The synthesis .from l4CC0, of various endo-and exo-3-I4Cdehydro-2-norbornyl and 2-norbornyl derivatives, suitable for use in isotopic scrambling studies, is described.
INTRODUCTION.
In the original work of Roberts and coworkers ( l , 2, on the solvolyses of exo-and end0-2,3-~~C,-2-norbornyl brosylates (exo-and endo-I-OBs-2,3J4C), because the label was located at both C-2 and C-3, a direct observation of 3,2-hydride shifts was not possible. A singly labeled substrate would have obvious advantages in this regard. Thus about 6 rearrangement of the 1-label from C-2 to C-3 was observed in the formolysis at 250 C of exo-I-OBs-2-t (3). Similarly, the acetolysis of exo-or endo-I-OBs-2-t was found to give a small amount (1-2 "/,) of overall 3,2-shifts (4), most, if not all, of which could be attributed to the subsequent ionization and rearrangement of the initially formed product, exo-I-OAc-x-t, in the reaction medium (5). Such subsequent reactions of exo-I-OAc in the acetolysis medium apparently involved an extraordinarily large extent of 3,2-shifts relative to Wagner-Meerwein and 6,2-shifts. Of interest also is the n.m.r. study of Fraenkel and coworkers on the behavior of exo-L-OH in F,CCOOH-H2S04 which led to the conclusion that 3,2-and 6,2-shifts proceeded faster than Wagner-Meerwein rearrangement under these conditions. On the other hand, when the x-route to the norbornyl cation from solvolyses of 2-(A3-cyclopentenyl)-2-14C-ethyl p-nitrobenzenesulfonate (l1-ONs-2-l4C) was studied under conditions that were more likely to be kinetically controlled ('), essentially no 3,2-shifts occurred, and the 14C-label in the resulting exo-2-norbornyl product was located only at C-3, C-5 and C-7. It is, therefore, of interest to synthesize 2-norbornyl derivatives singly labeled with 14C at C-3 which may, for example, be utilized in investigations that will provide further data on 3,2-shifts and for comparison with the isotopic scrambling data from x-route solvolyses.