Jan. 5, 1959
237
COMMUNICATIONS TO THE EDITOR
species CuAf and B-. I t can be formed by a com- dimethylcyclohexene was converted into 1,2-dibination of Cu(Z-Asp)+ and d-Asp- or from CU methylcyclohexanol, b.p. 94' a t 40 mm., nBn 1.4639, m.p. 24-25'.' (d-Asp) + and I-Asp-. Statistical arguments give In each case the reaction products were examined [ CU(I-Asp)( d - A ~ p ) ] = 1 [ CU,I-Asp)(d-Asp)] Ka = (5) by gas chromatography (glycerol column for 22 [ CU(l-Asp)1' [&ASP-1 [ CUA+] [B-1 riiethylcyclohexanol, Carbowax column for others). ( 0 , (4) and (5) give In each of the four cases, the crude reaction product Kz = 2K1 1 + 5Ka 1 or Ks = 2 Kz - & I ) (6) was shown to contain a t least 97-98y0 of the isomer We have found K1 and K Z to be 2.82 X lo6 and indicated, with a maximum of 2-3% of the other 1.74 X lo6, respectively. Equation (6) thus isomer present. Not only does this hydration occur cis, but it gives a value of 7 X 1oj for Kt, which is the formation constant of the mixed complex. The non- takes place predominantly from the less hindered mixed complex is thus favored as compared to the side of a double bond. Thus, norbornene is converted to exo-norborneol, m.p. 125-126', 3,5-dimixed one. Equation (6) further indicates that if the mixed nitrobenzoate, m.p. 104-105'.* a-Pinene yields an alcohol, m.p. 35-38'. On complex did not form a t all the value of Kz would basis of proposed rules, this should be isopinocambe one-half of K1. Also, if no preferential formation of non-mixed complexes existed Kz would equal phenol.9 Examination is continuing. The following procedure is typical. Excess diK1. And, finally, in the case that the mixed com- borane (from 3.8 g. of sodium borohydride in diplexes were favored K.2 would be greater than K1. The experimental details of this and the results glyme and boron trifluoride etheratelo was passed of further experiments will be reported in a later into 16.4 g., 0.2 mole, of 1-methylcyclopentene, b.p. 74-75' a t 744 mm., n% 1.4313, in 60 ml. of publication. tetrahydrofuran a t 0' over a period of two hours. DEPARTMENT OF CHEMISTRY WILLIAM E. BENNETT After 1 hour a t room temperature, several small STATEUNIVERSITY OF IOWA pieces of ice were added to hydrolyze the excess IOWACITY,IOWA RECEIVED NOVEMBER 1, 1958 diborane. The reaction mixture was immersed in an ice-bath, 45 ml. of 3 M sodium hydroxide was added,. and then 25 ml. of 3Oy0hydrogen peroxide, A STEREOSPECIFIC CIS HYDRATION OF THE DOUBLE BOND IN CYCLIC DERIVATIVES over a period of 1 hour. After 1 hour a t room temperature, the upper layer was separated, the aqueSir: The hydroboration of olefins, followed by oxida- ous phase was extracted with ether, and the comtion of the product with hydrogen peroxide, pro- bined extracts were dried. Gas chromatographic vides a highly convenient procedure for the anti- examination of the organic phase showed the presMarkownikoff hydration of double In ence of 9S% tians-1-methylcyclopentanol,with a applying this reaction to cyclic olefins we have ob- small neighboring peak of 2% which may be the served that the reaction proceeds stereospecifically cis derivative. The product was isolated by fracto add the elements of water, hydrogen and hy- tionation in an efficient column. (7) G. Chiurdoglu, Bull. Soc. chim. Belg , 47, 241 (1938). reports droxyl, in a cis configuration to the double bond. cis-1,2-dimethylcyclobexaool,b.p. 82.8O at 25 mm., n*oHe 1.4649, In this way 1-methylcyclopentene has been con- m.p. 23 2'; trans-, b.p. 74' at 25 mm., nmHe 1.4614, m.p. 13.2". verted in a yield of 85% to trans-2-methylcyclo(8) K . Alder and H. F. Rickert, A n n . , 643, 1 (1939), report czopentanol, b.p. 152-153O at 745 mm., n% 1.4488, oorboroeol m p. 12&12Q0, 3.5-dinitrobeozoate, m p. 105O; endo-, m.p. of 3,5-dinitrobenzoate, 86-87°.3 Similarly, 1- m.p. 149-150°, 3,5-dinitrobeozoate, m.p. 123". (9) H. Schmidt, B e y . , 77, 544 (1944). methylcyclohexene has been converted in a yield of (10) H. C. Brown and P. A. Tieroey, THISJOURNAL, 80, 1552 90% to trans-2-methylcyc1ohexano1, b.p. 166.5' a t (1958). 745 mm., n 2 0 D 1.4614, m.p. of 3,5-dinitrobenzoate, RICHARD B . WETHERILL LABORATORY 113-115°.4~5 C. BROWN PURDUEUNIVERSITY HERBERT INDIANA GEORGE ZWEIFEL I n these cases the cis hydration results in the for- LAFAYETTE, RECEIVED DECEMBER 4, 1958 mation of the thermodynamically more stable isomer Consequently, the hydroboration of 1,2dimethylcyclopentene and 1,2-dimethylcyclohexene THE SYNTHESIS OF DIPHENYLCYCLOPROPENONE was examined. I n these cases, cis hydration would Sir : form the less stable isomers. 1,2-DimethylcycloTo date no stable compound is known containing pentene yielded cis-l,2-dimethylcyclopentanol,b.p. a carbonyl group in a three-membered ring. For 66-68' a t 21 mm., m.p. 23-24°.8 Similarly, 1,2- this reason cyclopropenones are of special interest, (1) H. C. Brown and B . C. Subba Rao, THISJOURNAL, 1 8 , 5694 for although the greater expected strain in the un(1956). saturated cyclic ketones would seem likely to (2) H. C. Brown and B. C. Subba Rao, J . Org. Chem., 2 2 , 1135 make them even less stable than the saturated (1957). (3) W. Huckel and H. D. Sauerland, B n . , 87, 1003 (1954), report compounds, cyclopropenones should be aromatic b p. 149-151.2° at 735 mm., nmo 1.4501, m.p. of 3,5-dinitrobeozoate, (being the analogs in the two-r-electron system of 88'. tropone in the six).l So, the preparation of a cyclo(4) M. G. Vavon, A. Perlio and M. A. Horeau, Bull. Sac. chim.
(
France, 61, 644 (1932). report b.p. 165" at 750 mm. (5) L. M. Jackman, A. K. Macbeth and I. A. Mills, J . Chcm. Soc., 1717 (1949). report n% 1.4616, m.p. of 3,5-dioitrobenzoate, 117'. (6) L. W. Trevoy and W. G. Brown, THIS JOURNAL, 71, 1675 (1949). report cir-1,2-dimethylcyclopentaool, b.p. 62O at 17 mm., m.p. 24-26'; trans-, b.p. 51' at 17 mm., m.p. 2425O.
(1) Our calculations, using the L.C.A.O. method with all the usual approximations, except that on is taken as oc 8 , show that cyclopropeoooe should have a vertical resonance energy of 1.48, and that this value is esseotially the same for diphenylcyclopropeoone if one corrects for the stilbene system. I t is thus possible that our observed stability will also be found for the simpler cyclopropenooe.
+
1-01, s1
COMMUNICATIONS TO THE EDITOR
24s
propenone seemed attractive as additional demonstration of the validity of such analogies2 1Ye considered that the interesting reaction between a carbene and a ketene acetal to furnish a cyclopropanone ketal, which has been described by M ~ E l v a i n ,could ~ be adapted to this purpose. Since diphenylcyclopropenes are formed readily by base-catalyzed eliminations from appropriately substituted cyclopropanes,4 we selected the reaction of phenyl ketene dimethyl acetalj with benzal chloride and potassium f-butoxide. The expected product was the dimethyl ketal of diphenylcyclopropenone (I), but we find that with neutral aqueous processing, this hydrolyzes,fi the only crystalline product isolated being (I) itself, m.p. 121-121.3° from cyclohexane-benzene. Calcd. for C15H100: C, 87.35; H, 4.89; mol. wt., 206. Found: C, 87.71, 87.52; H, 4.87, 4.93; mol. wt. (cryoscopic, CBrJ, 10S. In the ultraviolet the compound shows maxima (CH3CW) a t 297 (4.3), 282 (4.25), 226 (4.1:3), and 220 (4.16) nip, with a shoulder a t 310 m p (4.04). Its infrared spectrum (in CCl,) is in striking agreement with the proposed structure, with weak absorption a t 3.1 p (aromatic C-H), a strong band a t 5.40 1.1 (C=O stretching), and rather strong bands a t 6.1 (conjugated C=C), 6.7 and 6.9 (benzene ring) and 7.45 1(C=O bending). The only other major absorptions are two bands (in CS?) a t 13.0 and 14.5 p (monosubstituted benzene). Ahfurther evidence, we have studied thermal decomposition. IVhile the melting a t 121" is reversible, heating to 130-140" causes evolution of a gas which we have identified as carbon monoxide.7 From the residue one can isolate, in 20% yield, diphenylacetylene identical with authentic material. This mode of decomposition is not surprising for (I), but the relatively high temperature a t which i t occurs, and the fact that (I) can be isolated from hydroxylic medium, show that the cyclopropenone system must have strong resonance stabilization indeed to compensate for its high angle strain. C aHa-,=7-
C r Hi
L/
I
O
(2) T h e stable s-triiihenylcycloprol)enyl cation, reported by K . Breslow a n d Chin Yuan. ' h i s J O U R K A T . , in press, furnishes a similar analogy to tropylium ion. (3) S. M. hIcElvain and P. I,, U'eyna, I m e r . Chem. Soc. hleeting Abstracts, Chicago, Sept., 1958, p. 1-P. (4) S. F. Darling and E. W. Spanagel, ?'HIS J O U R N A L , 63, 1117 (1931). (6) S.M. AlcElvain and J. T. Venerable, ibid., 7 2 , 1661 (1950). (6) T h e ready hydrolysis must occur because t h e intermediate in t h e reaction is a derivative of a cyclopropenyl cation. (7) E. G. Voiret and A. L. Bonaimd. A n n . chim. anal., 2 6 , 11 (1914).
DEPARTMENT OF CHEMISTRY ROKALD BRESLOK COLUMBIA UXIVERSITY ROE~ERT HAYNIE SEW YORK27, S.Y . JOSEPH MIRRA RECEIVED A-OVEMBER 29, 1958 RESOLUTION OF A NON-HETEROCYCLIC
_ . QUATERNARY PHOSPHONIUM IODIDE Szr: We wish to report the first completely successful resolution of a quaternary phosphonium salt in which the phosphorus atom is not a member of a heterocyclic ring. Both enantiomorphs of methyl-
ethylphenylbenzylphosphonium iodide have been obtained by way of the d ( -)-dibenzoylhydrogentartrate and I ( +)-dibenzoylhydrogentartrate salts. The iodides were found to be optically stable even in solution, and this fact disposes of the suggestion that the numerous previous failures* to resolve asymmetric phosphonium salts of the type RR1RpR3P+,Xwere attributable to their rapid racemization in solution by a dissociation-equilibrium mechanism? K R I R ~ R ~',XP
RK1R.P t RIS
The only previous successful resolutions of phosphonium salts have been with compounds in which the phosphorus atom was a member of a heterocyclic ring. Holliman and Mann, proceeding through the d-camphorsulfonate, were on one occasion able to isolate pure crystalline dextrorotatory 2-phenyl-2-p-hydroxyphenyl- 1,2,3,4-tetrahydroisophosphinoliniuni bromide, but later they were unable to repeat their initial success. Recently, Hart and Mann4 accomplished the resolution of Pspiro - bis - 1,2,3,4 - tetrahydrophosphinoliniuni iodide into its dextro arid levo isomers aia the d,lphosphonium I-menthoxyacetate. Racemic methylethylphenylbenzylphosphonium iodide, m.p. 166-167", was prepared by the method of Meisenheimer, ef aZ.lf,5 Treatment with silver d ( - )-dibenzoylhydrogentartrate,6 in methanol gave the phosphonium d ( - ) -dibenzoylhydrogentartrate, which was crystallized several times from n-propyl alcohol. There was obtained a diastereoisomer of m.p. 142--14.3O, [a]% - 54.0" (c 1.281 in methanol). Anal. Calcd. for C34H3308P:C, 68.00; H, 5.67; P,
