1444 J. Org. Chem., Vol. 40, No. 10,1975
Pasto and Scheidt
Registry No.-1, 886-38-4;2a, 504-29-0;2b, 1603-40-3;2c, 695-34-1;2d, 1603-41-4;2e, 1624-81-3; 3a, 54531-99-6; 3b, 5453200-2;3c, 54532-01-3;3d, 54532-02-4; 3e, 54532-03-5;4a, 54532-045a, 54532-08-0; 6;4b, 54532-05-7;4c, 54532-06-8;4d, 54532-07-9; 5b, 54532-09-1;5c, 54532-10-4; 5d, 54532-11-5;6a, 54531-96-3; 6b, 54531-98-5; 6 ~ 54531-97-4; , 6d, 54575-95-0; 7, 5439-14-5; 8, 2402500-1;ethyl acrylate, 140-88-5.
References and Notes (1) For a recent review of cyciopropenone chemistry, see K. T. Potts and J. S. Baum, Chem. Rev., 74, 189 (1974). (2) E. V. Dehmlow, TetrahedronLett., 5177 (1967). (3) J. Ciabattoni, P. J. Kocienski, and G. Melloni, Tetrahedron Lett., 1883 (1969). (4) F. Toda, T. Mitote, and K. Akagi, Bull. Chem. SOC.Jpn., 42 1777 (1969). (5) J. W. Lown and K. Matsumoto, Can. J. Chem., 49, 1165 (1971). (6) A. Hassner and A. Kascheres, J. Org. Chem., 37,2328 (1972).
(7) N. Enomoto and M. Kondo, Bull. Chem. SOC.Jpn., 45, 2665 (1972). (8) The cis-2,3-diphenylacrylic acid shows the olefinic absorption at 6 7.97, while the olefinic absorption of the trans-2,3-diphenylacrylic acid appears at 6 6.97. (9) For a recent review of the steric course in concerted olefin-forming eliminations, see J. Sicher, Angew. Chem., lnt. Ed. Engl., 11, 200 (1972). (IO) R. Adams and I. Pachter, J. Am. Chem. Soc., 74, 5491 (1952). (1 1) R. Adams and I. Pachter. J. Am. Chem. Soc., 74,4906 (1952). (12) M. Krishnan. Proc. lndian Acad. Sci., Sect. A, 49, 31 (1959). (13) R. A. Abramovitch and D. L. Struble, Tetrahedron, 24, 357 (1968). (14) T. L. Gilchrist, C. J. Harris, and C. W. Rees, J. Chem. Soc., Chem. Commvn., 481 (1974). (15) All melting points were obtained on a Mettler FP 52 melting point apparatus and are uncorrected. Infrared spectra were taken on a PerkinElmer 337 spectrophotometer. NMR spectra were recorded with a Varian T-60 spectrometer using tetramethylsilane as an internal standard. The elemental analyses were performed by Alfred Bernhardt Laboratories, West Germany.
X-Ray and Dynamic Nuclear Magnetic Resonance Structural Study of a 1,2-Bis Exocyclic Diene. An Example of a Severely Skewed Diene Daniel J. Pasto* and W. Robert Scheidt Department of Chemistry, University of Notre Dame, Notre Dame, Indiana 46556 Received August 29,1974
The X-ray structure determination of 3-p-bromophenyl-6,7-bisisopropylidene-8,8-dimethyl-l,3,5-triazabicyclo[3.3.0]octane-2,4-dione (5a)and a DNMR study of the debromo derivative 5b have been carried out. Steric interactions between functions attached to the diene chromophore of highly substituted 1,3-dienes result in a forcing of the diene to adopt nonplanar, chiral conformations. Considerable interest has recently arisen in the synthesis and structures of highly substituted dienes, and in the measurement of the barriers for rotation about the central carbon-carbon bond (i.e., enantiomerization) of such diene systems. Acyclic dienes have the potential of undergoing enantiomerization of the nonplanar chiral conformations via either s-cis or s-trans transition states. Mannshreck, Kobrich, and coworkers1 have studied the enantiomerization of several highly substituted acyclic 1,3dienes by NMR techniques and rotation barriers corresponding to enantiomerization via the lower energy s-trans transition states have been measured. Enantiomerization via the higher energy s-cis transition states cannot be studied with such acyclic systems. 1,2-Bisalkylidenecycloalkanes also contain skewed diene chromophores as evidenced by their u l t r a v i ~ l e t ~and ,~ NMR3,4 spectral properties, the decreased chemical reactivity in cycloaddition reactions,3r5 and the formation in our laboratories of the first reported optically stable, optically active dienes of structure 1 and 2.6 In contrast to the
1
2
X =z 0; Y = NSOzCl X a NSOzCl; Y 0 acyclic dienes, the enantiomerization of chiral 1,2-bisalkylidenecycloalkanes is restricted to occur only via the s-cis transition states, and thus provides opportunities for
studying such processes. Kiefer and coworkers4 have reported results of DNMR studies on 3 and 4 which possess CH,
3, R = H, CH:,
4
CH3 ‘CH,
0
X = Br b,X-H enantiomerization barriers of 3 4 7 , ) and were considered to be observed. Only the observed data were used in the solution and refinement of structure. The structure was solved by the standard heavy-atom method17 and refined by full-matrix least-squares techniques18 to a final R = 2llFd - IFdl/zlFd of 0.043 and a weighted Rz = [2w(lF,J - IFd)2/zwIFd2]1 of 0.055. The shift errors in the last cycle of refinement were all less than 0.05. All hydrogen atom positions were determined from a difference Fourier synthesis; electron density maxima appropriately located for hydrogen atom positions were about three times higher than the general background level in the map. These hydrogen atoms were included in the final cycles of least-squares refinement as fixed contributors, A final difference Fourier map was essentially featureless with the largest peak being 0.15 e/A.3 (See paragraph a t end of paper regarding supplementary material.) Variable-Temperature NMR Studies with 5b. A dilute solution (-1%) of 5b3 in 1:l dideuteriodichloromethane-trichlorofluoromethane (the low concentration was necessitated by the limited solubility of 5b in the chosen solvent system a t low temperatures) was triply freeze degassed in an NMR tube and sealed under a nitrogen atmosphere. The NMR spectra were recorded on a Varian XL100-15 spectrometer equipped with a variable-temperature prohe and a Transform Technology TTlOO Fourier transform. Because of the low concentration of the substrate and the different Tl’s of the hydrogens in 5b the spectra were recorded using the Nicolet T1 Program/II (ten scans) with D1 = 10 sec, conditions
J. Org. Chem., Vol. 40, No. 10,1975 1447
Photochemical Reactions of Acids, Esters, and Nitriles under w h i c h t h e hydrogens o f 5b are >98% relaxed giving singlets o f appropriate relative intensities.
Acknowledgments. The authors thank the Computing Center of the University of Notre Dame for an allocation of computing time, and Mr. Donald Schifferl for assistance in recording the NMR spectra. D.J.P. also wishes to acknowledge helpful discussions with Professor Kiefer, Department of Chemistry, University of Hawaii. R e g i s t r y No.-5a,
54595-52-7; 5b, 40755-74-6.
S u p p l e m e n t a r y M a t e r i a l A v a i l a b l e . A l i s t i n g o f atomic coordinate positions a n d anisotropic t h e r m a l parameters w i l l appear following these pages in t h e m i c r o f i l m edition o f t h i s volume of t h e journal. Photocopies of t h e supplementary m a t e r i a l f r o m t h i s paper o n l y or microfiche (105 X 148 mm, 24X reduction, negatives) containing a l l t h e supplementary m a t e r i a l f o r t h e papers in t h i s issue m a y be obtained f r o m t h e Journals Department, American Chemical Society, 1155 1 6 t h St., N.W., Washington, D.C. 20036. R e m i t check or money order for $4.00 for photocopy or $2.50 for microfiche, referring t o code number JOC-75-1444.
References a n d Notes A. Mannschreck, V. Jonas, H.-0. Bodecker, H.-L. Elbe, and 8. Kobrich, Tetrahedron Lett., 2153 (1974): G. Kobrich, B. Kolb, A. Mannschreck, and R. A. Misra, Chem. Eer., 106, 1601 (1973); G. Kobrich, A. Mannschreck, R. A. Misra, G. Rissman, M. Rosner, and W. Zundorf, ibid., 105,
3794 (1972). J. E. Starr and R. H. Eastmann, J. Org. Chem., 31, 1393 (1966), and references cited therein: W. F. Forbes, R. Chilton, and A. Baiasubramanian, ibid., 29, 3257 (1964);K. B. Alberman, R. N. Haszeidine, and F. B. Kipping, J. Chem. Soc., 3287 (1952). D. J. Pasto, A. F.-T. Chen, and G. Binsch, J. Am. Chem. SOC.,95, 1553
(1973). E. F. Kiefer, T. J. Levek, and T. T. Bopp, J. Am. Chem. SOC., 94, 4751 (1972).
I. N. Nazarov and N. V. Kuznetzov, Bull. Acad. Sci. USSR, Div. Chem.
Sci., 236 (1960). D. J. Pasto and J. K. Borchardt, J. Am. Chem. Soc., 96, 6220, 6937,
6944 (1974). Racemization studies with Iand 2 have thus far been precluded owing to the difficulty of access to sufficient quantities of the chiral compounds. C. K. Johnson, "ORTEP. .a Fortran Thermal-Ellipsoid Plot Program for Crystal Structure Illustrations", ORNL-3794, Oak Ridge National Laboratory, Oak Ridge, Tenn., 1965. The X-ray structure of the acyclic diene 2,3-diisopropylidene-1,4-b~tanedioi has been recently reported: T. Ottersen, L. W. Jelinski, E. F. Kiefer, and K. Seff, Acta Crysta//ogr., Sect. E, 30, 960 (1974). A. Bondi, J. Phys. Chem., 68, 441 (1964). (The value of 1.7 ,& for the van der Waals radius of the methyl group is less than the value of 2.0 A suggested by Pauling: L. Pauling, "The Nature of the Chemical Bond", 2nd ed, Cornell University Press, Ithaca, N.Y., 1940, p 189.) A. B. Evnin, D. R. Arnold, L. A. Karnischky, and E. Strom, J. Am. Chem. SOC.,92, 6218 (1970). The fact that symmetrical singlets are observed at low temperatures precludes assignment of the dynamic process to slowed rotation of two methyl groups of identical, or very similar, chemical shift. Slowed rotation of methyl groups would result in the formation of superposed AsX spin systems which would appear as much more complex patterns. G. J. Karabatsos, G. C. Sonnichsen, N. Hsi, and D. J. Fenogiio, J. Am. Chem. Soc., 89, 5067 (1967). B. J. Price, I. 0. Sutherland. and F. 0 . Williamson, Tetrahedron, 22,
3477 ( 1 966). R. C. Cookson, S. S.H. Gilani, and I. D. R. Stevens, J. Chem. SOC.C, 1905 (1967). W. R. Scheidt. J. Am. Chem. SOC.,96, 84 (1974). The Fourier program ALFF was used: C. R. Hubbard, C. 0. Quicksall, and R. A. Jaoobson, "The Fast Fourier Algorithm and the Programs ALFF, ALFFDP, ALFFPROJ, ALFFT, and FRIEDEL". 18-2625, Ames Laboratory, Iowa State University, Ames Iowa 1971.' The function minimized was f4 AFJ)*. The computations followed W. R. Busing, K. 0. Martin, and H. A. Levy, "OR-FLS, a Fortran Crystallographic Least-Squares Program", ORNL-TM-305, Oak Ridge National Laboratory, Oak Ridge, Tenn., 1962. Atomic form factors were from D. T. Cromer and J. B. Mann, Acta Crystallogr., Sect. A, 24, 321 (1968), with corrections, real and imaginary, for the anomalous scattering of the bromine atom from D. T. Cromer and D. Liberman. J. Chem. fhys., 53, 1891 (1970).
24
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Photochemical Reactions of cu,&UnsaturatedAcids, Esters, and Nitriles Thomas S. Cantrell Chemistry Department, T h e American University, Washington, D.C. 20016 Received January 9, 1975 Cyclohexene-1-carboxylicacid, t h e corresponding m e t h y l ester, a n d cyclohexene-1-carbonitrileundergo slow a d d i t i o n t o electron-rich alkenes u p o n irradiation. Reaction occurs, very slowly, a t the carbon-carbon double 21 cycloadducts, sometimes accompanied by products o f ene-like reacb o n d o f t h e ester a n d n i t r i l e t o give [2 tions. Cyclohexene-1-carboxylicacid gives ester 15 a n d lactone 16 via retro-type I1 processes.
+
The photochemical behavior of five- and six-membered ring conjugated enones is diverse and interesting, with reactions such as a-cleavage, oxetane formation, [2 21 cycloaddition t o the carbon-carbon double bond, the lumirearrangement to bicyclo[3.l.0]hexanones (in certain cases), and others being observed, depending on the presence or absence of coreactants.' It is believed that these molecules have lowest lying n,r* and T,T* triplet states of approximately equal energies, and that the precise structural details of the compound defines which state is of lowest energy, but that reactions from either state are possible in most cases. On the other hand, the photochemical behavior of a,Punsaturated acids and their derivatives, such as esters and nitriles, has, with the exception of a few specific compounds, been much less thoroughly investigated. The structures of the several [2 21 photodimers produced on irradiation of cinnamic acid in the solid state have been well worked out.2 Cinnamic esters have been reported to undergo [2 21 photochemical addition to olefins in solu-
+
+
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t i ~ n Maleic .~ anhydride, fumaric acid, and maleic acid, and 21 photodimerization also fumaronitriles, undergo [2 most efficiently in the solid state.* Coumarin undergoes direct and sensitized dimerization and sensitized addition to olefins, the former process apparently occurring via both singlet and triplet excited ~ t a t e s . a-Phenylcinnamic ~~,~ acids on irradiation close to P-lactones.6 Acrylonitrile dimerizes in the [ 2 21 fashion on photosensitization, whereas 2-cyanobutadiene undergoes two types of electrocyclic ring closure? just as does butadiene itself. This would imply that the reactive excited states of butadiene and t h e 2cyano derivative are similar (i.e., r,a*). In other simple a,P-unsaturated acids, esters, and nitriles which have been examined, the photochemistry which has been observed has been similar to that exhibited by acylic ketones. Both classes of compounds undergo processes such as (a) migration of the double bond to the P,r position, probably via hydrogen abstraction by the carbonyl oxygen, as in the type I1 elimination (this has been observed in crotonic acid and crotonic e ~ t e r s ) ;(b) ~ , ~cis-trans isomeriza-
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