Synergistic Steric Effects in the Development of a Palladium‐Catalyzed Alkyne Carbohalogenation: Stereodivergent Synthesis of Vinyl Halides |
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Authors: | Christine M. Le Perry J. C. Menzies David A. Petrone Prof. Dr. Mark Lautens |
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Affiliation: | Department of Chemistry, University of Toronto, 80 St. George St. Toronto, Ontario (Canada) http://www.chem.utoronto.ca/staff/ML/index.php |
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Abstract: | We report our finding that by exploiting the synergistic steric effects between substrate and catalyst, an intramolecular Pd‐catalyzed alkyne carbohalogenation can be achieved. This operationally simple method uses the bulky Pd/Q‐Phos combination and allows access to tetrasubstituted vinyl halides from the corresponding aryl chlorides, bromides, and iodides. Steric effects in the substrate play a key role by promoting C‐halogen reductive elimination and enabling catalytic turnover. Through a reversible oxidative addition mechanism, a thermodynamically driven isomerization reaction is observed at elevated temperatures. Thus by changing the reaction temperature, both stereoisomers of the reaction become readily accessible. |
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Keywords: | carbohalogenation cyclization palladium reversible oxidative addition |
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