96, 1256 (1974).(2) (a) For a recent review of alkaloids based on these ring systems, see J. E. Saxton in the "Alkaloids," Vol. 2, Specialist Periodical Reports of the Chemical Society, London, 1972. (b) For recent synthetic methods in the pyrrolizidine series, see N.

The instrument used to record the 2H NMR spectra was funded in part by the NSF.

No abstract

Pseudo-first order rate constants have been determined for the reactions of 2-bromopyridine (I), 2-bromoquinoline (11), 2-chloroquinoline (111) and 2-chlorothiazole (IV) with piperidine a t various temperatures in the range between 40.00 and 90.00'.The reactions of 2-chloropyrimidine (V) and 2-chlorobenzothiazole (VI) with piperidine have been shown to proceed much more rapidly than the reactions of compounds I to IV, too rapidly, in fact, to permit quantitative rate measurements under similar temperature conditions. Comparison of rate constants calculated a t a common temperature of 50.00' establishes the following order of decreasing activity:

No abstract