M. Christl, E. Brunn, F. Lanzendoerfer
Apr 24, 1984
Citations
0
Influential Citations
31
Citations
Journal
Journal of the American Chemical Society
Abstract
The reaction of benzvalene (4) with tetracyanoethylene (TCNE) affords a mixture of tetracyclo[3.3.0.02.4.0J·6]octane derivative 5, tricyclo[3.3.0.02•6]oct-7-ene derivative 6, and tricyclo[3.3.0.02•8]oct-6-ene derivative 7. By means of dideuterated benzvalene 4a and the solvent effect on the ratio of the products the mechanisms have been studied. Accordingly, the formation of the main products 5 and 6 involves zwitterionic intermediates, which arise from electrophilic attack of TCNE at the olefinic portion of 4. The third compound 7 is thought to be produced in a concerted 1,4-addition of TCNE to the vinylcyclopropane moiety of benzvalene (4). Treatment of 4 with 2,3-dichloro-5,6-dicyano-p-benzoquinone gives rise to a 1: 1 adduct, which is structurally analogous to TCNE adduct 7 and which is most probably formed in a one-step process as evidenced by the positions of the deuterons when 4a was utilized. In a reinvestigation of the reaction between chlorosulfonyl isocyanate and 4 the new compounds 18a, a 4-azatricyclo[3.3.0.02,8]oct-6-en-3-one derivative, and 19, an 8-azatetracyclo[ 4.2.0.02,4.0J·l]octan-7-one derivative, have been discovered in addition to the known products 2a and 3a. Even at low temperatures benzvalene (4) and sulfur dioxide react to give a mixture of the four-membered ring sulfone 23 and the sultine 24, with the ratio being dependent on the solvent polarity. That 23 is not the precursor of 24 follows from rate measurements, according to which the rearrangement 23 24 is much slower than the formation of 24 from 4 and S02' The experiment utilizing dideuterated benzvalene 4a has revealed a competition between two processes, a concerted 1,4-addition of S02 to the vinyl cyclopropane system of 4 yielding 23 and an electrophilic attack of S02 at Col (C-6) of 4 with formation of the zwitterion 25 with a sulfinate function and an allyl cation moiety. The latter species cyclizes with almost the same rates via an oxygen atom or the sulfur atom to give rise to 24 and another portion of 23, respectively. In the stepwise processes TCNE and S02 approach 4 at different sites. This phenomenon is discussed in terms of the HSAB principle. Due to its high-lying HOMO benzvalene (4) reacts with numerous electrophiles.2 In most cases the attack takes place at the double bond since the HOMO is largely localized there. M Exceptions are the protonation ' -7 and the mercuration8 generating products, which indicate addition of the electrophile to the bicyclo[1.1.0]butane skeleton. Also, Ag+ and several metals interact with the q system and catalyze automerizations of 4 and, finally, isomerizations to benzene and fulvene, respectively.9 Katz and co-workers have studied the reactions of 4 with 4phenyl-I,2,4-triazolin-3,5-dione (PTAD)IO and chlorosulfonyl isocyanate (CSI).ll By means of 1,6-dideuterated benzvalene (4a) it has been shown that both of these electrophiles attack the double bond with formation of zwitterionic intermediates. Subsequently, the latter undergo a Wagner-Meerwein rearrangement. In the PTAD addition only the bicyc1o[l.l.Ojbutane-bridgehead carbon, which is oriented trans relative to the PTAD portion, migrates thus ultimately giving rise to 1 as the single product. In the intermediate formed in the CSI addition migration can also take place on the side of the anionic substituent thus producing a 3:1 mixture of 2a and 3a by collapse of the rearranged zwit(I) Presented at the Euchem Conference on Pericyclic Reactions, Ferrara, Italy, Sept 1982. (2) Review: Christl, M. Angew. Chem.I981, 93, 515-531; Angew. Chem., Int. Ed. Engl. 1981, 20, 529-546. (3) Bischof, P.; Gleiter. R.; Muller, E. Tetrahedron 1976, 32, 2769-2773. Gleiter, R. Top. Curr. Chem. 1979. 86, 197-285. (4) Harman, P. J.; Kent, J. E.; Gan, T. H.; Peel, J. B.; Willelt, G. D. J. Am. Chem. Soc. 1977, 99, 943-944. (5) Kaplan, L.; Rausch, D. J.; Wilzbach, K. E. J. Am. Chem. Soc. 1972, 94, 8638-8640 and references cited. (6) Katz, T. J.; Wang, E. J.; Acton, N. J. Am. Chem. Soc. 1971, 93, 3782-3783. (7) Christ!, M.; Freitag, G., unpUblished results cited in ref 2. (8) Miiller, E. Chem. Ber. 1975, 108, 1394-1400. (9) Burger, U.; Mazeno