Conformational effects on the excited state 1,2-hydrogen migration in alkyldiazomethanes

Tetrahedron Letters

Volumn 37, Issue 40, 1996, Pages 7209-7212

  Reed, Sasha C ^a   Modarelli, David A ^a  

^a Center for Language and Brain   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AZO COMPOUND;

ARTICLE; DRUG SYNTHESIS; MOLECULAR DYNAMICS;

EID: 0030607201     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/0040-4039(96)01569-9     Document Type: Article

References (25)

1. 1. Platz, M.S.; White, W.R.; Modarelli, D.A. Res. Chem. Interned. 1994, 20, 175.
2. 2. Çelebi, S.; Leyva, S.; Modarelli, D.A.; Platz, M.S. J. Am. Chem. Soc. 1993, 115, 8613.
3. 3. (a) Chidester, W.; Modarelli, D.A.; White, W.R., III; Whitt, D.E.; Platz, M.S. J. Phys. Org. Chem. 1994, 7, 24.
4. (b) White, W.R.; Platz, M.S. J. Org. Chem. 1992, 57, 2841.
5. 4. (a) Reed, S.C.; Ichimura, A.S.; Modarelli, D.A.; manuscript in preparation.
6. (b) Evanseck, J.D.; Houk, K.N. J. Am. Chem. Soc. 1990, 112, 9148.
7. (c) Jones, W.M. In Rearrangements in Ground and Excited States; de Mayo, P., Ed.; Academic Press: New York, 1980; pp. 95-160.
8. (d) Press, L.S.; Shechter, H. J. Am. Chem. Soc. 1979, 101, 509.
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10. (f) Freeman, P.K.; Hardy, T.A.; Balyeat, J.R.; Wescott, L.D. J. Org. Chem. 1977, 42, 3356.
11. (g) Kyba, E.P.; Hudson, C.W. J. Am. Chem. Soc. 1976, 98, 5696.
12. (h) Gaspar, P.P.; Hammond, G.S. In Carbenes; Moss, R.A.; Jones, M., Jr., Eds.; Wiley: New York, 1975; Vol. II, pp. 207-362.
13. (i) Nickon, A.; Huang, F-chih; Weglein, R.; Matsuo, K.; Yagi, H. J. Am. Chem. Soc. 1974, 96, 5264.
14. 4i have found that thermal generation of brexanylidene leads to a 138:1 ratio of exo/endo hydrogen migration, while photochemical generation of the carbene was found to yield a 4:1 ratio. Our data indicates the excited state migration may be responsible for the change in selectivity in the photochemical reaction. The endo hydrogen, which in the ground state carbene is not well aligned, becomes better aligned upon photoexcitation and presumably then undergoes a more favorable migration.
15. 6. (a) Platz, M.S.; Maloney, V.M. In Kinetics and Spectroscopy of Carbenes and Biradicals; Platz, M.S., Ed.; Plenum: New York, NY, 1990.
16. (b) Jackson, J.E.; Platz, M.S. In Advances in Carbene Chemistry, Vol. I; Brinker, U., Ed; JAI Press: Greenwich, CT, in press.
17. (c) Modarelli, D.A.; Platz, M.S. J. Am. Chem. Soc. 1993, 115, 470.
18. (d) Modarelli, D.A.; Morgan, S.C.; Platz, M.S. J. Am. Chem. Soc. 1992, 114, 7034.
19. (e) Modarelli, D.A.; Platz, M.S. J. Am. Chem. Soc. 1991, 113, 8985.
20. 300nm ∼1.0) in neat methanol at 25°C; the only products from these photolysis were the corresponding olefins and methyl ethers formed from O-H insertion which were identified in a GC/MS by co-injection with known compounds or by mass spectral data.
21. -1 for several alkylarylcarbenes (ref. 2).
22. Sat). This process was repeated for each diazo compound three separate times.
23. 10. Diazo geometries were optimized on a Silicon Graphics Indigo2 workstation at the ab initio level of theory (RHF/6-31G*) using the SPARTAN computational package (SPARTAN version 4.0, Wavefunction, Inc.; 18401 Von Karman Ave., #370; Irvine, CA 92715). Dihedral angles are quoted as the difference between 90° and the angle between the a hydrogen and the plane formed by the diazo carbon and the two adjacent a carbons.
24. 11. Yamamoto, N,; Bernardi, F.; Bottoni, A.; Olivucci, M.; Robb, M.A.; Wilsey, S. J. Am. Chem. Soc. 1994, 116, 2064.
25. 12. Calculations of the excited state geometries of diazo compounds and reaction coordinate surface are currently in progress, Ichimura, A.S.; Modarelli, D.A.