Intramolecular reactions. Part X. Transition states in the cyclisation of N-ω-halogeno-alkylamines and sulphonamides

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Abstract
Rates of cyclisation of a series of N-ω-halogenoalkylamines- in dioxan–water and ethanol–water and of sulphonamides in alcohol–alkoxide media have been determined. Particular attention has been paid to the effect on rate of the ring-size formed, the leaving group, and the placement of aryl groups on nitrogen and on carbon adjacent to nitrogen. Five-membered rings are formed faster than three-, four-, or six-membered rings in each series. For amines (25°) the order is 6 > 3 > 4. For sulphonamides (55°) the order is 3 > 6 > 4. In three-membered ring formation, bromide:chloride ratios are 28 for the amines studied and 79 for the sulphonamides. Placement of a phenyl group on nitrogen or on carbon adjacent to nitrogen in the amines studied has very little effect on the rate or on the activation parameters. The results are discussed in terms of conjugative control of cyclisation reactions and it is concluded that there is little C–N bond formation in the transition state for these cyclisations.

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