Acetylenic ketone allylic alcohol from

Conjugate addition of the complete allylic alcohol fragment is possible with the mixed cuprate reagents 33 prepared by asymmetric reduction (chapter 26) of acetylenic ketones 29 to give the alcohols 30, protection as a silyl ether 31 and hydroboration-iodination. Lithiation and reaction with hexynyl copper (I) gives the mixed cuprate 33 from which the less stable anion is transferred selectively to an enone.3 This approach has been widely used in the synthesis of prostaglandins. 

The classification is unaffected by allylic, vinylic, or acetylenic unsaturation appearing in both starting material and product, or by increases or decreases in the length of carbon chains for example, the reactions f-BuOH f-BuCOOH, PhCHgOH PhCOOH, and PhCH=CHCH20H PhCH=CHCOOH would all be considered as preparations of carboxylic acids from alcohols. Conjugate reduction and alkylation of unsaturated ketones, aldehydes, esters, acids, and nitriles have been placed in Sections 74D and 74E (Alkyls from Alkenes), respectively. 

Z-Trisubstituted allylic alcohols are obtained from protected a-hydroxy-ketones in a lithium-free Wittig reaction and 1-bromo-olefins (and hence acetylenes) are produced from the reaction of Ph3P=CHBr with aldehydes. References to two syntheses of substituted-allenes have appeared Ph3P=C(R )C02R and R R C=C=0 (generated in situ from the acid chloride... 

This preliminary rationale is accommodated in a mechanistic model that begins with the departure of alcohol as water prompted by the strongly acidic medium, and the trapping of the resulting allyl cation IV with the acetylene function. Although vinyl cation V would have been a proposition open to public ridicule years ago, today it is a well established reactive intermediate. Its actual participation in this reaction was seen by the isolation of ketone VIII from the reaction, which may have been derived from the attack of water on this cation (Va) (see Scheme 44.1). Also, ample precedent exists for the attack of alkynes on cationic centers. ... 

Acetylenic carbinols, which are manufactured from aldehydes or ketones and acetylenes, can be partially hydrogenated, with the exception of propargyl alcohol itself. Hydrogenolysis is a minor side reaction unless the hydrogenation is completed to the alkane. Nickel boride (PI or P2) catalysts achieve the saturation of propargyl and allylic compounds in the presence of double bonds without hydrogenolysis, such as in 2 an intermediate in the total synthesis of the sesquiterpene sesquicarene ... 

Oxammonium salts such as 81 are new and powerful oxidizing agents for the selective oxidation of alcohols to aldehydes or ketones. 28 Such salts can be generated catalytically from small amounts of a nitro-xide in the presence of a secondary oxidation procedure, either chemical or electrochemical,. 29 or with two equivalents of acid and 2 equivalents of a nitroxide. When 81 was mixed with acetylenic alcohol 82 in dichloromethane, aldehyde 83 was isolated in 93% yield. The reaction can be monitored as the initial yellow slurry changes to a white slurry and the presence of unreacted oxidant can be checked with starch. 3l It is not necessary to use anhydrous conditions, and it was discovered that the rate of reaction was enhanced by the presence of silica gel. This reagent is compatible for the mild oxidation of many alcohols, including aliphatic primary and secondary as well as allylic and benzylic alcohols. 

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