Tandem Schiff-Base Formation/Heterocyclization: An Approach to the Synthesis of Fused Pyrazolo–Pyrimidine/Isoxazolo-Pyrimidine Hybrids

Synlett ◽  
2019 ◽  
Vol 30 (05) ◽  
pp. 586-592 ◽  
Author(s):  
Manoranjan Behera ◽  
M. Sambaiah ◽  
Poosa Mallesham ◽  
K. Shiva Kumar ◽  
Yamini Bobde ◽  
...  
Keyword(s):  
Schiff Base ◽  
Pyrimidine Ring ◽  
Stille Coupling ◽  
New Synthesis ◽  
Schiff Base Formation ◽  
Key Steps ◽  
Base Formation

A new synthesis of pyrazolo[4,3-d]pyrimidines and isoxazolo[4,5-d]pyrimidines is described. Key steps in the synthesis involve Stille coupling of 4,6-dichloro-2-phenyl-pyrimidine with tributyl(1-ethoxyvinyl)stannane and tandem Schiff-base formation/heterocyclization of 2,6-di-aryl-5-fluoro-4-acetylpyrimidine with hydrazines or ­hydroxylamine to give pyrazolo[4,3-d]pyrimidines and isoxazolo[4,5-d]pyrimidines, respectively. The position of the fluoro group in the ­pyrimidine ring is important for the success of heterocylization reaction.

Schiff Base Formation upon Complexation of Tris(acetylacetonato)iron with N[(CH2CH2NH2)(CH2CH2OH)(CH2CH2CH2OH)]

2004 ◽  
Vol 630 (13-14) ◽  
pp. 2558-2561 ◽  
Author(s):  
F. Ekkehardt Hahn ◽  
Christoph Jocher ◽  
Thomas L�gger ◽  
Tania Pape
Keyword(s):  
Schiff Base ◽  
Schiff Base Formation ◽  
Base Formation

scholarly journals Thermal Healing, Reshaping and Ecofriendly Recycling of Epoxy Resin Crosslinked with Schiff Base of Vanillin and Hexane-1,6-Diamine

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 293 ◽  
Author(s):  
Van-Dung Mai ◽  
Se-Ra Shin ◽  
Dai-Soo Lee ◽  
Ilho Kang
Keyword(s):  
Schiff Base ◽  
Epoxy Resin ◽  
Elevated Temperatures ◽  
Relaxation Times ◽  
Diglycidyl Ether ◽  
Original Material ◽  
Crosslinked Polymer ◽  
Schiff Base Formation ◽  
Hydrolysis Of ◽  
Base Formation

A bio-derived dihydroxylimine hardener, Van2HMDA, for the curing of epoxy resin was prepared from vanillin (Van) and hexamethylene-1,6-diamine (HMDA) by Schiff base formation. The epoxy resin of diglycidyl ether of bisphenol A was cured with Van2HMDA in the presence of the catalyst, 2-ethyl-4-methylimidazole (EMI). The crosslinked epoxy resin showed thermal-healing properties at elevated temperatures. Moreover, the crosslinked epoxy resin can be reshaped by heating via imine metathesis of the hardener units. The imine metathesis of Van2HMDA was confirmed experimentally. Stress-relaxation properties of the epoxy resin crosslinked with Van2HMDA were investigated, and the activation energy obtained from Arrhenius plots of the relaxation times was 44 kJ/mol. The imine bonds in the epoxy polymer matrix did not undergo hydrolysis after immersing in water at room temperature for one week. However, in the presence of acid, the crosslinked polymer was easily decomposed due to the hydrolysis of imine bonds. The hydrolysis of imine bonds was used for the ecofriendly recycling of crosslinked polymer. It is inferred that thermal-healing, reshaping, and reprocessing properties can be implemented in the various crosslinked epoxy resins with the bio-derived dihydroxylimine hardener, albeit the recycled epoxy resin is of inevitably lower quality than the original material.

Understanding non-enzymatic aminophospholipid glycation and its inhibition. Polar head features affect the kinetics of Schiff base formation

2011 ◽  
Vol 19 (15) ◽  
pp. 4536-4543 ◽  
Author(s):  
Catalina Caldés ◽  
Bartolomé Vilanova ◽  
Miquel Adrover ◽  
Francisco Muñoz ◽  
Josefa Donoso
Keyword(s):  
Schiff Base ◽  
Polar Head ◽  
Schiff Base Formation ◽  
Kinetics Of ◽  
Base Formation
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