New N-acyl- as well as N-phosphonoylmethyl- and N-phosphinoylmethyl-a-amino- benzylphosphonates by acylation and a tandem Kabachnik-Fields protocol

Diethyl alpha-benzylamino-and alpha-amino-benzylphosphonates obtained by the Kabachnik-Fields reaction were useful intermediates in the synthesis of other derivatives. Acylation of alpha-aminophosphonates with acyl chlorides led to the corresponding N-acyl species existing under a dynamic equilibriu...

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Published inOrganic & biomolecular chemistry Vol. 21; no. 8; pp. 1709 - 1718
Main Authors Varga, Petra Regina, Karaghiosoff, Konstantin, Sari, Eva Viktoria, Simon, Andras, Hegedus, Laszlo, Drahos, Laszlo, Keglevich, Gyorgy
Format Journal Article
LanguageEnglish
Published CAMBRIDGE Royal Soc Chemistry 22.02.2023
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
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Summary:Diethyl alpha-benzylamino-and alpha-amino-benzylphosphonates obtained by the Kabachnik-Fields reaction were useful intermediates in the synthesis of other derivatives. Acylation of alpha-aminophosphonates with acyl chlorides led to the corresponding N-acyl species existing under a dynamic equilibrium of two conformers. Judging from the broad NMR signals, the sterically most crowded N-benzoyl-N-benzyl derivative suffered a hindered rotation around the N-C axis to the acyl carbon atom at 26 degrees C. Low temperature NMR measurements at -10 degrees C showed the presence of two distinct rotamers that were characterized. The other acylated alpha-amino-benzylphosphonates prepared revealed a less hindered rotation. Single crystal X-ray diffraction of the NH-propionyl species showed a dimer, in which the two molecules were held together by rare intermolecular PvO?HN bonds. On the other hand, substituted alpha-benzylamino-benzylphosphonates prepared by phospha-Mannich reactions were employed, as a new approach, in a second Kabachnik-Fields condensation by reaction with formaldehyde and dialkyl phosphites or secondary phosphine oxides to afford novel N-phosphonoylmethyl-and N-phosphinoylmethyl-alpha-amino-ben-zylphosphonates. The structure of the new products was confirmed by two-dimensional NMR spectroscopy. A symmetrical bis derivative was prepared in a diastereoselective manner. A related tris(phosphonoylmethyl )amine species was also synthesized.
ISSN:1477-0520
1477-0539
DOI:10.1039/d3ob00010a