Secondary o-hydroxybenzene sulfonamides have been explored as bis-electrophilic partners in a practically simple, atom-economical approach to dibenzo[b,f][1,4,5]oxathiazepine-5,5-dioxides and their heterocyclic analogs, which is an underexplored version of privileged tricyclic scaffolds for drug design. The reaction proceeds smoothly and regiospecifically under conventional heating conditions and delivers the target compounds in good to excellent yields. The approach represents a completely new disconnection of the dibenzo[b,f][1,4,5]oxathiazepine-5,5-dioxide scaffolds and allows accessing a new chemical space in terms of the substitution pattern. In particular, heterocycles can be conveniently varied within the tricyclic frameworks by altering the nature of the bis-electrophilic aromatic partner in the cyclization. This has been demonstrated by the synthesis of three hitherto undescribed heterotricyclic scaffolds. The cyclizations were shown to proceed via the Smiles rearrangement, as had been observed by us for a range of similar ring-forming processes. (C) 2016 Elsevier Ltd. All rights reserved.