Conjugation ketones

The saturated ketone is more reactive than the conjugated ketone so we shall need to protect the one before reducing the other. 

This and other aromatic cross conjugated ketones give deeply colored... 

These are usually obtained from the isomeric conjugated ketone, and are sometimes useful as intermediates, offering an alternative to enol derivatives. They may also be formed as a result of double bond introduction or by oxidation of homoallylic alcohols if so the conditions must be mild because they generally represent a less stable isomer. 

I. ORGANOMETALLIC ADDITIONS TO KETONES, CONJUGATED KETONES AND EPOXIDES... 

In a useful modification of this method, la-methyl-A -3-keto steroids are obtained by methylation of the A -3-keto systems (20). However, it is unexpectedly difficult to convert the intermediate la-methyl-A -3-keto compound (21) into the conjugated ketone (22). 

The addition of diazomethane to a,/l-unsaturated ketones, e.g., benzalace-tone and benzalacetophenone, results in A -pyrazolines (16) which decompose thermally to the conjugated ketones (17). Cyclopropane formation is not observed in this instance. 

A-ring conjugated ketones do not normally interfere with the epoxidation reaction, but hydride reduction will reduce any ketone groups to alcohols. These can be reoxidized by conventional means. 

The reaction is remarkably specific hydroxyls (even at C-21), saturated as well as conjugated ketones, ketals and even hindered isolated double bonds e.g., are left substantially unattacked. Another advantage of this... 

Grignard additions to conjugated ketones preparation of la-methyl-17,20 20,21-bismethylenedioxypregna-4,6-diene-... 

TMM cycloadditions to cyclic and conjugated ketones have also been reported (Scheme 2.22) [31]. The steric nature of the substrate does play a critical role in determining product formation. Thus the cyclic ketone (73) produced 55% yield of the tetrahydrofuran, but no cycloadduct could be obtained from the cyclic ketone (74). The enone (75) gave only carbonyl cycloaddition, whereas enone (76) yielded only olefin adduct. Interestingly, both modes of cycloaddition were observed with the enone (77). The ynone (78) also cycloadds exclusively at the carbonyl function [34]. 

Prior to tlie advent of tripbenylpbospbine-stab dized CuH [6a, b, 11], Tsuda and Saegusa described use of Gve mole percent MeCu/DtBAL in THE/HMPA to effect bydtoaluminaiion of conjugated ketones and esters [26], Hie likely aluminium etiolate intermediate could be quendied witli water ot TMSCl, ot alkylated/acylated widi various electrophiles fsudi as Mel, allyl bromide, etc. Sdieme 5.5). Mote... 

Aldol condensation of the methoxymethyl ether of m-methoxybenzaldehyde (83) with cyclohexanone affords the conjugated ketone 84. Michael addition of dimethyl amine leads to the ami noketone Reduction of the ketone... 

The Michael reaction occurs with a variety of a,/3-unsaturated carbonyl compounds, not just conjugated ketones. Unsaturated aldehydes, esters, thio-esters, nitriles, amides, and nitro compounds can all act as the electrophilic acceptor component in Michael reactions (Table 23.1). Similarly, a variety of different donors can be used, including /3-diketones, /3-keto esters, malonic esters, /3-keto nitriles, and nitro compounds. 

In a related coupling reaction, the reaction of diethyl 2,7-nonadien-l,9-dioate and Mg/MeOH generated a five-membered ring via coupling of an intermediate radical.Treatment of conjugated ketones with Smij in HMPA gave the coupled diketone via Wurtz-type coupling. 

Other nucleophiles add to conjugated systems to give Michael-type products. Aniline derivatives add to conjugated aldehydes in the presence of a catalytic amount of DBU (p. 488). Amines add to conjugated esters in the presence of InCla, La(OTf)3, or YTb(OTf)3 at 3kbar, for example, to give P-amino esters. This reaction can be initiated photochemically. An intramolecular addition of an amine unit to a conjugated ketone in the presence of a palladium catalyst, or... 

Related compounds have been generated from BocRNCH2SnR 3 and s-butyllithium/ CuCN which also added to conjugated ketones. Other amino-cuprates are known to give conjugate addition reactions... 

Vinyl boranes add to conjugated ketones in the presence of a rhodium catalyst (with high asymmetric induction in the presence of BINAP) 7 Alkynyl-boranes also add to conjugated ketones, in the presence of... 

Similar reactions have been carried out on acetylene. Aldehydes add to alkynes in the presence of a rhodium catalyst to give conjugated ketones. In a cyclic version of the addition of aldehydes, 4-pentenal was converted to cyclopen-tanone with a rhodium-complex catalyst. In the presence of a palladium catalyst, a tosylamide group added to an alkene unit to generate A-tosylpyrrolidine derivatives. ... 

Aziridines can be prepared directly from double-bond compounds by photolysis or thermolysis of a mixture of the substrate and an azide. The reaction has been carried out with R = aryl, cyano, EtOOC, and RSO2, as well as other groups. The reaction can take place by at least two pathways. In one, the azide is converted to a nitrene, which adds to the double bond in a manner analogous to that of carbene addition (15-62). Reaction of NsONHC02Et/ CuO [Ns = A(/7-toluenesulfonyl-inimo)] and a conjugated ketone, for example, leads to the A-carboethoxy aziridine derivative.Calcium oxide has also been used to generate the nitrene.Other specialized reagents have also been used." ... 

The titanium reagent also dimethylates aromatic aldehydes." Triethylaluminum reacts with aldehydes, however, to give the mono-ethyl alcohol, and in the presence of a chiral additive the reaction proceeds with good asymmetric induction." A complex of Me3Ti-MeLi has been shown to be selective for 1,2 addition with conjugated ketones, in the presence of nonconjugated ketones." ... 

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