β-Phenylethylamines and the isoquinoline alkaloids

Recent progress towards gold-catalyzed synthesis of N-containing tricyclic compounds based on ynamides

The recent advances in the gold-catalyzed construction of N-containing tricycles based on ynamides are reviewed by highlighting their specificity and applicability, and the mechanistic rationale.

BF3·Et2O mediated one-step synthesis of N-substituted-1,2-dihydropyridines, indenopyridines and 5,6-dihydroisoquinolines

A simple and efficient one-pot ring annulation provides quick access to N-substituted-1,2-dihydropyridines, indenopyridines and 5,6-dihydroisoquinolines.

Synthesis of fused isoquinolines via gold-catalyzed tandem alkyne amination/intramolecular O–H insertion

A novel gold-catalyzed tandem alkyne amination/intramolecular O–H insertion has been developed. A variety of [1,4]oxazino[3,2-c]isoquinolines are readily accessed under mild reaction conditions by utilizing this strategy, thereby providing an efficient and practical route for the construction of synthetically useful fused isoquinolines.

Ir(iii)-catalyzed synthesis of isoquinolines from benzimidates and α-diazocarbonyl compounds

We report herein a tandem Ir(iii)-catalyzed C–H activation and annulation reactions for the synthesis of isoquinolines. This novel method affords an alternative strategy for the construction of diverse and useful isoquinoline derivatives.

Phosphine-catalyzed highly enantioselective [3 + 3] cycloaddition of Morita-Baylis-Hillman carbonates with C,N-cyclic azomethine imines

The first phosphine-catalyzed highly enantioselective [3 + 3] cycloaddition of Morita-Baylis-Hillman carbonates with C,N-cyclic azomethine imines is described. Using a spirocyclic chiral phosphine as the catalyst, a novel class of pharmaceutically interesting 4,6,7,11b-tetrahydro-1H-pyridazino[6,1-a]iso-quinoline derivatives were obtained in high yields with good to excellent diastereoselectivities and extremely excellent enantioselectivities (98->99% ee).

Naturally occurring plant isoquinoline N-oxide alkaloids: their pharmacological and SAR activities

The present review describes research on novel natural isoquinoline alkaloids and their N-oxides isolated from different plant species. More than 200 biological active compounds have shown confirmed antimicrobial, antibacterial, antitumor, and other activities. The structures, origins, and reported biological activities of a selection of isoquinoline N-oxides alkaloids are reviewed. With the computer program PASS some additional SAR (structure-activity relationship) activities are also predicted, which point toward new possible applications of these compounds. This review emphasizes the role of isoquinoline N-oxides alkaloids as an important source of leads for drug discovery.

Rh-catalyzed sequential oxidative C–H activation/annulation with geminal-substituted vinyl acetates to access isoquinolines

The concise synthesis of 3-substituted or non-C3-substituted isoquinolines through Rh-catalyzed sequential oxidative C–H activation/annulation with geminal-substituted vinyl acetates was developed.

An efficient [4+3] cycloaddition reaction of aza-o-quinodimethanes with C,N-cyclic azomethine imines: stereoselective synthesis of 1,2,4-triazepines

An efficient [4+3] cycloaddition reaction of in situ generated aza-o-quinodimethanes with C,N-cyclic azomethine imines has been developed.

Cyclization of sulfide, ether or tertiary amine-tethered N-sulfonyl-1,2,3-triazoles: a facile synthetic protocol for 3-substituted isoquinolines or dihydroisoquinolines

A novel cyclization reaction of sulfide, ether or tertiary amine-tethered N-sulfonyl-1,2,3-triazoles, has been developed, efficiently affording 3-substituted isoquinoline or dihydroisoquinoline derivatives.

Antimicrobial Activity of Extracts and Isoquinoline Alkaloids of Selected Papaveraceae Plants

Alkaloidal extracts of seven selected plants of the family Papaveraceae were studied with respect to their activity against six strains of pathogenic bacteria and their alkaloidal fingerprint. Twenty-four alkaloids were determined by GC/MS, and twenty of them identified from their mass spectra, retention times and retention indexes. In the antibacterial assay, three Gram-positive ( Enterorococcus faecalis, Staphylococcus aureus and S. hyicus), and three Gram-negative ( Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa) strains were used. The most promising antimicrobial activity was shown by the alkaloidal extract of Macleaya cordata with MIC values of 16 μg/mL for Staphylococcus aureus, 32 μg/mL for Enterococcus faecalis and 64 μg/mL for Staphylococcus hyicus and Escherichia coli. All the tested pure isoquinoline alkaloids were considered inactive within the tested concentrations.

Amine-catalyzed enantioselective 1,3-dipolar cycloadditions of aldehydes to C,N-cyclic azomethine imines

Amine-catalyzed enantioselective 1,3-dipolar cycloadditions of aldehydes to C,N-cyclic azomethine imines were developed. The reactions between diversely substituted C,N-cyclic azomethine imines and aldehydes proceeded smoothly in the presence of chiral prolinol silyl ether catalyst and gave the C-1-substituted tetrahydroisoquinolines in a highly stereoselective manner. These tetrahydroisoquinolines could be efficiently transformed to several other useful polycyclic frameworks.

Carboxylic acid free novel isocyanide-based reactions

In order to develop a practical method for the construction of drug-like and heterocyclic compounds, we have designed a novel Passerini- or Ugi-type reaction system where a compound (which we write in the general form as Z-X) composed of an electrophilic (Z) and a nucleophilic group (X) could essentially perform the same function as the carboxylic acid. Based on this concept, we have developed the O-silylative Passerini reaction and the borinic acid catalyzed α-addition of isocyanides to aldehydes and water. In addition, we have designed and demonstrated the addition reaction of isocyanides to nitrones in the presence of TMSCl to afford the corresponding 1,2,3,4-tetrahydroisoquinoline-1-carboxyamides. Furthermore, a novel [5 + 1] cycloaddition of isocyanide was explored with C,N-cyclic N'-acyl azomethine imines as a "1,5-dipole" via a strategy involving intramolecular trapping of the isocyanide.

Synthesis of enantiomerically enriched indolines and tetrahydroisoquinolines from (S)-amino acid-derived chiral carbocations: an easy access to (3S,4R)-demethoxy-3-isopropyl diclofensine

Enantiomerically enriched indolines and tetrahydroisoquinolines were synthesized in high yields from easily accessible (S)-amino acid-derived chiral carbocations.

Microwave assisted [RuCl2(p-cymene)2]2 catalyzed regioselective endo-tandem cyclization involving imine and alkyne activation: an approach to benzo[4,5]imidazo[2,1-a]pyridine scaffold

A microwave assisted efficient route to the synthesis of benzimidazole fused heterocycles through metal catalyzed endo-cyclization strategy involving imine and alkyne activation has been developed.

A Selective Synthesis of 4-Bromoisoquinoline and 4-Bromoisquinolone

2-Alkynyl benzyl azides smoothly underwent an electrocyclic reaction catalysed by palladium to selectively afford either 4-bromoisoquinoline and 4-bromoisquinolones under different conditions. 4-Bromoisoquinoline was synthesised in the presence of PdBr2/CuBr2/LiBr in MeCN, and 4-bromoisoquinolone was selectively produced with PdBr2/CuBr2/HOAc in CH2ClCH2Cl. A bromine was introduced into the products which makes the methodology more attractive for organic synthesis.

Synthesis of pyrido[2,1-a]isoquinolin-4-ones and oxazino[2,3-a]isoquinolin-4-ones: new inhibitors of mitochondrial respiratory chain

Benzo[a]quinolizine is an important heterocyclic framework that can be found in numerous bioactive compounds. The general scheme for the synthesis of these compounds was based on the preparation of the appropriate dihydroisoquinolines by Bischler-Napieralski cyclization with good yields, followed by the Pemberton method to form the oxazinones or pyridones derivatives via acyl-ketene imine cyclocondensation. All the synthesized compounds were assayed in vitro for their ability to inhibit mitochondrial respiratory chain. Most of the tested compounds were able to inhibit the integrated electron transfer chain, measured as NADH oxidation, which includes complexes I, III and IV, in the low micromolar range. Oxazino[2,3-a]isoquinolin-4-ones displayed greater activity than their pyrido[2,1-a]isoquinolin-4-ones analogs. Indeed, the presence of a furan ring in C₂ position of oxazino[2,3-a]isoquinolin-4-ones provided the compound (1g) with the most potent biological activity. Therefore, these compounds and especially the oxazinone derivatives are in the tendency of the new less toxic antitumor agents that target mitochondrial electron transport chain in a middle range potency.

Palladium-catalyzed regio- and chemoselective ortho-benzylation of C-H bond using a functionalizable primary amide directing group: a concise synthesis of dibenzo[b,e]azepin-6-ones

A palladium-catalyzed regio- and chemoselective direct benzylation of primary benzamides with 2-bromobenzyl bromides under a mild basic condition has been developed affording various substituted diarylmethanes in good yields. Furthermore, the directing amide group (-CONH2) was subjected to intramolecular N-arylation with the aryl bromide moiety present in diarylmethanes leading to a concise synthesis of dibenzoazepinones.