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2001.9 - 2005.6 Nankai University, College of Chemistry, B. S.
2005.9 - 2010.6 Nankai University, SKLEOC, Ph. D.
<Copper-catalyzed Carbenoid Insertion into Hetroatom–hydrogen Bonds>
The transition metal-catalyzed insertion of α-diazocarbonyl compounds into X–H (X = C, Si, N, O, S etc.) bonds is a powerful organic transformation for preparing highly versatile building blocks. Great achievements have been made in the methodology for catalytic diazo insertion into C–H bonds including its asymmetric version. By contrast, insertions into heteroatom-hydrogen bonds have been less exploited. Not until quite recently, few breakthroughs have been obtained in asymmetric N–H and O–H bonds insertion reactions. However, extreamly low enantioselectivities (≤ 23% ee ) were reported in asymmetric S–H bonds insertion reactions so far. The copper-catalyzed carbenoid insertion into Si–H bonds only afforded moderate enantioselectivities. As for B–H bond insertion, there is no catalytic process documented.
Chiral spiro bisoxazoline ligands were found highly efficient in copper-catalyzed asymmetric N–H and O–H insertion reactions. In this thesis, we realized the asymmetric S–H bond insertion reactions of α-diazo esters by using copper complexes of spiro bisoxazolines. A wide range of mercaptan and thiophenols reacted with diazoesters to produce chiral α-mescaptoesters with moderate to good enantioselectivities (up to 85% ee). This result represents the best enantioselectivity in the catalytic asymmetric carbenoid S–H bond insertion reactions.
To improve the enatioselectivity of copper-catalyzed asymmetric Si–H bond insertion reaction, we developed a new Schiff base ligand containing a chiral spirobiindane backbone. With the novel spirodiimine/copper catalyst, high yields with enantioselectivities of up to 99% ee were achieved in the carbenoid insertion into Si–H bond.
Catalytic carbenoid BH bond insertion reaction was also studied in this dissertation. By using phosphorous or amine adducts of borane, we realized the first metal-catalyzed BH bond insertion reaction. Under very mild conditions, a wide range of α-dizao carbonyl compounds reacted with the activated borane smoothly, affording the BH bond insertion products with good to excellent yields. Boronic acid pinacol ester was also synthesized in high yield through this method. This work offered a novel way for the construction of BC bond. Asymmetric version of this reaction was studied with spiro bisoxazoline/copper complex as catalyst, and up to 92% ee enantioselectivity was obtained. This work provides a new method for the synthesis of chiral borane compounds.
key words: chiral spiro bisoxazolines, chiral spiro diimines, SH bond insertion, SiH bond insertion, BH bond insertion
1. Yong-Zhen Zhang, Shou-Fei Zhu, Yan Cai, Hong-Xiang Mao, Qi-Lin Zhou*, Copper-catalyzed enantioselective carbenoid insertion into S–H bonds, Chem. Commun. 2009, 5362-5364.
2.Yong-Zhen Zhang, Shou-Fei Zhu, Li-Xin Wang, Qi-Lin Zhou*, Copper-catalyzed highly enantioselective carbenoid insertion into Si–H Βonds, Angew. Chem. Int. Ed. 2008, 47, 8496-8498.
3.Shou-Fei Zhu, Jian-Βo Xie, Yong-Zhen Zhang, Shen Li, Qi-Lin Zhou*, Well-defined chiral spiro Ir/phosphine-oxazoline cationic complexes for highly enantioselective hydrogenation of imines at ambient pressure,J. Am. Chem. Soc. 2006, 128, 12886-12891.