Enone , conjugate carbonyl reaction with water

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. 

Dehydration sometimes occurs under the conditions in which the aldol addition is carried out, without additional heating. In such cases, the S-hydroxycarbonyl compound is an intermediate and the enone is the final product of the reaction. For example, the 8-hydroxyketone formed from the aldol addition of acetophenone loses water as soon as it is formed, because the double bond formed by loss of water is conjugated not only with the carbonyl group, but also with the benzene ring. Conjugation stabilizes the dehydrated product and therefore makes it relatively easy to form. 

Reaction with Cyclic Enones. Conjugate addition of azide ion to cyclic enones in water using sodium azide in the presence of Lewis base resulted in the formation of 8-azido carbonyl compounds (eq 55). The Schmidt reaction of benzopyranones with sodium azide led to pyrano[3,2-b]azepines in reasonable yields (eq 56). 

Reactions with Nucleophiles. As an enone tropone is readily susceptible to attack by nucleophiles in Michael-type reactions which might take place at any site in the ring. An early reported example was the formation of 2-aminotropone by reaction with either hydrazine or hydroxyl amine [169]. Reaction olsviously proceeds by conjugate attack (preferred over attack at the carbonyl group) followed by elimination of water or ammonia ... 

When the double bond is conjugated with a carbonyl group, a different type of product is formed. In the presence of water a hydrative cyclization was performed by reaction of yne-enones, leading to cyclic 1,5-diketones in good yields by using the system CpRu(CH3CN)3PF6/camphorsulfonic acid as a catalyst. In anhydrous acetone, pyrans were produced in place of 1,5-diketones [77] (Eq. 56). 

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