Thwarting β-Hydride Elimination: Capture of the Alkylpalladium Intermediate of an Asymmetric Intramolecular Heck Reaction

Martin Oestreich; Philip R Dennison; Jeremy J Kodanko; Larry E Overman

doi:10.1002/1521-3773(20010417)40:8<1439::AID-ANIE1439>3.0.CO;2-F

Thwarting β-Hydride Elimination: Capture of the Alkylpalladium Intermediate of an Asymmetric Intramolecular Heck Reaction

Angew Chem Int Ed Engl. 2001 Apr 17;40(8):1439-1442. doi: 10.1002/1521-3773(20010417)40:8<1439::AID-ANIE1439>3.0.CO;2-F.

Authors

Martin Oestreich¹, Philip R Dennison¹, Jeremy J Kodanko¹, Larry E Overman¹

Affiliation

¹ Department of Chemistry University of California, Irvine 516 Rowland Hall, Irvine, CA 92697-2025 (USA) Fax: (+1) 949-824-3866.

PMID: 29712379
DOI: 10.1002/1521-3773(20010417)40:8<1439::AID-ANIE1439>3.0.CO;2-F

Abstract

In spite of containing three conformationally accessible β-H atoms, palladacycle 1 a is an isolable intermediate in the asymmetric Heck cyclization of 2 a. Although 1 a is stable in the presence of the hydrotriflate salt of 1,2,2,6,6-pentamethylpiperidine, it is converted into the oxindole Heck product when exposed to the more acidic hydrotriflate salt of 2,6-di-tert-butylpyridine. Heck cyclization of 2 b is also believed to proceed by way of a palladacyclic intermediate 1 b, which in this case undergoes β-methoxide elimination. Bn=benzyl.

Keywords: Heck reactions; alkaloids; asymmetric catalysis; cyclization; palladium.