Indirect electrochemical oxidation of 4,4¢-(arylmethylene)bis(1H-pyrazol-5-ols) in methanol in an undivided cell in the presence of sodium bromide results in highly efficient formation of the corresponding bis(spiro-2,4-dihydro-3H-pyrazol-3-one)cyclopropanes with 85-96% substance yields and 70-80% current efficiency. NMR and single crystal X-ray diffraction indicate that the products are formed exclusively as (R*,R*)-isomers. The application of this effective indirect electrochemical approach to the corresponding pharmacologically promising bis(spiro-2,4-dihydro-3H-pyrazol-3-one)cyclopropanes allows facile and convenient reaction conditions, and is valuable from the viewpoint of environmentally benign synthesis and large-scale processes.
Cyanine and polymethine dyes T 1300Reactions of β-Dimethylaminoacrolein Aminal and 3-Dimethylamino-1,1,3-trimethoxypropane with 3-(Dicyanomethylidene)indan-1-one and 1,3-Bis(dicyanomethylidene)indan. -The reaction affords only the corresponding trimethine salts. Replacement of the title aminal by aminoacetal (VII) gives oxanine salt (VIII), which can be easily transformed into novel ionic polymethine dyes such as (IX). -(KRASNAYA*, Z. A.; TRET'YAKOVA, E. O.; ZLOTIN, S. G.; Russ.
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