Mechanistic Dichotomy in CpRu(CH3CN)3PF6 Catalyzed Enyne Cycloisomerizations
- 12 April 2002
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 124 (18), 5025-5036
- https://doi.org/10.1021/ja012450c
Abstract
Enynes are easily accessible building blocks as a result of the rich chemistry of alkynes and thus represent attractive substrates for ring formation. A ruthenium catalyst for cycloisomerization effects such reaction of 1,6- and 1,7-enynes typically at room temperature in acetone or DMF under neutral conditions. The reaction is effective for forming five- and six-membered rings of widely divergent structure. The alkyne may bear both election-donating and election-withdrawing substituents. The alkene may be di- or trisubstituted. Introduction of a quaternary center at the propargylic position of an ynoate, however, completely changes the nature of the reaction. In the case of a 1,6-enynoate, a seven-membered ring forms in excellent yield under equally mild conditions. Evidence is presented to indicate a complete change in mechanism. In the former case, the reaction involves the intermediacy of a ruthenacyclopentene. In the latter case, a C−H insertion to form a π-allylruthenium intermediate is proposed and supported by deuterium-labeling studies. A rationale is presented for the structural dependence of the mechanism.Keywords
This publication has 23 references indexed in Scilit:
- Oxidatively Induced Carbonylation and Cyclization of Ruthenium(II) Vinyl−Olefin Complexes Prepared via Allyl/Alkyne CouplingOrganometallics, 2000
- Synthesis and Odor of Chiral Partial Structures of Khusimone. Part 1Helvetica Chimica Acta, 1997
- Pd-Catalyzed Cycloisomerization to 1,2-Dialkylidenecycloalkanes. 2. Alternative Catalyst SystemJournal of the American Chemical Society, 1994
- Rhodium(I)‐Catalyzed ‘Metallo‐Ene’ Cyclizations/β‐EliminationsHelvetica Chimica Acta, 1993
- The Efficient Preparation Of Isomeric (1,3-Dioxanyl/1,3-Dioxolanyl)PhenolsSynlett, 1993
- An Approach to Botrydianes: On the Steric Demands of a Metal Catalyzed Enyne MetathesisSynthesis, 1993
- The Atom Economy—A Search for Synthetic EfficiencyScience, 1991
- Annulation via alkylation-Alder ene cyclizations. Palladium-catalyzed cycloisomerization of 1,6-enynesJournal of the American Chemical Society, 1991
- Cycloisomerization approach to tetrahydrofuransThe Journal of Organic Chemistry, 1989
- Intramolecular carbametalations. A [2 + 2 + 2] cycloaddition as evidence for a palladacyclopentene intermediateJournal of the American Chemical Society, 1987