Aluminum derivatives of a new chiral binucleating ligand

作者：Greco JF; McNevin MJ; Hagadorn JR^*

来源：Organometallics, 2005, 24(21): 5167-5171.

DOI：10.1021/om050579f

A new chiral bis(beta-amino alcohol) ligand, LH2, has been prepared in 40% yield by the Cu-catalyzed coupling of 4,6-diiododibenzofuran with diphenylpyrrolidin-2-yl-methanol, the latter of which is prepared from L-proline. The protonolysis reaction of LH2 with 2 equiv of (AlBu3)-Bu-i forms LAl2(i)BU(4) (1), which was isolated in 40% yield. In the solid state, compound 1 adopts a conformation that gives the molecule approximate C-2 symmetry. Each half of the molecule features a distorted tetrahedral Al center that interacts with a chelating beta-amino alcoholate and two Bu-i anions. The reaction of LH2 with 2 equiv of AlMe3 failed to yield isolable product, but the use of excess AlMe3 formed LAl4Me10 (2) in 79% isolated yield. Compound 2 has a structure that is similar to that of 1 except that the alcoholate oxygen of each deprotonated ligand is also coordinated to an AlMe3 group. H-1 NMR spectroscopic data of 1 in C6D6 solution are consistent with overall C-2 symmetry. Thus the two Bu-i groups on each Al center are inequivalent, and four resonances are observed for the diastereotopic alpha-CH2 protons of these Bu-i ligands. The addition of 4 equiv of pyrimidine to the solution results in rapid exchange of the two inequivalent iBu groups. A different process occurs in the presence of a large excess of D-6-methyl sulfoxide (D-6-DMSO). Under these conditions, the iBu groups no longer possess diastereotopic alpha-methylenes. This indicates that the Bu-i groups are being removed from the chiral environment, at least temporarily.

• 出版日期2005-10-10