Cyclobutanes are an important class of motifs present in a wide range of natural products and other biologically significant molecules. A photocatalytic [2 + 2] cycloaddition between pyridones or isoquinolones and ethenesulfonyl fluoride was achieved, providing a portal to a class of unique cyclobutane-fused pyridinyl sulfonyl fluorides with quaternary rigid rings (30 examples). Further applications of these novel sulfonyl fluoride molecules in SuFEx click chemistry were also accomplished, providing the corresponding sulfonates and sulphonamides with reasonable yields.