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Reaction of B(4)‐acylmethyl o‐carborane with 2‐azido‐1,3‐dimethylimidazolinium hexafluorophosphate (ADMP) in the presence of 1,8‐diazabicyclo[5.4.0]‐undec‐7‐ene (DBU) in acetonitrile at 25 °C for 3 h produced a wide range of o‐carboranyl‐acyl‐substituted diazo compounds in high yields with good functional group tolerance. [ABSTRACT FROM AUTHOR]

We have developed Pd‐catalyzed oxidative cyclization reactions of a wide range of azulene‐2‐carboxylic acids with a large number of activated as well as unactivated 1,3‐dienes, consequently allowing a streamlined synthetic method for the selective preparation of monosubstituted alkenyl dihydroazulenolactones and their derivatives. [ABSTRACT FROM AUTHOR]

Sequential C(2)‐bromoarylation reaction and intramolecular CO bond formation from azulene‐1‐carboxylic acids and di(2‐bromoaryl)iodonium salts produced azulenolactones in one pot. The sequential reaction proceeded smoothly through the copper(I)‐mediated cyclization of 2‐(2‐bromoaryl)azulene‐1‐carboxylic acids derived from the regioselective iridium(III)‐catalyzed C(2)‐bromoarylation reaction without decarboxylation. [ABSTRACT FROM AUTHOR]

An efficient synthetic method for structurally various isochromenoindolones has been demonstrated through Rh(III)‐catalyzed C−H activation followed by a cyclization reaction of N‐methoxyarylamides with 3‐diazooxindoles. The sequential reaction involves the streamlined formation of C−C and C−O bonds in one pot. The present method provides a broad range of isochromenoindolones as a new privileged scaffold in moderate to good yields with the release of methoxyamine and molecular nitrogen and has the benefits of a broad substrate scope and good functional group tolerance. [ABSTRACT FROM AUTHOR]

The synthetic methods of isocoumarins and phosphaisocoumarins from the C‐H activation reaction of aromatic compounds having carboxylic acid and phosphoryl groups as directing groups activation with alkynes, vinyl acetates, cyclic 2‐diazo‐1,3‐diketones, benzoquinone‐1,3‐dienes, bromoalkynes, and epoxides were reviewed. CH activation followed by oxidative cyclization using aromatic carboxylic acids affords isocoumarin derivatives in good to excellent yields in the presence of a variety of transition metal catalysts such as rhodium, iridium, cobalt, ruthenium, and palladium. In addition, the synthetic methods used for obtaining phosphaisocoumarins were accessed using phosphoryl groups as directing groups through CH activation catalyzed by rhodium, ruthenium, and palladium. [ABSTRACT FROM AUTHOR]

A synthetic method for ethyl 4‐(alkyl or arylsulfonamido)‐2‐naphthoates from ethyl (E)‐α‐ethynyl‐β‐aryl‐α,β‐unsaturated esters (1) and N‐sulfonyl azides (2) in the presence of 2,6‐lutidine in THF at 60 °C for 3 h was developed in one step, in which a copper(I)‐catalyzed 1,3‐dipolar cycloaddition, ketenimine formation, and 6π‐electrocyclization followed by [1,3]‐H shift tandem reaction took place. This method enabled efficient synthesis of a wide range of 1‐aminonaphthalene and 3‐aminobenzofuran and 3‐aminobenzothiophene derivatives with the release of molecular nitrogen. [ABSTRACT FROM AUTHOR]

A regioselective C3‐alkylation based on the reaction of 2‐arylimidazo[1,2‐a]pyridines with a wide range of aryl α‐diazoesters in the presence of a Rh(II) catalyst in dichloroethane at room temperature was developed. This method could be applied in the synthesis of benzoimidazoquinolizinone and cycloheptaimidazopyridinone, which are novel heterocyclic scaffolds. [ABSTRACT FROM AUTHOR]

A rhodium-catalyzed cyclization reaction of sulfoximines with 3-diazoindolin-2-imines is described. This protocol provides a wide range of indolo-1,2-benzothiazines in moderate to excellent yields together with the release of molecular nitrogen and p-toluenesulfonamide. The present method involves the N-H/C-H activation of S-aryl sulfoximines and has the advantages of a broad substrate scope. [ABSTRACT FROM AUTHOR]

Iridium(III)-catalyzed regioselective B(4)-H amination is developed from the reaction of o -carborane acids with sulfilimines without any oxidants under mild conditions, which leads to a wide range of B(4)-H aminated o -carboranes in good yields with a broad substrate scope. Moreover, the selective B(3,6)-diamination reaction of the o -carborane acid was achieved. The present reaction is attractive from a practical point of view because dibenzothiophene is quantitatively recovered and reused.

An iridium(III)-catalyzed regioselective acylmethylation of the cage B(4)-H bond in o -carborane acids with sulfoxonium ylides is demonstrated through B(4)-H activation in ethanol under very mild conditions, affording a number of B(4)-acylmethylated o -carboranes. Additionally, the selective sequential B(4)- and B(6)-acylmethylation reactions finally gave B(3,5)-diacylmethylated o -carboranes in one pot.

A direct B(4)-H monoacyloxylation via a Pd-catalyzed regioselective B(4)-H activation of o -carborane acids with phenyliodonium dicarboxylates was developed, and a series of B(4)-H monoacyloxylated o -carboranes decorated with active groups were synthesized with moderate to good yields as well as excellent selectivity. In addition, a direct B(4,5)-H diacetoxylation from o -carborane acids with phenyliodonium diacetate was demonstrated.

Rhodium-catalyzed oxidative [4 + 2] cyclization reactions through the C-H activation of azulene carboxylic acids as nonbenzenoid aromatic compounds with symmetrical and unsymmetrical alkynes were developed under aerobic conditions, which produced azulenolactone derivatives with a wide substrate scope and excellent functional group tolerance. Interestingly, azulenic acids in reaction with alkynes underwent iridium-catalyzed [2 + 2 + 2] cyclization accompanied by decarboxylation to afford tetra(aryl)-substituted benzoazulene derivatives. The reactivity order for C-H activation reaction is greater toward azulene-6-carboxylic acid, azulene-1-carboxylic acid, and azulene-2-carboxylic acid. For the first time, the expansion of azulenes having directing group as nonbenzenoid aromatic compounds for C-H activation was successful, indicating that nonbenzenoid aromatic compounds can be used as good substrates for the C-H activation reaction. Therefore, the research area of C-H activation will certainly expand to nonbenzenoid aromatic compounds in future.

A regioselective synthetic method for the preparation of indolopyrazines was demonstrated through a sequential Rh-catalyzed formal [3+3] cycloaddition and aromatization reaction of a wide range of diazoindolinimines with azirines. Because the previously reported synthetic methods afforded mixtures of indolopyrazines, the present method using unsymmetrical azirines has a strong advantage from a regioselectivity viewpoint.