Enantioselective Zr-Catalyzed Carboalumination Plus Cu-Catalyzed Cross-Coupling

Key words

zirconium - neomenthylindenyl ligands - cryptochirality

Significance

Deuterium-labeled chiral compounds can be excellent tools for probing reaction mechanisms. Commonly used strategies for their synthesis include the use of chiral auxiliaries in stoichiometric quantities (J. Haesler et al. Nature 2007, 446, 526). The authors present an asymmetric zirconium-catalyzed carboalumination. Following ee upgrades by lipase treatment, deuterium was incorporated to generate cryptochiral molecules (G. Zhang et al. J. Am. Chem. Soc. 2006, 128, 6026).

Comment

The products of the zirconium-catalyzed reaction were produced in modest ee’s (80–88%), which were then upgraded to >99% ee by lipase treatment. Introduction of deuterium was accomplished by treatment with LiAlD₄ or via copper-catalyzed cross-coupling. The enantiomeric ratios were determined via Mosher’s method (see recent Review below).

Review

J. M. Seco, E. Quiñoá, R. Riguera Chem. Rev. 2004, 104, 17–118.