Three-Component Synthesis of Dioxaphosphorane-Fused Diphosphacycles Exhibiting Unique Dynamic Fluorescence "On/Off" Properties.

Rigidly planar polycyclic phosphacycles featuring an internal dioxaphosphorane are promising photofunctional materials. However, the lack of efficient synthetic methods resulted in limited structural diversities which significantly hampered extensive study. Herein, we report a straightforward three-component synthesis of novel dioxaphosphorane-fused diphosphacycles with distinctive photophysical properties. Control experiments and theory calculations were performed to account for a plausible reaction mechanism. We also systematically investigated the structure-property relationships of these unprecedented platforms by combining experiments (X-ray analysis, optical and redox properties) and theoretical computations. Based on their unique structure and properties, a novel fluorescent switch for pH sensing was revealed by a dynamic ring-opening/ring-closing process.

P(v) intermediate-mediated E1cB elimination for the synthesis of glycals.

Glycals are highly versatile and useful building blocks in the chemistry of carbohydrate and natural products. However, the practical synthesis of glycals remains a long-standing and mostly unsolved problem in synthetic chemistry. Herein, we present an unprecedented approach to make a variety of glycals using phosphonium hydrolysis-induced, P(v) intermediate-mediated E1cB elimination. The method provides a highly efficient, practical and scalable strategy for the synthesis of glycals with good generality and excellent yields. Furthermore, the strategy was successfully applied to late-stage modification of complex drug-like molecules. Additionally, the corresponding 1-deuterium-glycals were produced easily by simple t BuONa/D2O-hydrolysis-elimination. Mechanistic investigations indicated that the oxaphosphorane intermediate-mediated E1cB mechanism is responsible for the elimination reaction.