I Leverett R. Smith' SUNY College of Environmental Science and Forestry Syracuse, New York, 13210
I
Schemes and Transformations
(
The "valence isomers of cyclooctatetraene
in the (CH). Series
T h e study of strained ring chemistry in general and of (CH), isomeric "families" in particular has grown to become a major sport of organic chemists in the past decade or two ( I ) . One family receiving some attention has been the ( C H k compounds, the series whose "parent" is the well-known cyclooctatetraene (COT) (2).Since many of the interconversions of COT valence isomers were discussed in an excellent review (3) of several years ago, the emphasis in this discussion will be on briefly placing an updated scheme of known (CHISinterconversions in the context of the numerous as-vet-unknown isomt.rs and the presently estahlished routrs to the known ones. There is also n wealth of interesting chemtstrv 01' d r Will be r e ~ t ~ i c t to ed rivatives oithis system. l ~thisaccount t tht. aarent ist,mers f t ~ rthe iakt of manaaenhilirs ( 4 ) . In listing plnusil,le isomers oiagiven formuh 1.5 1. tlnr must be somewhat arbitrarv tn what toomit. This mav he the case in Figure 1 (61, around whose edge sit 21 (CHIS structures. Criss-crossing Firure 1are lines (referenced and "translated"
"
Table 1. lnterconvertive Schemes for Figure 1 Lener
Rationale
a
[,2, + 2 , l . h" L4.1, huor [,6,1, A [,%I. hu or P.1.A I,2. 2.1. hv [,2, A1, hv L2, -2.1, hn [ A + 2, + 2 , 1 . A [ A f 2,+ ,ZS1. A [,2, + -2. + "2.1. A
b c
d e 1 9 h
i
i k !
+ + +
k l . hu ("4, + s2s1. A L2.+ 2.1, A
Notes tor use of mble I: Leners refer to the labels in Figure 1. Orient ~igvre1 a that the lenw of interest sits abave the line it labels, and the "reaction" will read m m lee to rigM. Bracketed ndstion is that of ret. (I);hu or A indicates whether the process should be photochemical or thermal. (The uae of this notation is less common wim eledrocyclic reactions. such as path "b." but appears here fa consistency.)
in Table 1)indicating some conceivable (if not always likely) Woodward-Hoffman "allowed" (7) conversions. A hrief look should convince the reader that this scheme could he made more complicated both by including labels for reverse reactions, and by the inclusion of additional paths. If one were to consider the possibility of degenerate rearrangements (e.g., semibullvalene into itself), of non-concerted reactions (aided bv relief of rine strain.. hieh .. tem~eratures. . or ~hotochemical . sensitizers), or of catal?.zrd transformations 1e.g.. using transition metills) (8).the iieure would luok verv com~lirated indeed. However, the number of preparativel; direit interconversions now known is more limited. Figure 2 presents n sharply simplifird nmtrast to Figurr 1, the more so when one notes that catalytic and "forhiddm" routes appear. Even allowing for ~ i g u r e2's ignoring of degenerate processes, intermediates, and reactions that result in exits from the (CH)s series (cf. ref. (3), as well as those cited below), it is apparent that much remains to be explored in ( C H h chemistrv. Although svntheses of future members of the known series will no d i u h i b e more difficult than previous ones. 9 of the 11known isomers are stable a t room temDerat u r e ( t h e exwptions: hicycl~,l4.2.0(octa-?,4.7-rrieneand tri1'rt.at.m address: 1)rpartrnent of Chemlsrry. Oberlin College, Oberlin, Ohio 44074. ~
~
'
Figure 1. The (CHI8 "manifold."
Volume 55, Number 9, September 1978 / 569
Table 2. Reference Key to Figure 3 Letter
\
Ref.
Ref. numbers
Letter
numbers
Ref. numbers
Letter
fRhr11
@-@
synthesis (10) in the 1940's. In more recent times, the other known isomers and their chemistry have come via a variety of routes, most of which (as space permitted) are outlined in Figure 3. In this view, the diversity and interconnectedness of known (CH)s chemistry appear both in the variety of preparations employed and in the many indirect interconversions not indicated in Figure 2.Since an attempt to outline reagents and reaction conditions in Figure 3 would have been a hopeless task, each arrow (sometimes representing combined steps) is labeled by a letter. These letters are in turn translated into literature references via Table 2. The eleventh and most recent (CH)fiisomer, tetracyclo[3.3.0.02~4.0~~~]oct-7-ene, was prepared from the p-toluenesulfonylhydrazone of bicyclo[2.2.l]hepta-2,5-diene-7-carboxaldehyde (34). I t has not yet been related chemically to the other (CH)s compounds.
~ i g u r 2. e Preparatively direct (CH). imercanvwsions.
Literature Cited Liebman,J. F..and Greenberg. A.. Chem. Re".. 76.311 (1976). Paquette, L. A,, Tetrahedron. 31,2855 (19751. Scott, L.T., and Jones,Jr., M., Chem Re", 72.181 (19721. A uniquely mmprehenrivc ersmple in the (CCF81s aeries e l l he mentioned, thou&: Pe1oni.L. F..and Miller, W.T., J. Amor C h e m Soc. 98.4311 (19761. (5) Baiaban,A.T,Rm Roum. Chim.. 11,1097 (19581. (61 Figure 1 ia expanded Bom s similar scheme to he found in: van Vuuren. P. J.. Ph.D. Dissertation. Cornell University. 1970. p. 13. I71 Woodward, R. B.,snd Hoffmsnn, R.,"ThcConservstion of Orbital Symmetry."Academic Press, New York, 1978. (8) B i s h o ~ l l lK. , C., Chem.Reu.. 76,461 (1976). (91 Willststler,R.,and Waser. E..Chem.Ber., 44,3423 (19111. (10) Reppe. W.. Sehlichting, 0..Klager. K.. and Tape1.T.. Liebigs Ann., 560,l (19481. (111 Eaton.P.E.,andCole,T. W., J. Amer Chem. Soe.. 86.3157 (1964). (121 Avrsm, M.. Dinulescu, I. G.. Maria. E.. Matoeacu, G..Sliam. E.. andNenitzeseu,C. (11 (21 (31 (41
>CgD*
D..Chem. Ben. 97,382 (19641. sndMasamlme,S..Chem. Commun.. 660(18661. (131 Chin,C.G.,Cuts,H. (14) Dauben. W. G., Rivers. G.T.,Tweig. R. J.,and Zimrnermsn. T., J . O r # Chem.. 41, 887 11976). (151 Sanders.A..and Giering, W.P.,J. O~gonomofol.Cham.. 104.49 (1976). (161 Cassar. L., ato on, P E., and ~ a l p c mJ., , J. ~ m e them r SO^., 92.3515 (190). (171 Merh, W.,andPettit.R., J. Amw. Chsm. Sm.,89.4788(1967). (18) Smith, I. R., Gmsm, G. E., and Meinwsld, J., J . Or& Chom.. 42,927 (1977). (191 Case. R. Dewar. M. J. S..Kirrehner, Pettit. R.. and Slegier, J. Amer. Cham. Soc.. 96,7581 (19741. (201 Maier, G.. and Hoppe, B., Telrohedron Lett.. 861 (1973). (211 Paquette. L. A.. James. D. R.. and Rimberg. G. H.. J. Amer. Chem Soe. 96, 7454 (1974). R., Angew. Chem. Int. Ed. Engl., 3,442 (19641. (221 Vogel. EL Kiefer, H.. and Roth, (231 Askani, R.. Chrm. Be,., 102.3304 (19691. (241 Casasr. L., Eaton. P. E.. and Hslpern, .I.. J. Amer Chom. Sac. 92.6166 (1970). (25) Bsrharak, J.C.. Watb.1... sndPettit.R.. J. Amer Chem Soc. 88.1328(1966). (26) Meinwsld. J., and Schmidt. D., J. Amer Chsm. Soc.. 91.5877 (1969). (27) Zimmcrman. H. E., Rohbins. J. D.. and Sehsntl. J.. J. A ~ D IChom. Soc.. 91.5678 (1969). (28) Meinwsld. J.. and Tsuruta, H.. J Amer Chom. Sor., 91.5878 (18691. 1291 Meinwsld, J., and Tnuruta, J. Amen Chem. Sac..92,2579 (19701. (301 Zimrnerman, H. E., ~ i ~ k l e y . ~civens, . R. G ~ ~G. I . ~. , s ~ shewin, ~ ~ M.~ A,. J. ~ m e cr h a m ~1.8a16(19691. (31) Zirnmarman. H. E.. Roeheher. R. J.. Buehler, N. E..Keeh,G. E.,and Stainmetz, M. G.J. Amor. Chem Sm..98.76N)(1976). (321 Zimmeman, H. E.. Grunewald. G. L.,~ s u w e r . ~ . ~ . , ashowin, nd M. A,. J Chem. Sue, 91.23Ml19691. (331 Malhe,be, R., Acto, 56, 2u5 (19731. (341 Klumpp. G. w.,andstaporsms, ~ e t r e h a d r ~ ~ 747 ~ ~ it w t .7, 1 .
W.,
W.
S.,
S.,
W.,
W.
Figure 3. A summary of chemistry related to me (CHh compounds.
~clo[3.3.0.0~~~1octa-3,7-diene) and a t least some of the others might he also. Of the known (CH)8 compounds, the parent COT has the longest history and most thoroughly studied behavior (2). First reported WillsCtter and Wager in 1911 ( 9 , it hecame available in useful quantities with the advent of the Reppe
570 / Journal of Chemical Education
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