Synthesis of Liquid Crystalline 4H-Benzo[1,2,4]thiadiazines and Generation of Persistent Radicals

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• 作者：J&oacute ; zef Zienkiewicz ; Anna Fryszkowska ; Katarzyna Zienkiewicz ; Fengli Guo ; Piotr Kaszynski ; Adam Januszko ; David Jones
• 刊名：Journal of Organic Chemistry
• 出版年：2007
• 出版时间：April 27, 2007
• 年：2007
• 卷：72
• 期：9
• 页码：3510 - 3520
• 全文大小：396K
• 年卷期：v.72,no.9(April 27, 2007)
• ISSN：1520-6904

文摘

Four substituted 4H-benzo[1,2,4]thiadiazines 2 were prepared by condensation of the appropriate anilinesand benzonitriles followed by oxidative cyclization. The preparation of three fluorinated derivatives 2b-2d proceeded smoothly, while the synthesis of 2a was problematic, presumably due to the relativelyhigh electron density of the benzene ring. The four-ring derivatives 2c and 2d exhibited liquid crystallineproperties (2c: Cr 95 SmA 158 I and 2d: Cr 142 SmA 212 I). 4H-Benzo[1,2,4]thiadiazines 2 wereoxidized with AgO to generate the corresponding persistent radicals 1 (g = 2.0057). The stability of theradicals followed the order 1b ~ 1d > 1c 1a, and the two fluorinated radicals 1b and 1d were isolatedas crude solids. The lower stability of 1c is presumably due to the presence of the reactive benzylic CHposition, and 1a lacks the stabilizing effect of the three fluorine atoms. ESR spectra for 1 were simulatedusing DFT-derived hfcc as the starting point.