SHORT COMMUNICATIONSIt is well known that phenols readily undergo condensations with various carbonyl compounds. Among these transformations, the most interesting are those leading to oxygen-containing heterocyclic compounds which exhibit significant biological activity. We previously reported on reactions of methyl 3-hydroxyphenylcarbamate (I) with ethyl acetoacetate, ethyl benzoylacetate, and L-malic acid in the presence of concentrated sulfuric acid, which afforded 23-87% of carbamate coumarin derivatives [1].While developing studies in this line, we examined the condensation of methyl 3-hydroxyphenylcarbamate (I) with ethyl 4-chloro-3-oxobutanoate in concentrated sulfuric acid and 85% polyphosphoric acid (PPA). The reaction in concd. H 2 SO 4 was carried out at room temperature (reaction time 24 h). The reaction in PPA was carried out under different conditions with variation of the temperature (70-90°C) and time. The optimal conditions were heating of the reaction mixture for 1 h at 70°C, followed by keeping for 24 h at 25°C. Raising the temperature and reaction time led to the formation of a lot of tars. In both cases, the condensation product was identified by IR and 1 H NMR spectroscopy as methyl 2-oxo-4-chloromethyl-2H-chromen-7-ylcarbamate (II) which was obtained in 58 and 35% yield, respectively (Scheme 1). The 1 H NMR spectrum of II, apart from other signals, contained a singlet at δ 3.71 ppm from three protons in the carbamate fragment and a singlet at δ 4.55 ppm from two protons in the chloromethyl group. Thus carbamate I behaved similarly to resorcinol in analogous reaction [2].It is known that an allylic chlorine atom can be replaced by nucleophiles. The reaction of chloromethyl-substituted chromene II with morpholine in dioxane at room temperature gave the expected product, methyl 4-(morpholin-4-ylmethyl)-2-oxo-2H-chromen-7-ylcarbamate (III) whose structure was confirmed by the IR, 1 H NMR, and mass spectra (Scheme 1).
Synthesis and Application of Chalcones to the Preparation of Heterocyclic Structures. -Condensation of carbamate (I) with aromatic aldehydes can be performed under basic and acidic conditions. Resulting chalcones undergo further reaction with hydrazine, hydroxylamine, guanidine, and thiourea to afford pyrazole (VII), isoxazole (VI), and pyrimidine derivatives. With selenium dioxide the corresponding selenadiazole (XV) is formed. -(VELIKORODOV*, A. V.; IONOVA, V. A.; TEMIRBULATOVA, S. I.; TITOVA, O. L.; STEPKINA, N. N.; Russ. J. Org. Chem. 49 (2013) 11, 1610-1616, http://dx.doi.org/10.1134/S1070428013110080 ; Astrakhan State Univ., Astrakhan 414000, Russia; Eng.) -M. Bohle 26-035
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