Photochemical Oxidation of Thiazolidines and Oxazolidines Enables Access to Reactive Oxygen Species (ROS) Sensitive and Chitin-Derived Heterocycles.

The development of sustainable synthetic methodologies is crucial to advancing greener processes. In this work, a mild and chemoselective photochemical oxidation of thiazolidines to the corresponding thiazolines under an oxygen-free atmosphere and oxazolidines to oxazolines under an oxygen atmosphere is described. The transformation proceeds efficiently with the inexpensive organophotocatalyst 9-fluorenone for thiazolidines, while both [Ru(bpy)3](PF6)2 and 3CzClIPN proved effective for oxazolidines. The reaction tolerates a wide range of functional groups, including oxidation-sensitive moieties such as dimethylamines and boronic acids, and delivers up to 94% yield across 28 substrates. Importantly, this methodology enables the late-stage functionalization of the chitin-derived synthon 3-acetamido-5-formylfuran (3A5F), a challenging aldehyde prone to decomposition, expanding the chemical space of nitrogen-containing renewable scaffolds. The synthetic utility of the process is further demonstrated through the total synthesis of the antibacterial natural product Aerugine in 20% overall yield. This sustainable and versatile approach opens new avenues for the preparation of heterocycles and bioactive molecules from renewable resources.