H-1, C-13 AND F-19 NMR-STUDY OF AR,AR'-DIFLUORO[2.2]PARACYCLOPHANES, AR,AR'-DIFLUORO-2,11-DITHIA[3.3]PARACYCLOPHANES AND THEIR MONOFLUORO ANALOGS, LONG-RANGE F-19,F-19 SPIN-SPIN COUPLING

The four isomeric difluoro-2,11-dithia [3.3] paracyclophanes, 3F(2), w ith one fluorine substituent per aromatic ring were prepared as a 1:1: 1:1 mixture. They were converted into the bissulphones, which were pyr olysed to yield the ar,ar'-difluoro [2.2] paracyclophanes, 2F(2), as a mixture of pseudogeminal, pseudoortho-, pseudometa- and pseudopara-is omers in a ratio of 1:2:3:2. The H-1, C-13 and F-19 NMR spectra of the mixture of starting materials, 3F(2), and of the mixture of products, 2F(2), were analyzed by the use of two-dimensional shift correlations (H-1,H-1-COSY,C-13,H-1- and F-19,H-1-HETCOR) and by comparing the exp erimental H-1 and C-13 chemical shifts with those predicted by assumin g additivity of substituent chemical shifts (SCS). The SCS values were derived from the spectra of the monofluoro compounds, 2F and 3F. Larg e through-space F-19,F-19 coupling constants were observed for the pse udogeminal isomers of 2F(3) (13.7 Hz) and 3F(2) (7.2 Hz). Smaller J(F, F) values were found for the pseudoortho- (0.6 Hz) and, surprisingly, for the pseudopara-isomer (2.8 Hz) of 2F(2). The latter coupling is pr obably transmitted through the pi-electron system(s) of the [2.2]parac yclophane deck. A number of through-space J(F,C) and J(F,H) couplings were also observed. (C) 1997 John Wiley & Sons, Ltd.