Palladium-catalyzed N-arylation Research Articles

Construction of Tricyclic Nitrogen Heterocycles by a Gold(I)-Catalyzed Cascade Cyclization of Allenynes and Application to Polycyclic π-Electron Systems.

A novel approach to the direct construction of tricyclic nitrogen heterocycles based on gold-catalyzed cascade cyclization of aminoallenynes is described. The expected biscyclization reaction of hydroxyisobutyryl-protected aminoallenynes was efficiently promoted by a catalytic amount of BrettPhosAuNTf2 in the presence of iPrOH to produce 1,2-dihydrobenzo[cd]indole derivatives in good yields. When the reaction was combined with Friedel-Crafts acylation or palladium-catalyzed N-arylation, the resulting tricyclic products were efficiently converted into nitrogen-containing polycyclic aromatic compounds (N-PACs) with highly conjugated π-electron systems. A newly obtained hexacyclic indolium salt showed characteristic concentration-dependent absorption and emission properties.

Recent Progress Concerning the N-Arylation of Indoles.

This review summarizes the current state-of-the-art procedures in terms of the preparation of N-arylindoles. After a short introduction, the transition-metal-free procedures available for the N-arylation of indoles are briefly discussed. Then, the nickel-catalyzed and palladium-catalyzed N-arylation of indoles are both discussed. In the next section, copper-catalyzed procedures for the N-arylation of indoles are described. The final section focuses on recent findings in the field of biologically active N-arylindoles.

Palladium-Catalyzed N-Arylation of Amino Acids and Ketoxime Peptide Ligation

Key words palladium catalysis - N-arylation - amino acid esters - ketoxime peptide ligation

Palladium-catalyzed N-Arylation of 1-substituted-1H-tetrazol-5-amines

A palladium-catalyzed N-arylation of 1-substituted-1H-tetrazol-5-amines has been described for the first time. The reaction provides good yields of desired products with broad substrate scope and good functional group tolerance.

One-Pot Synthesis of 1,2-Disubstituted 4-, 5-, 6-, and 7-Azaindoles from Amino-o-halopyridines via N-Arylation/Sonogashira/Cyclization Reaction.

A direct synthesis of several 1,2-disubstituted 4-, 5-, 6-, and 7-azaindoles from available amino-o-halopyridines is described. This procedure involves a palladium-catalyzed N-arylation followed by a Sonogashira reaction and subsequent cyclization in a one-pot manner, exhibiting a wide scope and compatibility with electron-withdrawing and electron-donating groups. The strategy represents an advancement in azaindole chemistry with a straightforward approach toward 1,2-disubstituted azaindoles, while avoiding complex N-arylations of hindered 2-substituted azaindoles and difficult purification steps of intermediates.

Palladium-Catalyzed N-Arylation of Amines and Amides with Aryltrimethylgermanes

Described herein is a novel palladium-catalyzed C–N bond-formation reaction employing aryltrimethylgermanes as the new arylating reagents. Primary/secondary amines or even amides could be smoothly arylated to provide the corresponding N-arylation products in moderate to excellent yields.

Regioselective Synthesis of 1,2- and 1,4-Dihydroquinolines by Palladium-Catalyzed Intramolecular N-Arylation

A series of 1,2- and 1,4-dihydroquinolines has been successfully prepared. The Pd-catalyzed intramolecular N-arylation of Z-enamines, formally prepared by the Horner–Wadsworth–Emmons olefination, proceeded efficiently to furnish the cyclized products. Depending on the cyclization conditions, substituted 1,4-dihydroquinolines and further isomerized 1,2-dihydroquinolines were independently obtained in high yields with an excellent control of isomerization of the double bond.

ChemInform Abstract: Total Synthesis of (—)‐Aspergilazine A.

The total synthesis of (−)-aspergilazine A, an alkaloid possessing a rare N1′ to C6 bisindole bond, is described. A palladium-catalyzed N-arylation was used to selectively install the N1′–C6 bond in the presence of three other possible arylation sites. The ligand XPhos displayed a unique capability to efficiently carry out the N-arylation while simultaneously suppressing epimerization of the sensitive C9 stereocenters. This total synthesis has confirmed that aspergilazine A is a dimer of brevianamide F.

Total synthesis of (-)-aspergilazine A.

The total synthesis of (-)-aspergilazine A, an alkaloid possessing a rare N1' to C6 bisindole bond, is described. A palladium-catalyzed N-arylation was used to selectively install the N1'-C6 bond in the presence of three other possible arylation sites. The ligand XPhos displayed a unique capability to efficiently carry out the N-arylation while simultaneously suppressing epimerization of the sensitive C9 stereocenters. This total synthesis has confirmed that aspergilazine A is a dimer of brevianamide F.

ChemInform Abstract: Stereoselective Synthesis of Indoline, Tetrahydroquinoline, and Tetrahydrobenzazepine Derivatives from o‐Bromophenyl N‐tert‐Butylsulfinyl Aldimines.

The diastereoselective addition of an allylic indium intermediate to chiral o-bromophenyl sulfinyl imine 4 proceeded with good levels of diastereoselectivity. The resulting homoallylic amine derivatives were transformed into lactams 7 and 12, which upon copper-mediated intramolecular N-arylation led to the formation of benzo-fused 1-azabicyclo[j.k.0]alkanes 8 and 13. Benzo-fused 2-allyl-substituted heterocycles 14 could also be prepared by means of a palladium-catalyzed N-arylation of the corresponding free amines. The synthesis of the alkaloid (−)-angustureine was easily accomplished from (S)-2-allyltetrahydroquinoline (14b).

Palladium-catalyzed N-arylation of 2-aminobenzothiazole-4-carboxylates/carboxamides: facile synthesis of PARP14 inhibitors

We have developed a palladium-catalyzed N-arylation of the biologically interesting, but synthetically rather challenging 2-arylaminobenzothiazoles bearing multiple functionalities. This protocol was successfully used to readily synthesize our initial PARP14 inhibitor followed by a limited structural optimization. A more potent PARP14 inhibitor with an IC50 value of 1.69 μM was identified, and the interaction was ascertained by the X-ray co-crystal structure of the catalytic domain of PARP14 in complex with compound 8.

Stereoselective Synthesis of Indoline, Tetrahydroquinoline, and Tetrahydrobenzazepine Derivatives from o-Bromophenyl N-tert-Butylsulfinyl Aldimines

The diastereoselective addition of an allylic indium intermediate to chiral o-bromophenyl sulfinyl imine 4 proceeded with good levels of diastereoselectivity. The resulting homoallylic amine derivatives were transformed into lactams 7 and 12, which upon copper-mediated intramolecular N-arylation led to the formation of benzo-fused 1-azabicyclo[j.k.0]alkanes 8 and 13. Benzo-fused 2-allyl-substituted heterocycles 14 could also be prepared by means of a palladium-catalyzed N-arylation of the corresponding free amines. The synthesis of the alkaloid (−)-angustureine was easily accomplished from (S)-2-allyltetrahydroquinoline (14b).

Palladium catalyzed synthesis of quinazolino [1,4] benzodiazepine alkaloids and analogous

A concise synthesis of enantiopure quinazolino [1,4] benzodiazepine was accomplished by palladium-catalyzed N-arylation of amidines with o-bromobenzoates followed by intra molecular cyclization. The strategy was successfully applied to the total synthesis of pyrrolo quinazolino [1,4] benzodiazepine alkaloids such as circumdatin H, J and other analogues.

Synthesis of Tricyclic Nitrogen Heterocycles by a Sequence of Palladium-Catalyzed N–H and C(sp3)–H Arylations

A range of tricyclic nitrogen heterocycles were synthesized in a straightforward and efficient manner via a sequence involving palladium-catalyzed N-arylation and C(sp(3))-H arylation as the key steps. Whereas the C(sp(3))-H arylation furnished fused 6,5,6-membered ring systems efficiently, the formation of the more strained 6,5,5-membered systems proved to be more challenging and required a subtle adjustment of the reaction conditions.

Palladium-Catalyzed N-Arylation of 3-Functionalized 2-Amino-4,5-dimethylpyrroles

A versatile class of 2-aminopyrroles containing various electron-withdrawing substituents at the 3-position have been N-arylated on the amine using a palladium-catalyzed cross-coupling reaction. Using this methodology, a pyrimidone-based tricyclic system has been prepared in just one step from a starting 2-aminopyrrole.

Efficient palladium-catalyzed N-arylation of a sulfoximine with aryl chlorides

The efficient N-arylation of a sulfoximine with aryl chlorides was developed by using Pd(2)(dba)(3) as a catalyst and various ligands. The reactions using RuPhos as a ligand afforded the coupled products in fair to excellent yields.

Concise, flexible syntheses of 4-(4-imidazolyl)pyrimidine cyclin-dependent kinase 2 (CDK2) inhibitors

A flexible six-step synthesis of potential cyclin-dependent kinase 2 (CDK2) inhibitors is reported. The synthesis involves the condensation between 3-chloro-4,4-dimethoxy-2-butanone and amidines, which provides acetyl-imidazoles and late stage palladium-catalyzed N-arylation to give the target pyrimidine derivatives.

Practical Synthesis of Quinoxalinones via Palladium-Catalyzed Intramolecular N-Arylations

A practical and highly efficient route to the synthesis of pharmaceutically interesting quinoxalinone scaffolds is reported. The key step involves an intramolecular palladium-catalyzed N-arylation under microwave irradiation. The developed methodology tolerates a variety of bromoanilides to afford a diverse collection of bicyclic and polycyclic quinoxalinones in high yield.

Efficient and regioselective functionalization of imidazo[1,2- b]pyridazines via palladium-catalyzed cross-coupling reaction and S NAr

The synthesis of 3,6-disubstituted-2-phenylimidazo[1,2- b]pyridazine derivatives by palladium cross-coupling and S NAr reactions is described. Sonogashira and Stille cross-coupling reactions were investigated to introduce alkynyl, alkenyl, and aryl at the 3-position of imidazo[1,2- b]pyridazines. Then, at the 6-position, palladium-catalyzed N-arylation and direct S NAr were used to introduce amines and alcohols.

Palladium‐Catalyzed N‐Arylation Reactions with Aziridine and Azetidine.

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