylic secondary alcohols by a different mechanism.292... 

Sharpless epoxidation reactions are thoroughly discussed in Chapter 4. This section shows how this reaction is used in the asymmetric synthesis of PG side chains. Kinetic resolution of the allylic secondary alcohol ( )-82 allows the preparation of (R)-82 at about 50% yield with over 99% ee (Scheme 7-23).19... 

BINAP-Ru(II) diacetate complex also allows the resolution of chiral allylic secondary alcohols (66) (Scheme 32). 

Pyridinium dichromate, prepared from chromium trioxide in a minimum amount of water and pyridine, forms a bright-orange solid and is soluble in water, dimethylformamide, dimethyl sulfoxide, and dimethyl-acetamide sparingly soluble in dichloromethane, chloroform, and acetone and almost insoluble in hexane, toluene, ether, and ethyl acetate. Allylic secondary alcohols are oxidized more rapidly than their saturated analogues. Oxidations are carried out in dichloromethane solutions at 25 °C, and ketones are obtained in high yields (equation 251) [603. ... 

The allylic secondary alcohol l,5-hexadiene-3-ol reacts with phosphorus tribromide plus 2 drops of 48% hydrobromic acid to give in high yield a mixture of... 

Selective oxidation of an allylic secondary alcohol group without attack of saturated secondary alcohol groups was demonstrated by Mancera, Rosenkranz, and Sondheimer. Adrenosterone (I) on reduction with lithium aluminum hydride... 

Morphine has three sites which are subject to methylation, namely, the phenolic group, the tertiary-amino group, and the allylic secondary-alcohol group. Of these it is the tertiary-amino group which seriously interferes with monomethylation to give codeine. When the tertiary-amino function is protected by AT-oxidation then monomethylation gives good yields of codeine... 

Recently atactic poly (5 )-methyl-2-butylvinylketone has been reduced gradually by Merle etal [182] into copolymers of allyl-secondary alcohols and vinylketones they can exist, partially in the tautomeric cyclic hemiacetal form [182, 184]. 

CHoOH Note greater reactivity of primary allylic alcohol vs. secondary alcohol. 

A white solid, m.p. 178 C. Primarily of interest as a brominaling agent which will replace activated hydrogen atoms in benzylic or allylic positions, and also those on a carbon atom a to a carbonyl group. Activating influences can produce nuclear substitution in a benzene ring and certain heterocyclic compounds also used in the oxidation of secondary alcohols to ketones. 

Alcohols are oxidized slowly with PdCh. Oxidation of secondary alcohols to ketones is carried out with a catalytic amount of PdCh under an oxygen atmo-sphere[73.74]. Also, selective oxidation of the allylic alcohol 571 without attacking saturated alcohols is possible with a stoichiometric amount of PdfOAc) in aqueous DMF (1% H OifSll],... 

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]. 

A secondary alcohol was selectively protected in the presence of a secondary allylic alcohol with TBDMSOTf, 2,6-lutidine at —78°. ... 

Yields of the primary alkyl acrylates vary somewhat, owing to occasional losses through formation of polymer, but are usually in the range of 85-99%. Some secondary alcohols react very slowly, others readily. The method has been applied to more than fifty alcohols, some of which (with percentage yields) are listed below ethyl, 99% isopropyl, 37% -amyl, 87% isoamyl, 95% -hexyl, 99% 4-methyl-2-pentyl, 95% 2-ethylhexyl, 95% capryl, 80% lauryl, 92% myristyl, 90% allyl, 70% fur-furyl, 86% citronellyl, 91% cyclohexyl, 93% benzyl, 81% (3-ethoxyethyl, 99% /S-(/3-phenoxyethoxy) ethyl (from diethylene glycol monophenyl ether), 88%. 

In this example, the product can be variously described as a secondary alcohol, a ben-zylic alcohol, and an allylic alcohol. Can you identify the structural reason for each classification ... 

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. 

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. 

Allylsilanes are available by treatment of allyl acetates and allyl carbonates with silyl cuprates17-18, with antarafacial stereochemistry being observed for displacement of tertiary allyl acetates19. This reaction provides a useful asymmetric synthesis of allylsilanes using esters and carbamates derived from optically active secondary alcohols antarafacial stereochemistry is observed for the esters, and suprafacial stereochemistry for the carbamates20,21. 

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... 

In 2003, Sigman et al. reported the use of a chiral carbene ligand in conjunction with the chiral base (-)-sparteine in the palladium(II) catalyzed oxidative kinetic resolution of secondary alcohols [26]. The dimeric palladium complexes 51a-b used in this reaction were obtained in two steps from N,N -diaryl chiral imidazolinium salts derived from (S, S) or (R,R) diphenylethane diamine (Scheme 28). The carbenes were generated by deprotonation of the salts with t-BuOK in THF and reacted in situ with dimeric palladium al-lyl chloride. The intermediate NHC - Pd(allyl)Cl complexes 52 are air-stable and were isolated in 92-95% yield after silica gel chromatography. Two diaster corners in a ratio of approximately 2 1 are present in solution (CDCI3). 

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