2-methylcyclohexanone, lithium

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 ... 

Methoxytrimethylsilane, 123 Methyl acetoacetate, 92 Methyl bromoacetate, 107 Methyl 11-hydroxyundecanoate, 58 Methyl lithium, 27,28 Methyl 10-undecenoate, 58 2-Methyl-l, 3-dithiane, 81 (fl/ ,5 )-Methyl-3-phenyldiniethyl-silyl-3-phenylpropionic acid, 53-4 2-Methyl-3-Phenylprop-2-cnal, 111 2-Methyl 2-lrimethylsilyl-1,3-dithiane, 81 2-Methyl-l-(trimcthylsilyloxy)cyclo-hex-l-ene, 100,109 2-Melhyl-l-lrimethylsilyloxy)cyclo-hcx-6-enc, 100 2-Methyl-2-trimethylsilyloxy-pentan-3-one, 132 2-Methylacetophenone, 42-3 2-Methylbutyraldehyde, 85 2-Methylcyclohexanone, 99,100 2-Methylcyclohexanone, 131 4-Methyldec-4-ene, 67-8 Methylenation, 63 2-Methylpropen-l-ol, 131 Methyltriphenylphosphonium bromide, 27 Michael addition, 85 Monohydridosilanes, 128 Monohydroalumination, 29... 

The anion of cyclohexanone /V,/V-dimclhyl hydrazone shows a strong preference for axial alkylation.122 2-Methylcyclohexanone N,N-dimethylhydrazonc is alkylated by methyl iodide to give d.v-2,6-dimclhylcyclohcxanone. The 2-methyl group in the hydrazone occupies a pseudoaxial orientation. Alkylation apparently occurs anti to the lithium cation, which is on the face opposite the 2-methyl substituent. 

Coleman, Kobylecki, and Utley studied the electrochemical reduction of the conformationally fixed ketones 4-tert-butylcyclohexanone and 3,3,5-tri-methylcyclohexanone 82>. Stereochemically, the cleanest reductions took place at a platinum cathode in a mixture of hexamethylphosphoramide and ethanol containing lithium chloride. Under these conditions the equatorial alcohol predominated heavily (95% from 4-fer/-butylcyclohexane and 91% from 3,3,5-trimethylcyclohexanone).In acidic media roughly equal quantities of axial and equatorial alcohol were produced. It was suggested that organo-lead intermediates are involved in the reductions in aqueous media. This is reasonable, based upon the probable mechanism of reduction in acid 83F Reductions in acid at mercury cathodes in fact do result in the formation of... 

Reduction of 2-methylcyclohexanone gave the following percentage proportions of the less stable m-2-methylcyclohexanol (with axial hydroxyl) with lithium aluminum hydride 25%, with diborane in tetrahydrofuran 26%, with di-sec-amylborane in tetrahydrofuran 79%, with dicyclohexylborane in diglyme 94%, and with diisopinocampheylborane in diglyme 94% (the balance to 100% being the trans isomer) [837. ... 

The deuteriated (97%) imines 363 and 365, and the hydrazone 364 have been prepared396-399 by treating 2,6,6-trideuterio-2-methylcyclohexanone and 2,2,6,6-tetradeuteriocyclohexanone with the corresponding deuteriated ammonium salts (RND3CI) and used in the KIE studies of the metalation of the above C=N compounds with lithium diisopropylamide (LDA) in THF, in N, N, N A -tetramethyl ethylenediamine (TMEDA) and in dimethylethylamine (DMEA) solvents (equation 200). The rates, d[imine]/dt of that of imines 363 and 364 metalation are zero order with respect to [THF], [TMEDA]... 

Metalation of unsymmetrical mines. Pioneering studies on the metalation and subsequent alkylation of unsymmetrical imines indicated that the reaction occurs predominantly at the less substituted a-position.5 This pattern has since been observed generally with lithium diethylamide, LDA, and ethylmagnesium bromide. Recent studies6 indicate that the site of alkylation is independent of the alkylating group but is dependent on the substituent on the imine and particularly on the basicity of the base. Butyllithium ( -, sec-, and /-) can abstract a proton from the more substituted a-carbon of the acyclic imine 1 to some extent. In the case of the cyclic imine 2, alkylation at the more substituted position is actually the main reaction. However, only substitution at the less substituted position of the dimethylhydrazone of 2-methylcyclohexanone is observed with either LDA or jcc-butyllithium (7,126-128). 

Our research group developed catalytic enantioselective protonations of preformed enolates of simple ketones with (S,S)-imide 23 or chiral imides 25 and 26 based on a similar concept [29]. For catalytic protonation of a lithium eno-late of 2-methylcyclohexanone, chiral imide 26, which possesses a chiral amide moiety, was superior to (S.S)-imide 23 as a chiral acid and the enolate was pro-tonated with up to 82% ee. 

The reaction of allylindium sesquibromide with 4 equiv. of bulky lithium alkoxide results in modified reagents 7, which show unusual degrees of chemo- and diastereoselectivity in the reactions with carbonyl compounds for example, allylation of 2-methylcyclohexanone gives a high ratio of axial alcohol 8/equatorial alcohol 9 (Scheme 15).128... 

Other reducing agents, which lead to unsaturated glycols of type 182, include thiourea,182 aluminum amalgam,214 and lithium aluminum hydride.192,218 The reaction of dihydroascaridole (181) with ferrous sulfate or titanous chloride yields propane and 4-hydroxy-4-methylcyclohexanone while ascaridol gives 3,6-endoxo-4-isopropyl-6-methylcyclohexane-1,2-diol and 4-hydroxy-3-isopropylcyclohexa-... 

Epoxides may undergo rearrangement in the presence of protic or Lewis acids to give carbonyl compounds. However, the nature of the products may depend quite subtly on the reaction conditions. For example, 1-methylcyclohexene oxide has been reported to give the ring-contracted aldehyde as the major product with lithium bromide, but with lithium perchlorate, 2-methylcyclohexanone is the major product (Scheme 2.22a). In the presence of a strong base such as lithium diethylamide, an allylic alcohol may be formed from an epoxide (Scheme 2.22b). 

An unsymmetrical ketone can form two different enolates. In some situations it is possible to distinguish between them by trapping the separate enolates as their silyl enol ethers. The anions may then be regenerated from the silyl enol ether in an aprotic solvent under non-equilibrating conditions using fluoride ion. The rapidly formed kinetic enol of 2-methylcyclohexanone may be trapped using lithium di-isopropylamide as the base (Scheme 3.77a). On the other hand, the thermodynamically more stable enol is trapped with a milder base such as triethylamine (Scheme 3.77b). ... 

Stereoselectivity, the exclusive or predominant formation of one of several possible stereoisomeric products, exemplified by the preferential formation of c/5-3-methylcyclohexanol on reduction of 3-methylcyclohexanone with lithium aluminum hydride in THF or Et20... 

Regioselective alkylations at C-6 of 2-methylcyclohexanone have been accomplished via the alkylation of thermodynamically unstable trisubstituted lithium, lithium triethanolamine borate, potassium triethylboron, tri- -butyltin and benzyltrimethylammonium enolates (c/. 2). Alkylation is faster than equilibration for the more reactive alkylating agents. Although enolate equilibration has been shown to compete with butylation using n-butyl iodide under certain conditions, butylation of the enolate (2 M = Li) in liquid ammonia-THF gave a mixture of cis- and /ra/ij-2-methyl-6-butylcyclohexanone along with 2-methylcyclohexanone in an 83 17 ratio in 90% yield no 2,2-dialkylcyclohexanone was obtained in this reaction (Scheme 8). ... 

A sample of racemic 2-methylcyclohexanone-1- 3 was prepared by methylation of the lithium cyclohexanolate-l-13 , with methyl iodide (VI ) The enolate was prepared from the cyclohexanone-1-13c by way of the trimethyl silyl derivative following the pro-" cedure of House and coworkers (12). A sample of trans-D,l-2-methylcyclohexanol-l -13C was then obtained by reduction of the ketone with lithium aluminum hydride in the presence of aluminum chloride as prescribed by Eliel and coworkers (13). 

This new reagent is an active reducing agent and reduces cyclic and bicyclic ketones with superstereoselectivity.1 Thus reduction of 2-methylcyclohexanone (1) gives m-2-methylcyclohexano) in 99.3 % purity. Note that reduction with lithium trimethoxy-aluminum hydride alone yields (2) in 69 % yield. Thus increasing the size of the alkyl substituents on boron enhances the stereoselectivity of the borohydride anion. Even... 

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