4-/-Butyl-2,2-dimethylcyclohexanone

Tlie bifunctional sulfenyl chloride 213 was obtained by chlorination of 144 in good yield, although excessive chlorination led to the saturated compound 214 (94CB533). A series of compounds 215-220 were obtained from 213 by reactions with secondary amines ferf-butyl methyl ketone hexane-2,4-dione 2,6-dimethylcyclohexanone diethyl malonate and acetylacetone, respectively. 

Examples of palladium-catalyzed reduction are 4-chloro-2,6-di-r-butyl-phenol to 2,6-di-t-butylcyclohexanone (750 psig, 25 C) with loss of halogen 24), 1,8-dihydroxynaphthalene to 8-hydroxy-1-tetralone 30), and 2,4-dimethylphenol to 2,4-dimethylcyclohexanone (27). 

It is also possible to achieve enantioselective enolate formation by using chiral bases. Enantioselective deprotonation requires discrimination between two enantiotopic hydrogens, such as in d.v-2,6-dimethylcyclohexanone or 4-(/-butyl)cyclohcxanonc. Among the bases that have been studied are chiral lithium amides such as A to D.22... 

Dimethylcyclohexanone and 2-benzyl-2-methylcyclohex-anone have been prepared similarly in yields of 60% and 55%, respectively.2 The procedure has been extended to the synthesis of 9-methyl-, 9-w-butyl-, and 9-benzyl-l-decalone from the dianion of 2-formyl-l-decalone in yields of 55%, 48%, and 58%, respectively.2... 

Yamamoto and Saito reported that the kinetically controlled generation of the more substituted enolate of unsyimnetrical dialkyl ketones can be realized by the combined use of ATPH and LDA [175]. Precomplexation of ATPH with 2-methyl-cyclohexanone (175) at -78 °C in toluene was followed by treatment with LDA in THF, and the mixture was stirred for 1 h. Subsequent treatment with methyl trifluoro-methanesulfonate (MeOTf) furnished 2,2-dimethylcyclohexanone (177) and 2,6-dimethylcyclohexanone (176) in the ratio 32 1 (53 % isolated yield). Use of ter/-butyl-dimethylsilyl triflate (TBSOTf) in place of alkyl triflates in this alkylation system produced siloxybutylated product 178 as a result of THF ring-opening alkylation occurred similarly at the more hindered a-carbon of the unsymmetrical ketone 175 (Sch. 136) [176]. 

The hydrolysis and isomer content of enamines of 2,3- and 2,5-dimethylcyclohexa-nones falls into a broadly similar pattern. Enamines of 2,6 dimethylcyclohexanones can exist only as (234), with the 6-methyl group axial or equatorial. Both pyrrolidine and morpholine enamines undergo hydrolytic decomposition to give ca. 50 50 mixtures of cis- and trans-ketones. The 4-t-butyl derivative (235), on hydrolysis, gave... 

Vibrational Spectroscopy. A Raman investigation of the conformation of cyclohexyl halides trapped in thiourea clathrates has been made. The chloro- and bromo-cyclohexanes are present in the clathrate only as axial conformers whereas the iodide exists in both axial and equatorial forms. From a study of the i.r. spectra of 4-methylcyclohexanone, 4-methylcyclohex-2-enone, and several halogeno-4-methyl-cyclohexanones in the 1350-580 cm region characteristic axial and equatorial (CHj) frequencies were located. This work was subsequently extended to halo-genated 4,4-dimethylcyclohexanones and related t-butyl systems. 

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