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Lewis Acids as Mild and Effective Catalysts for the Synthesis of 3,5‐Bis[(hetero)arylidene]piperidin‐4‐ones
Author(s) -
Leonova Evgeniya,
Makarov Mihail,
Klemenkova Zinaida,
Odinets Irina
Publication year - 2010
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.201000005
Subject(s) - chemistry , lewis acids and bases , catalysis , substituent , alkyl , medicinal chemistry , amine gas treating , organic chemistry
The aldol‐crotonic condensation reactions of N ‐alkyl‐ and N H‐piperidin‐4‐one derivatives with (hetero)aromatic aldehydes promoted by Lewis acids or bases were examined. This comparative study has revealed three effective catalytic systems based on Lewis acids, i.e. , LiClO 4 and MgBr 2 (in the presence of tertiary amine), and BF 3 ⋅Et 2 O, for the synthesis of N ‐alkyl‐substituted 3,5‐bis(heteroarylidene)piperidin‐4‐ones, including those bearing acid‐ or base‐labile groups both in the (hetero)aromatic groups and in the alkyl substituent at the N‐atom. The highest reaction rate was observed for LiClO 4 ‐mediated synthesis. Both MgBr 2 ‐ and LiClO 4 ‐mediated syntheses were inefficient in the case of N H‐piperidin‐4‐one, while BF 3 ⋅Et 2 O provided the final compounds in high yields. This catalyst is especially advantageous as it allows simultaneous condensation and deprotection in the case of O ‐protected piperidin‐4‐one.