NOTES 3445

sans grandes difficult&; il aurait toutefois kt6 difficile de p r a i r e avec certitude le cours que prendraient ces rkactions.

REMERCIEMENTS

Les auteurs remercient le Conseil National de Recherches et Bristol Laboratories pour l'aide financihre apportke sous forine d'octrois de recherches.

1. J. C. RICHER e t C. LAMARRE. Can. J. Chem. 43, 715 (1965). 2. 0. F ISHE~~ et W. I ~ E R N . J. Prakt. Che~ii. 94, 34 (1916). 3. F. BELL et J . R. GAR~IIE. J. Chern. Soc. 4258 (1961). 4. P. R. \\-ELLS et P. G. E. ALCORN. Australian J. Chem. 16, 1108 (1063). 5. R. SCHOOI.L, C. SEER, R. \YEIZENBOCH et A. ERTL. Monatsh. 42, 407 (1921). 6. I. S. IOAFFE et N. M. FEDO~~O\~A. J . Gen. Chcm. USSR Engl. Transl. 6, 1079 (1936). 7. R. ADAMS, PI. \V. MILLER, 5;. C. MCGREW et A. W. ANDERSON. J . A I ~ . Chern. Soc. 64, 1795 (1942). 8. F. BELL, J . A. GIBSON et R. D. WILSON. J. Chen~. Soc. 2335 (1956). 9. R. D. \\:ILSOX. Tetrahedron, 3, 236 (1958).

10. R. G. COOKE, B. L. JOHNSON et \Y. I<. OWEN. Australian J . Chem. 13, 256 (1960). 11. R. D. \&'ILSON. Tetrahedron, 11, 263 (1960). 12. M. MESARD, L. ~/ I ITCHELL, J. KOAILOSSY, A. WRIGLEY et F. L. CHUBB. Can. J. Cheni. 39, 729 (1961). 13. R. D. \\:ILSON. J . Chern. Soc. 3304 (1965). 14. \V. M. STANLEY et I<. ADANS. J. Am. Chem. Soc. 52, 1200 (1930).

CONFIGURATION AND CONFORMATION OF 2,3-DICHLORO-1,4-DIOXANE, M.P. 52"

Considerable confusion has arisen recently concerning the configuration and conforrna- tion of the higher melting (52") isomer, A, of 2,s-dichloro-l,4-dioxane. The compound was originally assigned the cis configuration by Suinillerbell and Lunk (1). This conclusion was arrived a t after the compound was found to be less stable than the second isomer, B (m.p. 31°), which was proved to be trans by the deinonstration that i t was capable of kinetic resolution into one enantioiner. Subsequently, Altona and co-workers verified the assigninent of the trans configuration to isoiller B and established the configuration to be diaxial (2) through X-ray analysis, infrared spectra, and dipole moment studies. The dipole inornent of isomer A \\.as in agreeinent with the cis configuration. More recently, Caspi et al. (3) examined the nuclear magnetic resonance spectrum of isoiner A and observed a single peak a t 4.3 T for the tertiary protons, and an AzBz pattern for the hydrogens a t the 5 and 6 positions. From the appearance of an AzBz pattern they con- cluded that the dioxane ring possessed a rigid conformation. The single peak a t 4.3 7 then led them to deduce the conforination to be an eclipsed boat, with oxygen occupying the "bowsprit" positions. Such conclusions were entirely unwarranted. A pair of rapidly interconverting chair conforn~ations \vould also give rise to the observed spectrum. Unfortunately their findings were accepted in part by Chen and Le F h r e (4), who measured the dipole n~oments, polarization, and polarizability of the two isomeric 2,3-dichloro- and 2,3-diphenyl-l,4-dioxanes. Because they accepted Caspi's conclusion that isomer A possessed a rigid conformation, they were forced, by elimination, to assign the trans diequatorial conforillation to it. If assignmeilt of either the cis boat conformation or the trans diequatorial conformation \\-ere correct, then some of the fundamental

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3446 CANADIAN JOURNAL OF CHEMISTRY. VOL. 43. 1965

energetic concepts in conformational analysis would be invalidated. For this reason we have undertaken a rigorous analysis of the AzBz absorption pattern of isomer A in an attempt to clarify the existing discrepancies.

The nuclear magnetic resonance spectrum of a 15% solution (w/v) of isomer A in chloroform was measured. Figure 1A shows the high-field half of the AzBz absorption.

FIG. 1. High-field half of the A2B2 absorption of 2,3-dichloro-1,4-dioxane in chloroform (A) and in benzene (B). The spectra calculated from the parameters in the text are shown in C, for chloroform, and in D, for benzene. The points designated 0 refer to the midpoints of the A2Bz patterns.

The analysis of this pattern was achieved in the standard manner as recently described by Abraham (5). Assignment of the lines to specific transitions was relatively straight- forward, since the spectrum closely resembled tha t solved by Abraham for 2-methyl- 1,3-dioxolane. The parameters K, L, M , N, and 6 were adjusted until agreement between calculated and observed line positions was obtained to within 0.15 c.p.s. (Fig. 1C). T o check the parameters, we measured the spectrum of a 50% solution (w/v) of isomer A in benzene, and again obtained agreement to within 0.15 c.p.s. between the observed line positions and those calculated from the same values of K , L, M, and N and a n adjusted 6. Figure 1 shows the agreement between the observed and calculated spectra in chloroform and in benzene. From the parameters the following coupling constants were found: JA = J B = 3.1 c.P.s.; J = -12.25 c.P.s.; J' = 6.45 c.P.s.; 6cHc,, = 22.95 c.P.s.; 6,,,,,,, = 31.1 c.p.s.; where the coupling constants represent the interactions shown below.

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SOTES 3447

In Fig. 2 all reasonable configurations and conformations for isoiner A are shown. If the compound were cis and in a rigid chair conformation, we would expect two signals for the protons labelled X and Y in case I . We would also expect an ABCD pattern for the four hydrogens on carbons 5 and 6. Since neither expectation is fulfilled, we can eliminate structure I.

I C I S r i g i d c h o i r

H c H Y d$C1 "D c I

II T R A N S r i g i d c h o i r

Ill T R A N S i n t e r c o n v e r t i n g c h a i r s

IV C I S i n t e r c o n v e r t i n g c h a i r s

FIG. 3. The four considered representations for 2,3-dichloro-l,4-dioxane, n1.p. 52".

I f the compound is trans and has its chlorines in either the rigid diaxial or the rigid diequatorial conformation, we would expect an A2B2 absorption pattern for the 5 and 6 hydrogens. But in this A2B2 system, JA and JB should have widely different magnitudes, one typical of diaxial protons and the other typical of diequatorial protons. Since we found J.., = JB, this case is eliminated.

Should the compound possess the trans configuration and be rapidly interconverting between the diaxial and diequatorial conformations, there would lilcely be an unequal population of the two conformations. In this case JA would not equal JB, and so this possibilitj~ is eliminated. If the two conformations were of equal stability, \ye would observe coupling constants which are an average of the two coiltributing structures. This would require JA = JB = (J6,1 + J180)/2 (observed value 3.1 C.P.S.), J = J,,,, and J' = J G ~ (observed value G.45 c.p.s.), \\illere the subscripts represent 4, the dihedral angle between

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3448 CANADIAN JOURNAL OF CHEMISTRY. VOL. 43, 1965

the interacting protons. The experimental results would then require that J 6 0 be more than twice as large as (J60 -/- J180)/2. This completely revokes the Karplus relation between J,, and +. Although the relation is far from quantitative, i t is completely reliable in predicting J 1 8 0 > J 6 0 (6). Thus I11 is eliminated.

In case IV the observed parameters compare favorably with those encountered in similar six-membered rings. The best model for comparison is the 1,3-dioxane system (Fig. 3), whose analysis gave the following parameters (7): J 6 0 = JAB, = 3.8 c.p.s.;

FIG. 3. The chair for111 of l,3-dioxane showing the four protons whose coupling constants have beell determined (7).

(J60 -/- Jla0)/2 = (JArB' -/- JA~)/:! = 6.7 C.P.S.; J A A f = -11.0 C.P.S. (a better model in this case might be CHS-CH-CH20H, in which J,,, = - 11.9 C.P.S. (8)). In 1,4-dioxane,

I OH

J 6 0 = 2.7 c.p.s. and (J60 4- Jla0)/2 = 6.1 C.P.S. (9). In view of the good agreement between the coupling constants for isomer A and those

predicted from the cis configuration for interconverting chairs, any consideration of the relatively high energy boat conformations is entirely unwarranted. We therefore conclude that the 52" isomer of 2,3-dichloro-l,4-dioxane has the cis configuration and undergoes rapid chair-chair interconversion a t room temperature. This is, of course, the original conclusion of Summerbell and Lunk, and is entirely compatible with all other existing physical data.

We are currently examining the isomeric 2,3-diphenyl-l,4-dioxanes, whose original structural assignments have also been questioned by Le F h r e and Chen.

NOTE ADDED IN PROOF: We have learned of an independent investigation by D. Jung, whose results and conclusions are in complete agreement with our own. Dr. Jung's paper will appear in Chemische Berichte.

EXPERIMENTAL d,5-Dichloro-1,4-dioxane

This conlpound was prepared by the procedure of Summerbell and Lunk (I), and after several recrystal- lizations from pentane-ether melted from 52 to 53 "C.

The nuclear magnetic resonance spectra were recorded on a Varian V-4302 60 Mc spectrometer, and the experimental line positions were obtained from the average of a t least six traces, with the standard deviation in all line positions being less than 0.15 c.p.s. Calculations of line positions were carried out on our IBM 1620 computer, using the Frequint IVA program, which was kindly provided by Professor P. C. Lauterbur.

ACKNOWLEDGMENT

This research was supported by a grant from the National Research Council of Canada.

1. R. I<. SUMMERBELL and H. E. LUNK. J. Am. Chem. Soc. 79,4802 (1057). 2. C. ALTONA, C. ROMERS, and E. HAVINGA. Tetrahedron Letters, 10, 16 (1050). 3. E. C a s ~ r , T . A. WITTSTRUCR, and D. M. PIATAK. J. Org. Chem. 27, 3183 (1062). 4. C. Y. CHEN and R. J. LE F ~ V R E . J. Chem. Soc. 558 (1065). 5. R. J. ABRAHASI. J. Chem. Soc. 256 (1065).

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6. M. I~ARFLUS. J. Am. Chem. Soc. 85, 2870 (1963). 7. C. BARBIER, J. DEL~IAU, and J . RANFT. Tetrahedron Letters, 45, 3330 (1964). 8. Varian Nuclear Magnetic Resollance Spectra Catalog. 1962. p. 45. 0. W. SIIEPPARD and J. TURNER. Proc. Roy. Soc. London, Ser. A, 252, 206 (1961).

REACTION OF ARALKYL KETONE PHENYLHYDRAZONES WITH CARBON MONOXIDE; THERMAL INDOLIZATION OF ARALKYL KETONE PHENYLHYDRAZONES

This note summarizes the principal results obtained when aralliyl ketone phenyl- hydrazones were caused to react with carbon monoxide using dicobalt octacarbonyl as a catalyst. In earlier work (1, 2) i t was sho\vn that aromatic ketone and aldehyde phenyl- hydrazones containing a C=N group which was conjugated to an aromatic ring cyclized with carbon n~onoxide to yield N-substituted phthalimidines. Under similar conditions, aralliyl ketone phenylhydrazones might be expected to undergo ring closure to afford heterocyclic substances having six or more members.

Reaction of desoxybenzoin phenylhydrazone with carbon monoxide a t 3 500 p.s.i. and a temperature of 235" for 3 h in the presence of preformed dicobalt octacarbonyl afforded mainly 2,3-diphenylindole (I), 3-benzylphthalimidine-N-carboxyanilide (11), 3-benzyl-2- phenylphthalimidine (111), and synz-diphenylurea (IV) in 20, 22, 11, and 27% yields,

respectively. Separation of these components was achieved by thin-layer chromatography on silica gel G using benzene-methanol (95:5 v:v) as developer or by alumina column chromatography.

Compounds I and IV were identified by direct comparison with authentic samples of 2,3-diphenylindole and sym-diphenylurea, respectively. Reaction of 3-benzylphthaliinidine with phenylisocyanate afforded an authentic sample of 3-benzylphthalimidine-N-carboxy- anilide which was identical (melting point and infrared spectrum) with conlpound 11. Condensation of benzylidene phthalide with aniline afforded 3-benzylidene-2-phenyl- phthaliinidine. Reduction of the latter substance with 1 mole of hydrogen over platinu~n

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