## 3 Results and Discussion
### Synthesis
The bridge-head proton H-9 of the isomer**_anti_ **6** **appeared at $ 5.12 ppm and assigned as singlet, on the other hands, the proton H-10 appeared at 5.38 ppm as triplet with coupling constants J 2.8 Hz, while the signal of the corresponding proton H-9**\({}^{\prime}\) **of the isomer**_syn_ **6** **appeared at $ 4.41 ppm, as triplet with coupling constants J 2.8 Hz, indeed, the proton H-10**\({}^{\prime}\) **appeared at $ 6.09 ppm as broad singlet, as well, the proton H-9**\({}^{\prime\prime}\) **of the dechlorinated isomer**_dec_ **7** **appeared at upfield $ 4.36 ppm, as triplet, with coupling constants J 2.0 Hz. Finally, the proton H-10**\({}^{\prime\prime}\) **appeared at $ 5.07 ppm as singlet. The upfield shifting of the H-9**\({}^{\prime\prime}\) **signals in the isomer**_dec_ **6, comparison to the isomer**_anti_ **7, may be attributed to the absence of chlorine atoms (Cl).**  
**The DA reaction of 1,8-dichloroanthracene 1 with phenyl vinyl sulfone 4 gave the isomers; 7**_anti_**, 7**_syn_**, and 7**_dec_ **in a ratio 6.58:1.70:1, respectively, as deduced from NMR spectrum of their crude (Table 3, Figures S4 and S5). It is clear that isomer 7**_anti_ **is the major, because the steric effect resulted from the bulk phenyl sulfone group. In case of DA reaction of phenyl vinyl sulfone 4 with 10-allyl-1,8-dichloroanthracene, anti and syn isomers were obtained in a ratio 2:1 [25]. The increasing ratio of 7**_syn_ **may due to the steric hindrance of the phenyl group, and its close position to the allyl substituent that enforces the formation of the syn isomer in a more quantity than in case of 1,8-dichloroanthracene 1, where no allyl substituent [25]. The signal that assigned to bridge-head protons H-9 and H-10 of the isomer**_anti_ **7** **appeared at chemical shifts $ 5.31 ppm, as triplet, and 8 4.82 ppm, as doublet, with coupling constants J 2 and 2.6 Hz, respectively, while the signal of the corresponding proton H-9**\({}^{\prime}\) **of the isomer**_syn_ **7** **appeared at chemical shift $ 4.31 ppm, as triplet, with coupling constants J 2.6, and its signal assigned to the proton H-10**\({}^{\prime}\) **appeared at $ 5.56 ppm as broad singlet. Moreover, the signals assigned to the protons H-9**\({}^{\prime\prime}\) **and H-10**\({}^{\prime\prime}\) **of the dechlorinated isomer**_dec_ **7** **appeared at upfield chemical shifts $ 4.25 ppm, as triplet, and 4.71 ppm, as doublet, with coupling constants J 2.4 and 2 Hz, respectively. The upfield shifting of the H-9**\({}^{\prime\prime}\) **and H-10**\({}^{\prime\prime}\) **signals in the isomer**_dec_ **7, comparison to the isomers**_anti_ **7** **and**_syn_ **7, may be attributed to the absence of chlorine atoms (Cl). The H-NMR signals assigned to the 7**_dec_ **is well-matched to the signals of this compound reported in the literature [26]. It is noteworthy to report, here, that the obtaining unexpected dechlorination products 5**_dec_**, 6**_dec_**, and 7**_dec_ **is establishing a new dechlorination method that could be utilized and developed in the field of removal of chlorinated aromatic pollutants. ** \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Chemical Shift**} & \multicolumn{6}{c}{**Chemical Shift**} \\ \cline{2-11}
**Isomer** & \multicolumn{2}{c}{**H-9**} & \multicolumn{2}{c}{**H-9\({}^{\prime}\)**} & \multicolumn{2}{c}{**H-9\({}^{\prime\prime}\)**} & \multicolumn{2}{c}{**H-10**} & \multicolumn{2}{c}{**H-10\({}^{\prime}\)**} & \multicolumn{2}{c}{**H-10\({}^{\prime\prime}\)**} \\ \cline{2-11}  & **\(\delta\)** & **J** & \(\delta\)** & **J** & \(\delta\)** & **J** & \(\delta\)** & **J** & \(\delta\)** & **J** & \(\delta\)** & **J** \\ \hline
**6**_anti_ & 5.38 & t; 2.8 & & & & & 5.12 & s & & & \\
**6**_syn_ & & & & 4.41 & t; 2.8 & & & & & 6.09 & s & & \\
**6**_dec_ & & & & & 4.36 & t; 2 & & & & & 5.07 & s \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The distinguishing between the isomers **6**_anti_**, **6**_syn_**, and **6**_dec_ **using chemical shifts. **