1H, 13C and 19F NMR study of ar,ar′-difluoro[2.2]paracyclophanes, ar,ar′-difluoro-2,11-dithia[3.3]paracyclophanes and their monofluoro analogues. Long-range 19F,19F spin–spin coupling

✍ Scribed by Ludger Ernst; Kerstin Ibrom

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 374 KB
• Volume: 35
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199712)35:12<868::aid-omr195>3.0.co;2-6

✦ Synopsis

The four isomeric diÑuoro-2,11-dithia [ 3.3 ] paracyclophanes, with one Ñuorine substituent per aromatic ring 3F 2 , were prepared as a 1 :1 :1 :1 mixture. They were converted into the bissulphones, which were pyrolysed to yield the ar,arº-diÑuoro [ 2.2 ] paracyclophanes, as a mixture of pseudogeminal, pseudoortho-, pseudometaand 2F 2 , pseudopara-isomers in a ratio of 1 : 2 : 3 : 2. The 1H, 13C and 19F NMR spectra of the mixture of starting materials, and of the mixture of products, were analyzed by the use of two-dimensional shift corre-3F 2 , 2 F 2 , lations (1H,1H-COSY, 13C,1Hand 19F,1H-HETCOR) and by comparing the experimental 1H and 13C chemical shifts with those predicted by assuming additivity of substituent chemical shifts (SCS). The SCS values were derived from the spectra of the monoÑuoro compounds, 2F and 3F. Large through-space 19F,19F coupling constants were observed for the pseudogeminal isomers of (13.7 Hz) and (7.2 Hz). Smaller J(F,F) values were found for 2F 2 3F 2 the pseudoortho-(0.6 Hz) and, surprisingly, for the pseudopara-isomer (2.8 Hz) of

The latter coupling is 2F 2 . probably transmitted through the p-electron system(s) of the [ 2.2 ] paracyclophane deck. A number of throughspace J(F,C) and J(F,H) couplings were also observed. 1997