## 3 Results and Discussion  
The most straightforward synthetic route to furan-silole ladder compounds may be the reaction of the dimetalated dibenzofuran with R\({}_{2}\)SiCI\({}_{2}\) (Scheme 1), a similar procedure was reported for the synthesis of dibenzofuran-fused phosphoble [40]. Effectively, the treatment of iodo-substituted benzofuran **1** with two equivalents of \(n\)BuLi produces the corresponding dianion, which was then quenched with Me\({}_{2}\)SiCI\({}_{2}\) at \(-\)78 \({}^{\circ}\)C leading to compound **2** in moderate yield (26%). This compound was fully characterized by NMR spectroscopies. In particular, a singlet at about \(\delta\) = +0.60 ppm in \({}^{1}\)H NMR spectrum and a \({}^{13}\)C NMR signal at \(-\)3.55 ppm confirmed the presence of Si-CH\({}_{3}\) bond. High Resolution Mass Spectrometry and elemental analysis also confirmed the proposed structure. However, under similar conditions, the reaction with Ph\({}_{2}\)SiCI\({}_{2}\) provided only negligible amount of compound **4**, as already published by [PERSON] et al. [14] This might be due to the low reactivity of the dilithiated intermediate **1 Li**. Thus, the procedure was modified to prepare compounds **4-6**from the reaction of **1 Li** with highly reactive and less bulky SiCl\({}_{4}\). Dichloro-substituted silole **3** was formed in situ, then the reaction mixture was treated with two equivalents of the corresponding aryl substituted Grignard reagent. This stepwise introduction of aryl groups on the silicon atom was successful for the preparation of bisaryl-substituted siloles since compounds **4-6** have been isolated in good yields after column chromatography (31-50%) and were characterized by HRMS, elemental analysis, and multinuclear NMR spectroscopies. All these data are consistent with the proposed structures. Furthermore, the \({}^{29}\)Si and \({}^{13}\)C NMR shifts around the silole rings of these novel ladder furan-siloles derivatives are different from their thiophene and indole analogues [41; 42; 43], (\({}^{29}\)Si NMR: \(\delta\) (ppm) = \(-\)23.2 (indole based derivative [32]); \(-\)18.8 (Benzodiiophene-based derivative [32]); \(-\)21.1 (**4**)) suggesting that the different aromaticity's of the O-, N- and S- fused cycles influences the electronic distribution within the fused frameworks. The crystal packing of compound **4** was investigated by X-ray diffraction (XRD) measurements. Single crystals of **4** were obtained by slow evaporation of hexane-dichloromethane mixture solution at room temperature (Figure 2 and Table S1) The fused conjugated system featuring the five heterocycles is almost planar. However, the rather long C-Si bond (d = 1.8692(19) A) causes a slight distortion of the backbone (Si-C\({}_{1}\)-C\({}_{2}\)-C\({}_{3}\) = 11.8(4)\({}^{\circ}\) for **4** for example) (see Table S2). The bond length alternation inside the silole ring are classical (d\({}_{\text{C-C}}\) = 1.346(3) A; d\({}_{\text{C-C}}\) = 1.445(4) A). As observed for its P-analog, the bond lengths in the furan ring are dissymmetric (d\({}_{1}\) = 1.393(3) A; d\({}_{2}\) = 1.346(3) A for **4**) reflecting the aromaticity differences of the ring it is fused to (respectively phenyl and siloles). At the intermolecular level, Compound **4** crystallizes as infinite columns in which the fused benzofuran moieties of two different molecules are in \(\pi\)-stacking interactions (d = 3.636 A) (see Figure 2). The optical properties (UV-vis absorption and fluorescence) of compounds **2**, **4-6** were studied in dichloromethane (Figure 3, and Table 1). As anticipated, the four compounds **2**, **4-6** show similar absorption with a broad band in the visible range (\(\lambda_{\text{max}}\approx\) 370 nm, Figure 3). This absorption band is attribute to a \(\pi\)-\(\pi^{\text{\text{\  
show intense fluorescence around 430 nm with a small blue-shift for the derivative **2** (\(\Delta\lambda\) = 10 nm). Excitation spectra also confirmed the observations made for the UV-vis absorption of compounds **2**, **4-6**. (see Figure S1).