July 5, 1957
TRANSANNULAR RINGCLEAVAGE OF CYCLOALKANE DERIVATIVES
driodic acid was refluxed for 36 hours and then hydrolyzed by adding 35 ml. of 30y0 aqueous potassium hydroxide and refluxing for 12 hours in the dark under nitrogen. The reaction mixture was extracted with ether, the aqueous layer separated, acidified with 2 N hydrochloric acid and extracted with chloroform. The chloroform solution, after washing to neutrality with water and drying over sodium sulfate, was O 1.84 g. (80%) of concentrated and distilled in ~ C U yielding 6,8-dithioloctanoic acid (VI), b.p. 180° (bath temperature) (1.5 mm.), ~ * Z D 1.5225; infrared spectrum 1285, 1235 (OHcarboxyl), 1710 (CO-carboxyl) cm.-l. -4naZ. Calcd. for C8Hl6O2SZ:C, 46.12; H, 7.74. Found: C, 46.37; H , 7.74. 6-Thioctic Acid (DL-a-Lipoic Acid) (VII).--1.01 g. of dithiol-acid (VI) were dissolved in 2.3 ml. of 2 A' sodium hydroxide, diluted with 17 ml. of water containing 3.5 mg. of iron trichloride hexahydrate, yielding a dark red solution, through which a slow stream of oxygen was bubbled for 10 hours. The resulting pale yellow solution was washed with chloroform. The aqueous layer, acidified with 2 N hydro-
[ C O S TRIl1UI'IOy FROM THE BAKER
3505
chloric acid, was extracted with chloroform and this was washed t o neutrality and evaporated to dryness. The yellow oily residue crystallized upon trituration with petroleum ether (boiling range 40-60"). After one crystallization from petroleum ether, 0.8 g. of pure 6-thioctic acid (DLa-lipoic acid) (VII) (80%) was obtained, m.p. 61-62'; ultraviolet spectrum 333 mfi (E 147); infrared spectrum bands a t 1285, 1235 (OH-carboxyl), 1700 (CO-carboxyl) cm. -I. Anal. Calcd. for C ~ H M O Z SC, ~ : 46.57; H , 6.68; S, 31.13. Found: C, 46.66; H, 6.90; S,31.20. S-Benzylisothiuronium salt, m.p. 153-154'1* (from absolute methanol). Anal. Calcd. for C16H&20&: C, 51.61; H, 6.45; K , 7.53; S, 26.79. Found: C, 51.53; H, 6.73; N, 7.56; S,25.99. NAPOLI,ITALY (18) M.p. 132-134°" has been observed once. This discrepancy may be due t o crystallization and drying conditions.
LABORATORY O F CHEMIS'I'RY
AT C)ORNlALL 1JNI\.ERSITP]
Many-membered Carbon Rings. XIV. Transannular Ring Cleavage of Certain Cycloalkane Derivatives1 BY A. T. BLOMQUIST AND PETER R. TAUSSIG~ RECEIVED DECEMBER 4, 1956 Pyrolysis of cyclononyl acetate a t 500' affords mainly 1,8-nonadiene (70%) together with cis-cyclonoiiene (2770) and trans-cyclononene (1.5%). Thermal decomposition of cyclononyl S-methyl xanthate a t various temperatures indicates that formation of 1,S-nonadiene occurs only a t temperatures above 400". Pure trans-cyclononene rearranges a t 500" to 1,8nonadiene (85%) and cis-cyclononene (15%) while pure cis-cyclononene, a t 500°, yields only ca. 20% 1,8-nonadiene and 80% unchanged cis-cyclononene. Conformational analysis suggests two possible paths for the formation of the diene from cyclononyl acetate.
The discovery in recent years of transannular reactions314has done much t o stimulate research in the chemistry of medium size rings. This has included several studies concerned with the course of elimination reactions of various derivatives of the cycloalkanes such as their amines, halides, acetates and xanthates.j-' This article presents studies of the thermal decomposition of the acetate and Smethyl xanthate of cyclononanol. I n an earlier study of the pyrolysis of cyclodecyl acetate and cyclodecyl xanthate,6 it was observed that a mixture of cis- and trans-cyclodecenes was produced rather than exclusively one stereoisomer as might have been expected. Further, it was noted that pyrolysis of cyclodecyl acetate gave, as a minor (1) (a) For t h e preceding paper in this series see A . T. Blomquist and P . R. Taussig, THISJ O U R N A L , 7 7 , 6399 (1955). (b) Presented before t h e Division of Organic Chemistry a t t h e Xational Meeting of t h e American Chemical Society a t Miami, Florida, April 7-12, 1957. (2) Du P o n t Post-Graduate Teaching Fellow. T h e work reported here was abstracted f r o m iiart of the dissertation uresented b s Peter R. Taussig in September, 19iS. t o t h e Graduate School of Cornell University in partial fulfillment of t h e rcqriiremcnts for t h e degree of Doctor of Philosophy (3) V. Prelog and K . Schenker, H e l v . Chim. Acln, 35, 2044 (1052); v. Prelog, K. Schenker a n d Kbng, ibrd., 3 6 , 4 7 1 (1953); v. Prelog, 11. J. Urech, A. A. Bothner-By and J. Wurch, i b i d . , 38, 1095 (1955); V. Prelog a n d V . Boarland, i b i d . , 38, 1776 (1955). (4) A. C . Cope, S. W . Fenton a n d C. F. Spencer, THISJ O U R N A L , 74, 5884 (1952). ( 5 ) A. T. Blornquist, It. E. Rtirpe and A. C . Sucsy, ibid., 74, 3636 (1 052). (6) A. T. Hlomqiiist and A . Goldstein, ibid.,7 7 , 1001 (1065). ( 7 ) A. C. C O ~ Kl,
