Palladium-catalyzed C-C bond formation of arylhydrazines with olefins via carbon-nitrogen bond cleavage

The unactivated carbon-nitrogen bond of various aryl hydrazines was cleaved under very mild conditions by Pd(0) with the assistance of Pd(II). The in situ generated aryl palladium complex readily takes part in the C-C bond formation with olefins. This study offered a new mode of C-Pd bond formation, which will spur the development of palladium-catalyzed cross-coupling in the future.     

Palladium-catalyzed carbonation-diketonization of terminal aromatic alkenes via carbon-nitrogen bond cleavage for the synthesis of 1,2-diketones

A palladium-catalyzed carbonation-diketonization reaction of terminal alkenes via carbon-nitrogen bond cleavage under an atmosphere of oxygen has been developed. A series of 1,2-diketones were readily prepared from the reaction of aromatic terminal alkenes with nitroalkanes.     

Iron-catalyzed oxidative homo-coupling of indoles via C-H cleavage

A new method for the homo-coupling of indoles has been developed by the use of FeCl₃ as catalyst and molecular oxygen as the only oxidant. The protocol provides a practical and straightforward approach toward 3,3′-biindolyls.     

Efficient synthesis of 1,3,5-trisubstituted benzenes via three Pd-mediated carbon-sulfur, carbon-nitrogen and carbon-carbon bond formation reactions

An efficient synthesis of 1,3,5-trisubstituted benzenes via a sequential Pd-mediated carbon-sulfur, carbon-nitrogen, and carbon-carbon bond formation reactions is reported. Selective amidation and sulfonamidation reactions are accomplished via Pd-catalyzed reactions between aryl chlorides and an acetamide or a methanesulfonamide.     

Iron-catalyzed synthesis of phenanthrenes via intramolecular hydroarylation of arene-alkynes

An Fe(OTf)₃-catalyzed intramolecular hydroarylation of arene-alkynes with high functional group tolerance has been reported, affording a series of phenanthrene derivatives efficiently. A low catalytic amount of Fe(OTf)₃ is applied in this reaction. This transformation provides a convenient and practical method for the preparation of phenanthrenes.     

Novel synthesis of benzoxaphosphacycloalkane derivatives via palladium-catalysed intramolecular formation of carbon-phosphorus bond

A novel synthesis of benzoxaphosphacycloalkane derivatives by palladium-catalysed intramoleclar cyclization of the corresponding alkane-or benzenephosphonous acid mono(ω-o-bromophenylalkyl)ester is presented.     

Iron-catalyzed C-H and C-C bond cleavage: a direct approach to amides from simple hydrocarbons

Something functional: The title reaction proceeds in the presence of azide and water to deliver amides in high yields, and it can be used in a ring-expansion strategy to generate lactams. A mechanism is proposed based on experimental results. This reaction offers a new approach to functionalizing simple and readily available hydrocarbons. DDQ = 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.     

Iron-catalyzed synthesis of functionalized 2H-chromenes via intramolecular alkyne-carbonyl metathesis

An iron-catalyzed intramolecular alkyne-aldehyde metathesis strategy of the alkynyl ether of salicylaldehyde derivatives has been developed which works under mild reaction conditions to produce the functionalized 2H-chromene derivatives. This protocol is compatible toward a wide range of functional groups, such as methoxy, fluoro, chloro, bromo, and phenyl groups. This method provides an atom-economical and environmentally friendly approach for the synthesis of a series of substituted 2H-chromenes.     

A versatile method for carbon-nitrogen bond formation via ene reactions of acylnitroso compounds

The use of acylnitroso compounds of the general formula RCONO as enophiles in the formation of carbon-nitrogen bonds is described. Both inter- and intramolecular ene reactions have been studied. For the intermolecular examples, nitrosocarbonylmethane, thermally liberated from its Diels-Alder adduct with 9,10-dimethylanthracene, is reacted with various olefins giving the corresponding N-alkylhydroxamic acids in moderate to high yields, providing an efficient method for allylic amidation. The regiochemistry of the intermolecular reaction is observed to be the result of kinetic control, and the direction of addition is consistent with attack by the olefin on electron-deficient nitrogen. Several examples of intramolecular ene cyclization are demonstrated, providing efficient entry into both spiro and fused bicyclic nitrogen containing systems which can be viewed as derived from annulation of 5- and 6- membered nitrogen containing rings onto 5- and 6-membered carbocycles, respectively. Various examples of this hetero-annulation scheme are described. Experimental details are also privided describing typical reaction procedures.     

Selective synthesis of poly-substituted fluorine-containing pyridines and dihydropyrimidines via cascade C-F bond cleavage protocol

Fluorinated azaheterocycles are frequently found in pharmaceuticals, drug candidates, ligands for transition metal catalysts, and other molecular functional materials, so efficient methods for the synthesis of these compounds are of significant value. We herein describe a selective strategy for the synthesis of poly-substituted pyridines and fluoroalkyl dihydropyrimidines based on C-F bond breaking of the anionically activated fluoroalkyl group. An array of pyridines and dihydropyrimidines were prepared through this domino process in high yields under noble metal catalyst-free conditions, making this method a valuable supplement to azaheterocycle synthesis.     

Copper-catalyzed 1,2-hydroxysulfenylation of alkene using disulfide via cleavage of the S-S bond

Copper-catalyzed 1,2-hydroxysulfenylation of alkenes can be carried out by the use of disulfides and acetic acid in air. This reaction regio- and anti-selectively gave the corresponding 1,2-acetoxysulfides. Furthermore, the present method enables the use of both organosulfide groups of disulfide.     

O-selective condensation using P-N bond cleavage in RNA synthesis without base protection

In RNA synthesis without base protection, a new method for O-selective condensation with more than 99% selectivity was developed by 6-nitro-HOBt-mediated cleavage of undesired P(III)-N bonds on nucleobase moieties. Moreover, we for the first time succeeded in synthesizing oligoRNAs without base protection.     

Rhenium-catalyzed synthesis of naphthalene derivatives via insertion of aldehydes into a C-H bond

A rhenium complex, [ReBr(CO)₃(THF)]₂, catalyzed reactions of aromatic ketimines and aldehydes with dienophiles, followed by dehydration, to give naphthalene derivatives in good to excellent yields. This reaction proceeds via C-H bond activation, insertion of an aldehyde, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline and Diels-Alder reaction. After dehydration, naphthalene derivatives were formed.     

Iron-catalyzed direct alkenylation of 2-substituted azaarenes with N-sulfonyl aldimines via C-H bond activation

A novel iron-catalyzed alkenylation of 2-substituted azaarenes through sp(3) C-H bond activation has been developed. A favorable E2-elimination is proposed as a key step to cleavage of C-H and C-N bonds for the construction of a C═C bond in high stereoselectivity. This transformation represents an efficient way to synthesize 2-alkenylated azaarenes from simple starting materials.     

N-arylation of carbamate-protected glycine derivatives via palladium catalysis

A synthesis of N-aryl and N-heteroaryl amino acid derivatives using palladium catalysis is described. Several carbamate-protected glycine derivatives react with aryl and heteroaryl halides using a palladium/Xantphos catalyst system to access the desired synthons.     

Ring opening of methylenecycloalkenes via the C-C bond cleavage

3-Methylenecycloalkene-1,1-dicarboxylates underwent facile ring opening via the cleavage of the unactivated C-C bond to yield aliphatic alkenes. The reaction (intramolecular deallylation) was catalyzed by "Ni-H" species generated in situ from a NiX2(phosphine) n/R3Al mixture and proceeded under ambient conditions. In addition, the skeletal rearrangement of a diene could be carried out by a one-pot cycloisomerization/deallylation sequence.