EXPLORING THE DYNAMIC ROLE OF THE ANIONIC LIGANDS IN Ru-CATALYZED ASYMMETRIC OLEFIN METATHESIS

The vast development of the metathesis reaction over the years have enabled the promotion of asymmetric metathesis by chiral ruthenium pre-catalysts.¹ Extensive studies discussing the replacement of the commonly used chloride ligands in the known ruthenium alkylidenes by different halides and pseudo-halides, showed that fine-tuning of the anionic ligands can lead to different reactivity and selectivity of the pre-catalysts.² We have recently developed an innovative protocol for the synthesis of benzylidene type ruthenium pre-catalysts, bearing amino acids as chiral anionic ligands, and established their application in asymmetric metathesis. The use of amino acids as chiral ligands enables a facile protocol as well as easily tuned properties. Due to the dynamic nature of the anionic position, reduction of the lability of the carboxylate ligands was found to be crucial in improving the observed enantioselectivity.³ Exploration of the types of processes to which the anionic ligands are subjected to⁴ will provide vital information and further the synthesis of an efficient and economical chiral catalyst for asymmetric metathesis.

References:

1 Wang, F.; Liu, L. –J.; Wang. W.; Li, S.; Shi, M. Coord. Chem. Rev. 2012, 256, 804.

2 Anderson, E. B.; Buchmeiser, M. R. Synlett 2012, 2, 185.

3 Ivry, E.; Ben-Asuly, A.; Goldbergb, I.; Lemcoff, N. G. Chem. Commun. 2015, 51, 3870.

4 Tanaka, K.; Böhm, V. P. W.; Chadwick, D.; Roeper, M.; Braddock, D. C. Organometallics. 2006, 25, 5696.