Bridged Bicyclic γ-Sultams by Intramolecular Flow Photochemical [2 + 2] Cycloaddition

An elegant synthetic approach to the construction of a novel saturated heterocycle─2-thia-3-azabicyclo[2.1.1]hexane 2,2-dioxide─was designed. The key step included intramolecular flow photochemical [2+2] cycloaddition of appropriately substituted dienes, which were in turn obtained from readily available starting materials on a multigram scale. Further synthetic transformations of the resulting bicyclic compounds enabled the preparation of numerous functionalized derivatives useful for early drug discovery programs as promising isosteres of pyrrolidine, pyrrolidone, and γ-sultams. These studies also demonstrated the tolerance of the title bicyclic system to typical organic chemistry reaction conditions.