The reaction of 3-bromo-2-hydroxy-2-phosphacoumarin 2-oxides with sodium nitrite proceeds as the replacement of bromine atom by the nitro group, which affords the corresponding 3-nitro derivatives as sodium salts. X-ray diffraction study for the two representatives demonstrates that their structures can be classified as coordination polymers.
Sawdust-templated Ce0.8Zr0.2O2 catalysts modified with Ag, KNO3, and K2CO3 were studied in soot oxidation under tight-contact conditions. The silver-modified catalyst was more efficient than Ce0.8Zr0.2O2 at low and medium temperatures, and the K2CO3-modified one, only at low temperatures; both potassium salts caused side reactions along with the combustion of soot and significant modification of the porous structure of Ce0.8Zr0.2O2. The effectiveness of chemical modifiers was determined by the effect on redox properties provided that the optimal texture of the original mixed oxide was maintained, which ensured contact between the soot and the catalyst.
The reaction of fluorinated anilines with the KSCN/Br2/AcOH reagent system at room temperature affords the corresponding 4-thiocyanatoanilines when the substrates contain para-positioned hydrogen atom; if this position is occupied by fluorine, the ‘NCS+’ attack occurs at the ortho position thus leading to fluorinated 2-aminobenzothiazoles. The diazotization of these amino derivatives enables the facile synthesis of new bromine- and iodine-containing analogues. In such 2-bromo(polyfluoro)benzothiazoles, the bromine atom can be readily replaced by organylthio, aryl, or alkylamino groups.
The electrophilic fluorination of 1-tert-butyl-3-methyl- and 1-tert-butyl-5-methylpyrazoles with Selectfluor affords the corresponding 4-fluoropyrazoles, in distinction to N-unsubstituted 3-methylpyrazole. 1-tert-Butyl-4-fluoro-5-methylpyrazole readily undergoes HCl-assitied N-de-tert-butylation yielding 4-fluoro-3-methylpyrazole whereas the isomer with 3-positioned methyl group tolerates the deprotection. The procedure is practical (aqueous medium), scalable, and employs commercial reagents.
Dimethyl dispiro[2.1.2.0]heptane-4,4-dicarboxylate containing three spiro-linked cyclopropane rings has been proven to be a valuable building block for the Lewis acid catalyzed rearrangements to give a set of products involving the cleavage of two or three cyclopropane rings. Among various Lewis acids tested, GaCl3 was able to selectively generate a non-classical 2-cyclopropylallyl carbocation that further isomerized to produce (3-methylcyclopent-2-enylidene)malonate as almost exclusive product.
