[CONTRIBUTION FROM
THE
CHEMICAL LABORATORIES OF THE UNIVERSITY OF CALIFORNIA AT Los ANGELES AND
THU
ILLINOIS INSTITUTE OF TECHNOLOGY ]
The Role of Neighboring Groups in Replacement Reactions. V. The Effect of the Neighboring Acetoxy Group on the Course of the Replacement of the Tosylate Group of trans-2-Acetoxycyclohexylp-Toluenesulfonate' BY S . WIKSTEIN, H. I-.HESS .4ND R. E. BUCKLES In a recent communication it was reported that This is further indicated by the loss of activity' the erythro- and threo-2-acetoxy-3-bromobutanes which is experienced when the replacement procand truns- 1-acetoxy-2-bromocyclohexane are con- ess is carried out with the acetate-tosylate deverted by silver acetate in dry acetic acid to di- rived from active trans- l,%-cyclohexanediol by acetates with retention of configuration.2 This first tosylating and then acetylating the glycol. steric result and the loss of optical activity when Almost pure levorotatory glycol, m. p. 11l0, active 1-acetoxy-2-bromocyclohexane was treated [a]D30.2O, (0.221 g. in 25.0 ml. solution, chlorowith silver acetate in dry acetic acid led to the form as solvent) when converted to active acetateidea that the acetoxy group participated in the tosylate, then to diacetate and then back to glyreplacement process to give rise to the intermedi- col, gave rise to completely inactive, almost pure ate I. The presence of enough water i n the acetic trans-glycol. This, on recrystallization, yielded pure inactive trans-glycol, m. p. 104'. This is a CHa more satisfactory demonstration of the loss of I activity due to a neighboring acetoxy group than was possible before. ' I > k--C< In the presence of enough water in the acetic I acid, the acetate-tosylate gave rise to the ester of acid used a,s a medium for the action of silver ace- pure cis-glycol, and intermediate amounts of tate on the halides mentioned gave rise to an odd water caused the production of esters of both cisnumber of inversionsS in contrast to the even and truns-glycol.6 il series of experiments was number of inversions under anhydrous conditions. carried out in which small amounts of acetate We now report quite analogous results in the tosylate were treated with potassium acetate in homogeneous solvolysis of trans-2-acetoxycyclo- acetic ncid of varying water content. The crude hexyl p-toluenesulfonate* I1 in acetic acid con- diacetate was saponified and the resulting crude glycol was recrystallized. Under the conditions of taining potassium acetate. concentration employed, acetic acid of higher H. c----cH t melting point than 15.75' yielded a glycol mixture from which trans-glycol could be obtained by HrC(/OAc H\ CK2 recrystallization. Acetic acid of melting point - cI / below 15.50' yielded a mixture from which cisI glycol was obtained. H Otosyl I1 'Table I summarizes the results of the series of experiments. The third column indicates where When trans-2-acetoxycyclohexyl tosylate is revery low recoveries of pure glycol were obtained fluxed with potassium acetate in dry acetic acid by the recrystallization. The arrows indicate the a diacetate is produced which is at least 93% of increase in these recoveries. Indirections trans so that retention of coniiguration is by far the predominant steric resuk6 Thus the bulk of cluded in Table I are the results of three other the replacement process must be by way of the qualitative experiments which yielded glycols intermediate I, which reacts with acetate ion.2 very largely cis. Several larger runs were made in which the (1) A portion of the material reported in this paper was presented before the Organic Division at the S t Louis meeting of the .4merican acetate-tosylate was treated with potassium aceChemical Society, April, 1941 tate in acetic acid of varying water content and (2) Winstein and Buckles, THIS JOURNAL, 64, 2780 (1942)
\A
(3) Winstein and Buckles, ibJd , 64, 2787 (1942). (4) Criegee and Stanger, BLY, 6BB, 2753 (1936) (5) cis-Diacetate is not transformed to tram under the conditions of the replacement prores.
( 6 ) Criegee and Stanger4 have recommended the reaction of the fioni-acetate-tosylate with potassium acetate in acetic acid for prr paring cJs-1,2-cyclohexanciol. These authors must have used acetic ncid with a considerable water content
Dec., 1942
SOLVOLYSIS OF t~U%s-2-ACETOXYCYCI~OHEXYL ~~-TOI,UENESULFONA.IT 2797
TABLE I product and found it to be pure monoacetate. SUMMARY OF QUALITATIVE EXPERIMENTS ON THE EFFECT Potassium acetate can be dispensed with. When OF WATER CONTENTOF ACETIC ACID ON THE STERIC the trans-acetate-tosylate is heated in absolute RESULTOF
CONVERSION OF h'anS-2-ACETOXYCYCLOHEXYL
p-TOLUENESULFONATE TO MONOAND DIACETATE M. p. of AcOH,
Config. of recryst. glycol
Recovery on recryst.
16.7" 16.0 15.85 15.75 15.50 15.30 15.0 14.6 14.1 13.1 10.4 16.7"lb 14.6b
trans trans trans trans
low
OC.
1
i
Cis Cis
CiS
Cis
cis Cis Cis CiS
high high
CiS
high
cis
c
I
>c-c
