Aug. 5, 1954
SULFONATION OF CYCLOPENTENE AND CYCLOHEXENE [CONTRIBUTION FROM THE CHEMICAL
Sulfonation of Olefins. VI,
3957
LABORATORY O F NORTHWESTERN UNIVERSITY 1
Stereochemistry of the Reaction with Cyclopentene and Cyclohexene
BY F. G. BORDWELL AND MARVIN L. PETER SON^ RECEIVED FEBRUARY 22, 1954 Sulfonation of cyclopentene with an equimolar quantity of dioxane-sulfur trioxide gave, on hydrolysis, trans-2-hydroxycyclopentanesulfonic acid (111). The formation of I11 is consistent with the presence of a 8-sultone intermediate, indicated by previous work, and this hypothesis is strengthened by the formation of the dipolar ion, trans-2-( I-proto-1-pyridy1)cyclopentanesulfonate (IV), on treatment of the sulfonation mixture with pyridine. Use of a double molar quantity of sulfonating agent gave, on hot acid hydrolysis, cis-2-hydroxycyclopentanesulfonicacid (V). Sulfation of V gave cis-2-hydrosulfatocyclopentanesulfonicacid (VI), which was also obtained by cautious hydrolysis of the sulfonation solution, which is believed to contain the cyclic sulfonate-sulfate anhydride intermediate VII. From previous work it is clear that only sulfur-oxygen bonds are cleaved in the hydrolysis of VI1 to VI, and of VI to V, so~VIImust also have a cis structure. Sulfonation of cyclohexene with a double molar amount of sulfonating agent gave, on hydrolysis, cis-2-hydrosulfatocyclohexanesulfonic acid and, from this, cis-2-hydroxycyclohexanesulfonicacid. Salts of these acids were previously prepared in a similar manner by Sperling, but assigned a trans configuration. The significanceof these results with regard to the mechanism of the sulfonation reaction is discussed.
Previous papers in this series have established that the sulfonations of unbranched olefins, such as styrene2 and 1-hexene3 give, on hydrolysis, (3-hydroxysulfonic acids, which may have been formed by the hydrolysis of a (3-sultone intermediate (B)2,3 or a cyclic sulfonate-sulfate anhydride intermediate(I).
tion of cyclopentene with an equimolar quantity of dioxane-sulfur trioxide reagent gave, after hydrolysis, 3% of sulfuric acid and 8% of unsaturated sulfonic acids (by bromate-bromide titration). The remainder of the product (79% based on the total acids in the aqueous layer) was presumably a 0hydroxycyclopentanesulfonic acid. Crystallization of the sodium salt from 95yo alcohol gave a salt RCH-CHz RCH-CHz free of unsaturated sulfonates. p-Toluidine and S/ \ I I p-chlorobenzy1)-thiuronium derivatives failed to 0 0-so2 form from even concentrated solutions of this salt, soz-0 but addition of equivalent amounts of p-toluidine or B I aniline to the aqueous solution from hydrolysis of In order to learn more concerning the formation the sulfonation mixture gave the p-toluidine and and reactions of these intermediates the stereo- aniline salts on evaporation. The p-toluidine salt chemical nature of the P-hydroxysulfonic acids was converted to the barium salt, an equivalent from the sulfonation of cyclopentene and cyclohex- amount of an aqueous solution of S-(p-chlorobenzy1)-thiuronium sulfate added, and the derivative ene has been investigated. Sperling4 reported that the dioxane-sulfur triox- obtained by evaporation of the filtrate. A 0-hydroxycyclopentanesulfonate identical to ide complex reacts with cyclohexene to form 2-cythat described above was obtained by the reaction clohexene-1-sulfonic acid, and, after hydrolysis and neutralization, barium “transJ’-2-bariosulfato-of either cyclopentene oxide or trans-2-chlorocy1-cyclohexanesulfonate. On further hydrolysis the clopentanol with ammonium sulfite, as shown by latter gave barium “trans”-2-hydroxy-2-cyclohex- mixed melting point comparison of the p-toluidine anesulfonate. The “cis” isomer of the P-hydroxy- salts in each instance with the p-toluidine salt of sulfonate was reported as being formed by the re- the sulfonation product. There appears t o be no action of cyclohexene oxide and ammonium sulfite. doubt but what this is a salt of trans-2-hydroxycyThe structure assignments were made on the basis clopentanesulfonic acid (111),since trans opening of of the relative solubility of the isomeric barium epoxide rings in the reaction with nucleophilic reproducts salts in water, and the “inability” of the less soluble agents has been firmly established.s I r a n ~ barium salt to form an S-benzylthiuronium deriva- are also the rule for displacement reactions of cyclic tive. The formation of isomeric products from halohydrins, the reaction proceeding either by way these two sources has been confirmed in the present of the oxide or a cyclic bromonium ion. The formation of trans-2-hydroxycyclopentanestudy, but the configurations of the compounds are just the opposite of those assigned by SperlingI4 sulfonic acid (111)from the hydrolysis of the sulfonas will be brought out in the discussion which fol- ation solution is consistent with the presence of a p-sultone intermediate (11),analogous to B. lows. Sulfonation of Cyclopentene.Since the major product from the sulfonation of cyclohexene was found to be the unsaturated sulfonic acid, 2cyclohexene-1-sulfonic acid, we turned our attenH’ HO’ tion to the cyclopentane series, where elimination I1 111 reactions are frequently not so dominant. SulfonaThe fusion of the four- and five-membered rings in (1) Procter and Gamble Research Fellow, 1948-1951. I1 must of necessity be cis. Ring opening of I1 by (2) F. G. Bordwell, M. L. Peterson and C. S. Kundestvedt, THIS
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76, 3945 (1954). (3) F. G. Bordwell and 31. L. Petersuii, i b i d . , 7 6 , 3 3 5 2 ( l Y C 4 ) . (4) R. Sperling, J . Chem. SOC.,1925 (1949).
JOUKNAL.
( 5 ) (a) C . E. Wilson and H. J. Lucas, THISJOUKNAI., 68, 2396 (1936); (b) W. E. Grigsby, J. Hind. J. Chanley and F. H. Westheitner I ibid., 61, 2606 (1942).
F. G. BORDWELL AND MARVIN L. PETERSON
3958
attack of a water molecule would be expected to lead to inversion no matter whether the hydrolysis ~ mechanism, alproceeds by an S N 1 or S N type though the presence of some of the cis isomer would be anticipated from an Sx1 reaction. A minimum of 57% of the trans isomer is present by isolation. It is improbable that more than a small amount of the cis isomer is present, since derivatives of the cis isomer are less soluble than those of the trans isomer, and would have separated first. The formation of the dipolar ion, trans-2-(1proto-1-pyridy1)-cyclopentanesulfonate (IV),6 by addition of pyridine to the sulfonation solution is considered, by analogy with previous work,203 to be additional evidence for the presence of a psultone intermediate (11).
Vol. 76
with retention of configuration (albeit with some racemization) and (2) aryl hydrogen sulfates may be hydrolyzed readily in acidic solutions.8b Therefore, the fact that VI hydrolyzes to cis-2-hydroxycyclopentanesulfonic acid (V) shows that VI must also have a cis configuration. This assignment was confirmed by showing that VI could be produced by sulfation of anilinium cis-2-hydroxycyclopentanesulfonate with dioxane-sulfur trioxide. Burwell has shownaa that sulfation of optically active 2-butanol proceeds with retention of configuration, and with very little loss of optical purity. Also, the sulfation of primary and secondary alcohols with sulfuric acid is known to involve sulfuroxygen rather than carbon-oxygen fission.g
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Reaction of cyclopentene with a two molar quantity of dioxane-sulfur trioxide reagent gave different results. The sulfonation products were hydrolyzed by pouring into water and heating the aqueous solution for several hours. The acids were neutralized Kith barium carbonate, barium sulfate was removed and the filtrate was evaporated 1.11 to yield 85sc of a barium salt containing only 3y0 of unsaturated sulfonates. The p-toluidine salt /\/S03H H,O/\/SOIH was prepared by treating an aqueous solution of the H/i l,0S03H (heat) H”:,OH barium salt with equivalent amounts of sulfuric t acid and p-toluidine. This p-toluidine salt was H/ OC4HsOS03 H” different from, but isomeric with, that obtained 1-1 v from cyclopentene and one mole of sulfonating The representation of the fission of VI1 during agent, and must be the p-toluidine salt of cis-2hydroxycyclopentanesulfonic acid (V) . The S- hydrolysis as involving the sulfonate-oxygen rather (p-chlorobenzyl)-thiuronium salt of the cis isomer than the sulfate-oxygen link is based on the be(V), unlike that of the trans isomer (111),was pre- havior of aniline in a similar instance.3 Sulfation of the aniline salt of trans-2-hydroxycypared directly from the barium salt in concentrated aqueous solution and was crystallized from small clopentanesulfonic acid (111) with dioxane-sulfur quantities of water. The aniline salt of V also was trioxide gave a hydrogen sulfate ester isomeric with VI, which must be trans-2-hydrosulfatocycloprepared and shown to differ from that of 111. Hydrolysis of a sulfonation reaction, involving pentanesulfonic acid. The same trans-hydrogen one mole of cyclopentene and two of the sulfonating sulfate ester also was obtained by sulfation of the agent, with cold water and neutralization with barium salt of 111. Sulfonation Mechanism.-Unbranched alkenes barium carbonate gave, on evaporation, the barium salt of the hydrogen sulfate ester of V. This bar- generally react rapidly a t 0” with an equimolar ium salt of a 2-hydrosulfatocyclopentanesulfonic7 quantity of dioxane-sulfur trioxide in ethylene chloacid (VI) could be refluxed in aqueous solution for ride solution to give a soluble sulfonation interseveral hours without hydrolysis, but in the pres- mediate. On the basis of the reaction of this ence of 1 S hydrochloric acid, barium sulfate began intermediate with water, aniline, pyridine, excess to precipitate within 3 to 10 minutes. X sample of sulfonating agent, etc., either a /I-sultone structure the pure sodium salt of VI gave 98.9L;,‘oof the theo- (I3 or 11) or a dioxane-solvated-carboniumsulfonate retical yield of sulfate ion on hydrolysis for 2 hr. ion (such as A) may be used to represent the intermediate. For styrene the 6-sultone structure is with 1 il‘ hydrochloric acid. -kid-catalyzed hydrolysis of alkyl hydrogen sul- favored because a substance agreeing with this fate esters is known to proceed by cleavage of the formula may be precipitated from the solution by sulfur-oxygen rather than the carbon-oxygen addition of pentane.* For 1-hexene the formation bond since, (I) optically active 2-butyl hydrogen of a structure comparable to (A) from the p-sultone sulfate hydrolyzes in acid medium to 2-butanol in the presence of excess dioxane has been suggested +
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lbJ i c t ri f d io1 d d i ~ c u z s i o not the nuinenclature of dlpoldr ions oi this t y p e (71 The y r e f i x t a h>drosulidtu, sudiohulfato and bartosulfato are u i d f c r the k r < ’ u p b HOJSO 0,bO and Bat+’.! 0850-
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