| Popis: |
Cyclization of N-(1-aryl-1-chloro-2,2,2-trifluoroethyl)-N -arylcarbodiimides with 3-substituted 1-phenylpyrazol-5-ones yields 6-aryl-4-arylimino-1-phenyl-6-trifluoromethyl-1,4,5,6-tetrahydropyrazolo[4,3-e][1,3]oxazines. N-(1-Chloroalkyl)carbodiimides are used as 1,3-dielectrophilic components in the synthesis of various nitrogen-containing heterocyclic compounds [2, 3]. In particular, we previously showed that condensation of these reagents with 1,3-diketones (which act as O,Cdinucleophiles) yields 1,3-oxazine derivatives [4]. With the goal of synthesizing relatively difficultly accessible fused pyrazolo[4,3-e][1,3]oxazine systems [5], in the present work we examined reactions of N-(1-aryl-1-chloro-2,2,2-trifluoroethyl)-N -arylcarbodiimides Ia Ic with such O,C-dinucleophiles as 3-substituted 1-phenylpyrazol-5-ones IIa IIc. We have found that N-(1-chloroalkyl)carbodiimides Ia Ic react with 1-phenylpyrazol-5-ones IIa IIc containing an electron-acceptor substituent R in position 3 to afford 3-R-4-aryl-6-arylimino-1-phenyl-4-trifluoromethyl-1,4,5,6-tetrahydropyrazolo[4,3-e][1,3]oxazines IIIa IIIe (Scheme 1). The reactions occur in benzene in the presence of triethylamine at room temperature and take 3 days. |
