Unimolecular @-eliminationo f HBr from the CH&H2Br end of o--OCBH40(CH2),-4Bhar s 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-, lo-, 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.
Ring-closure reactions. 21. Intramolecular .beta.-elimination competing with ring formation from o-(.omega.-bromoalkoxy)phenoxides over a wide range of ring sizes / DALLA CORT, Antonella; Mandolini, Luigi; Bernardo, Masci. - In: JOURNAL OF ORGANIC CHEMISTRY. - ISSN 0022-3263. - STAMPA. - 48:22(1983), pp. 3979-3982. [10.1021/jo00170a020]
Ring-closure reactions. 21. Intramolecular .beta.-elimination competing with ring formation from o-(.omega.-bromoalkoxy)phenoxides over a wide range of ring sizes
DALLA CORT, Antonella;MANDOLINI, Luigi;
1983
Abstract
Unimolecular @-eliminationo f HBr from the CH&H2Br end of o--OCBH40(CH2),-4Bhar s 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-, lo-, 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
