Highly enantioselective borane reduction of heteroaryl and heterocyclic ketoxime ethers catalyzed by novel spiroborate ester derived from diphenylvalinol: application to the synthesis of nicotine analogues.
An asymmetric synthesis for the preparation of nonracemic amines bearing heterocyclic and heteroaromatic rings is described. A variety of important enantiopure thionyl and arylalkyl primary amines were afforded by the borane-mediated enantioselective reduction of O-benzyl ketoximes using 10% of catalyst 10 derived from ( S)-diphenylvalinol and ethylene glycol with excellent enantioselectivity, in up to 99% ee. The optimal condition for the first asymmetric reduction of 3- and 4-pyridyl-derived O-benzyl ketoxime ethers was achieved using 30% of catalytic loading in dioxane at 10 degrees C. ( S)- N-ethylnornicotine ( 3) was also successfully synthesized from the TIPS-protected ( S)-2-amino-2-pyridylethanol in 97% ee.
Huang
Kun
K
Department of Chemistry, University of Puerto Rico-Humacao, CUH Station, Humacao, PR 00791, USA.
Merced
Francisco G
FG
Ortiz-Marciales
Margarita
M
Meléndez
Héctor J
HJ
Correa
Wildeliz
W
De Jesús
Melvin
M
D001880:Boranes / Q000737:chemistry*; D002384:Catalysis; D004952:Esters; D004987:Ethers; D008401:Gas Chromatography-Mass Spectrometry; D006571:Heterocyclic Compounds / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D009538:Nicotine / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D010084:Oxidation-Reduction; D010091:Oximes / Q000737:chemistry*; D013237:Stereoisomerism; D014633:Valine / Q000031:analogs & derivatives* / Q000737:chemistry
D001880:Boranes; D004952:Esters; D004987:Ethers; D006571:Heterocyclic Compounds; D010091:Oximes; C040994:valinol; D009538:Nicotine; D014633:Valine