AICCASLAXD, FURUTA, JOHNSOS, AND SHOOLERY
894
point with a specimen of 2a,4~dibromocholestan-3-one,m.p. 190-192.5' dec., was 184-190" dec., undepressed. Debromination of the Bromochlorocho1estanones.-(a) A solution of 200 mg. (0.40 mmole) of 5 and 63 mg. (0.43 mmole) of freshly recrystallized 2-naphthol in 5 ml. of carbon disulfide was t'reated with 1 ml. of glacial acetic acid containing 22 mg. of hydrogen bromide. After 3.5 hr. at room temperature, the reaction mixture was dilut,ed with ether and washed successively with water, dilute sodium bicarbonate solution, dilute sodium hydroxide solution, and saturated sodium chloride solution. The dried organic solution was evaporated to leave 157 mg. (93%) of 2a-chlorocholestanone. One recrystallization from chloroform-methanol gave 117 mg., m.p. 184-185' (cap.) (reported,g m.p. 185-186"), whose infrared spectrum in carbon disulfide (20 mg./O.l ml.) was identical with that of authentic 2a-chlorocholestanone. Anal. Calcd. for C?iH4sOC1(421.09): C1, 8.43. Founds5: C1, 8.57; Br, 0.71.37 Acidification of the sodium hydroxide washes and extraction with ether gave 82 mg. which was recrystallized from petroleum ether. There was obtained 14 mg. of 1-bromo-2-naphthol, m.p. 81-83.5" (reported,36 m.p. 84'). ( b ) A 200-mg. (0.40 mmole) sample of 4 was treated exactly as in part (a)except the reaction time was 4 hr. Work-up as described in ( a ) gave 162 mg. (96%) of crystalline 2a-chlorocholestanone. One recrystallization from chloroform-methanol yielded 128 mg., m.p. 185.5-186.5' (cap.), whose infrared spectrum in carbon disulfide (20 mg./O.l ml.) a-as identical with that of authentic %a-chlorocholestanone. -4nal. Calcd. for C27H4:OC1 (421.09): C1, 8.q3. Found": CJl, 7.86; Br, 1.2'3.37 -
(36) A. J. Smith. J . Chem. Soc., 36, 789 (1879). (37) The small amount of bromine is probably from 2a-bromoeholestanone present a s a contaminant in the starting material 4 or 6, or formed from 21 (small ainount present in 4) by debromination.
VOL. 28
Acidification of the sodium hydroxide washes and extraction with ether gave 77 mg. which was recrystallized from petroleum ether. There was obtained 31 mg. of 1-bromo-2-naphthol, m.p. 78-82'. Relative Rates of Debromination of 4 and 5.-.4 solution of 00 mg. (0.18 mmole) of 4 or 5 and 27 mg. (0.187 mmole) of freshly recrystallized 2-naphthol in 0.50 ml. of carbon disulfide was pipetted into a solution of 0.35 mg. of hydrogen bromideinO.lOm1. of carbon disulfide contained in an n.m.r. sample tube. The spectrum of the capped tube (temperature = 37") was recorded periodically over the region of C-19 methyl absorption (sweep width 250 cycles, sweep time 250 sec., spectrum amplitude 16, filter bandwidth 1, radio frequency 0.16). The 2-naphthol caused a 3 c.p.s. upfield shift of the C-19 methyl peak of both 4 and 5 . The area under the diminishing C-19 methyl peak was determined by the cut-and-weigh technique. The debromination was treated as a pseudo first-order reaction since the hydrogen bromide concentration will remain constant. First-order rate constants were determined graphically from a plot of log weight of C-19 methyl peak us. time elapsed. The ratio k& obtained in this manner wa9 2.3. As a check the ratio of the rates of appearance of the C-19 methyl peak of 2a-chlorocholestanone wm determined in the same way and found to be 2.5.
Acknowledgment.-The author wishes to thank the National Science Foundation for support under grant G15752 and for a generous departmental grant G1879.5 toward the purchase of the nuclear magnetic resonance spectrometer, without which this work could not have been done. He also wishes to thank Dr. R. J. Highet and Mrs. I
