R. Singh, R. M. Singh
Sep 1, 2000
Citations
0
Influential Citations
1
Citations
Journal
ChemInform
Abstract
The 4-(N,N-dimethyl aminomethylene)-2-alkyl-2-oxazolin -5-ones 4 h~ve been synthesised from N-acyI-U-arnino acids 2 an d meth yl esters 3 with Vil smeier-Haack reagent. The reaction of oxazo10nes 4a,c with primary aJkylamines 7 in acetonitril e takes pl ace at exocyclic olefinic carbon to afford substituted product 4-aJkylaminomethylene-2-aJkyl-2-oxazolin5-ones 8 , whereas the reaction of oxazolones 4a-d with hydrazi nc hydrate gives cyclised product 4-acyla mino-5 hydroxypyrazoles 9a-d, respectively . The methanolysis of oxazolones 4c,d with sodium methoxide in methanol takes place at lacto ne carbonyl carbon to g ive meth yl 2-acy lamino-3-dimethylaminopropenoates 12c,d. However, the ethanolysis with sodium ethoxide In ethanol occurrs at exocyclic carbon to afford 4-hydroxymethylene-2-oxazolin-5-ones 14c,d and N-acyl a-amino acids 15c,d at room an d reflu x temperature, respectively. Literature reveals that the acyl derivatives of a amino acid esters have been extensively used in the des igning of , oxazoles' -4, affording S-alkoxyoxazole via cyclodehydration as th e sol e productS. Besides, the N-acyl-a-amino acids have also been used in the synthesis of 4-alkyllarylidene-2-oxazolin-S-ones 6 . 7 . Recently , we repot1ed th e reacti on of N-aroyl-a amino acid esters and anilides with Vilsmeier-Haack reagent to afford the synthesis of 4-(N,N-di methylamino-methyl ene)-2-aryl -2-oxazolin -S-ories 8 . 9 . However, th e reactions of N-acyl- a-amin o acids and the ir derivatives with Vil sme ir-Haack reagent have not been explored 8 , In this paper, we report the synthesis of 4-(N,N-dimethylamino-meth ylene)-2alk yl-2-oxazolin-S-ones from the N-acy l- a-amino ac id s and the ir methyl esters with V -H reagent and their reaction s with va ri o us N-and O-nuc leophiles. When th e reacti on of either aceturi c acid or its meth yl ester was conducted with V -H reagent in DMF at va ri ous temperature, the formati on of product was accompli shed at room tempe rature in overnight followed by neutra li sati on at 0 to SoC to afford brownish yell ow coloured compound, which was characte ri sed from physical, spectral and chemical data as 4-(N,N-dimethylanunomethylene)-2-methyl-2oxazolin-S-ones 4a (Scheme I) . In contrast, ne ut ra li sation 8 . 9 at room te mperature afforaed only dimeth ylformamide. The maximum yield of the product 4a was optimized and achieved by using 1:3 mola r ratio of th e substrate 2a and V -H reagent o R-~-NH