Seunghwan Cho

The direct functionalization of heterocyclic compounds has emerged as one of the most important topics in the field of metal-catalyzed C-H bond activation due to the fact that products are an important synthetic motif in organic synthesis, the pharmaceutical industry, and materials science. This critical review covers the recent progresses on the regioselective dehydrogenative direct coupling reaction of heteroarenes, including arylation, olefination, alkynylation, and amination/amidation mainly

Two catalytic protocols of the oxidative C-C bond formation have been developed on the basis of the C-H bond activation of pyridine N-oxides. Pd-catalyzed alkenylation of the N-oxides proceeds with excellent regio-, stereo-, and chemoselectivity, and the corresponding ortho-alkenylated N-oxide derivatives are obtained in good to excellent yields. Direct cross-coupling reaction of pyridine N-oxides with unactivated arene was also developed in the presence of Pd catalyst and Ag oxidant, which affo

New synthetic procedures for intramolecular oxidative C-N bond formation have been developed for the preparation of carbazoles starting from N-substituted amidobiphenyls under either Cu-catalyzed or metal-free conditions using hypervalent iodine(III) as an oxidant. Whereas iodobenzene diacetate or bis(trifluoroacetoxy)iodobenzene alone undergoes the reaction to provide carbazole products in moderate to low yields, combined use of copper(II) triflate and the iodine(III) species significantly impr

It is shown for the first time that N-sulfonyl amides can be efficiently prepared by an unconventional approach of the hydrative reaction between terminal alkynes, sulfonyl azides, and water in the presence of copper catalyst and amine base under very mild conditions. The present route is quite general, and a wide range of alkynes and sulfonyl azides are readily coupled catalytically with water to furnish amides in high yields. A variety of labile functional groups are tolerated under the condit

A new synthetic approach toward intermolecular oxidative C-N bond formation of arenes has been developed under transition-metal-free conditions. Complete control of chemoselectivity between aryl sp(2) and benzylic sp(3) C-H bond imidation was achieved by the choice of nitrogen sources, representatively being phthalimide and dibenzenesulfonimide, respectively.

Going to the source: Formamides or parent amines were used as an amino group source for the silver-mediated amination of benzoxazoles. Although reactions with formamides proceeded at high temperatures, the direct amination with amines took place under much milder conditions (see scheme). Optically active amino groups could also be installed without racemization.

Reported herein is an unprecedented base-promoted deborylative alkylation of pyridine N-oxides using 1,1-diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of pyridine N-oxides and 1,1-diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C-H arylation and methylation of pyridine N-oxides. The reaction also can be applied for the direct introduction of a methyl group to 9-O-methylquinine N-oxide, thu

Rhod to Addition: A highly efficient and convenient rhodium catalyst system was developed for the title transformation. A base co-catalyst was found to facilitate the key arene CH bond-activation step and substrate scope was very broad, including both electron-deficient pyridine N-oxides, and electron-rich azoles. The catalytic system was effective for the hydroheteroarylation of both alkenes and alkynes and gave excellent regio- and stereoselectivity. Detailed facts of importance to specialist

Eine Base als Cokatalysator eines hoch effizienten und bequemen Rhodium-Katalysatorsystems erleichtert die entscheidende Aktivierung einer Aren-C-H-Bindung in der Titelreaktion. Das Substratspektrum reicht von elektronenarmen Pyridin-N-oxiden bis hin zu elektronenreichen Azolen, und das Katalysatorsystem vermittelt Hydroheteroarylierungen von Alkenen und Alkinen mit herausragenden Regio- und Stereoselektivitäten. Detailed facts of importance to specialist readers are published as ”Supporting Inf

We describe a regioselective diborylation of primary benzylic C–H bonds catalyzed by [Ir(COD)OMe]2 and 4,4′-di-tert-butyl-2,2′-bipyridine (dtbpy). The hydrosilyl group acts as a traceless directing group, providing access to a range of 1,1-benzyldiboronate esters in good yields. Transformations of the 1,1-benzyldiboronate ester products include chemoselective Suzuki–Miyaura cross-couplings and synthesis of tetrasubstituted alkenyl boronate esters.

Making rings: A new Cu-catalyzed three-component coupling reaction between 1-alkynes, sulfonyl azides, and pyrrole derivatives has been developed for making 2-functionalized pyrrole rings (see scheme). This CC bond formation offers high efficiency and selectivity, mild reaction conditions, and a wide substrate scope.

Reported herein is a copper-catalyzed S(N)2'-selective allylic substitution reaction using readily accessible allylic chlorides and 1,1-diborylalkanes, a reaction which proceeds with chemoselective C-B bond activation of the 1,1-diborylalkanes. In the presence of a catalytic amount of [Cu(IMes)Cl] [IMes=1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene] and LiOtBu as a base, a range of primary and secondary allylic chlorides undergo the S(N)2'-selective allylic substitution reaction to produce b

Most functionalizations of C-H bonds by main-group reagents occur at aryl or methyl groups. We describe a highly regioselective borylation of secondary benzylic C-H bonds catalyzed by an iridium precursor and 3,4,7,8-tetramethyl-1,10-phenanthroline as the ligand. The reaction is directed to the benzylic position by a hydrosilyl substituent. This hydrosilyl directing group is readily deprotected or transformed to other functional groups after the borylation reaction, providing access to a diverse

Chemo- and stereoselective transformations of polyborylalkanes are powerful and efficient methods to access optically active molecules with greater complexity and diversity through programmed synthetic design. Among the various polyborylalkanes, <i>gem</i>-diborylalkanes have attracted much attention in organic chemistry as versatile synthetic handles. The notable advantage of <i>gem</i>-diborylalkanes lies in their ability to generate two key intermediates, α-borylalkyl anions and (<i>gem</i>-d