Visible‐Light‐Photosensitized Aryl and Alkyl Decarboxylative Functionalization Reactions

Despite significant progress in aliphatic decarboxylation, an efficient and general protocol for radical aromatic decarboxylation has lagged far behind. Herein, we describe a general strategy for rapid access to both aryl and alkyl radicals by photosensitized decarboxylation of the corresponding carboxylic acids esters followed by their successive use in divergent carbon–heteroatom and carbon–carbon bond‐forming reactions. Identification of a suitable activator for carboxylic acids is the key to bypass a competing single‐electron‐transfer mechanism and “switch on” an energy‐transfer‐mediated homolysis of unsymmetrical σ‐bonds for a concerted fragmentation/decarboxylation process.     

Iron‐Catalyzed anti‐Selective Carbosilylation of Internal Alkynes

Reported is the anti ‐selective carbosilylation of internal alkynes with silylborane and alkyl halides using a FeBr₂/DPPE catalyst system. The iron catalyst allows simultaneous introduction of a carbon electrophile and a silicon nucleophile to simple internal alkynes, including diaryl‐, dialkyl‐, and aryl/alkyl‐substituted alkynes, in a highly stereoselective manner. Alkyl halides are applicable as the electrophiles, thereby enabling the synthesis of a variety of tetrasubstituted alkenylsilanes. In addition, syn ‐selective carbosilylation was achieved through stereoswitching, by using a silylborane having oxygen functionality on the silyl group. This novel iron‐catalyzed carbosilylation is a useful tool for expedient synthesis of stereodefined multisubstituted olefins, a fundamental structural motif in organic chemistry.     

Cobalt‐Catalyzed Diastereo‐ and Enantioselective Hydroalkenylation of Cyclopropenes with Alkenylboronic Acids

Catalytic diastereo‐ and enantioselective hydroalkenylation of 3,3‐disubstituted cyclopropenes with readily accessible alkenylboronic acids, promoted by a chiral phosphine/Co complex, is presented. Such a process constitutes the unprecedented and direct introduction of a wide range of alkenyl groups onto the cyclopropane motif to afford multisubstituted cyclopropanes in up to 95 % yield with greater than 95:5 d.r. and 99:1 e.r. Functionalization of the products delivered enantioenriched cyclopropanes that are otherwise difficult to access.     

Iridium‐Catalyzed Distal Hydroboration of Aliphatic Internal Alkenes

The regioselective hydroboration of aliphatic internal alkenes remains a great challenge. Reported herein is an iridium‐catalyzed hydroboration of aliphatic internal alkenes, providing distal‐borylated products in good to excellent yields with high regioselectivity (up to 99:1). We also demonstrate that the C?B bond of the distal‐borylated product can be readily converted into other functional groups. DFT calculations indicate that the reaction proceeds through an unexpected Ir^III/Ir^V cycle.     

Quaternary Centers by Nickel‐Catalyzed Cross‐Coupling of Tertiary Carboxylic Acids and (Hetero)Aryl Zinc Reagents

This work bridges a gap in the cross‐coupling of aliphatic redox‐active esters with aryl zinc reagents. Previously limited to primary, secondary, and specialized tertiary centers, a new protocol has been devised to enable the coupling of general tertiary systems using nickel catalysis. The scope of this operationally simple method is broad, and it can be used to simplify the synthesis of medicinally relevant motifs bearing quaternary centers.     

Reductive Molybdenum‐Catalyzed Direct Amination of Boronic Acids with Nitro Compounds

The synthesis of aromatic amines is of utmost importance in a wide range of chemical contexts. We report a direct amination of boronic acids with nitro compounds to yield (hetero)aryl amines. The novel combination of a dioxomolybdenum(VI) catalyst and triphenylphosphine as inexpensive reductant has revealed to be decisive to achieve this new C?N coupling. Our methodology has proven to be scalable, air and moisture tolerant, highly chemoselective and engages both aliphatic and aromatic nitro compounds. Moreover, this general and step‐economical synthesis of aromatic secondary amines showcases orthogonality to other aromatic amine syntheses as it tolerates aryl halides and carbonyl compounds.