A systematic study on the regioselective cyclization of benzene‐ and naphthalene‐based unsymmetrical diols with HBr (33 %) in acetic acid at room temperature led to the formation of annulation products. By using this method, synthesis of a wide variety of anthracene, tetracene and naphtho[b]thiophene analogues was achieved in good to excellent yields. By employing HBr (33 %) in acetic acid as a catalyst for regioselective cyclization of unsymmetrical diols was very facile and devoid of commonly encountered dihydroisobenzofuran formation.

A straightforward and general method for the synthesis of annulated thiophene, dibenzothiophene, and carbazoles analogues has been achieved involving alkylation of 2-bromo-1-(phenylsulfonylmethyl)arene/heteroarene with arylmethyl bromides/heteroarylmethyl bromides using t-BuOK as a base in DMF, followed by Pd(0)-mediated intramolecular Heck coupling in the presence of KCO in DMF at 80-140 °C. The attractive feature of this protocol is that a wide variety of π-conjugated heterocycles could be readily accessed by an appropriate choice of arylmethylsulfones and benzylic bromides.

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A triflic acid mediated heteroarylation of phthalaldehydic acid in 1,2-dichloroethane at reflux temperature leads to the formation of 3-heteroarylphthalides. This method for the phthalidation of heteroarenes can be utilized for the successful preparation of mono-, bis-and tris-heteroarylphthalides.

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Diels‐Alder reaction of 1,3‐diarylisobenzofurans with cyclopenten‐1‐one as well as 2‐cyclohexen‐1‐one in the presence of TMSOTf in DCM at 0 °C furnished 4,5‐diarylbenzo[e]inden‐1‐ones and 6,7‐diarylbenzo[f]α‐tetralones. The benzo[e]inden‐1‐ones/benzo[f]α‐tetralones upon Fischer indolization led to the formation of indeno[b]indoles and dihydronaphtho[a]carbazoles, respectively.

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