OXYMERCURATION OF A~-[~,~,~]-BICYCLOOCTENE~

D. D. I<. CIIIU AND GEORGE I; WRIGHT

It has now been shown that an earlier assignment of configuration in which 1,4-Tr-ethylene- A:-cyclohexenedicarbosylic acids and their derivatives were presumed to form with lnercllric salts 5-~-liydroxy-6-~-a~iioi~on~erc~~ri-l,4-~~-ethylei~ec~~clohexa~~eclic~~r~~oxylic acid clerivatives is illcorrect. Instead 5-~-hydrosy-6-~-a~~ionomcrc~~ri-l,4-~~-ethylenecsclo1iex~~~ieclicarboxylic acid derivatives are formed, similarly ~ r i t h the homologous 5-L-hydroxy-6-~-ai1ionornercuri-1,4- n1ethyle11ecyclohexane-2,3-dicarbox~~lic acid deri\.atives. 'l'his similarity is exemplified by comp~rable dipole nlomcnts. T h e exception is 5 - ~ - 1 ~ ~ d r o x ~ - ( ~ - ~ - c l ~ l o r o m c r c u r i - l , ~ - ~ ~ - 1 ~ ~ e t h ~ l - enecyclohesanc-2,3-~J-dici~rboxylic acid, ;,-lactonc, \vhich has a configuration opposite to all of the others of these series having boat-type cyclohexai~e ring col~forniations. The cscep- tion is attrib~ifecl to steric elfects.

The osymercuration of As-[2,2,21-13ic)-clooctene has bee11 reportecl and the stereo- chenlistry has been specifiecl ( I ) . I t has 1101~ been proved that this co~lligurational assign- nlent is incorrect. The error may be su~nnlarizecl in t e r~ns of t~vo for~ilulae reproducecl here, together with their identifying numbers, from page 719 of the previous report (1).

HgOAC G O H3 A C= 0 C- 0

COOMe COOH

ilccording to the statenlent of McXeely c t al. ( I ) , the structure of 2-J-carbo:llethoxy-5- ~-hydroxy-G-J-acetoxymerc~~~-i-l,4-~~-ethyle~~ec~~clohcsa~~e-3-~-carboxylic acid, 7-lactone (XXI), wras proved by its careful sap3nihcation to 5-J-hydrosy-av~hytEro-[G-J-liydrosy- 1nercuri-2-J-carbox~~]-1,~l-~~-ethyle1~ecyclol1exa1~e-:3-~-carboxylic acid, 7-lactone (XXIV), the ~nolec~llar weight of which was clcnlo~istrated cryoscopically in diphenylmercury. I t will be shown that McKeely ct al. clid not have XXIV a t all, but, instead, an hydroxy- nlerc~~rial diastereo~neric lvith XI11 (A = OH) which was conta~ni~lated with its chloro- mercurial. The content of this nlixture has now been shown by a critical study of the X-ray diffraction pattern (1) of what McXecly et al, thought to be XXIV.

D ~ ~ r i n g the present investigation it has been found that the salile dicarbox)ilic acid, y-lactone, may be obtained by oxy~llercuration of 1,4-ethylene-aj-c~~cloI1exe1~e-2,3-J~- dicarboxylic anhydride (I) as was fornlerly obtained from dimethyl 1,4-TT-etlzyIeue- ~5-c~~clohesene-2,~3-JJ-dicarbos~~late. The anh!~dride seelils to survive as such in aqueous media. However, a ~nercuric salt is formed by aclditioll of mercuric cllloride to the aqueous solution of the anhydride. Oxy~llercuration occurs very rapidly in this acidic system, and neutralization is required only to avoid an equilibriu~ll due to the reverse reaction, de- or;)~mercuration. By analozy with the oxy~nercuratio~l reactions of the 1,4-TT-methylene-

1ilTu~z11.~cri/)t rcc~il~cd Apri l 8 , 1061). Contrib1~tio7t fi.0~17 thc Dcpurt~,tel~t of C l ~ e ~ ~ r i s t r y , UT~-islersity of Toro7tto, Tormzto, 07ttari0, Canada.

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1426 CANADIAN JOURNAL OF CHEMISTRY. VOL. 37, 1959

A5-cyclohexene system (2) the reaction with the homologue, I , should be acid-catalyzed and should lead to a TJ (trans) configuration of the oxy and mercuri addends. Then the product is 5-J-liydroxy-6-T-chloroniercuri-l,4-T~-methylenecyclohexane-2,3-JJ-dicarbox- ylic acid, y-lacto~ie (11), unless lactonization has occurred with inversion.

A re-examination of the oxyniercuration of dimethyl 1,4-ethylene-A5-cyclohexene-2,3- JJ-dicarboxylate (111) shows that inversion during lactonization is very unliltely. The product is clearly dinlethyl 5-J-hydroxy-6-~-acetoxymercuri-1,4-~~-ethylenecyclohexane- 2,s-JJ-dicarboxylate (IV). However, this substance (m.p. 126-137') is quite unstable. Methanol is eliminated during crystallization and especially a t the melting point, where- upon resolidification occurs. The remainder after loss of methanol melts a t 188-18g0, and is 2-J-carbo~nethoxy -5-J- hyclroxy -6-T-acetoxymerc~~ri- 1,4-TT-ethylenecyclohexane-3 -J- carboxylic acid, y-lactone (V). This substance (reported previously (1) as having acetoxy- mercuri in the J configuration) is thus for~llecl under co~lditio~ls where inversion is unlikely.

coon +

COOMa

HCL : CHIN, 1 H20 CH,OH NaOH 1 A

Treatment of V with aqueous sodium clilosicle converts it to 2-J-carbomethoxy-5-J- h~-d1-osy-6-~-cl1lo1-omercur-i-1,4-~~-eth~~lc1~ecyclohex~~1ic-3-J-carboxylic acid, y-lactone (VI). This ester may be saponified by use of tlie stoicliiomctric quantity of 10% alkali to the acid identical with 11. 'Therefore, it u-ould seem that tlie anhydride ( I ) and the ester (111) were osymercurated to the same product unless some rearrangemelit occurred during tlie saponification.

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CHIU A N D WRIGHT: 0XYMERCUR.ATION 1427

In order to eliiniilate this possibility we have converted the acid (11) to the ester (VI) by treatment with diazomethane in diethyl ether - methanol. Although this reagent attacks oxymercurials vigorously, forilliilg chloroii~ethylmercuric chloride (3), the esterificatioil inay be acco~nplished in fair yield a t a reaction temperature of -SO0. The product is idelltical with the ester (VI), thus precluding rearrangement during the saponification of VI.

When a chloroinercurial such as I1 is treated with alkali the hydroxyrnercurial, 5-J- hydroxy-G-~-hydrox~ercuri-l,4-~~-ethylenecyclohexane-',,3-dicarboxylic acid, y-lactone (VII), is expected. In order to ensure absence of chloromercurial, silver oxide should be included, and acidification should be effected with carbonic acid. In these circumstances the product seems to be VII. Although the ele~ilental ailalyses show percentage errors of 2y0 for carbon and 13% for hydrogen they are still inuch closer to theoretical values than was reported by i\iIcNeely et al. ( I ) for their substance, which a t any rate colitaiiled the chloromercurial I1 accordiilg to its X-ray diffraction pattern.

Indeed the poor analysis is more to be espected of the free hydroxyrnercurial than of the 5-J-hydroxy-anhydro-[G-~-hydroxyinercuri-2-~-carboxy]-l,4-~~-ethyle1~ec~~clo1~exai1e- 3-J-carboxylic acid, y-lactone, which McNeely et al. thought the product t o be. Hydroxy- inercuri compounds are difficult to purify, partly because they react with carboil dioxide. Of course, the a~ialysis does not differentiate, a t best, between the structure VII and that of the diastereoineric 5-J-h~~droxy-anhydro-[G-~-11~drosymercuri-2-J-carboxy]-l,4-~~- ethylenecyclohexane-3-J-carboxylic acid predicated on the configurational assig~linent by n'IcNeely et ab. However, a potentioinetric titration in which only 1 equivalent of allcali is consumed vitiates the possibility of this alternative non-lactonic isomer. I11 any circun~stance there is no evidence for the anhydro structure ancl hence no evidence for the JJ addition reported previously.

Proof lor structure I1 is afforded by its high dipole inonlent (7.30, Table I) which compares with '7.19 Debye for 5-~-hydroxy-G-~-cl~loromerc~iri-l,4-ii~ethylenecyclohexane- 2,3-JJ-dicarboxylic acid, r-lactone, of proved structure (2). Since the moments of 1 ,4-~~-~iietl~ylenec~~clohexane-2,3-JJ-di~arbox5~lic ailhydride (4.8 D) (4), 1,4-rT-111ethyl- enecycloI1exane-2-J-3-~-dicarboxylic acid (2.19 D) , and 5-I-hydroxy-l,4-TT-methylene- c~~clohexai1e-2,3-JJ-dicarboxylic acid, y-lactone (4.85 D), also are closely coinparable with those of the higher l~oinologues (Table I) the structural ailalogy seems to be reasonable.

A similar comparison can be made between 5-J-hydroxy-6-T-chloromerc~iri-l,4-ethyl- enecyclohexane-2-T-3-J-clicarbosylic acicl, y-lactone (X, 6.91 D) , and the methyleile h o i ~ ~ o l o g ~ ~ e (1 = 6.40) (2). The synthesis of X has been effected by prolonged treatment ol VI with alltali ( I ) , ancl also by treatment of 1,4-~~-etl1~lene-A~-cyclohexene-2-J-3-~- dicarboxylic acicl ( IX) (5) with aqueous mercuric chloride. The postulated prototropic configurational shift of 2-cnrboxyl in I1 by action ol allcali is thus confirmed.

Unfortunately, for a col~lpletc de~nonstration of configurational differences by com- parison of dipole moi~ients we have becn unable to convert I1 to the diastercoineric 5-~-hydroxy-G-J-anioi~oi~~ei-~~~ri-1,4-~~-etl~~le~~ecJ~clol~esa~~e-2,3-JJ-clicarboxylic acid, y- lactone (XII I , A = CI). \\iIien I1 is treated with hydrazine hydrate a mixture of products is obtained, one of which is the origi~ial substance, 11. The other seeins to be either a hydrolyzate or a polyinorph of I1 since it may be coilvertecl to I1 when it is maintained for a few minutes a t a teiuperature belonr the melting point. Probably some of XI11 is a c t ~ ~ a l l y formed but we have been unable to isolate it.

In summary the [2,2,2]-bicyclo-2-octenes seem to oxymercurate lilce the hoinologous

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1428 CANADIAN JOURNAL O F CHEMISTRY. VOL. 37, 1959

TABLE I Dipole mornents o f 1,4-ff-ethylenecyclohexanes i n dioxane at 20'

RD Substance de/dw dV/dw PT calc. U , D

1,4-TT-Ethylenecyclohexane-2,3-LL-dicarboxylic anhydride

5 - ~ - t 1 ~ d r o x ~ - 1 , 4 - e t h ~ l e n e c ~ c l o h e s a n e - ~ - d i c a r b o x ~ l i c acid, ?-lactone ( V I I I )

5-~-~~dros~-6-~-chloron~ercuri-l,4-~~-eth~lenec~clohexane 2,3-LL-dicarboxylic acid, ?-lactone (11)

5-L-Hydrox y - 6 - ~ - c h l o r o m e r c u r i - l , 4 - e t h y l a n e - 2 - T-3-L-dicarboxylic acid, r- lacto~le ( X )

1,4-~~-~tl~~lenec~clohexane-2-~-3-~-dicarbox~lic acid ( I X )

Dimethyl 1,4-TT-ethylene-~~c~clohesene-2,3-~~-dicarbox- ylate (111)

2-~-~arbomethox~-5-~-h~drox~-6-f-chloromerc~1ri-l,4-f~- eth~lei~ecyclohesa~~e-3-J-carbox> lic acid, ?-lactone ( V I )

[2,2,1]-bicyclo-2-heptencs in a manner which is different from that occurl-ing xlrith cyclohesenes, cyclopentenes, a-terpineol, and the stilbt-nes. Reaction with the bicyclic c o m p o u ~ ~ d s seems to be acid-catalyzed. An over-all T L (trans) addition occurs in cont~-adistinctio~l to tha t observed xvitll the other allcenes. T h e fised boat c o n f o n ~ ~ a t i ~ ~ of the bicyclic alkenes may be involved in this abnol-mality.

One diiference in osymercuration between the bicj-cloheptene and bicycloijcte~ie series is apparent. Although 1,4-n~etl~yle1~e-4~-c~~clo11e~e1~e-2,~3-JJ-dicarboslic acid seems to oxylnercurate by an ionic mechanism, it nevertheless >-iclds a 2,:3,;J,(i-LLLL-diastereomer. Ey contrast I ,4-~~-etllylene-il"-cyclol1ese11e j-ields the 2,2,5-LLL-6-T-diastereomer. I t would seem that in one instance (XI) the mercuric ion is endo-co-ordinatecl, while in XI1 exo-co-orclination maintains. T h e difrerence is thus defined as a steric one.

+ 'kg/ ..O-. -0 CL- -0

c-0 oo \,,GO do

The authors are grateful to the National Research Council for financial aid.

EXPERIMENTAL"'

1 ,4-TT-Etlzylenecyclolzexane-2,J-LJ-dicnyZc d nlzyrlrjde A solution of 0.20 g (0.00112 mole) of 1,4-~~-etl~j~lene-A5-cyclohexene-2,3-~~-carbos~~lic

anhydride (6) (I) in 20 1111 of absolute ethanol was reduced within 25 minutes by hydrogen in presence of 0.018 g of platinum oxide containing 0.002 g of Dal-co. T h e product (0.20 g, 79y0, m.p. 17(j-l77O) n7as crystallized from 1:2 comnlercial hexane - acetone (30 nll/g), 111.p. 186-186.8'. X-Ray diffraction pattern was [lo] 5.38; [(j] 3.15, 5.02; [5 ] 3.61; [4] 7.02; [3] 4.60, 3.06, 2.66; [2] 2.96, 3.30, 3.17; [ l ] 3.04, 3.11, 6.29, 4.15, 3.43, 2.50, 2.19, 2.38, 1.99, 1.93.

" i ~ ~ e l t i ~ r g poilzts Izave bee72 cor~.octi:d agai7zst reliable standards ( C a ~ z . J . Tec1~)zol. 34, 89 (1956)). The X-ray diffraction patterns are recorded for CLI K, (Ni-jiltered) radiation i~z 1: at relative i~ztensities [I/I11.

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CHIU AND WRIGHT: OXYMERCURATION 1429

5-~-~Iyd~oxy-6-~-chlorome~curi-l,~-~~-ethylenecyclolzexanc-2~3-~~-dzcarboxylzc .-Icid, y-Lactone (11)

T o a solution of 34.0 g (0.191 mole) of I in 2840 1111 of water a t SO0 .was added 51.8 g (0.191 mole) of mercuric chloride with vigorous agitation. A precipitate appeared irn- mediately and a test for mercuric ion was almost negative. After 10 hours alliali was acldecl to a pH of 4.5. The systern tested negatively (20% allcali) for mercuric or mercurous ion. The precipitate was filtered, thrice \vashecl with clistilled \\-atel-, and vacuum-clriecl, 73 g (83%), 111.p. 197-1'30' (clecomp.). Cr)lstallization from acetone (4 ml/g) I-aised this melting point to 205-208.3° (decomp.); yo C , 27.7; Cjo H , 2.G7. The S-I-a), cliffractior~ pattern was obtained as follo\vs: [lo] 8.1!); [9] 6.13; [S] 4.16; [(i] 3.28; [4] 4.54; [3] 3.51, 5.19, 6.77; [2] 3.94, 5.57,2.'32,4.10; [ I ] 3.19, 3.14, 3.01,2.5(3, 2.74, 2.G4. When thesubstance was treated for 1 hour \vith con cent^-ated hydrochloric acicl the anhydride (I) was re- generated and identified b). mixtiire ~nelting point (1 47-148"). IVhel~ I1 was clissolved in 4 equivalents of allcali and bncli-titrated with hydrochloi-ic acid it neutralized 2 eq~~ivalents .

Dimethyl 5-~-11~drox~-6-~-chloronze~rcz~l.i-l ,~ . -~~-e thYle~zecyc lohexc~~ze- 2,3-LL-dicc~rboxyIl~tc (IV)

A suspension of 12 g (0.0335 mole) of dimethyl l,-l--~~-ethyle11ecycl011exane-2,3-J~- clicarboxylate (111) (7, S) (m.11. 70-70.5") in a solution of 17 g (0.0535 mole) of mercuric acetate in 120 ml of water was stirred for 5 hours. The filtered precipitate weighed 13.7 g (51yG) ailcl ~neltecl a t 1%5-l::iO, with evolution of m e t h a ~ ~ o l , demonstrated as the dini- trobenzoate. The melt then resolidifietl and remelted a t 153-155' (decomp.). The dif- fraction pattern of the filtered precipitate was [lo] 6.91; [9] 8.43,; [S] 4.09; [7] 5.34, 5.12; [6] 3.52; [5] 3.50; [4] 3.29; [3] 4.84, 2.75. Crystallization of this substance from any n~edium that we tried, but specifically from methanol (4 ml/g), converted it to 3,-L-carbomcthosy- 5-~-l1yclroxy-6-~-acetox~i~~e1-c~11-i-l,4-~~-ethylenec~clol1esane-3-J-cnrbosylic acid, y-lac- tone (V), 111.p. 188.5-ISI)', X-ray pattern [lo] 10.84; [Dl 4.56; [S] 6.44, G.GS; [5] 4.27; [-I] 3.57; [:3] 2.80, 3.75, 5.54. IVhe11 this product was treatecl with aclueous sodium chloride it ,.ielcled VI.

2-~-Cu~rbonzetlzo.~-y-cT-~-1zyd~roxy-6-~-c1~loromercz~r-f ,d.-TT-etl~~lenecyclohexane-3-L-cui'boxylic .Icid, y-Lactone (VI)

1Iethanol (SO0 ml) a t 0" Ivas freed from acidic substances by tl-eatment wit11 a solution containing 0.0064 mole of diazomethane in diethyl ether which hacl previously been driecl over potassium hydrosicle. Into this colorless methru~ol-ether mist~lre was dissolvecl 0.93 g (0.00216 mole) of 5-J-l~~~droxy-G-~-cl1loromerc~11-i-2-~-carbosy-l,4-~~-etl1ylene- cycloI1esane-3-~-carboxylic acid, y-lactone (11), a t 0'. This solution a t - SO0 was then mixed with a solution a t -SO0 of ethereal cliazolnethane (0.0174 mole). The system as allowed to warm to 20" during several hours. Then a gray precipitate was filtered off. The vacuum-evaporated filtrate left O.G5 g, 111.p. 182-184' (decomp.). Crystallization from acetone (4 ml/g) gave 0.12 g of unchanged I1 (mixturc melting point). Partial evaporation of the mother liquor gave 0.16 g (17%), m.p. 199-201'. This melting point was raisecl to 204-205" by crystallization from acetone; a mixture melting point with VI prepared by treatment of V with aqueous soclium cllloride nras not lowered although admixture with I1 lowered the melting point 20'.

5-L-ITydroxy-6-T-chloromercz~ri-1 ,./t-~~-etlzy1enecyclohexane-2-~-3-~-dicarboxylic 11 cid, y-Lactonr (X)

T o a solution of 0.64 g (0.00327 mole) of 1,4-~~-ethylene-45-cyclohesene-3,-~-3-~-dicar- boxylic acid (IX) (9) in 52 ml of water a t 70' was added 0.88 g (0.00327 mole) of mercuric

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1430 CANADIAN JOURNAL OF CHEMISTRY. VOL. 37, 1959

chloride. After it was cooled to room temperature the system was neutralized to pH 5.6-6.0 (2 ml 10% aqueous sodium hydroxide). A precipitate appeared which redissolved upon addition of 3.5 ml more of the alkali (pH 7.6, no mercuric oxide). After 20 hours the solution was acidified a t 0' by addition of 2.2 ml of 10% hydrochloric acid (pH 3.0). The precipitate, 0.81 g (58%), melted a t 194-200' (decomp.). Crystallization from acetone (10 ml/g) raised this melting point to 208.5-20g0, mixture melting point with I1 lowered to 194'. No depression was observed upon adnlixture with the substance obtained by McNeely et al. by 1-day saponification (3 equivalents alltali) of 2-j-carbomethoxy-5- j-hydroxy-6-~-acetoxymercuri-l,4-~~-ethylenecyclol~exane-3-j-carboxylic acid, y-lactone, and subsequent acidification with hydrochloric acid. The X-ray diffraction pattern was [lo] 4.79; [8] 8.79, 3.24; [7] 1.95; [GI 5.45; [5] 5.98; [4] 6.91; [3] 2.81; [2] 3.00, 2.30; [I.] 3.08, 2.70, 2.61. Calc. for C10H11C1Hg04: C, 27.8; H , 2.60. Found: C, 28.0; H, 2.67. Treatment of this product with concentrated hydrochloric acid yielded 1,4-TT-ethylene- a5-cyclohexene-2,3-Tj-dicarboxylic acid, m.p. 210-211'.

5-j-Hydroxy-6-~-hydroxymercuri-1,~-ethylenecyclohexane-2,S-~~-dicarboxylic Acid, y-Lactone (VII)

A solution of 3.40 g (0.0073 mole) of 2-j-carbomethoxy-5-j-hydroxy-6-~-acetoxy- mercuri-l,4-~~-ethylenecyclohexane-3-j-carboxylic acid, y-lactone (V), in 29 nll of 1% aqueous sodium hydroxide was let stand for 34 hours. precipitate weighed 1.5 g (53%), m.p. 222-226' (decomp.). This melting point was raised to 239-241" by washing with chloroform, methanol, and diethyl ether. Further purification was effected by solu- tion in ly0 aqueous alkali (pH 10) followed by acidification by means of gaseous carbon dioxide. The precipitate, washed with acetone, melted a t 244-244.5". Calc. for CloHlz05Hg: C, 29.1; H , 2.93. Found: C, 28.5; H , 3.17. The X-ray diffraction pattern was found to be [lo] 8.72; [9] 6.25; [8] 3.33; [6] 4.27; [5] 2.67; [4] 3.05; [3] 3.65, 4.50, 1.97; [2] 3.92, 3.44, 3.25; [I] 2.03, 7.85, 6.93, 5.55. The same diffraction pattern was obtained for the product obtained when I1 (0.65 g, 0.0015 mole) in 2.45 in1 of 5% aqueous alkali containing 0.46 g (0.002 mole) of silver oxide Lvas filtered and then acidified by means of carbon dioxide gas. A comparison of the diffraction pattern with that reported by McNeely et al. shows that their coinpound must have been a mixture of VII and 11.

Treatment of 5-j-FIydroxy-6-T-chloromercuri-1 ,4-TT-ethylenecyclohexane-2,s-jj-dicarboxYlic Acid, y-Lactone (11) , with FIydrazine Hydrate

To an alkaline solution of 5.0 g (0.0116 mole) of I1 in 46.5 ml (0.058 mole) of 5% aqueous sodium hydroxide was added 0.6 1111 (0.012 mole) of hydrazine hydrate. After 1 day the filtered system was acidified (pH 3) by use of hydrochloric acid a t 0'. Slow precipitation yielded 3.0 g, 1n.p. 181-183', which upon crystallization from inethanol (10 ml/g) melted a t 208-208.5', mixture melting point with I1 not lowered (loyo). The filtrate upon evaporation leit a residue which was crystallized from methanol (1 ml/g), 1n.p. 207.5-208' (4%). Although this substance seemed to be different from I1 in respect of its solubility in illethanol and also in respect of its X-ray diffraction pattern: [lo] 6.41; [8] 8.84; [5] 5.12, 4.19; [4] 3.17; [3] 3.77, 3.46, 4.31; [2] 3.90, 3.26; [I] 4.56, 4.49, 3.39 (and despite the fact that a mixture melting point with I1 was got depressed), it was evidently configurationally the same as 11. Thus when it was heated to 195' for 5 minutes its X-ray diffraction pattern becanle identical with 11. Moreover, i t would not form an anl~yclrornerc~~rial when it was converted to the l~ydroxymercurial by treatment with silver oxide and alkali. I t inay be a polyillorph or, alternatively, the 11011-lactonic hydroxy acid.

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CHIU A N D WRIGHT: OXYMERCURATION 1431

5-~-Hydroxy-1,~-~~-ethylenecyclokexane-2,3-~~-dicarboxylic Acid, y-Lactone (VIII) The substance was prepared by the recorded method (5) by heating 2.0 g (0.0112

mole) of 1,4-TT-ethylenecyclohexane-2,3-11-dicarboxylic anhydride (I) in 22 g of 50% (w/w) sulphuric acid for 5 hours a t 90'. After neutralization with sodium bicarbonate (pH 3) the precipitate was dissolved by extraction with chloroform. Evaporation of this solvent left 1.15 g (52%), m.p. 168-178'. Two crystallizations from acetone raised this melting point to 108-198.5'. The X-ray diffraction pattern was [lo] 5.82; [9] 5.60; [GI 6.72; [5] 4.29; [4] 3.85, 2.90; [3] 4.94, 4.60; [2] 5.15, 2.98, 4.07; [I] 2.76, 3.18, 3.33. Potentio- metric titration showed that 1 equivalent of alkali neutralized this substance. Calc. for C10H4012: C, 61.2; H , 6.16. Found: C, 61.3; H , 6.11.

1,4-~~-Ethylene-A5-cyclohexene-2,3-~~-dica~boxylic Acid (IX) T o a solution of 9.56 g (0.0625 mole) of fuinaryl chloride in 55 ml of dry diethyl ether

a t -10' was gradually added a solution of 10 g (0.125 mole) of 1,3-cyclohexadiene in 55 rnl of dry ether a t - 10'. After 1 hour a t this temperature the system was maintained a t 25' for 12 hours and then was shaken with 20 ml of 10% aqueous sodium hydroxide for 4 hours. Acidification of the aqueous layer yielded 8.40 g (68%), n1.p. 199-204". Crystallization from commercial hexane - acetone (1 :5, 5 ml/g) raised the melting point to 210-211". Calc. for C10H1204: C, 61.3; H , 6.16. Found: C, 61.0; H , 6.05.

I ,4-Ethylenecyclohexane-2,3-~~-dicarboxylic Acid A solution of 0.20 g (0.002 mole) of 1,4-~~-ethylene-A5-cyclohexene-2,3-~~-dicarboxylic

acid in 20 n ~ l of absolute ethanol plus 0.02 g of platinum oxide with 0.002 g of Darco was reduced within 35 minutes by 26.7 ml of hydrogen. After filtration of the catalyst the solution was evaporated, leaving 0.20 g (99%), m.p. 234-235'. After crystallization from co~nnlercial hexane - acetone (1 :5, 60 inl/g) it melted a t 235.0-235.5'.

REFERENCES

1. ~ICNEELY, I<. H., RODGMAN, A., and WRIGHT, G. F. J. Org. Chem. 20, 714 (1955). 2. ABERCROMBIE, M. J., BHAI~UCHA, I<. R., RODGMAN, H., and WRIGHT, G. F. Can. J . Chem. 37,

1328 (1959). 3. SAWATZKY, H. and WRIGHT, G. F . Can. J . Chem. 36, 1555 (1958). 4. I<WART, H. and I~APLAN, L. J. Am. Chem. Soc. 75,3356 (1953). 5. ALDER, I<. and STEIN, G. Ann. 514, 1 (1934). 6. DIELS, 0. and ALDER, K. Ann. 460, 98 (1928). 7. BODE, H. Ber. 70, 1167 (1937). 8. WEST, T. F. J. Chem. Soc. 140 (1941). 9. ALDER, I<. and STEIK, G. Ann. 514, 197 (1934).

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