A,0-Unsaturated alcohols

Other advances over the past few years have been the development of (a) homogeneous hydrogenation catalysts for substrates normally not readily reduced, e.g., aromatics, isonitriles, and nitro compounds, and (b) a number of catalyst systems with unusual selectivity properties, e.g., with the capability of reducing a,/3-unsaturated aldehydes to the corresponding a,/3-unsaturated alcohols (see Sections II,B,2 and VII). 

In the region of the C—O stretching vibrations, an important increase in absorbance was observed with maxima at 1060 cm-1 (a, (3-unsaturated ether bridges and a, (3-unsaturated alcohols), 1094 cm 1 (saturated secondary alcohols and saturated ethers) and 1175 cm-1 (lactone). 

The oxidahon of olefins with aqueous hydrogen peroxide in methanol can produce several products, by different reachon paths double bond epoxidation, allylic H-abstraction, epoxide solvolysis, alcohol and glycol oxidation (Scheme 18.6). Normally, oxide catalysts of Group IV-Vl metals are poorly selechve, because of their acidic properhes, the inhibition they are subject to in aqueous media and homo-lytic side reachons with hydrogen peroxide. The only excephon concerns the epoxidahon of a,(3-unsaturated alcohols and acids, which are able to bind on the... 

A different type of ester formation takes place when a,(3-unsaturated alcohols are oxidized with manganese dioxide and subsequently treated with sodium cyanide, acetic acid, manganese dioxide, and methanol. The final result is shown by the sequence of reactions in equation 238 [382]. 

Carroll, M. F. Addition of a, 3-unsaturated alcohols to the active methylene group. I. The action of ethyl acetoacetate on linalobi and geraniol. J. Chem. Soc. 1940, 704-706. 

Ary lotion of allylic alcohols Aryl iodides and allylic alcohols undergo a Heck-ivpc reaction to form /3-ary l-a,/3-unsaturated alcohols in the presence of Pd(OAc)2 and P(C6H5)3 as catalysts and 1 equiv. of AgOAc to prevent isomerization to carbonyl compounds. 

When a,/3-unsaturated alcohols, which react at relatively low temperatures, are used it is advisable to use a high concentration of hydrogen-acceptor. Cinnamaldehyde has proved particularly valuable as hydrogen-acceptor in the preparation of aliphatic aldehydes, and anisaldehyde in preparation of alicyclic aldehydes. The alcohol to be oxidized is first converted into alkoxide by the calculated amount of aluminum triisopropoxide and is then brought into redox equilibrium with 120 — 200% of the higher-boiling aldehyde. 

Reduction of steroid ketones. 3-Ketosteroids are reduced by triethylaminoaluminum hydride in THF mainly to the 3j8-alcohol (75-95% yield). a,P-Unsaturated 3-ketosteroids are reduced to the a,)3-unsaturated alcohols. 

Reduction of 01,0-unsaturated ketones. This reducing agent is the reagent of choice for reduction of enones of type (1) to the a, 3-unsaturated alcohols (2). Usual reducing agents favor 1,4-reduction to the saturated alcohol. 

Ends and Enones a, /3-Unsaturated Alcohols, Aldehydes, and Ketones... 

Dinitrophenylhydrazone Mixture of epimeric a, 3-unsaturated alcohols (XLIV and XLV) (A -Veratramine) Hydrochloride... 

The formation of die C-3 adduct relies on the fact that the a,3-unsaturated alcoholate, produced, as mentioned above, by attack of the organometallic at the a-site of the a,p-unsaturated cartionyl compound, can rearrange to the enolate resulting from C-3 attack. This isomerization has been more conveniently achieved by raising the temperature to 20 C (Scheme 153, compare d to b Scheme 154 compare c to b)." It has also been performed by adding to the medium (Scheme 152, g Schemes 153... 

This reaction allows the synthesis of (i) 3,P -dienols by oxidation of -hydroxy-y-alkenyl sel-enides or more conveniently from a-liAioalkyl selenoxides and enones (Scheme 136 and 166) (ii) P,S-dienols from l-lithio-3-alkenyl phenyl selenoxides and carbonyl compounds (Scheme 177) and (iii) 2-(r-hydroxyalkyl)-1,3-butadienes from 1-methylselenocyclobutyllithium and carbonyl compounds (Scheme 178). a,3-Unsaturated alcohols bearing a methylselenoxy or a phenylselenoxy group at the a-posidon do not lead on thermolysis to propargyl alcohols however, those bearing a (trifluoro-methylphenyl)selenoxy moiety at the a-position are valuable precursors of such compounds (Scheme... 

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