displayed H-bonding with a lysine side chain, benefiting from the expanded size of the thietane dioxide compared to a methyl sulfone. 5 Syngenta patented a series compounds containing pendant thietane dioxides as insecticides. 6 Preliminary investigations have also studied thietane dioxide derivatives as replacements for carbonyl groups in carboxylic acids which maintained some acidity in comparison to oxetanols, 7 including in ibuprofen analogues, and in spirocyclic morpholine analogues as solubilizing motifs (Figure ). We have been interested in the synthesis of 3,3-disubstituted aryl-oxetanes and azetidines through the catalytic generation of carbocationic intermediates. The use of Lewis (Li + , Ca 2+ , and Fe 3+ salts) and Brønsted acid catalysts has proven useful in selectively activating the 4-membered ring benzylic tertiary alcohols for Friedel-Crafts alkylation, 9 and alkylation of thiols 10 and alcohols. 11,12 We envisaged that a similar approach may be viable on thietane dioxides, and as such provide a facile route to 3,3- disubstituted thietane dioxides, exploiting thietane-3-one as a readily available precursor. 13 Here we report the development of a calcium catalyzed reaction of 3-aryl-thietan-3-ol dioxides with arene and thiol nucleophiles, and a Brønsted acid catalyzed reaction with alcohols. This strategy provides arylthietane dioxide derivatives in a short divergent route expanding the available chemical space of 4membered heterocycles. The 3,3-disubstituted products display high chemical stability and potential for further diversification.