Zirconium-catalysed N-acylation of lactams using unactivated carboxylic acids

[Display omitted] •New method for the catalytic N-acylation of lactams with carboxylic acids.•Screening of Lewis acid catalysts for N-acylation of pyroglutamic acid methyl ester.•Yields up to 97% were reached with 10 mol% Zr(propoxide)4.•Substrate scope was investigated; with 57–97% yield achieved.•...

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Vydáno v:Tetrahedron letters Ročník 59; číslo 17; s. 1646 - 1650
Hlavní autoři: Hulsbosch, Joris, Claes, Laurens, De Vos, Dirk E.
Médium: Journal Article
Jazyk:angličtina
Vydáno: OXFORD Elsevier Ltd 25.04.2018
Elsevier
Témata:
Aniracetam
Catalysis
catalysts
chemical reactions
Chemistry
Chemistry, Organic
drugs
Lactam
lactams
Lewis acids
moieties
N-Acylation
palmitic acid
pesticides
Physical Sciences
Science & Technology
surfactants
temperature
zirconium
Zirconyl chloride
Zirconyl chloride
Catalysis
Aniracetam
Lactam
N-Acylation
CHEMISTRY
DISORDERS
CHLORIDE
ISSN:0040-4039, 1873-3581
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Shrnutí:[Display omitted] •New method for the catalytic N-acylation of lactams with carboxylic acids.•Screening of Lewis acid catalysts for N-acylation of pyroglutamic acid methyl ester.•Yields up to 97% were reached with 10 mol% Zr(propoxide)4.•Substrate scope was investigated; with 57–97% yield achieved.•The drug aniracetam can be produced in 84% yield. A large number of chemicals including surfactants, nootropic drugs and pesticides contain an N-acylated lactam moiety in their molecular structure. In this work, the direct, catalytic N-acylation of a number of lactams with various unactivated carboxylic acids is reported. Several Lewis acid catalysts were evaluated for their activity in the N-acylation of pyroglutamic acid methyl ester with palmitic acid; the highest activities were observed for zirconium-based catalysts. Yields of up to 97% were obtained utilising 10 mol% Zr(propoxide)4 in mesitylene at reflux temperature, but ZrOCl2·8H2O was determined as the most stable catalyst. The substrate scope was investigated and a number of lactam-carboxylic acid combinations were successfully converted into the desired products in 57–97% yield. This method provides an alternative synthetic pathway towards the drug aniracetam, which can be produced in 84% yield. A plausible catalytic mechanism is presented based on kinetic experiments.
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ISSN:0040-4039
1873-3581
DOI:10.1016/j.tetlet.2018.03.047