Enantioselective Formal C(sp2)−H Vinylation

An enantioselective formal C(sp²)?H vinylation of prochiral 2,2‐disubstituted cyclopentene‐1,3‐dione is presented. This vinylative desymmetrization is realized by using a two‐step procedure that consists of a catalytic enantioselective vinylogous Michael addition of deconjugated butenolides to cyclopentene‐1,3‐dione and a base‐mediated decarboxylation. The overall process utilizes deconjugated butenolides as the source of the highly substituted vinyl unit. Five‐membered carbocycles containing a remote all‐carbon quaternary stereogenic center are obtained in good yields and with good to high enantioselectivities.     

Metal-Free Phosphorus-Directed Borylation of C(sp2)−H Bonds

Spectacular progress has recently been achieved in transition metal-catalyzed C?H borylation of phosphines as well as directed electrophilic C?H borylation. As shown here, P-directed electrophilic borylation provides a new, straightforward, and efficient access to phosphine–boranes. It operates under metal-free conditions and leverages simple, readily available substrates. It is applicable to a broad range of backbones (naphthyl, biphenyl, N-phenylpyrrole, binaphthyl, benzyl, naphthylmethyl) and gives facile access to various substitution patterns at boron (by varying the boron electrophile or post-derivatizing the borane moiety). NMR monitoring supports the involvement of P-stabilized borenium cations as key intermediates. DFT calculations reveal the existence and stabilizing effect of π-arene/boron interactions in the (biphenyl)(i-Pr)₂P→BBr₂⁺ species.     

Iron‐Catalyzed Intramolecular C(sp2)−H Amination

The nucleophilic iron complex Bu₄N[Fe(CO)₃(NO)] (TBA[Fe]) catalyzes the direct intramolecular C?H amination of α‐azidobiaryls and (azidoaryl)alkenes into the corresponding carbazoles and indoles, respectively, under mild conditions and with low catalyst loadings. These features and the broad functional‐group tolerance render this method a particularly attractive alternative to established noble‐metal‐based procedures.