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The use of simple and low-cost chromium chloride salts as catalysts or precatalysts for the development of cost-effective methods is of significant synthetic and mechanistic interest. Here, recent advances in chromium-catalyzed organic transformations are highlighted. 1 Introduction 2 Arylmagnesiation of Alkynes 3 Catalytic Functionalization of C(aryl)–O Bonds 4 Catalytic Functionalization of C(aryl)–N Bonds 5 Catalytic Functionalization of C(aryl)–H Bonds 6 NHK-Type Reactions 7 Hydrogenation 8 Conclusions [ABSTRACT FROM AUTHOR]

Reported here is a straightforward process in which a cyclic (alkyl)(amino)carbene/Rh catalyst system facilitates the preferential addition of hydrogen to the substitution sites of difluoromethylated and trifluoromethylated arenes and heteroarenes, leading to dearomative reduction. This strategy enables the diastereoselective synthesis of cis‐difluoromethylated and cis‐trifluoromethylated cycloalkanes and saturated heterocycles, and even allows formation of all‐cis multi‐trifluoromethylated cyclic products with a defined equatorial orientation of the di‐ and trifluoromethyl groups. Deuterium‐labeling studies indicate that hydrogen preferentially attacks the substitution sites of planar arenes, resulting in dearomatization, possibly with heterogeneous Rh as the reactive species, followed by either reversible or irreversible hydrogen addition to the nonsubstitution sites. [ABSTRACT FROM AUTHOR]

We herein report the hydrogenation of substituted aryl‐ and heteroaryl boronate esters for the selective synthesis of cis‐substituted borylated cycloalkanes and saturated heterocycles. A cyclic (alkyl)(amino)carbene‐ligated rhodium complex with two dimethyl groups at the ortho‐alkyl scaffold of the carbene showed high reactivity in promoting the hydrogenation, thereby enabling the hydrogenation of (hetero)arenes with retention of the synthetically valuable boronate group. This process constitutes a clean, atom‐economic, as well as chemo‐ and stereoselective route for the generation of cis‐configured, diversely substituted borylated cycloalkanes and saturated heterocycles that are usually elusive and difficult to prepare. [ABSTRACT FROM AUTHOR]

Review: [24 refs. [ABSTRACT FROM AUTHOR]

Wereport here that mono-N-protected amino acids (MPAAs), an importantenvironmentally compatible structural motif, enable acceleration ofPd(II)-catalyzed dehydrogenative Heck reactions between pyridinesand electron-deficient arenes with simple alkenes, leading to diverselyfunctionalized C3- or meta-selective alkenylatedpyridines and benzenes via non-chelate-assisted C–H activation.A comprehensive theoretical study by DFT calculations discloses thatthe amino scaffold of the MPAA ligand facilely converts to an X-typeligand by an initial N–H activation, resulting in a relativelylow activation barrier for the C–H cleavage of pyridine. Thena property reversal of the amino group from X-type to L-type ligandallows the alkene substitution to take place smoothly, while the carboxylgroup enables the formation of an intramolecular hydrogen bond, significantlydecreasing the activation barrier for the carbopalladation. The resultsof calculations and the kinetic isotopic effect measurement supporta rate-limiting C–H activation by a mechanism involving a concertedmetalation/deprotonation pathway, with an endothermicity of 31.0 kcal/molin the process. [ABSTRACT FROM AUTHOR]

Two novel rhodium complexes, DMCR and CYCR, are prepared and successfully applied as catalysts for the highly chemoselective hydrogenation of aromatic ketones and phenols. [ABSTRACT FROM AUTHOR]