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Title: Synthesis and Evaluation of C2-Symmetric SPIROL-Based bis-Oxazoline Ligands
This communication describes the synthesis of new bis-oxazoline chiral ligands (SPIROX) derived from the C2-symmetric spirocyclic scaffold (SPIROL). The readily available (R,R,R)-SPIROL (2) previously developed by our group was subjected to a three-step sequence that provided key diacid intermediate (R,R,R)-7 in 75% yield. This intermediate was subsequently coupled with (R)- and (S)-phenylglycinols to provide diastereomeric products, the cyclization of which led to two diastereomeric SPIROX ligands (R,R,R,R,R)-3a and (R,R,R,S,S)-3b in 85% and 79% yield, respectively. The complexation of (R,R,R,R,R)-3a and (R,R,R,S,S)-3b with CuCl and Cu(OTf)2 resulted in active catalysts that promoted the asymmetric reaction of α-diazopropionate and phenol. The resultant O–H insertion product was formed in 88% yield, and with excellent selectivity (97% ee) when ligand (R,R,R,R,R)-3a was used.  more » « less
Award ID(s):
1955069
PAR ID:
10335734
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Symmetry
Volume:
13
Issue:
9
ISSN:
2073-8994
Page Range / eLocation ID:
1667
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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