Secondary chiral Grignard reagents, synthesis

After discovery of the higher stereoselectivities made possible by the zinc chloride catalysis, the synthesis was applied to several secondary alcohols having two or more stereocenters15. The first of these (35,4S)-4-methyl-3-heptanol, was first made with (S)-pinanediol as the chiral director, but has since been made more stereoselectively with (R,R)-2,5-dimethyl-3,4-hexanedi-ol (Section 1.1,2.1.2.1.). Another insect pheromone, eldanolide, requires the use of (R)-pinane-diol in order to obtain the natural enantiomer, and introduces the use of an enolate as well as an allylic Grignard reagent for C-C bond formation15. 

Hoffmann, R. W. Holzer, B. Knopff, O. Harms, K. Asymmetric synthesis of a chiral secondary Grignard reagent. Angew. Chem. Int. Ed. 2000, 39, 3072-3074. 

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