Search

Borylations of inert carbon-hydrogen bonds are highly useful for transforming feedstock chemicals into versatile organoboron reagents. Catalysis of these reactions has historically relied on precious-metal complexes, which promote dehydrogenative borylations with diboron reagents under oxidant-free conditions. Recently, photoinduced radical-mediated borylations involving hydrogen atom transfer pathways have emerged as attractive alternatives because they provide complimentary regioselectivities and proceed under metal-free conditions. However, these net oxidative processes require stoichiometric oxidants and therefore cannot compete with the high atom economy of their precious-metal-catalyzed counterparts. Herein, we report that CuCl 2 catalyzes radical-mediated, dehydrogenative C(sp 3 )-H borylations of alkanes with bis(catecholato)diboron under oxidant-free conditions. This is a result of an unexpected dual role of the copper catalyst, which promotes oxidation of the diboron reagent to generate an electrophilic bis-boryloxide that acts as an effective borylating agent in subsequent redox-neutral photocatalytic C-H borylations.

A green and highly efficient one-pot method for α-diaryl-β-alkynol derivatives in water at room temperature was developed using the cocatalysis of a Lewis acid and meso-tetraphenylporphyrin iron(III) chloride (FeTPPCl). The unprecedented transformation was promoted by a modulation of the charge properties of propargylic carbocation chemistry and the use of an in situ-generated oxonium ylide as a matching nucleophile. The reaction was performed in water at room temperature with a highly step-economic manipulation in good to excellent yields and with a broad substrate scope. Water also acts as the third reactant for the one-pot transformation. Notably, the FeTPPCl catalyst can be directly reused four times with a slight discount in yields.