Page 281 - Mechanism and Theory in Organic Chemistry

Chapter 6

INTRAMOLECULAR

REARRANGEMENTS

In this chapter we shall discuss intramolecular rearrangements to electron-
deficient carbon, nitrogen, and oxygen.

6.1 1,Z-SHIFTS IN CARBENIUM IONS1

The intramolecular migration, shown in Equation 6.1, of a hydrogen, an alkyl,
or an aryl group with its pair of electrons from a P carbon (migration origin) to the
adjacent carbocationic center (migration terminus) is called a 1,2-shift (or in the case
of migration of an alkyl or an aryl group, a Wagner-Meerwein shift).

The new carbocation thus formed can subsequently add to a Lewis base, lose a
proton from an adjacent atom, or rearrange further.
The first such rearrangement to be studied was that of pinacol (1) to
pinacolone (2) in acid solution (Equation 6.2).2

For review articles, see: (a) J. L. Fry and G. J. Karabatsos, in Carbonium Ions, G. A. Olah and
P. v. R. Schleyer, Eds., Wiley-Interscience, New York, 1970, Vol. 11, p. 521; (b) C. J. Collins,
Quart. Rev. (London), 14, 357 (1960); (c) D. M. Brouwer and H. Hogeveen, Prog. Phys. Org. Chem., 9,
179 (1972); and (d) S. P. McManus, Organic Reactive Intermediates, Academic Press, New York,
1973.
R. Fittig, Justus Liebigs Ann. Chem., 114, 54 (1860).

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