Application of the aza-Wittig reaction for the synthesis of carboranyl Schiff bases, benzothiazoles and benzoselenazolines†

The aza-Wittig reaction was successfully applied to the synthesis of carboranyl-imines, which are difficult to obtain by classical methods. A variety of functionalized carboranyl Schiff bases was obtained proving the great scope of the methodology. All compounds were fully characterized, including the solid-state structures of six of them. The aza-Wittig reaction was modified to permit the synthesis in one step of carboranyl-benzothiazole and carboranyl-benzoselenazoline derivatives. The stability studies show that the carboranyl-imines and benzothiazole promote deboronation to the nido-derivatives, which is achieved by simple reaction with methanol or protic solvents. The structures of the nido-derivatives were also studied by X-ray diffraction. In contrast, the saturated derivatives, amine and benzoselenazoline, do not promote deboronation and are stable in protic solvents.