Ring-Closure Reactions. 21. Intramolecular β-Elimination Competing with Ring Formation from o-(ω-Bromoalkoxy)phenoxides over a Wide Range of Ring Sizes

Article abstract of DOI:10.1021/jo00170a020

Unimolecular β-elimination of HBr from the CH2CH2Br end of o-^-OC6H4O(CH2)_n-4Br has been interpreted as an E2-type reaction promoted by the distal phenoxide group acting as a base.Combination of careful product analyses with kinetic data has provided rate constants and effective molarities for intramolecularly assisted elimination reactions occurring through 7-, 8-, 9-, 10-, and 14-membered ring transition states.A comparison is carried out with the competing intramolecular substitution reactions leading to ring formation.Attention is called to the specific entropic and geometrical requirements of intramolecular elimination in which the donor-proton-acceptor arrangement is a part of a cyclic structure.The importance of the present results in the general field of intramolecular acid or base catalysis phenomena is discussed.