Mechanism of the Stille Reaction. 2. Couplings of Aryl Triflates with Vinyltributyltin. Observation of Intermediates. A More Comprehensive Scheme

Autor:	and Pablo Espinet, Ana M. Gallego, A. Casado
Rok vydání:	2000
Předmět:	Coupling Chemistry Aryl Vinyltributyltin General Chemistry Photochemistry Biochemistry Medicinal chemistry Oxidative addition Catalysis Stille reaction Solvent chemistry.chemical_compound Transmetalation Colloid and Surface Chemistry Trifluoromethanesulfonate
Zdroj:	Journal of the American Chemical Society. 122:11771-11782
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja001511o
Popis:	The mechanism of the [PdL4]-catalyzed couplings between R−OTf (R = pentahalophenyl; L = PPh3, AsPh3) and Sn(CHCH2)Bu3 has been studied. The addition of LiCl favors the coupling for L = AsPh3 in THF but retards it for L = PPh3. Separate experiments show that for L = AsPh3, LiCl accelerates the otherwise very slow and rate-determining oxidative addition of the aryl triflate to [PdL4], leading to trans-[PdRClL2]. Therefore, the overall process is accelerated. For L = PPh3, the rate-determining step is the transmetalation. Complex trans-[PdRXL2], with X = Cl, is formed in the presence of LiCl, whereas an equilibrium mixture mainly involving species with X = TfO, L, or S (S = solvent) is established in the absence of LiCl. Since the transmetalation is slower for X = Cl than for the other complexes, the overall process is retarded by addition of LiCl. The transmetalation in complexes trans-[PdRXL2], with X = Cl, follows the SE2(cyclic) mechanism proposed in Part 1 (Casado, A. L.; Espinet, P. J. Am. Chem. Soc. 1...
Databáze:	OpenAIRE
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