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Mannich and Ring Closure; 1,3-Oxazinecoumarine

SyntheticPage 516
DOI: 10.1039/SP516
Submitted Oct 17, 2011, published Oct 18, 2011
Baris Kiskan (kiskanb@itu.edu.tr)
A contribution from Yagci


			Reaction Scheme: <IMG src="/images/empty.gif">Mannich and Ring Closure<IMG src="/images/empty.gif">

Chemicals Used

Chloroform  (HPLC grade, Aldrich)
potassium carbonate
p-toluidine
paraformaldehyde (Merck)
resorcinol (Acros)
All reagents were used without further purification.  

Procedure

4-methyl-7-hydroxycoumarin (5 g, 28.4 mmol) and p-toluidine (3 g, 28.0 mmol) were separately dissolved in 1,4-dioxane (100ml each) . Paraformaldehyde (1.7g, 54.8 mmol) and  NaOH (0.1 g) were dissolved in methanol (3 ml) with heating. This solution was added to the cold 1,4-dioxane solution of p-toluidine. This combined solution was poured into the 4-methyl-7-hydroxycoumarin solution and heated to reflux for 24 h. At the end of the reaction, dioxane was distilled off and the remaining solid was dissolved in chloroform, and washed successively with 0.1 N K2CO3 solution and deionized water until the light blue colour of the water phase disappeared. Subsequently, the organic layer was dried with anhydrous Na2SO4 and chloroform was evaporated to yield crude benzoxazine-coumarin. Recrystallization from minimum amount of THF in a refrigerator gave white crystals. (56% yield)

Author's Comments

The reaction most probably takes about 6-8 h,  however I left it 24 h. 

Data

m.p: 163°C, 13C-NMR (62.8 MHz, CDCl3): δ 18.6, 20.5, 46.4, 80.3, 108.8, 111.6, 112.3, 113.5, 118.7, 123.5, 129.9, 131.6, 145.5, 151.2, 153.0, 157.3, 160.9)


Lead Reference

Baris Kiskan, Yusuf Yagci, Thermally Curable Benzoxazine Monomer with a Photodimerizable Coumarin Group, J. Polym. Sci. Part A: Polym. Chem., 2007, 45, 1670–1676.

Supplementary Information

DSC (Dynamic Scanning Calorime (COUMARIN dsc.tif)
H NMR (coumarin H nmr.tif)

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Get structure file (.cdx, .sk2, .mol)

Keywords: addition, Benzoxazine, Coumarine, heterocyclic compounds, nucleophilic, Polybenzoxazine, Thermosetting

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