Modular Access to Functionalized Oxetanes as Benzoyl Bioisosteres.

Bioisosterism is a valuable principle exploited in drug discovery to fine-tune physicochemical properties of bioactive compounds. Functionalized 3-aryl oxetanes, as an important class of bioisosteres for benzoyl groups (highly prevalent structures in approved drugs), have been rarely utilized in agrochemicals and pharmaceuticals due to significant synthetic challenges. Here, we present a modular synthetic strategy based on the unexplored yet readily available reagents, oxetanyl trichloroacetimidates, inspired by Schmidt glycosylation, enabling easy access to a library of functionalized oxetanes. This operationally simple protocol leverages the vast existing libraries of aryl halides and various nucleophiles. The power and generality of this approach is demonstrated by late-stage functionalization of complex molecules, as well as the rapid synthesis of oxetane analogues of bioactive molecules and marketed drugs. Preliminary mechanistic study suggests that the oxygen atom in the oxetane ring plays a crucial role in stabilizing the carbocation intermediates.