A reinvestigation of the Rh₂(OAc)₄-catalysed decomposition of 1-diazo-4-(2-methoxyphenyl)alkan-2-ones: evidence for ionic ‘ring-walk’ rearrangement in norcaradiene derivatives

Abstract

On Rh₂(OAc)₄-catalysed decomposition of 1-diazo-4-(2-methoxyphenyl)butan-2-one (9) and its methyl-substituted analogue (18), norcaradienones 10 and 19, respectively, were observed as the only regioisomers resulting from intramolecular cyclopropanation, indicative of attack by the metal carbene away from the methoxy group; to explain the transformation of 10 and 19 into dihydroazulenones 15 and 23, interconversion of 10 and 19 into their isomers 14 and 22 must be invoked, and an ionic ‘ring-walk’ rearrangement is suggested for such an isomerization.

References

1. (a) P. Manitto, D. Monti, S. Zanzola and G. Speranza, J. Org. Chem., 1997, 62, 6658; (b) M. Kennedy, M. A. McKervey, A. R. Maguire, S. M. Tuladhar and M. F. Twohig, J. Chem. Soc., Perkin Trans. 1, 1990, 1047.
2. A. J. Anciaux, A. Demonceau, A. F. Noels, A. J. Hubert, R. Warin and P. Teyssié, J. Org. Chem., 1981, 46, 873.
3. A. A. Cordi, J.-M. Lacoste and P. Hennig, J. Chem. Soc., Perkin Trans. 1, 1993, 3.
4. L. T. Scott, M. A. Minton and M. A. Kirms, J. Am. Chem. Soc., 1980, 102, 6311.
5. E. Wenkert and S. Liu, Synthesis, 1992, 323.
6. E. Ciganek, J. Am. Chem. Soc., 1967, 89, 1454; J. A. Berson, D. R. Hartter, H. Klinger and P. W. Grubb, J. Org. Chem., 1968, 33, 1669.
7. J. F. Liebman and A. Greenberg, Chem. Rev., 1989, 89, 1225.
8. C. S. Q. Lew, T.-H. Tang, I. G. Csizmadia and B. Capon, J. Chem. Soc., Chem. Commun., 1995, 175.
9. W. H. Donovan and W. H. White, J. Org. Chem., 1996, 61, 969.