Regioselectivities in deprotonation of 2-(4-chloro-2-pyridyl)benzoic acid and corresponding ester and amide |
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Authors: | Anne-Sophie Rebstock François Trécourt Guy Quéguiner |
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Institution: | Laboratoire de Chimie Organique Fine et Hétérocyclique, UMR 6014, IRCOF, Place E. Blondel, BP 08, 76131 Mont-Saint-Aignan Cedex, France |
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Abstract: | Upon treatment of ethyl 2-(4-chloro-2-pyridyl)benzoic acid, 2-(4-chloro-2-pyridyl)benzoate, and N,N-diisopropyl-2-(4-chloro-2-pyridyl)benzamide with LTMP at −75 °C in THF, the lithio derivatives at C5′ are generated regiospecifically, as demonstrated by subsequent quenching with electrophiles. The lithio derivative at C3′ is only evidenced from the benzamide at higher temperature (−50 °C), when treated with LTMP in THF; it instantly cyclizes to 1-chloro-4-azafluorenone. The latter is converted to onychine, an alkaloid endowed with anticandidal activity. |
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Keywords: | Metallation Pyridines Mechanism Onychine |
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