References

Mechanistic Conclusions
Based upon considerations from the article: Charette, A. B.; Juteau, H.; Lebel, H.; Molinaro, C. J. Am. Chem. Soc. 1998, 120, 11943-11952.

Cyclopropanation of allylic alcohols with dioxaborolane ligands demonstrates an enantioselectivity based upon the size and orientation of the ligand involved.  After the CO2Et group is converted to an OH group, the ligand must bind on the opposite side of the double bond due to sterics.  This stabilizes the bond, allowing for the cyclopropanation reaction to occur.  The Simmons-Smith zinc reagent acts as an effective chiral controller in this conversion of allylic alcohols into enantiomerically enriched cyclopropanes.  The reagent is complexed by the carbonyl amide of the dioxaborolane ligand as well as the oxygen atom of the allylic alkoxide.  This allows for the most stable configuration of the allylic chain, forming the an ideal conformation for the delivery of the methylene and thus predicting the absolute configuration for the cyclopropanation of the allylic alcohol.

This article is also cited by:
Zhang, H.; Tückmantel, W.; Eaton, J.B.; Yuen, P.; Yu, L.; Bajjur, K. M.; Fedolak, A.; Wang, D.; Ghavami, A.; Caldarone, B.; Paterson, N. E.; Lowe, D. A.; Brunner, D.; Lukas, R. J.; Kozikowski, A. P. J. Med. Chem., 2012, 55, 717-724.  
This article examines a reaction involving the cyclopropanation of an acetylene, and for this reason cites the above article as a reference for this mechanism.  

Wang, T.; Liang, Y.; Yu, Z. X. J. Am. Chem. Soc., 2011, 133, 9343-9353.  
This article involves a cyclopropanation reaction using the Charette chiral dioxaborolane ligand, and for this reason cites the above article as a reference for this reaction.