Pentaleno[1,2-c]pyrroles: Tricyclic 5/5/5 Fused Rings.

A novel method for the preparation of tetrahydropentaleno[1,2-c]pyrroles (8) is described via the reaction of anilines with 1-en-4-yn-3-ols in the presence of Lewis acid. Oxidation of 8 with Br2 gave pentaleno[1,2-c]pyrroles (10), which is the first reported tricyclic 5/5/5 ring with a fully conjugated system. Structures of these obtained compounds were characterized by spectroscopic methods, and compounds 8a,b and 10c were further confirmed by X-ray crystallographic determination.

Pd-Promoted Cyclization of (Z)-Pent-2-en-4-yn-1-yl Alkanoates Leading to Furans via an Acyl Group Shift and Further Synthetic Transformation.

Palladium-promoted acyl migration was observed in the reaction of (Z)-pent-2-en-4-yn-1-yl alkanoates in the presence of DBU to yield 2-(alkanoylmethyl)furan derivatives (2) in high yields. Compounds 2 then underwent oxidative decarbonylation to afford 2-acylfurans with O2 as the oxidant under mild and metal-free conditions. The mechanistic pathway of the reaction involving an intramolecular cyclization and acyl group shift is discussed.

Palladium-Catalyzed Vinylation of Cyclopentenes with Inverted Z,E-Isomerism of Vinylic Substrates.

A palladium-promoted Mizoroki-Heck type reaction employing a directing-group strategy to efficiently produce the coupled vinyl cyclopentenes with excellent regio- and stereoselectivity is reported. Typically, a Pd-catalyzed reaction of 2-(cyclopent-2-en-1-yl)-N-tosylacetamide (1a) with (E)-styryl bromides gave cis-2-((Z)-styryl)cyclopent-3-en-1-yl-N-tosylacetamide (3e), an allylic substitution product. Interestingly, we have found that the E,Z-stereochemistry of vinylic substrates is inverted in those products. The mechanism of this catalytic reaction is discussed.

N-Allylation versus C-allylation of intermediates from aza-Michael adducts of arylideneisoxazol-5-ones.

Reactions of arylidene-isoxazol-5-ones with intermediates from palladium-catalysed decarboxylation of allyl carbamates proceeded through aza-Michael addition and N-allylation to give the corresponding bis-adducts, ß-amido-N-allylated products, in good yields. In similar reactions with 4-vinyl-1,4-dihydro-2H-3,1-benzoxazin-2-one, a cyclic allyl carbamate, C-allylation took place to yield a series of spiro[isoxazole-4,3'-quinolin]-5-ones in high yields. Regio-selective N- versus C-allylation is illustrated to occur in an inter- versus intra-molecular fashion. The structure and stereochemistry of these products are determined by NMR spectroscopy and further confirmed by X-ray crystallography. This work offers an excellent method for the preparation of various substituted isoxazol-5-ones.

Synthesis of 2-arylamino-3-cyanoquinolines via a cascade reaction through a nitrilium intermediate.

A new method for the preparation of 2-amino-3-cyanoquinolines from readily available aryldiazonium salts, 2-aminoarylketones, and malononitrile via a cascade reaction is reported. This one-pot approach involves the in situ generation of an N-arylnitrilium intermediate from the direct reaction of aryldiazonium salts and malononitrile, which undergoes intermolecular amination, Knoevenagel condensation, and then aromatization to yield the desired compound in moderate to good yields. This methodology features a quick assembly of C2 and C3 functionalized quinolines.

Preparation of N-Arylquinazolinium Salts via a Cascade Approach.

An easy manipulation method for the preparation of N-arylquinazolinium salts is described from readily available aryldiazonium salts, nitriles, and 2-aminoarylketones in a one-pot operation. This method relies on the in situ generation of the N-arylnitrilium intermediate from the reaction of aryldiazonium salt with nitrile, which undergoes amination/cascade cyclization/aromatization, leading to N-arylquinazolinium salts in excellent yields. Nucleophilic addition of alkoxide to these N-arylquinazolinium salts provides functionalized dihydro- N-arylquinazoline.

Preparation of Quinazolinoquinazolinones via a Cascade Approach.

A one-pot synthesis of quinazolino[3,4- a]quinazolin-13-ones was realized from the direct reaction of o-(methoxycarbonyl)benzenediazonium salts, nitriles, and 2-cyanoanilines in moderate to good yields. This method utilizes the in situ generation of reactive N-arylnitrilium ion, which undergoes further amination/tandem cyclization/amidation to deliver the desired polycyclic scaffolds with consecutive formation of four N-C bonds. Flexibility in substitution patterns, mild reaction conditions, and operational simplicity are the salient features of this methodology.

Preparation of Ketimines from Aryldiazonium Salts, Arenes, and Nitriles via Intermolecular Arylation of N-Arylnitrilium Ions.

A transition-metal-free approach for the preparation of N-arylketimines has been developed from the direct reaction of aryldiazonium salts, arenes, and nitriles in a one-pot fashion with the consecutive formation of N-C and C-C bonds. This approach proceeds via an in situ generation of N-arylnitrilium intermediate, which then undergoes intermolecular arylation. This three-component strategy offers a step- and atom-efficient way to N-arylketimines from easily accessible reagents under mild reaction conditions. The characterization of stereochemistry of ketimine was achieved by X-ray crystallographic structure and theoretical calculation. Operational simplicity, shorter reaction time, excellent functional group compatibility, and scalability are the key features of this report.

Preparation of 3-hydroxyquinolines from direct oxidation of dihydroquinolinium salts.

A series of functionalized 3,4-dihydroquinolinium salts were prepared from the reaction of aryldiazonium salt with alkene in a nitrile solution. Further oxidation yielding either 3-hydroxyquinoline or quinoline products was investigated. A one-pot process from aryldiazonium salts, alkenes and nitriles leading to 3-hydroxyquinolines was also developed. Furthermore, an intramolecular trapping of an N-arylnitrilium ion with a vinyl group at the ortho position leading to 2-substituted quinolines was revealed.

Synthesis of Substituted Quinazolin-4(3H)-imines From Aryldiazonium Salts, Nitriles and 2-Cyanoanilines via A Metal-Free Tandem Approach.

A transition metal-free synthesis of multisubstituted quinazolin-4(3H)-imines has been realized by the direct reaction of aryldiazonium salts, nitriles, and 2-cyanoanilines in a one-pot fashion. This strategy utilizes the in situ formation of reactive N-arylnitrilium intermediate, which undergoes further tandem cyclization with consecutive formation of N-C bonds. Broad functional group compatibility, mild conditions, shorter time, and operational simplicity are the notable features of this report.

Preparation of Quinazolines via a 2+2+2 Annulation from Aryldiazonium Salts and Nitriles.

A (2+2+2) modular synthesis of multisubstituted quinazolines has been realized by the direct reaction of aryldiazonium salts with two equivalent of nitriles. Reaction of aryldiazonium salt with a nitrile provides the initial formation of a reactive nitrilium ion, which is attacked by another molecule of nitrile followed by electrophilic cyclization to deliver the desired product. Notable flexibility in the substitution patterns, readily available substrates, short reaction time, transition metal-free, and gram-scale synthesis are the advantages of this method.

Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino-pyridine.

Cationic methylpalladium complexes bearing hemilabile bidentate α-amino-pyridines can serve as effective precursors for catalytic alternating copolymerization of norbornene (N) and ethylene (E), under mild conditions. The norbornyl palladium complexes in the formula of {[RHNCH2(o-C6H4N)]Pd(C7H10Me)(NCMe)}(BF4) (R = iPr (2a), tBu (2b), Ph (2c), 2,6-Me2C6H3 (2d), 2,6-iPr2C6H3 (2e)) were synthesized via single insertion of norbornene into the corresponding methylpalladium complexes 1a-1e, respectively. Both square planar methyl and norbornyl palladium complexes exhibit facile equilibria of geometrical isomerization, via sterically-controlled amino decoordination-recoordination of amino-pyridine. Kinetic studies of E-insertion, N-insertion of complexes 1 and 2, and the geometric isomerization reactions have been examined by means of VT-NMR, and found in excellent agreement with the results estimated by DFT calculations. The more facile N-insertion in the cis-isomers, and ready geometric isomerization, cooperatively lead to a new mechanism that accounts for the novel catalytic formation of alternating COC.

One pot synthesis of α-ketoamides from ethylarenes and amines: a metal free difunctionalization strategy.

One-pot and metal free synthesis of α-ketoamides has been described through in situ generation of aryl ketones from easily available ethylarenes followed by amidation with various amines. This multiple oxidation protocol involves catalytic I2-pyridine-TBHP (t-butyl hydroperoxide) mediated oxidative benzylic carbonylation and sequential NaI-TBHP mediated oxidative amidation without using any solvent.

Correction: Synthesis of N-heterocyclic carbene rhenium(i) carbonyl complexes.

Correction for 'Synthesis of N-heterocyclic carbene rhenium(i) carbonyl complexes' by Chang-Hong Chen, et al., Dalton Trans., 2012, 41, 2747-2754.

Dinickel complexes with anthyridine-based ligands.

Two new dinickel complexes with anthyridine-based ligands, 5-phenyl-2,8-bis(2-pyridinyl)-1,9,10-anthyridine () and 5-phenyl-2,8-bis(6'-bipyridinyl)-1,9,10-anthyridine (), are reported. Complexation of Ni(OAc)2 with and in trifluoroacetic acid provided the corresponding dinickel complexes [{Ni2()(H2O)6(CF3COO)2}(CF3COO)2] () and [Ni2()(CF3COO)4(H2O)] (), respectively. Both complexes were characterized by spectroscopic methods and further confirmed by X-ray crystallography. Structural analyses of and revealed the NiNi distances in the complexes to be 5.4086(6) and 5.0138(7) Å, respectively. The catalytic activities of complexes and toward the reduction of carboxylic acids were evaluated. It appears that complex shows a good catalytic activity toward the reduction of carboxylates into the corresponding alcohols by diphenylsilane.

One-Pot Reactions for Synthesis of 2,5-Substituted Tetrazoles from Aryldiazonium Salts and Amidines.

One-pot sequential reactions of aryldiazonium salts with amidines followed by the treatment of I2/KI under basic conditions provide 2,5-disubstituted tetrazoles in moderate to excellent yields. This one-pot synthesis has several advantages such as mild reaction conditions, short reaction time, convenient workup, and high yields, making this methodology practical.

Preparation of substituted phenanthridines from the coupling of aryldiazonium salts with nitriles: a metal free approach.

A transition metal free approach for the synthesis of substituted phenanthridines from the coupling reaction of aryldiazonium tetrafluoroborates with nitriles has been developed. This operationally simple protocol proceeds through a substitution of aryldiazonium with nitriles followed by an intramolecular arylation to provide the corresponding phenanthridines in moderate to excellent yields.

Coordination chemistry of highly hemilabile bidentate sulfoxide N-heterocyclic carbenes with palladium(II).

Imidazolium salts, [RS(O)-CH2 (C3 H3 N2 )Mes]Cl (R=Me (L1a), Ph (L1b)); Mes=mesityl), make convenient carbene precursors. Palladation of L1a affords the monodentate dinuclear complex, [(PdCl2 {MeS(O)CH2 (C3 H2 N2 )Mes})2 ] (2a), which is converted into trans-[PdCl2 (NHC)2] (trans-4a; N-heterocyclic carbene) with two rotamers in anti and syn configurations. Complex trans-4a can isomerize into cis-4a(anti) at reflux in acetonitrile. Abstraction of chlorides from 4a or 4b leads to the formation of a new dication: trans-[Pd{RS(O)CH2(C3H2N2)Mes}2](PF6)2 (R=Me (5a), Ph (5b)). The X-ray structure of 5a provides evidence that the two bidentate SO-NHC ligands at palladium(II) are in square-planar geometry. Two sulfoxides are sulfur- and oxygen-bound, and constitute five- and six-membered chelate rings with the metal center, respectively. In acetonitrile, complexes 5a or 5b spontaneously transform into cis-[Pd(NHC)2(NCMe)2](PF6)2. Similar studies of thioether-NHCs have also been examined for comparison. The results indicate that sulfoxides are more labile than thioethers.

An unexpected semi-hydrogenation of a ligand in the complexation of 2,7-bispyridinyl-1,8-naphthyridine with Ru3(CO)12.

Thermal reaction of 2,7-bis(2-pyridinyl)-l,8-naphthyridine () with Ru3(CO)12 in the presence of moisture resulted in the formation of a formate-bridged diruthenium complex [(-H3)Ru2(µ-HCOO)(CO)4] (), in which the ligand was partially hydrogenated. Complex was fully characterized by spectroscopic analyses and X-ray single crystal determination. Regarding the partially reduced ligand in , it occurs through a water-gas shift type reduction. The bridging formate ligand can be substituted by other carboxylate ligands. Physical and chemical properties of the newly prepared complexes were investigated.

Copper-catalyzed activation of α-amino peroxy and hydroxy intermediates to iminium ion precursor: an access to C4-substituted 3,4-dihydroquinazolines via oxidative cross coupling strategy.

A simple and straightforward approach to access C4-substituted-3,4-dihydroquinazolines has been achieved, where copper-catalyzed activation of α-amino peroxide and hydroxide intermediates to iminium ion precursors has been realized as an important step. Reactions of these intermediates with alkynes, indoles, pyrrole, and silylenol ether afforded the structurally diverse C4-substituted-3,4-dihydroquinazoline derivatives in good yields.