Interconversion and rearrangement of radical cations. Part 2.1 Photoinduced electron transfer and electrochemical oxidation of 1,4-bis(methylene)cyclohexane

Abstract

The photoinduced electron transfer and electrochemical oxidation of 1,4-bis(methylene)cyclohexane (2) in acetonitrile have been studied in the presence and absence of a nucleophile (methanol). The photoinduced electron transfer reactions of 2 in acetonitrile–methanol solution with 1,4-dicyanobenzene (8) as the electron acceptor gives two products: 4-(methoxymethyl)-1-methylenecyclohexane (16) and 4-(4-cyanophenyl)-4-(methoxymethyl)-1-methylenecyclohexane (17). These products arise from nucleophilic attack on the radical cation followed by either reduction and protonation or combination with the radical anion of the electron acceptor, 1,4-dicyanobenzene (8^˙-). These results are in accord with the proposed mechanism of the photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. In the absence of a nucleophile, the photoinduced electron transfer reaction of 2 gives rise to several interesting and unexpected products 18–25 which result from complex reaction mechanisms involving radical, ionic and radical ion intermediates.The electrooxidation of 2 in acetonitrile in the presence of methanol leads to products 27–35. Under these conditions the radical cation 2^˙+ reacts with the nucleophile followed by a second oxidation and subsequent reactions leading to products (electrochemical–chemical–electrochemical, ECE). One of the products (28) is the result of protonation of 2 followed by nucleophilic attack. The electrochemical oxidation of 2 in acetonitrile (no methanol) yields 2^˙+ which is deprotonated and then further oxidized to give 39–43. These products arise from ionic intermediates (ECE); oxidation of 2 all the way to aromatic compounds was observed in 39–41.In none of these experiments was there any evidence for the formation of cyclized products, nor was there any indication of carbon–carbon bond cleavage in 2^˙+. The products are consistent with the initial formation of the intermediate radical cation. The products as well as the possible mechanisms of formation of these species are discussed.

References

1. H. J. P. de Lijser and D. R. Arnold, J. Phys. Chem., 1996, 100, 3996.
2. (a) Photoinduced Electron Transfer, Part A, eds. M. A. Fox and M. Chanon, Elsevier, Amsterdam, 1988; (b) S. L. Mattes and S. Farid, in Organic Photochemistry, ed. A. Padwa, Marcel Dekker, New York, 1983, vol. 6, p. 233; (c) G. J. Kavernos and N. J. Turro, Chem. Rev., 1986, 86, 401; (d) G. J. Gavernos, Top. Curr. Chem., 1992, 163, 131; (e) J. Mattay, Angew. Chem., Int. Ed. Engl., 1987, 26, 825; (f) A. Albini, M. Mella and M. Freccero, Tetrahedron, 1994, 50, 575.
3. L. Eberson, J. H. P. Utley and O. Hammerich, in Organic Electrochemistry, eds. H. Lund and M. M. Baizer, Marcel Dekker, New York, 3rd edn., 1991, p. 505.
4. (a) Ion-Molecule Reactions, ed. J. L. Franklin, Plenum Press, New York, 1972; (b) Tandem Mass Spectrometry, ed. F. W. McLafferty, Wiley, 1983; (c) J. R. O'Lear, L. G. Wright, J. N. Louris and R. G. Cooks, Org. Mass Spectrom., 1987, 22, 348; (d) J. L. Holmes, Org. Mass Spectrom., 1985, 20, 169; (e) P. C. Burgers and J. K. Terlouw, Mass Spectrom., 1989, 10, 35.
5. (a) T. Shida, E. Haselbach and T. Bally, Acc. Chem. Res., 1984, 17, 180; (b) M. C. R. Symons, Chem. Soc. Rev., 1984, 393.
6. (a) P. E. Eaton and G. H. Temme III, J. Am. Chem. Soc., 1973, 95, 7508; (b) K. B. Wiberg, G. A. Epling and M. Jason, J. Am. Chem. Soc., 1974, 96, 912; (c) J. J. Dannenberg, T. M. Provic and C. Hutt, J. Am. Chem. Soc., 1974, 96, 914; (d) K. B. Wiberg, W. E. Pratt and W. F. Bailey, J. Am. Chem. Soc., 1977, 99, 2297; (e) K. B. Wiberg and M. G. Matturro, Tetrahedron Lett., 1981, 22, 3481; (f) K. B. Wiberg, Acc. Chem. Res., 1984, 17, 379; (g) K. B. Wiberg, J. J. Cartingi, J. J. Matturro and M. G. Matturro, J. Am. Chem. Soc., 1990, 112, 5854.
7. (a) W.-D. Stohrer and R. Hoffmann, J. Am. Chem. Soc., 1972, 94, 779; (b) M. D. Newton and J. M. Schulman, J. Am. Chem. Soc., 1972, 94, 4391; (c) D. Feller and E. R. Davidson, J. Am. Chem. Soc., 1987, 109, 4133.
8. (a) R. G. Doerr and P. S. Skell, J. Am. Chem. Soc., 1967, 89, 3062; (b) P. S. Skell and R. G. Doerr, J. Am. Chem. Soc., 1967, 89, 4688; (c) F. Weiss, Q. Rev. Chem. Soc., 1970, 24, 278; (d) J. J. Gajewski, A. Yeshuran and E. J. Bair, J. Am. Chem. Soc., 1972, 94, 2138; (e) G. Maier, D. Jürgen, R. Tross, H. P. Reisenauer, B. A. Hess, Jr. and L. J. Schaad, Chem. Phys., 1994, 189, 383.
9. (a) P. Binger, Angew. Chem., Int. Ed. Engl., 1972, 11, 309; (b) P. Binger, Angew. Chem., Int. Ed. Engl., 1972, 11, 433; (c) W. R. Dolbier, Jr., D. Lomas, T. Garza, C. Harmon and P. Tarrant, Tetrahedron, 1972, 28, 3185; (d) M. J. Doyle, J. McMeeking and P. Binger, J. Chem. Soc., Chem. Commun., 1976, 376; (e) P. Binger, M. J. Doyle and R. Benn, Chem. Ber., 1983, 116, 1; (f) P. Binger, A. Brinkmann and P. Wedemann, Chem. Ber., 1983, 116, 2920.
10. (a) D. R. Arnold, X. Du and H. J. P. de Lijser, Can. J. Chem., 1995, 73, 522; (b) D. R. Arnold, X. Du and J. Chen, Can. J. Chem., 1995, 73, 307; (c) D. R. Arnold and X. Du, Can. J. Chem., 1994, 72, 403; (d) A. L. Perrott and D. R. Arnold, Can. J. Chem., 1992, 70, 272; (e) R. Popielarz and D. R. Arnold, J. Am. Chem. Soc., 1990, 112, 3068; (f) D. R. Arnold and M. S. Snow, Can. J. Chem., 1988, 66, 3012; (g) R. M. Borg, D. R. Arnold and T. S. Cameron, Can. J. Chem., 1984, 62, 1785; (h) R. A. Neunteufel and D. R. Arnold, J. Am. Chem. Soc., 1973, 95, 4080; (i) K. McMahon and D. R. Arnold, Can. J. Chem., 1993, 71, 450.
11. (a) J. P. Dinnocenzo, W. P. Todd, T. R. Simpson and I. R. Gould, J. Am. Chem. Soc., 1990, 112, 1462; (b) J. P. Dinnocenzo, D. R. Lieberman and T. R. Simpson, J. Am. Chem. Soc., 1993, 115, 366; (c) L. J. Johnston and N. P. Schepp, Pure Appl. Chem., 1995, 67, 71.
12. D. D. M. Wayner and D. R. Arnold, Can. J. Chem., 1985, 63, 871.
13. (a) D. R. Arnold, K. A. McManus and X. Du, Can. J. Chem., 1994, 72, 415; (b) D. A. Connor, D. R. Arnold, P. K. Bakshi and T. S. Cameron, Can. J. Chem., 1995, 73, 762; (c) K. A. McManus and D. R. Arnold, Can. J. Chem., 1995, 73, 2158; (d) D. R. Arnold, D. A. Connor, K. A. McManus, P. K. Bakshi and T. S. Cameron, Can. J. Chem., 1996, 74, 602; (e) P. S. Engel, D. M. Robertson, J. N. Scholz and H. J. Shine, J. Org. Chem., 1992, 57, 6178; (f) S. Hintz, A. Heidbreder and J. Mattay, Top. Curr. Chem., 1996, 177, 77.
14. (a) Q.-X. Guo, X.-Z. Qin, J. T. Wang and F. Williams, J. Am. Chem. Soc., 1988, 110, 1974; (b) F. Williams, Q.-X. Guo, D. C. Bebout and B. K. Carpenter, J. Am. Chem. Soc., 1989, 111, 4133.
15. L. S. Prasad, R. Ding, E. G. Bradford, L. D. Kispert and H. Wang, Isr. J. Chem., 1989, 29, 33.
16. K. A. McManus, M. S. W. Chan and D. R. Arnold, Can. J. Chem., 1996, 74, 2143.
17. D. Rehm and A. Weller, Isr. J. Chem., 1970, 8, 259.
18. M. St-Jacques and M. Bernard, Can. J. Chem., 1969, 47, 2911.
19. Ab initio calculations (MP2/6-31G*//HF-6-31G*) have shown that the spin and charge density in the phenyl radical and in the p-cyanophenyl radical are very similar and their behaviour should therefore also be similar.
20. J. C. Scaiano and L. C. Stewart, J. Am. Chem. Soc., 1983, 105, 3609.
21. (a) See for example: A. L. J. Beckwith, D. M. O'Shea and S. W. Westwood, J. Am. Chem. Soc., 1988, 110, 2565; (b) Yu. N. Ogibin, E. I. Troyanskii and G. I. Nikishin, Izv. Akad. Nauk. SSSR Ser. Khim., 1975, 1461; (c) R. A. Kaba, D. Griller and K. U. Ingold, J. Am. Chem. Soc., 1974, 96, 6202; (d) J. R. Shelton and C. W. Uzelmeier, J. Am. Chem. Soc., 1966, 88, 5222.
22. There is, to the best of our knowledge, only one specific example of a carbon-centred radical adding to the carbon of the nitrile in acetonitrile;^22a there are several examples in the literature of heteroatom radicals adding to acetonitrile: hydrogen atoms add to the CN triple bond in acetonitrile;^21b,c tertiary amine–boryl radicals add to nitriles to give iminyl radicals [R₃N→BH₂C(R′)]=N^●]^21d,e as do primary amine–boryl radicals,^21f and the ammonia–boryl radical;^21g reaction of the β-distonic radical cation ^●CH₂–CH₂–O–CH₂⁺ with acetonitrile is thought to proceed by either a ‘head on’ radical addition to the nitrogen of acetonitrile or a ‘side on’ electrophilic addition to the nitrogen.^21h (a) P. S. Engel, W.-K. Lee, G. E. Marschke and H. J. Shine, J. Org. Chem., 1987, 52, 2813; (b) P. Neta, G. R. Holdren and R. H. Schuler, J. Phys. Chem., 1971, 75, 449; (c) G. V. Buxton, C. L. Greenstock, W. P. Helman and A. B. Ross, J. Phys. Chem. Ref. Data, 1988, 17, 513; (d) J. A. Baban, V. P. J. Marti and B. P. Roberts, J. Chem. Soc., Perkin Trans. 2, 1985, 1723; (e) V. Paul and B. P. Roberts, J. Chem. Soc., Perkin Trans. 2, 1988, 1183; (f) J. N. Kirwan and B. P. Roberts, J. Chem. Soc., Perkin Trans. 2, 1989, 539; (g) V. P. J. Marti and B. P. Roberts, J. Chem. Soc., Perkin Trans. 2, 1986, 1613; (h) D. Wittneben and H.-F. Grützmacher, Int. J. Mass Spectrom. Ion Processes, 1990, 100, 545.
23. (a) H. D. Roth, Top. Curr. Chem., 1992, 163, 131; (b) H. D. Roth, Acc. Chem. Res., 1987, 20, 343; (c) N. L. Bauld, D. J. Bellville, B. Harirchian, K. T. Lorenz, R. A. Pabon, Jr., D. W. Reynolds, D. D. Wirth, H.-S. Chiou and B. K. Marsh, Acc. Chem. Res., 1987, 20, 371; (d) N. L. Bauld, D. J. Bellville, R. Pabon, R. Chelsky and G. Green, J. Am. Chem. Soc., 1983, 105, 2378; (e) R. A. Pabon and N. L. Bauld, J. Am. Chem. Soc., 1984, 106, 1145; (f) N. P. Schepp and L. J. Johnston, J. Am. Chem. Soc., 1994, 116, 6895; (g) N. P. Schepp and L. J. Johnston, J. Am. Chem. Soc., 1996, 118, 2872; (h) M. Kojima, A. Kakehi, A. Ishida and S. Takamuku, J. Am. Chem. Soc., 1996, 118, 2612.
24. (a) T. Shono and A. Ikeda, J. Am. Chem. Soc., 1972, 94, 7892; (b) T. Shono, A. Ikeda, J. Hayashi and S. Hakozaki, J. Am. Chem. Soc., 1975, 97, 4261; (c) P. G. Gassman and R. Yamaguchi, Tetrahedron, 1982, 38, 1113.
25. (a) A. J. Fry, Synthetic Organic Electrochemistry, Harper & Row, New York, 1972; (b) C. K. Mann and K. K. Barnes, Electrochemical Reactions in Nonaqueous Systems, Marcel Dekker, New York, 1970; (c) D. Kyriacou, Modern Electroorganic Chemistry, Springer-Verlag, New York, 1994.
26. A. M. de P. Nicholas and D. R. Arnold, Can. J. Chem., 1982, 60, 2165.
27. L. M. Harwood, Aldrichimica Acta, 1985, 18, 25.
28. A. Okamoto, M. S. Snow and D. R. Arnold, Tetrahedron, 1986, 42, 6175.
29. D. R. Arnold and D. D. M. Wayner, Can. J. Chem., 1986, 64, 100.
30. (a) R. S. Nicholson and I. Shain, Anal. Chem., 1964, 36, 706; (b) Anal. Chem., 1965, 37, 178.
31. C. L. Perris and R. M. Christenson, J. Org. Chem., 1960, 25, 1888.