Organocuprates, reaction with

Benzenesulfomc acid, 4-methyl, 2,2 dimeth ylpropyl ester [1-Propanol, 2,2-di-methyh, p-toluenesulfonate], 55, 112 Benzenesulfomc acid, 4-methyl-, esters [p-Toluenesulfonates], reaction with organocuprates, 55, 112 Benzenesultonic acid, 4-methyl-, ( )-4-hexen-l-yl ester ]( )-4-Hexen-l-yl p-toluenesulfonate], 55, 57 Benzenesulfomc acid, 4-methyl-, 1-methyl-heptyl ester [2-Octanol, p-toluenesulfonate], 55,112... 

Propiolaldehyde diethyl acetal has found numerous synthetic applications in the literature which may be briefly summarized. The compound has been utilized in the synthesis of unsaturated and polyunsaturated acetals and aldehydes by alkylation of metal-lated derivatives, " by Cadiot-Chodkiewicz coupling with halo acetylenes, " and by reaction with organocuprates. Syntheses of heterocyclic compounds including pyrazoles, isoxazoles, triazoles, and pyrimidines have employed this three-carbon building block. Propiolaldehyde diethyl acetal has also been put to use in the synthesis of such natural products as polyacetylenes " and steroids. ... 

Bicyclic or polycyclic enones may give slow or inefficient reaction with organocuprates. In particular, it is those enones which contain substituents arranged so as to create a steric hindrance on the carbon 3 to the carbonyl that see the greatest effect. The yields are often low to moderate, unless additional activation is provided. For example, when the bicyclic enone (23) was treated with R2C11U (R = 3-pentynyl), the -substituted product was formed in only 46% yield,69 while exposure of the same enone to RQ1BF3 (R = 3-pentynyl) gave the same (3-alkylated product in 76% yield (Scheme 9).70... 

The new derivatives obtained with the simpler procedure, that is, reaction with organocuprates, were evaluated for antitumor activity. 

Ethynyl carbinols (propargylic alcohols) such as 134 (Scheme 2.58) represent another important group of oxidation level 3 compounds. Their preparation involves nucleophilic addition of acetylides to the carbonyl group, a reaction that is nearly universal in its scope. Elimination of water from 134 followed by hydration of the triple bond is used as a convenient protocol for the preparation of various conjugated enones 135. Easily prepared O-acylated derivatives are extremely useful electrophiles in reactions with organocuprates, which proceed with propargyl-allenyl rearrangements to furnish allene derivatives 136. 

Finally, dihalo cyclopropanes can be converted to dialkyl cyclopropanes by reaction with organocuprates (Section 26.1). For example, cyclohexene can be converted to a bicyclic product having four new C-C bonds by the following two-step sequence cyclopropanation with dibromocarbene ( CBr2) and reaction with lithium dimethylcuprate, LiCu(CH3)2. 

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