Chiral 2,2'-Bipyridine-Type N-Monoxides as Organocatalysts in the Enantioselective Allylation of Aldehydes with Allyltrichlorosilane
Andrei V. Malkov, Monica Orsini, Daniele Pernazza, Ken W. Muir, Vratislav Langer, Premji Meghani and Pavel Kocovsky*
*Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK, Email:
p.kocovsky
chem.gla.ac.uk
A. V. Malkov, M. Orsini, D. Pernazza, K. W. Muir, V. Langer, P. Meghani, P. Kocovsky, Org. Lett., 2002, 4, 1047-1049.
DOI: 10.1021/ol025654m
Abstract
A heterobidenate bipyridine monoxide (PINDOX) catalyzes the Sakurai-Hosomi-type allylation of aromatic and heteroaromatic aldehydes with high enantioselectivities. The sterochemical outcome is mainly controlled by the axial chirality in PINDOX.
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proposed
transition state
Details
The document discusses the use of chiral 2,2′-bipyridine-type N-monoxides, specifically PINDOX, as organocatalysts in the enantioselective allylation of aldehydes with allyltrichlorosilane. The study highlights the high enantioselectivities achieved in the Sakurai-Hosomi-type allylation of aromatic and heteroaromatic aldehydes. The enantioselectivity is primarily controlled by the axial chirality in PINDOX, influenced by annulated terpene units. The oxidation of PINDY to N-monoxide (+)-8 and its use in the allylation reaction with benzaldehyde resulted in high enantioselectivity (up to 92% ee). The study also compares the performance of different catalysts, showing that (+)-8 and its dimethyl derivative (+)-9 provide high enantioselectivities. The research suggests that the stereoelectronic control in the transition state is crucial for the observed enantioselectivity. The document concludes that PINDOX-type catalysts, characterized by their heterobidentate nature, offer significant potential for high enantioselectivity in related reactions. Further applications and mechanistic studies are being investigated to expand the use of these catalysts. The research was supported by AstraZeneca, the University of Rome, and the University of Glasgow.
A. V. Malkov, M. Bell, F. Castelluzzo, P. Kocovsky, Org. Lett., 2005, 7, 3219-3222.
Key Words
Hosomi-Sakurai Reaction, Allylation, Organocatalysis
ID: J54-Y2002-730
