Facile synthesis of novel [alpha]-methylene-pyrazole-carboxylate substituted imines and trans-[beta]-lactams: Versatile synthons for diverse heterocyclic molecules
A simple, facile, and high yielding stereoselective approach for the integration of α-methylene-pyrazole-carboxylates at the [beta]-lactam nucleus is described. These monocyclic [beta]-lactams have been synthesized by treatment of 2-phenoxy/benzylthio/phenylthio ethanoic acids or acetoxyacetyl chlor...
Saved in:
Published in | Synthetic communications Vol. 48; no. 10; p. 1190 |
---|---|
Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Philadelphia
Taylor & Francis Ltd
15.05.2018
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | A simple, facile, and high yielding stereoselective approach for the integration of α-methylene-pyrazole-carboxylates at the [beta]-lactam nucleus is described. These monocyclic [beta]-lactams have been synthesized by treatment of 2-phenoxy/benzylthio/phenylthio ethanoic acids or acetoxyacetyl chloride/phthalimidoacetyl chloride 5a-e with novel α-methylene-pyrazole-carboxylate imines 4a-c using Et3N and POCl3 in refluxing toluene. All of the newly synthesized α-methylene-pyrazole carboxylate imines 4a-c and their [beta]-lactam derivatives 6a-h have been fully characterized by spectroscopic techniques such as FTIR, NMR (1H, 13C, and 13C DEPT-135), 2D-NMR (COSY and HSQC), and elemental analyses (CHN). The cycloaddition reaction was found to be highly stereoselective leading to the exclusive formation of trans-[beta]-lactams 6a-h and trans configuration was assigned with respect to coupling constant values of C3-H and C4-H. The novel [beta]-lactams 6a-h bearing α-methylene-pyrazole-carboxylate ring system will serve as useful synthons for highly functionalized acids, acetohydrazides/pyrazolones, alcohols, pyrazole carboxamides, peptides, and promising biologically active agents. |
---|---|
ISSN: | 0039-7911 1532-2432 |
DOI: | 10.1080/00397911.2018.1439174 |