The regiochemistry of palladium-catalyzed hydrostannations of terminal alkynes is dramatically influenced by ligand effects. Use of phosphines such as Cy3P, t-Bu2PCH2t-Bu, and t-Bu3P provides (E)-1-tributylstannyl-1-alkenes with regioselectivities up to >99:<1 for substrates where the commonly used Ph3P shows much lower regioselectivities.
1997organo-boron compounds, nonmetal heterocycles organo-boron compounds, nonmetal heterocycles S 0047
-199Contributions to the Chemistry of Boron. Part 236. In Quest of New and Stable Bis(organyloxy)boranes (RO)2BH for Catalytic Hydroboration.-The title compounds are tested quantitatively in the transition metal catalyzed hydroboration of cyclopentene and the dioxaborinane. Here, ( VIII) shows to be superior to the 1,3,2-dioxaborolanes (VI) and (XIV). -(LANG, A.; NOETH, H.; THOMANN-ALBACH, M.; Chem. Ber./Recl. 130 (1997) 3, 363-369; Inst. Inorg.
The Use of Phosphine Ligands to Control the Regiochemistry of Pd-Catalyzed Hydrostannations of 1-Alkynes: Synthesis of (E)-1-Tributylstannyl-1-alkenes. -Palladium-catalyzed hydrostannylation of terminal alkynes (I) is strongly influenced by the nature of phosphine ligand used. Thus, the title E-stannylalkenes (III) are obtained with high to excellent regioselectivity in the presence of ligands like PCy3, tBu3P or tBu2P-CH2-tBu. This is successfully applied for a short synthesis of pheromone (VII). In contrast, the regioselectivity is significantly diminished in the presence of PPh3. -(DARWISH, A.; LANG, A.; KIM, T.; CHONG*, J. M.; Org. Lett. 10 (2008) 5, 861-864; Guelph-Waterloo Cent. Grad. Work Chem., Univ. Waterloo, Waterloo, Ont. N2L 3G1, Can.; Eng.) -Mischke 31-194
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