The rate of exchange of 4-methyl protons was determined in 1.47 X 10-4 M base by integration of the singlet at 3.68 using the IV-methyl signal as standard.Acknowledgment. The authors express their appreciation to Dr. Louis Berkowitz for preparation of compound 13. They are also indebted to Mr. Thaddeus Novak for technical assistance and to Mr. Harold Klapper for the nmr spectra and their interpretation.

A study of the chromous chloride promoted addition of various N-chloro- and N-bromoamides (ZCONHX) to a variety of olefins shows that two types of addition products can be obtained, namely N-(2-haloalkyl)amides (1,2-adducts) which generally predominate and N-alkylamides (1,H-adducts). The total yield of addition products, the relative proportion of N-(2-haloalkyl)amide(s) and N-alkylamide, and the stereochemistry of 1,2-addition to cyclic olefins vary with the N-haloamide, that is with both Z and X, and also with the olefin. The best yields of 1,2-adducts were obtained with N-chlorocarbamates (Z = O-alkyl) and the proper choice of Z (e.g., 2,2,2-trichloroethoxy, benzyloxy) shows the potential of this method for the synthesis of N-protected β-chloro primary amines where the amino group is attached to the less substituted carbon atom. The use of an excess of N-haloamide results in high yields (>90%) of 1,2-addition based on the olefin, the excess of N-haloamide being simply reduced to the corresponding amide. N-Chloro-N-alkylamides (ZCONRCl) do not add to cyclohexene and are simply reduced to the corresponding amides.

A discussion on the mechanism of the chromous chloride promoted addition of N-haloamides to olefins is presented on the basis of the results already reported and some additional evidence. The mechanism proposed involves a radical chain addition in which the N-haloamide acts as the transfer agent, the termination steps being chromium(II) reduction of the amido radical and chromium(II) reduction of the intermediate adduct radical. The addition of N-chloro- and N-bromoacetamide to norbornadiene is described. The use of chromous chloride to initiate the reaction of N-chloropiperidine with ethyl vinyl ether and cyclohexene led to low yields of addition.

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