Unsaturated ketones with organometallic

Although the acylcobalt tetracarbonyls react with hydroxide ion under phase-transfer conditions, in the presence of alkenes and alkynes they form o-adducts rapidly via an initial interaction with the ir-electron system. Subsequent extrusion of the organometallic group as the cobalt tetracarbonyl anion leads to a,(J-unsaturated ketones (see Section 8.4). In contrast, the cobalt carbonyl catalysed reaction of phenylethyne in the presence of iodomethane forms the hydroxybut-2-enolide (5) in... 

A number of organometallic compounds show promise for LCEC study, and a few have already been examined in detail (especially mercury alkyls) [9]. More highly conjugated organic compounds such as a,a-unsaturated ketones and imines are occasionally good candidates, but at this time UV detectors frequently outperform electrochemical detectors for such systems. At this writing there have been only a few reported LCEC studies of metal ions or metal complexes. Perhaps the major reason for this is that very little modern LC has been carried out on them using any detector. It is difficult to compete with atomic spectroscopy techniques for the determination of most elements, but as speciation becomes more important, it seems likely that more LCEC methods will be developed for metal complexes. 

Enediamine 93 undergoes an easy C-alkylation with a,/ -unsaturated ketones under comparable conditions and no cyclocondensation products are observed36. Similar C-alkylations with other electrophilic olefins such as unsaturated lactones, propenonitrile, vinyl sulfoxide, sulfone and phenylphosphonium bromide have been achieved36. All the adducts 135 exist predominantly as the imine form (see Section II.A). Treatment with organometallic reagents transforms the C-alkylated products into... 

The reaction of an organometallic reagent with an a,j3-unsaturated ketone can occur by 1,2-addition to the carbonyl group and by 1,4-... 

Strontium enolate chemistry is almost nonexistent barium enolate chemistry is rare radium enolate chemistry is unknown. Allyl chlorides react with barium to form the corresponding organometallics, which in turn react with o ,/ -unsaturated ketones to form the metal enolate . These enolates may also be formed in situ by the reaction of a-chloroketones with barium metal in the presence of an aldehyde, resulting in addition products. These reactions and the enthalpies of formation of the precursor a-haloketones and enones are seemingly ideal candidates for calorimetric investigation. 

The reduction of unsaturated carbonyl compounds by metal hydrides, and the reaction of organometallic nucleophiles with them, is a complicated story.87 It is more common than not, in each case, to get direct attack at the carbonyl group, but reaction in the conjugate position is well known. Conjugate reduction of a/i-unsaturated ketones by metal hydrides increases88 in the sequences Bu2iAlH < LiAlH4 < LiAlH(OMe)3 < LiAlH(OBu )3 and... 

Protection or reductive deoxygenation of alcohols and ketones. Ireland et al.2 have found that N,N,N, N -tetramethylphosphoroiiamidates (TMPDA derivatives) of alcohols and of ketone enolates are reduced in high yield by lithium-ethylamine. They are readily prepared by phosphorylation of alcoholate or enolate anions. The complete sequence is as follows. The alcoholate anion is simply prepared by treatment of an alcohol with a slight molar excess of n-butyllitliium. The enolate anions of saturated ketones are prepared by treatment with lithium diisopropylamide. In the case of a,/J-unsaturated ketones, lithium-ammonia reduction or conjugate organometallic addition is suitable. For phosphorylation of the Jnion a fivefold excess of N,N,N, N -tetramethyldiamidophosphorochloridate in 4 ] dimethoxyethane (or THF)-N,N,-N. N -tetramethylethylenediamine (TMEDA) is used. The reaction is complete after... 

C. Bassin, A. Gusso, F. Pinna, G. Strukul, Platinum-catalyzed oxidations with hydrogen peroxide The (enantioselective) epoxidation of a,p-unsaturated ketones, Organometallics 14 (1995) 1161. 

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