Abstract
Four Schiff bases, from pyruvic acid (1) with amines containing N and S donor atoms, thiocarbohydrazide (2, 61%), 2-methyl-3-thiosemicarbazide (3, 26%), S-benzyldithiocarbazate (4, 51%) and S-n-octyldithiocarbazate (5, 63%) have been successfully synthesized. The conventional method was used and a series of novel linear and cyclic Schiff bases were obtained with or without catalyst. All the Schiff bases were fully characterized by CHN elemental analysis, FT-IR, 1H & 13C NMR, EI-MS and two of the Schiff bases were further characterized by X-ray crystallographic structure analysis. Compound 2 crystallizes in the triclinic space group P-1 and unit cell dimensions are: a = 4.1777(8), b = 5.9538(11), c = 13.458(3) Å, α = 92.759(6), β = 90.813(6), γ = 100.040(6)°, R1 = 0.0439. Compound 3 crystallizes in the orthorhombic space group P n a 2(1) and unit cell dimensions are: a = 5.5992(2), b = 11.3962(5), c = 10.6473(5), α = 92.759(6), β = 90.813(6), γ = 100.040(6)°, R1 = 0.0285. Compounds 2 and 3 were obtained as cyclic Schiff bases which are triazine derivatives.
Highlights
March 7, 2017 thyldithiocarbazate and S-n-octyldithiocarbazate [1] [2] [3] [4] as well as thiocarbohydrazide [5] [6] [7] and substituted thiosemicarbazide [8]. These dithiocarbazates were condensed with carbonyl compounds such as pyruvic acid to synthesize several novel Schiff bases which could lead to many potential applications
Thiocarbohydrazide has a general tendency to form N-amino compound in ring closure reaction such as condensation reaction with α-ketocarboxylic acids to form triazines [15] [16]. In view of their potential medical application and our continuing interest in the synthesis of new Schiff bases, we hereby report the preparation and characterization of new Schiff bases from pyruvic acid with S-n-octyldithiocarbazate and S-benzyldithiocarbazate along with the preparation and characterization of the Schiff bases obtained from pyruvic acid with thiocarbohydrazide and 2-methyl-3-thiosemicarbazide together with their X-ray crystallographic structure analysis
Schiff bases were synthesized from the condensation reaction of pyruvic acid with 2-methyl-3-thiosemicarbazide, thiocarbohydrazide, S-benzyldithiocarbazate and S-n-octyldithiocarbazate in absolute ethanol and refluxed for 1 - 2 hours
Summary
Much attention has been focused on Schiff bases derived from S-alkyl/aryl ester of dithiocarbazic acid such as S-benzyldithiocarbazate, S-me-. These dithiocarbazates were condensed with carbonyl compounds such as pyruvic acid to synthesize several novel Schiff bases which could lead to many potential applications. The terminal amino group in thiosemicarbazide and thiocarbohydrazide on the other hand, is highly nucleophilic toward C-eletrophiles because of the activating effect of its adjacent nitrogen which is susceptible to partake in different reactions such as amide formation and Schiff base formation [15] [16] Due to this phenomenon, these amines namely thiosemicarbazide and thiocarbohydrazide have been reported to yield a series of five, six and seven membered heterocycles when treated with different compounds such as carboxylic acid or esters. In view of their potential medical application and our continuing interest in the synthesis of new Schiff bases, we hereby report the preparation and characterization of new Schiff bases from pyruvic acid with S-n-octyldithiocarbazate and S-benzyldithiocarbazate along with the preparation and characterization of the Schiff bases obtained from pyruvic acid with thiocarbohydrazide and 2-methyl-3-thiosemicarbazide together with their X-ray crystallographic structure analysis
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