Mild and direct conversion of quinoline N-oxides to 2-amidoquinolines with primary amides

[reaction: see text] A simple, one-pot procedure is described for the direct conversion of quinoline N-oxides to alpha-amidoquinolines with primary amides. This methodology is complimentary to the Abramovich reaction, which is limited to the introduction of secondary amides via imidoyl chlorides. Although reaction conditions are quite similar, omission of the base is key for successful reaction with primary amides, which were found not to proceed through the intermediacy of an imidoyl chloride but rather through an acyl isocyanate.     

Amides as precursors of imidoyl radicals in cyclisation reactions

Amides have been successfully used as precursors of imidoyl radicals for radical cyclisation. The amides have been converted to imidoyl selanides via reaction with phosgene to yield imidoyl chlorides followed by reaction with potassium phenylselanide. Imidoyl selanides were reacted with tributyltin hydride (Bu₃SnH) as the radical mediator with triethylborane or AIBN as initiators to yield imidoyl radicals for cyclisation reactions. Imidoyl radicals have been cyclised onto alkenes to yield 2,3-substituted-indoles and -quinolines and also onto pyrroles and indoles to give bi- and tricyclic heteroarenes.     

Stereoselective synthesis of 2-alkylidene-3-iminoindoles by reaction of 1,1-dianions with oxalic acid bis(imidoyl) chlorides

Treatment of dilithiated nitriles and sulfones with oxalic acid bis(imidoyl) chlorides resulted in a new cyclization reaction which provided a variety of (3-imino-2, 3-dihydro-1H-indol-2-ylidene)acetonitriles and -sulfones in good yields. The reactions proceeded by condensation of the dianions with the first imidoyl chloride group of the bis(imidoyl) chloride, subsequent intramolecular attack of the ortho carbon of the arylimino group onto the second imidoyl chloride group, and final aromatization. Excellent stereoselectivities were observed in most cases.     

A new synthesis of N-substituted-2-alkyl(or aryl)quinazolin-4-amines by amide base-mediated cyclization of carbox-imidamides derived from 2-(trifluoromethyl)benzenamine

A one-pot preparation of carboximidamides (amidines) 11–14 involves treatment of amides 2–5 with phosphorus pentachloride followed by the treatment of the resultant crude imidoyl chlorides 7–10 with ammonia. Amidines 11–14 are cyclized to quinazolines 20–26 in lithium alkylamide-or dialkylamide-mediated reactions.     

Soluble oligoaramide precursors--a novel class of building blocks for rod-coil architectures

A new synthetic route is described that allows the reversible conversion of the inherently insoluble oligo-p-benzamides into soluble materials through the formation of imidoyl chlorides. Syntheses of the corresponding dimer, trimer, and tetramer are reported; these compounds can easily be purified by crystallization and are accessible on the multigram scale. Structural proof was obtained by single-crystal X-ray structures of the trimer and tetramer precursors. They can be selectively functionalized into amides or esters at the terminal carboxylic acid group followed by hydrolysis of the imidoyl chlorides to the parent amides. This new class of compounds gives access to strongly aggregating rigid rodlike materials in few synthetic steps, as is demonstrated by the preparation of poly(ethylene glycol)-co-oligo(p-benzamide) rod-coil block copolymers.     

A mild and general one-pot preparation of cyanoethyl-protected tetrazoles

Described herein is a mild and general one-pot procedure for the conversion of cyanoethyl amides to cyanoethyl-protected tetrazoles with azidotrimethylsilane via the intermediacy of imidoyl chlorides generated in situ with phosphorus pentachloride. This synthetic sequence works well with sterically hindered amides and is compatible with acid sensitive functionality.     

Hydrogenation of Secondary Amides using Phosphane Oxide and Frustrated Lewis Pair Catalysis

The metal-free catalytic hydrogenation of secondary carboxylic acid amides is developed. The reduction is realized by two new catalytic reactions. First, the amide is converted into the imidoyl chloride by triphosgene (CO(OCCl₃)₂) using novel phosphorus(V) catalysts. Second, the in situ generated imidoyl chlorides are hydrogenated in high yields by an FLP-catalyst. Mechanistic and quantum mechanical calculations support an autoinduced catalytic cycle for the hydrogenation with chloride acting as unusual Lewis base for FLP-mediated H₂-activation.     

Convenient synthesis of 2-alkylamino-6-carboxy-5,7-diarylcyclopenteno[1,2-b]pyridines via direct acylamination with imidoyl chlorides

A robust synthetic method for 2-alkylamino-6-carboxy-5,7-diarylcyclopenteno[1,2-b]pyridines via acylamination at the alpha position of the functionalized pyridine system has been developed. The key step in this method was achieved by treatment of the corresponding pyridine N-oxides with 2.5 equiv of imidoyl chlorides in the presence of triethylamine, thus producing the desired 2-acylaminopyridines in good yields (74-96%).     

Iron-catalyzed cross-coupling of imidoyl chlorides with Grignard reagents

[reaction: see text] A general, high yielding rapid iron-catalyzed cross-coupling reaction between Grignard reagents and imidoyl chlorides is described. These reactions are typically completed within 5 min, resulting in high yields of 71-96% using 5% iron catalyst in a THF-NMP solvent mixture. Functionalized imidoyl chlorides (e.g., R = CO(2)Me) gave excellent yields (89%).     

Synthesis and Structural Characterization of Pyridine-2,6-dicarboxamide and Furan-2,5-dicarboxamide Derivatives

Derivatives based on pyridine-2-6- and furan-2,5-dicarboxamide scaffolds reveal numerous chemical properties and biological activities. This fact makes them an exciting research topic in supramolecular and coordination chemistry and in discovering new pharmacologically-active compounds. This work aimed to obtain a series of symmetrical pyridine-2-6- and furan-2,5-dicarboxamides through a condensation reaction of the appropriate acyl chlorides and aromatic amides. Successful syntheses were confirmed with NMR spectroscopy. We solved their crystal structures for seven compounds; two pyridine and five furan derivatives. Based on our crystallographic studies, we were able to indicate supramolecular features of the crystals under investigation. Additionally, Hirshfeld surface analysis allowed us to calculate a distribution of intermolecular contacts in the dicarboxamide crystals.     

Reactions ANC Rearangements of Carboxamides Phosphorylated by Tervalent Phosphorus Chlorides

Abstract

We have found that N-substituted amides of carboxylic or thiocarboxylic acids (I) react with tervalent phosphorus chlorides to give N- and O(S)-phosphorylated derivatives (II) which isomerise into imidoyl(thio)phosphonates (III). The factors determining the ability of the initial products (II) and their iminated derivatives (IV) to participate in diad and triad rearrangements have also been studied.     

Ring-expanding reaction of cyclopropyl amides with triphenylphosphine and carbon tetrahalide

We succeeded in activating cyclopropyl amides (monoactivated cyclopropane) through the corresponding imidoyl halides prepared in situ in the presence of 2 equiv of PPh3 and 1 equiv of CX4, and the ring-expanding products (N-substituted pyrrolidin-2-ones) were obtained in good yields. The reaction mechanism was investigated on the basis of oxygen-18 tracer experiment.     

Synthesis of Nitrogen-Containing Polyaromatics by Aza-Annulative π-Extension of Unfunctionalized Aromatics

Nitrogen-containing polycyclic aromatic compounds (N-PACs) are an important class of compounds in materials science. Reported here is a new aza-annulative π-extension (aza-APEX) reaction that allows rapid access to a range of N-PACs in 11–84 % yields from readily available unfunctionalized aromatics and imidoyl chlorides. In the presence of silver hexafluorophosphate, arenes and imidoyl chlorides couple in a regioselective fashion. The follow-up oxidative treatment with p-chloranil affords structurally diverse N-PACs, which are very difficult to synthesize. DFT calculations reveal that the aza-APEX reaction proceeds through the formal [4+2] cycloaddition of an arene and an in situ generated diarylnitrilium salt, with sequential aromatizations having relatively low activation energies. Transformation of N-PACs into nitrogen-doped nanographenes and their photophysical properties are also described.     

2-Phospha-Allylic Systems

Abstract

Phosphamethincyanines prepared in 1964 by Dimroth and Hoffmann were among the first compounds with two-coordinate phosphorus. They are special cases of 2-phospha-allylic cations. Simple representatives of this type become available from the reaction of imidoyl chlorides with tris(trimethylsily1)phosphane.     

Synthesis of Nitrogen‐Containing Polyaromatics by Aza‐Annulative π‐Extension of Unfunctionalized Aromatics

Nitrogen‐containing polycyclic aromatic compounds (N‐PACs) are an important class of compounds in materials science. Reported here is a new aza‐annulative π‐extension (aza‐APEX) reaction that allows rapid access to a range of N‐PACs in 11–84 % yields from readily available unfunctionalized aromatics and imidoyl chlorides. In the presence of silver hexafluorophosphate, arenes and imidoyl chlorides couple in a regioselective fashion. The follow‐up oxidative treatment with p‐chloranil affords structurally diverse N‐PACs, which are very difficult to synthesize. DFT calculations reveal that the aza‐APEX reaction proceeds through the formal [4+2] cycloaddition of an arene and an in situ generated diarylnitrilium salt, with sequential aromatizations having relatively low activation energies. Transformation of N‐PACs into nitrogen‐doped nanographenes and their photophysical properties are also described.     

Intramolecular electrophilic cyclization of functional derivatives of unsaturated Compounds: I. Synthesis of 5-arylsulfanyl-6-phenylpiperidin-2-ones from cinnamylacetamides and arylsulfenyl chlorides

Sterically nonhindered N-alkyl(aryl)amides of cinnamylacetic acid in the reaction with phenyl(4-tolyl)sulfenyl chlorides in acetic acid in the presence of lithium perchlorate undergo a selective cyclization into 5-arylsulfanyl-6-phenylpiperidin-2-ones. Under similar conditions the reaction with arylsulfenyl chlorides of amides containing bulky substituents at the nitrogen atom resulted in 5-arylsulfanyl-6-phenyltetrahydropyran-2-iminium perchlorates, which by treatment with aqueous ethanol were converted into the corresponding derivatives of pyran-2-ones.     

Formation and Pyrolysis of 1-(2′-Thiazolo [5,4-b] Pyridyl)-5-Aryltetrazoles

1-(2′-Thiazolo [5,4-b] pyridyl)-5-aryltetrazoles (4) have been obtained by the reaction of 2-aroylaminothiazolo [5,4-b] pyridines (2) with phosphorus pentachloride and azidolysis of the resulting imidoyl chlorides. The products of pyrolysis of 1-(2′-thiazoio [5,4-b] pyridyl)-5-aryltetrazoles in decalin have been characterised as 2-aryl-1,2,4-triazolo [3′,2′:2,3]thiazolo[5,4-b] pyridines (6).     

A novel one-pot synthesis of α-keto-1,3,4-oxadiazole derivatives based on isocyanide-Nef reaction

Various α-keto-1,3,4-oxadiazole derivatives were synthesized through a sequential intermolecular dehydrochlorination/intramolecular aza-Wittig reaction of carboxylic acids and imidoyl chloride intermediates, which were generated by isocyanide-Nef reaction of acyl chlorides and (N-isocyanimine) triphenylphosphorane (1) in CH₂Cl₂ at room temperature.     

Copper-catalyzed synthesis of 1,2-disubstituted benzimidazoles from imidoyl chlorides

A strategy for the synthesis of 1,2-disubstituted benzimidazoles has been developed and a variety of 1,2-disubstituted benzimidazoles were obtained from imidoyl chlorides and o-haloanilines via copper(I)-catalyzed reaction in moderate yields.     

Reaction of 2-Phenyl-3-Hydroxy-4-Thioxo-3,4-Dihydroquinazoline Sodium Salt With Imidoyl Chlorides: Synthesis of Heteroaryl Sulfenamides

A number of heteroaryl sulfenamides have been prepared through [3,3]-sigmatropic rearrangement in the reaction of 2-phenyl-3-hydroxy-4-thioxo-3,4-dihydroquinazoline sodium salt with diaryl imidoyl chlorides under mild and neutral conditions.