Chiral Thiourea Catalysts Containing Fluxional Groups: Synthesis of Fluorinated Chiral Building Blocks

In this work, we describe the synthesis of a new class of chiral thiourea catalysts that feature a reactivity-enhancing pyridine group and a fluxional substituent that impacts selectivity. The synthesis of the chiral catalysts, which is modular, can be accomplished in four steps with good yields. We have evaluated the efficacy of the new catalysts in the conjugate addition of indoles to fluoroalkyl nitroalkenes. The reactions provide a variety of fluorinated chiral building blocks in 65-99% yield with 81-91% ee.