A facile preparation, spectroscopic and chemical properties, crystal structures, and electrochemical behavior of monocarbenium ion compounds stabilized by 3-guaiazulenyl and dihydroxyphenyl (or hydroxymethoxyphenyl) groups |
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Authors: | Shin-ichi Takekuma Ippei MiyamotoAkio Hamasaki Toshie Minematsu |
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Institution: | a Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1 Kowakae, Higashi-Osaka-shi, Osaka 577-8502, Japan b School of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka-shi, Osaka 577-8502, Japan |
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Abstract: | Reaction of guaiazulene (8) with 2,3-dihydroxybenzaldehyde (9) in methanol in the presence of hexafluorophosphoric acid (i.e., 65% aqueous solution) at 25 °C for 2 h gives (3-guaiazulenyl)(2,3-dihydroxyphenyl)methylium hexafluorophosphate (13) in 86% yield. Similarly, reaction of 8 with 2-hydroxy-3-methoxybenzaldehyde (10) or 3,4-dihydroxybenzaldehyde (11) or 4-hydroxy-3-methoxybenzaldehyde (12)] under the same reaction conditions as for 9 affords the corresponding monocarbenium ion compound 14 (63% yield) or 15 (43% yield) or 16 (77% yield)], respectively, each product of which is stabilized by 3-guaiazulenyl and dihydroxyphenyl (or hydroxymethoxyphenyl) groups. A facile preparation and crystal structures as well as spectroscopic, chemical, and electrochemical properties of 13-16, possessing two interesting resonance structures, respectively, i.e., a protonated o- (or p-) benzoquinonemethide form and a 3-guaiazulenylium ion form, in a solution of acetonitrile and further, in a single crystal, are reported. |
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Keywords: | Dihydroxybenzaldehydes Electrochemical behavior Facile preparation Guaiazulene 3-Guaiazulenylium ion Hexafluorophosphoric acid Intramolecular hydrogen bond Hydroxymethoxybenzaldehydes Monocarbenium ions NaBH4-reduction Protonated benzoquinonemethides Spectroscopic properties X-ray crystal structures |
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