Enones reagents

The prolinol 7 assists epoxidation of enones (reagent t-BuOOH), but good ee are obtained only with chalcones. ... 

Conjugate Additions to Enones. Reagent (1) effectively adds the dimethylphenylsilyl group to a,/8-unsaturated ketones, esters. 

Cydopentane reagents used in synthesis are usually derived from cyclopentanone (R.A. Ellison, 1973). Classically they are made by base-catalyzed intramolecular aldol or ester condensations (see also p. 55). An important example is 2-methylcydopentane-l,3-dione. It is synthesized by intramolecular acylation of diethyl propionylsucdnate dianion followed by saponification and decarboxylation. This cyclization only worked with potassium t-butoxide in boiling xylene (R. Bucourt, 1965). Faster routes to this diketone start with succinic acid or its anhydride. A Friedel-Crafts acylation with 2-acetoxy-2-butene in nitrobenzene or with pro-pionyl chloride in nitromethane leads to acylated adducts, which are deacylated in aqueous acids (V.J. Grenda, 1967 L.E. Schick, 1969). A new promising route to substituted cyclopent-2-enones makes use of intermediate 5-nitro-l,3-diones (D. Seebach, 1977). 

Conjugate addition of vinyllithium or a vinyl Grignard reagent to enones and subsequent oxidation afford the 1.4-diketone 16[25]. 4-Oxopentanals are synthesized from allylic alcohols by [3,3]sigmatropic rearrangement of their vinyl ethers and subsequent oxidation of the terminal double bond. Dihydrojasmone (18) was synthesized from allyl 2-octenyl ether (17) based on Claisen rearrangement and oxidation[25] (page 26). 

Regiocontrolled q- or / -alkenylation and arylation of cyclic enones are possible without protection of the ketone by applying the coupling reaction of the Q- or /3-halo enones 607 and 608 with aryl and alkenylzinc reagents[468,469]. 

Since this original synthesis, a great number of improvements (191—201) have been made in the stereoselective preparation and derivatization of the CO-chain precursor, in cuprate reagent composition and preparation, in protecting group utilization, and in the preparation and resolution of hydroxycyclopentenones. Illustration of some of the many improvements are seen in a synthesis (202) of enisoprost, a PGE analogue. The improvements consist of a much more efficient route to the enone as well as modifications in the cuprate reactions. Preparation of the racemic enone is as follows ... 

The formation of an epoxyketone (1) is generally favoured when the expected product of oxidation of an allylic alcohol is a cisoid enone. This type of reaction is promoted by acid conditions and may be prevented by using the chromium trioxide-pyridine reagent which gives only the unsaturated ketone (2) corresponding to the starting alcohol. ... 

Use of the imonium group for protection of enones was explored. Stability to peracids, lead tetraacetate, bromine, and acetic anhydride was claimed (727). The usual resistance of enamines (but not their salts) to additions of Grignard reagents was used for selective addition to a 3,17-diketosteroid by formation of the usual 3-monoenamine 728). 

Hindered ketones and enones fail to form the ketal because of competing decomposition of the silyl reagent. 

Cacchi and Palmier (83T3373) investigated a new entry into the quinoline skeleton by palladium-catalyzed Michael-type reactions. They found that phenyl mercurial 134 was a useful intermediate for the synthesis of quinoline derivatives, and that by selecting the reaction conditions the oxidation level of the heterocyclic ring in the quinoline skeleton can be varied. On such example is shown in Scheme 16. PdCla-catalyzed coupling between organomercurial reagent 134 and enone 135 delivered adduct 136 which was subsequently cyclized to quinoline 137 under acidic conditions. 

TL2403). Thus, or /io-cyclopalladation of acetanilide 138 gave organo-palladium reagent 139. The or /io-vinylation of 139 afforded enone 140, which was then cyclized to quinoline 141 under acidic conditions. Notice this reaction requires stoichiometric amounts of Pd(OAc)2. 

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