2- Methylcyclohexanone enolates

Since the conformational inversion of 2c-methylcyclohexanone is the key step in this sequence, the corresponding conformationally more stable system, i.e., cw-2-methyl-4-t-butylcyclohexanone (14), should fail to incorporate any deuterium. This was actually shown to be the case. Treatment of this ketone under identical conditions for d exchange did not show any d incorporation. This evidence also rules out the likelihood of any d incorporation via acid- or base-catalyzed enolization. 

Compare energies of the two enolates which may result from deprotonation of methylcyclohexanone. Which is preferred and by how much Next, compare energies of the corresponding methylcyclohexanone lithium enolates. Does the preference or the magnitude change ... 

Note in the ketone example that alkylation of 2-methylcyclohexanone leads to a mixture of products because both possible enolate ions are formed. In general, the major product in such cases occurs by alkylation at the less hindered, more accessible position. Thus, alkylation of 2-niethvTcyclohexanone occurs primarily at C6 (secondary) rather than C2 (tertiary). 

High-boiling products found in this procedure and in similar experiments involving cyclohex-2-enone derivatives5 probably result from bimolecular reduction processes.15 3-Methylcyclohexanone, which arises by protonation rather than alkylation of the enolate (and which made up ca. 12% of the volatile products), is probably the result of reaction of allyl bromide with liquid ammonia to form the acidic species allyl ammonium bromide.5 10... 

Allenyl Silyl enol ethers, 86 Allyl alcohol trimethylsilyl ether, 84 Allyl carbonates, 114-15 9 Allyl-ay 2 octalone, 34-5 2-Allyl-2 methylcyclohexanone, 106 (Allyldimethylsilyl)methyl chloride, 58, 59 (AUyldimethylsilyl)methylmagnesium chloride, 59... 

The low-temperature method is effective not only in the kinetic resolution of alcohols but also in the enantioface-selective asymmetric protonation of enol acetate of 2-methylcyclohexanone (15) giving (f )-2-methylcyclohexanone (16). The reaction in H2O at 30°C gave 28% ee (98% conv.), which was improved up to 77% ee (82% conv.) by the reaction using hpase PS-C 11 in /-Pt20 and ethanol at 0°C. Acceleration of the reaction with lipase PS-C 11 made this reaction possible because this reaction required a long reaction time. The temperature effect is shown in Fig. 14. The regular temperature effect was not observed. The protons may be supplied from H2O, methanol, or ethanol, whose bulkiness is important. 

Very significant acceleration in the rate of deprotonation of 2-methylcyclohexanone was observed when triethylamine was included in enolate-forming reactions in toluene. The rate enhancement is attributed to a TS containing LiHMDS dimer and triethylamine. Steric effects in the amine are crucial in selective stabilization of the TS and the extent of acceleration that is observed.18... 

The alternative electrophilic mechanism for the nitration of ESE with TNM requires a close approach of a hindered ESE to a N02 group on the quaternary carbon center of TNM. However, this transition state is sterically very demanding, and it will not readily account for the observed reactivity. Furthermore, the observed lack of regioselectivity in the nitration of the isomeric enol silyl ethers of 2-methylcyclohexanone that leads to the same 2-methyl-2-nitrocyclohexanone (in thermal as well as photochemical nitration) is not readily reconciled by a concerted (electrophilic) mechanism (equation 18). 

FORMATION AND ALKYLATION OF SPECIFIC ENOLATE ANIONS FROM AN UNSYMMETRICAL KETONE 2-BENZYL-2-METHYLCY-CL0HEXAN0NE AND 2-BENZYL— 6-METHYLCYCLOHEXANONE, 52,... 

Another example of the formation of a rearranged product is the palladium(0)-catalysed reaction of the enolate ion of 2-methylcyclohexanone with 3-methyl-3-nitro-l -butene... 

Benzyl-6-methylcyclohexanone has been prepared by the hydrogenation of 2-benzylidene-6-methylcyclohexanone over a platinum or nickel catalyst, and by the alkylation of the sodium enolate of 2-formyl-6-methylcyclohexanone with benzyl iodide followed by cleavage of the formyl group with aqueous base. The 2,6-isomer was also obtained as a minor product (about 10% of the monoalkylated product) along with the major product, 2-benzyl-2-methylcyclohexanone by successive treatment of 2-methylcyclohexanone with sodium amide and then with benzyl chloride or benzyl bromide. Reaction of the sodium enolate of 2-formyl-6-methylcyclohexanone with potassium amide in liquid ammonia formed the corresponding dianion which was first treated with 1 equiv. of benzyl chloride and then deformylated with aqueous base to form 2-benzyl-2-methylcyclohexanone.i ... 

A simple Sn2 alkylation reaction serves as example. As we have already seen, treating cyclohexanone with LDA gives the enolate anion, which can then be allowed to react with methyl iodide to give 2-methylcyclohexanone. 

Back in Section 10.5 we saw two methods of synthesizing 2-methylcyclohexanone, i.e. by direct alkylation of the enolate anion derived from cyclohexanone and by using an enamine derivative as the nucleophilic species. The latter route had the advantage of not using a strong base to generate the... 

Acetic Anhydride, Carbon Tetrachloride, and 2-Methylcyclohexanone. During acetylation of the enolized ketone, the 70% perchloric acid must be added last.6... 

Deprotonation of an unsymmetrically substituted ketone such as 2-methylcyclohexanone (Figure Si3.2) potentially gives rise to two isomeric enolate anions. Under kinetic conditions, deprotonation at the least substituted carbon atom is favoured and the enolate anion with the least substituted double bond is in excess. Under thermodynamic conditions however, equilibration between the two enolate anions occurs and the enolate anion with the more substituted double bond eventually predominates. 

Addition of a silylating reagent such as Me3SiCl to the reaction mixture traps the enolate anions and produces two silyl enol ethers in a ratio which reflects the ratio of the enolate anions. Thus if 2-methylcyclohexanone is added to the hindered base LDA at -78 °C and the mixture stirred for 1 hour at -78 °C and quenched with MeySiCl, then the major product is the silyl enol ether derived from the kinetic enolate. In contrast, heating 2-methylcyclohexanone, triethylamine, and Me3SiCl at 130 °C for 90 hours... 

---