2-Chloro-2-methylcyclohexanone

A. 2-Chloro-2-methylcyclohexanone. A 3-1. three-necked flask, fitted with a sealed mechanical stirrer with glass blade, a dropping funnel, and an outlet tube connected to a gas-absorption trap,1 2 is charged with... 

Chloroethyl benzoate, 30,11 a-Chloroethyl ethyl ether, 36, 60 Chlorohydroquinone, 35, 27 -Chloromandelic acid, 35,14 Chloromethylation, 30, 68 2-Chloro-2-methylcyclohexanone, 37, 8... 

The solvent is removed by distillation through a 15-cm. Vigreux column, first at atmospheric pressure and finally at reduced pressure (water aspirator). The residue is satisfactory for the preparation of 2-methyl-2-cyclohexenone described below (part B). Distillation through the column gives, after a small fore-run, 243-248 g. (83-85%) of colorless 2-chloro-2-methylcyclohexanone, b.p. 94 96°/27 mm., tin 1.4672, 1.088 (Note 3). 

The case of 2-chloro-2-methylcyclohexanone (2) presents no comparable steric difficulty, and here dehydrohalogenation by the Holysz method and with collidine both proceed rather poorly and in comparable yield. ... 

The reaction of 2-chloro-2-methylcyclohexanone with dimethyl sodiomalonate carried out at ice-bath temperature did not give the expected l-methylbicyclo[3.1.0]hexane derivative 24 (R = Me) but afforded only the substitution products 25 and 26 (R = Me) as a 52 48 mixture in 50% yield. The reaction with diethyl sodiomalonate likewise afforded a 27 73 mixture of the corresponding esters 25 and 26 (R = Et) in 43% yield. These results have been explained by the occurrence of a zwitterionic intermediate. By contrast, reaction of 2-chloro-4-methy 1-cyclohexanone with diethyl sodiomalonate under similar conditions gave 6-[bis(ethoxycar-bonyl]-3-methylbicyclo[3.1.0]hexan-6-ol (27) in 59% yield. This compound was tentatively assigned to have a more preferable boatlike conformation, which allows the bulky diester moiety to take the more favorable equatorial orientation. In a similar way, a 44 56 mixture of cn(/u-2-methyl- and exo-2-methyl-6-[bis(ethoxycarbonyl)methyl]-2-methylbicyclo-[3.1.0]hexan-6-ol (28) was obtained from the reaction of 2-chloro-5-methylcyclohexanone and diethyl sodiomalonate in 49% yield. 

Surprisingly, 2-chloro-2-methylcyclohexanone (11) reacted under the same conditions to yield a mixture of the regioisomeric substitution products 12 and 13. ... 

As expected for a Finkelstein reaction, phase-transferred halide ions behave as bases as well as nucleophiles. Bromocyclohexane is reported to react with 18-crown-6 activated potassium fluoride to quantitatively yield cyclohexene [2]. The corresponding reaction of chlorocyclohexane in which fluoride ion is associated with a resin-bound quaternary ion yields only 50% cyclohexene [5]. Quantitative alkene formation is observed, however, when sec-octyl bromide is treated with potassium fluoride in the presence of hexadecyltributylphosphonium ion [1]. A more complicated situation is encountered in the reaction of 2-chloro-2-methylcyclohexanone with fluoride ion. In this case, a mixture of elimination and substitution products is obtained (69% and 31% respectively, see Eq. 9.2) [2]. The elimination reactions of phase-transferred halide ions are included in Table 9.1. 

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