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DOI: 10.1055/s-2007-992446
Yttrium-Salen Catalyst for the Enantioselective Opening of Epoxides
Contributor(s):Hisashi Yamamoto, Marina NaodovicThe Ohio State University, Columbus, USA
Exceptionally Active Yttrium-Salen Complexes for the Catalyzed Ring Opening of Epoxides by TMSCN and TMSN3
J. Org. Chem. 2007, 72: 8648-8655
Publication History
Publication Date:
23 January 2008 (online)
Key words
yttrium - salen complexes - epoxides
Significance
This account describes the more detailed investigation of nucleophilic opening of epoxides in the presence of chiral yttrium-salen complexes. This catalytic system shows improvements regarding the amounts necessary for efficient conversion compared to catalysts previously reported by Hoveyda and co-workers (Angew. Chem., Int. Ed. Engl. 1996, 35, 1668) and Jacobsen and co-workers (Org. Lett. 2000, 2, 1001). The main significance of this report is the development of a highly reactive catalytic system that circumvents side reactions usually associated with previous catalysts.
Comment
The authors report structures of two catalysts tested for the opening of epoxides. It is proposed that in 1 the epoxide can be activated by displacement of the THF ligand while cyanide can by activated by displacement of the silylamide ligand. Comparing the asymmetric induction of 1 and 2 (2 gives higher ee values) indicates that the BINAP backbone provides a more tightly controlled ligand field. Hopefully, further adjustments can be achieved to improve the enantioselectivity.