Ketones 3-unsaturated, additions

The preparation of enamine ketones by addition of a,jS-unsaturated ketones to enamines is described in Chapter 4. 

Keywords 2-phenylcyclohexanone, a,/ -unsaturated ketone, Michael addition, phase transfer catalys, 1,5-dicarbonyl compound... 

The majority of recent publications still deal with the chiral hydrogenation of ketones containing other functional groups as well. The general characteristics of these reactions are illustrated by the asymmetric hydrogenation of a./f-unsaturated ketones. In addition, the purpose of the present review is to summarize the latest results of the chiral hydrogenation of ketones which do not contain other functional groups (dialkyl ketones and alkyl aryl ketones). 

There was only one reported example of successful RCM involving an a,(3-unsaturated ketone.17 RCM of a,fJ-unsaturated esters was known to be difficult unless special conditions, possibly not applicable to ketones (the addition of Lewis-acids), were used.1 0... 

Michael addition. DABCO is a particularly effective catalyst for Michael addition of /f-keto thiolesters to a,/ -unsaturated esters and ketones. The addition to enones provides an attractive route to 1,5-diketones that can undergo annelation to fused or... 

If other groups capable of conjugation are adjacent to the enamine system, they can also participate in the salt formation. Thus, in 8-amino-a,j8-unsaturated ketones, in addition to possible protonation at the a-carbon and the nitrogen, protonation could also occur on the carbonyl oxygen.200-202... 

A conjugated double bond system undergoes 1,4-addition (Thiele s rule) for example, butadiene and an equimolar quantity of bromine yield 1,4-dibromo-2-butene (90%). On the other hand, chlorination of butadiene in the liquid or vapor phase furnishes about equal amounts of 1,2-and 1,4-addition products. Other polyfunctional compounds resulting from this method of preparation include dihalogenated acids, esters, aldehydes, and ketones. < The addition of bromine to unsaturated ethers yields dibromo ethers which are used as intermediates in the synthesis of olefins (method 21) and olefinic alcohols (method 99) ... 

Scheme 8.12 Unsaturated ketones via addition of allylic alcohols to terminal alkynes.

In spite of these difficulties, suitably substituted unsaturated ketones undergo addition of dichlorocarbene at the double bond though the yields of cyclopropanes are often low (Houben-Weyl, Vol. 4/3, pl78 and Vol. E19b, ppl548, 1550). 

As with the parent cyclopent-2-enone vide supra), activation of the unsaturated ketone by addition of a stoichiometric amount of triethylborane as Lewis acid is required. The cycloaddition takes place diastereospecifically, with exclusive formation of the product resulting from attack of the C4. moiety at the least hindered face of the cycloalkenone. 

The Luche reduction is an excellent method for the 1,2-reduction of a,p-unsaturated ketones. In addition, ketones are reduced selectively in the presence of aldehydes. 

A wide variety of photoadditions to unsaturated oxygen and sulfur heterocycles has been reported. It has, however, proved difficult to classify these processes, especially as the reaction mechanisms are not fully understood in all cases. Most additions of solvent to oxygen heterocycles arise via hydrogen abstraction pathwyas, often initiated by added ketone. Polar addition is relatively rare in these compounds the addition of methanol to... 

The sequence can also be applied to the enolate anion formed by conjugate addition of organometallic reagents to a,/8-unsaturated ketones. Thus addition of diethyl phosphorochloridate to a mixture of A4-cholestene-3-one (4) and dimethyl-copperlithium gives the diethyl enol phosphate (5) in 55% yield. Reduction of the ester gives the olefin (6) in high yield. 

USE Analytical reagent for aldehydes and ketones. The addition of methoxyamine to a,ft-unsaturated ketones and the rearrangement of 6 -methoxyamino ketones is described... 

The reaction of acrylic esters with diazomethane is analogous the CH2 group of the diazomethane always adds in these reactions to the -carbon atom of an, / -unsaturated ester or ketone, although addition to the a-carbon atom has also been observed.110... 

---