The Cadogan reaction, a widely accepted route for the synthesis of nitrogen containing heterocycles, is modified by using microwave radiation as the source of heat instead of the conventional heating by reflux in a nitrogen atmosphere for several hours. Appropriate starting materials were mixed with triethyl phosphite or triphenylphosphine and irradiated with microwaves for several minutes at a specific power to give the desired products. The indazoles were prepared by irradiating N‐(2‐nitrobenzylidene) anilines with triethyl phosphite at 200 W for 12–14 min to give 85–92% product yields. Irradiation of the mixture of N‐benzylidene‐2‐nitroanilines and triphenylphosphine at 200 W for 3–5 min yielded 93–96% of the benzimidazoles. The carbonylindoles were obtained in 61–68% yields by irradiating 2‐nitrochalcone or alkyl 2‐nitrocinnamates and triphenylphosphine with microwaves at 80–200 W for 8–11 min. The mixture of 2‐nitrobiphenyl and triphenylphosphine yielded 96% of carbazole when irradiated with microwaves at 200 W for 2 min while 75% of phenazine was obtained by irradiating the mixture of 2‐nitrodiphenylamine and triphenylphosphine with microwaves at 200 W for 3.5 min. These results show that microwave‐assisted Cadogan reactions gave better product yields at shorter reaction times. J. Heterocyclic Chem., (2009).
New Water-Soluble Host Calixarenes Bearing Chiral Substituents.-Sodium p-hydroxybenzenesulfonate (I) reacts with (S)-1-bromo-2-methylbutane (II) in the presence of a base to yield the methylbutoxybenzenesulfonate (III). Analogous reaction of (II) with the calix(4)arene (IV) leads to the formation of the tetrasulfonatotetrakis((S)-2-methylbutoxy)calix(4)arene (V). The corresponding calix(6)arene and calix (8)arene are synthesized in the same manner. The conformation and complexation properties of the calixarenes prepared are studied by means of CD-spectroscopy. -(ARIMURA, T.; KAWABATA, H.; MATSUDA, T.; MURAMATSU, T.; SATOH, H.; FUJIO, K.; MANABE, O.; SHINKAI, S.; J. Org. Chem. 56 (1991) 1, 301-306; Dep. Org.
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Die Diamine und Aminophenole (I), (IV) und (VI) Werden mit Hexafluorpropen (II) in Dimethylformamid (DMF) zu den Heterocyclen (III), (V) und (VII) umgesetzt.
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