Fused heterocycles (both aromatic and saturated) are common structures present in a significant number of natural compounds and marketed drugs. Cycloaddition reactions are powerful tools to access such ring systems and generate complex molecular architectures in an efficient, atom-economic, regio-and stereoselective manner. While numerous examples illustrating this fact exist in various subfields of heterocyclic chemistry, the cycloaddition approach was rarely used for the construction of bicyclic sulfonamides (sultams). Meanwhile, sultams gained much attention in medicinal chemistry as three-dimensional isosteres of lactams and non-basic analogs of saturated heterocyclic amines. Fused bicyclic sultams have been identified as highly potent γ-secretase inhibitors, casein kinase II inhibitors, protease activated receptor 1 (PAR-1) antagonists, or androgen receptor (AR) antagonists (Figure ). In this work, we report a comprehensive study on the [3 + 2] cycloaddition reactions of five-and six-membered ,-unsaturated sultams of general formula 1 as a general approach to fused sp 3enriched heterocyclic building blocks for early drug discovery programs (Scheme 1, A). We established the scope and limitations of these transformations depending on the nature of the 1,3-dipolar component and demonstrated their high regio-and stereoselectivity. In addition to that, antiviral activity was found for some of the synthesized cycloadducts. It should be noted that a very limited number of similar cycloadditions was reported in the literature, including the Diels-Alder reaction of -sultams (B) and [3 + 2] cycloaddition of sulton 2 with nitrile oxides or nitrones (C).