✍ Scribed by Yury Yu. Rusakov; Leonid B. Krivdin; Elena Yu. Senotrusova; Elena Yu. Schmidt; Alexander M. Vasiltsov; Albina I. Mikhaleva; Boris A. Trofimov; Oleg A. Dyachenko; Anatolii N. Chekhlov; Olga N. Kazheva
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Conformational study of 2‐phenylazo‐1‐vinylpyrrole and 2‐(4‐bromophenyl)azo‐5‐methyl‐1‐vinylpyrrole was performed on the basis of the experimental measurements and high‐level ab initio calculations of their ^13^C^13^C and ^13^C^1^H spin–spin coupling constants, showing marked stereochemical behaviour upon the internal rotation of the vinyl group and the pyrrolyl moiety. In liquid phase, both compounds were found to adopt predominant s‐trans‐s‐trans conformation with the noticeable population (ca. 30%) of the higher‐energy s‐cis‐s‐trans conformation in the latter compound. As follows from the X‐ray data, 2‐phenylazo‐1‐vinylpyrrole crystallizes in s‐trans‐s‐trans conformation while the crystalline molecular structure of 2‐(4‐bromophenyl)azo‐5‐methyl‐1‐vinylpyrrole is s‐cis‐s‐trans. Copyright © 2006 John Wiley & Sons, Ltd.
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## Abstract New reactive dyes, 2‐arylazo‐1‐vinylpyrroles, have been synthesized in 52–94 % yield by a modified azo coupling of readily accessible 1‐vinylpyrroles with arenediazonium hydrocarbonates in aqueous ethanol (≈3:1) at 0 °C. The __λ__~max~ values for the UV/Vis absorption of the dyes ranges