Asymmetric Diamination of the In Situ Generated Difluoroenol Species Using Azocarboxamides as an N Source

The Rh2(esp)2 and Zn(II)-bisoxazoline (BOX) complex-cocatalyzed asymmetric diamination of in situ generated difluoroenol species with azocarboxamides has been disclosed. This reaction features a formal [3 + 2]-cycloaddition reaction using difluoroenol intermediate as a C2 synthon, providing an efficient and robust approach for the synthesis of difluorinated imidazolidin-2-ones in good yields with high to excellent stereoselectivity (up to 95% ee). This method offers a complementary approach for the direct assembly of chiral difluoromethylene incorporated heterocycles by introducing in situ formed difluoroenol species as a practical C2 synthon rather than using presynthesized gem-difluoroalkenes. With this protocol, further synthetic applications in fluorine chemistry could be envisioned through the strategic interception of difluoroenol via cycloaddition reactions with appropriate partners.