Synthesis of new bis-BINOL-2,2′-ethers and bis-H8BINOL-2,2′-ethers evaluation of their Titanium complexes in the asymmetric ethylation of benzaldehyde
作者:Artur R. Abreu、Mariette M. Pereira、J. Carles Bayón
DOI:10.1016/j.tet.2009.11.047
日期:2010.1
consist of two BINOL or H8BINOL fragments, joined by diverse linkages through the oxygen at the 2′-position of the arylic fragments. These ligands were applied to the Ti(OiPr)4 catalyzed asymmetric alkylation of benzaldehyde with Et2Zn. The performance of these catalysts is very sensitive to the nature of the ether linkage. The ligand with a propylene link shows better enantioselectivity (ca. 70%) than
an efficient catalytic system for the enantioselectiveaddition of alkyl Grignard reagents to a broad range of aliphatic aldehydes with good yields and enantioselectivities. Remarkably, the challenging methylmagnesium bromide (MeMgBr) can also be added to a variety of aliphatic aldehydes, providing versatile chiral methyl carbinol units with unprecedented yields and enantioselectivities in a simple
The authors acknowledge financial support from the Spanish Ministerio de Ciencia y Tecnologia (MCYT) (project numbers CTQ2007-65218/BQU and CTQ2011-24151), Consolider Ingenio 2010 (grant number CSD2007-00006), and Generalitat Valenciana (G. V. PROMETEO/2009/039 and FEDER). B. M. thanks the European Commision for a Marie Curie Career Integration Grant. E. F.-M. thanks the Ministerio de Educacion y Ciencia