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A series of new symmetrical s-tetrazine derivatives, coupled via a 1,4-phenylene linkage with a 4H-1,2,4-triazole ring, were obtained. The combination of these two rings in an extensively coupled system has significant potential applications, mainly in op

A formal reductive [3+2] annulation of 4,4,4-trifluorocrotonate and α-iminoketones was developed under Br?nsted base catalysis. A single phosphazene base efficiently catalyzes the one-pot tandem reaction involving two mechanistically different elementary processes, namely the chemoselective reduction of an imine moiety of α-iminoketones with thiols as the reductant and the subsequent intermolecular Michael addition of an enolate of α-aminoketones concomitant with lactam formation. This operationally simple method provides β-trifluoromethyl-substituted γ-lactams with a tetrasubstituted carbon as a single diastereomer.

Abstract: The reaction of carboxamides with phosphorus trichloride under heating at 75–80°C for 1 h in the presence of a 4-dimethylaminopyridine catalyst was used to synthesize imidoyl chlorides in yields of 63–99%.

A facile and regioselective synthesis of quinoxalines, an important motif in medicinal chemistry and materials sciences, was developed. Despite their prospective utility, the regioselective preparation of trisubstituted quinoxalines has not been previously established. In the reported system, hypervalent iodine reagents catalyzed the annulation between α-iminoethanones ando-phenylenediamines in a chemo/regioselective manner to afford trisubstituted quinoxalines. Excellent regioselectivities (6:1 to 1:0) were achieved using [bis(trifluoroacetoxy)iodo]benzene and [bis(trifluoroacetoxy)iodo]pentafluorobenzene as annulation catalysts.

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.

Imidoyl sulfoxonium ylides are presented for the first time as potential precursors to generate α-imino metal-carbene intermediates and applied in direct C-H functionalization reactions catalyzed by [Ir(cod)Cl]2 (4 mol %) to provide 2-substituted indoles (up to 70% yield) in just one step. This class of sulfur ylide is successfully obtained from imidoyl chloride and dimethylsulfoxonium methylide (23 new examples in 45-85% yield) or by imino group formation from the corresponding β-keto sulfoxonium ylides and anilines in the presence of TiCl4 as a Lewis acid (9 examples in 33-94% yield).

A silver-catalyzed cascade cyclization reaction of isocyanides with sulfoxonium ylides has been developed for the first time. This reaction provides a new and efficient method for the construction of highly functionalized 3-aminofurans and 4-aminoquinolines from readily available starting materials in a single step.

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.

A series of triazolium salts, selected for their varying electronic and steric properties, were prepared and their pKa values were determined in DMSO at 25 °C using the bracketing indicator method. The effect of each systematic structural variation upon the acidity of the triazolium cation has been considered, in particular examining the effects of systematically altering electronic properties, quantified through the use of Hammett σ parameters. The first pKa value for an azolium salt that generates a mesionic carbene is also reported. These new data allow for the selection of appropriate bases for the deprotonation of such triazolium salts and the potential to correlate the pKa values determined herein with the nucleophilicity of the corresponding carbenes.

A novel protocol for the activation of the Beckmann rearrangement utilizing the readily available and economical geminal dichloroimidazolidinediones (DCIDs) on a substoichiometric scale (10 mol %) has been developed. A unique self-propagating mechanism for the substoichiometric dichloroimidazolidinedione-activated transformation was proposed and validated. The substrate scope of the developed protocol has been demonstrated by 23 examples with good to excellent yields (mostly 90-98%) in a short time (mostly 10-30 min), including a substrate for synthesizing the monomer of nylon-12 and a complicated steroidal substrate on a preparative scale. This research not only unveils for the first time the synthetic potential of substoichiometric amounts of dichloroimidazolidinediones in promoting chemical transformation but also offers yet another important illustration of the self-propagating cycle in the context of the Beckmann rearrangement activated by a structurally novel organic promoter.

A catalytic hydrophosphination route to 1,1-diphosphines is yet to be reported: these narrow bite angle pro-ligands have been used to great effect as ligands in homogeneous catalysis. We herein demonstrate that terminal alkynes readily undergo double hydrophosphination with HPPh2 and catalytic potassium hexamethyldisilazane (KHMDS) to generate 1,1-diphosphines. A change to H2PPh leads to the formation of P,P-divinyl phosphines.

We, herein, report the synthesis, characterization, luminescence properties, anticancer, and antibacterial activities of a family of novel half-sandwich iridium(III) complexes of the general formula [(n5-Cpx)Ir(C^N)Cl]PF6- [Cpx = pentamethylcyclopentadienyl (Cp) or tetramethyl(biphenyl)-cyclopentadienyl (Cpxbiph)] bearing versatile imine-N-heterocyclic carbene ligands. In this complex framework, substituents on four positions could be modulated, which distinguishes this class of complex and provides a large amount of flexibility and opportunity to tune the cytotoxicity of complexes. The X-ray crystal structures of complexes 4 and 10 exhibit the expected "piano-stool" geometry. With the exception of 1, 2, and 11, each complex shows potent cytotoxicity, with IC50 (half-maximum inhibitory concentration) values ranging from 1.99 to 25.86 μM toward A549 human lung cancer cells. First, the effect of four positions bearing different substituents in the complex framework on the anticancer activity, that is, structure-activity relationship, was systematically studied. Complex 8 (IC50 = 1.99 μM) displays the highest anticancer activities, whose cytotoxicity is more than 10-fold higher than that of the clinical platinum drug cisplatin against A549 cancer cells. Second, their chemical reactivity including nucleobases binding, catalytic activity in converting coenzyme NADH to NAD+, reaction with glutathione (GSH), and bovine serum albumin (BSA) binding is investigated. No reaction with nucleobase is observed. However, these iridium(III) complexes bind rapidly to GSH and can catalyze oxidation of NADH to NAD+. In addition, they show moderate binding affinity to BSA and the fluorescence quenching of BSA by the iridium (III) complexes is due to the static quenching. Third, the mode of cell death was also explored through flow cytometry experiments, including cell cycle, apoptosis induction, reactive oxygen species (ROS) and mitochondrial membrane potential. It seems that cell cycle perturbation, apoptosis induction, increase of ROS level and loss of mitochondrial membrane potential together contribute to the anticancer potency of these complexes. Last, the use of confocal microscopy provides insights into the microscopic mechanism that the typical and most active complex 8 enters A549 lung cancer cells mainly through energy-dependent pathway and is located in lysosome. Furthermore, lysosome damage and nuclear morphology were detected by confocal microscopy. Nuclear condensation and apoptotic bodies may finally induce cells apoptosis. Interestingly, complex 8 also shows antibacterial activity against Gram-positive Staphylococcus aureus. This work may provide an alternative and effective strategy to smart design of potent organometallic half-sandwich iridium(III) anticancer drugs.

A family of novel imine-N-heterocyclic carbene ruthenium(II) complexes of the general formula [(η6-p-cymene)Ru(C^N)Cl]PF6? (where C^N is an imine-N-heterocyclic carbene chelating ligand with varying substituents) have been prepared and characterized. In this imine-N-heterocyclic carbene chelating ligand framework, there are three potential sites that can be modified, which distinguishes this class of ligand and provides a body of flexibilities and opportunities to tune the cytotoxicity of these ruthenium(II) complexes. The influence of substituent effects of three tunable domains on the anticancer activity and catalytic ability in converting coenzyme NADH to NAD+ is investigated. This family of complexes displays an exceedingly distinct anticancer activity against A549 cancer cells, despite their close structural similarity. Complex 9 shows the highest anticancer activity in this series against A549 cancer cells (IC50=14.36 μm), with an approximately 1.5-fold better activity than the clinical platinum drug cisplatin (IC50=21.30 μm) in A549 cancer cells. Mechanistic studies reveal that complex 9 mediates cell death mainly through cell stress, including cell cycle arrest, inducing apoptosis, increasing intracellular reactive oxygen species (ROS) levels, and depolarization of the mitochondrial membrane potential (MMP). Furthermore, lysosomal damage is also detected by confocal microscopy.

A single-pot procedure for the synthesis of 2,4-diarylquinazolines is described which involves a silver oxide-mediated C–H activation/C–N bond formation process. The generality of this method with respect to substituent effects is presented along with studies leading to process optimization. Mechanistic investigations provide support for the involvement of radical intermediates in the reaction process.

A fast catalytic synthesis of multisubstituted quinazolines from readily available amidines via visible light-mediated oxidative C(sp3)-C(sp2) bond formation has been established. This reaction is a metal-free oxidative coupling catalyzed by a photoredox organocatalyst. The protocol features low catalyst loading (1 mol %).

This manuscript describes modulation of the sensitivity to mechanical forces in diiodo boron diiminates by altering the substituent position of iodine groups. A series of modified complexes were prepared, and their solid-state luminescence properties base

The rhenium-catalyzed synthesis of 1,3-diiminoisoindolines and their related compounds from aromatic or heteroaromatic imidates and carbodiimides are reported via C-H bond activation. This reaction is the first example of a transition-metal-catalyzed inse

A new route from benzylic imines permits the synthesis of 1,2-borazaronaphthalenes in good yields. The reaction involves formation of the enamidyl dibromoborane, which undergoes base-promoted borylation of the nearby aromatic C-H bond. Electrophilic attack of the boron species onto the benzylic arene is supported by the slow borylation of arenes substituted with electron-withdrawing groups. The resultant boron bromides can be easily substituted with lithium reagents to provide a range of products. The electronic properties of these 1,2-borazaronaphthalene derivatives have been investigated by UV-vis and fluorescence spectroscopy.

The Chapman rearrangement of aryl N-arylbenzimidates to tertiary acyclic amides is accelerated in ionic liquids and proceeds at lower temperatures as 120-190°C.

Readily accessible nitrilium triflates are convenient imine building blocks for the expedient synthesis of a novel class of 1,3-P,N ligands as demonstrated for the reaction with primary phosphanes. This procedure allows variation of all substituents. X-ray crystal structures are reported for nitrilium ions, phosphaamidines, and three phosphaamidinate complexes. The lithium phosphaamidinate is N coordinated and its reaction with [AuCl(tht)] (tht=tetrahydrothiophene) gives a unique P-bridged gold trimer, while a P,N-bidentate complex results from [{RhCl(cod)}2]. The nitrilium ion methodology allows extension of the 1,3-P,N motive to bis(imino)phosphanes, which are the neutral phosphorus analogues of the valuable β-diketiminate ligand.

In this article, we report the unique optical characteristics of boron diiminates in the solid states. We synthesized the boron diiminates exhibiting aggregation-induced emission (AIE). From the series of optical measurements, it was revealed that the optical properties in the solid state should be originated from the suppression of the molecular motions of the boron diiminate units. The emission colors were modulated by the substitution effects (λPL,crystal = 448-602 nm, λPL,amorphous = 478-645 nm). Strong phosphorescence was observed from some boron diiminates deriving from the effects of two imine groups. Notably, we found some of boron diiminates showed crystallization-induced emission (CIE) properties derived from the packing differences from crystalline to amorphous states. The 15-fold emission enhancement was observed by the crystallization (φPL,crystal = 0.59, φPL,amorphous = 0.04). Next, we conjugated boron diiminates with fluorene. The synthesized polymers showed good solubility in the common solvents, film formability, and thermal stability. In addition, because of the expansion of main-chain conjugation, the peak shifts to longer wavelength regions were observed in the absorption/emission spectra of the polymers comparing to those of the corresponding boron diiminate monomers (λabs = 374-407 nm, λPL = 509-628 nm). Furthermore, the absorption and the emission intensities were enhanced via the light-harvesting effect by the conjugation with fluorene. Finally, we also demonstrated the dynamic reversible alterations of the optical properties of the polymer thin films by exposing to acidic or basic vapors.

A fast and simple divergent synthesis of multisubstituted quinazolines and benzimidazoles was developed from readily available amidines, via iodine(III)-promoted oxidative C(sp3)-C(sp2) and C(sp 2)-N bond formation in nonpolar and polar solvents, respectively. Further selective synthesis of quinazolines in polar solvent was realized by TEMPO-catalyzed sp3C-H/sp2C-H direct coupling of the amidine with K2S2O8 as the oxidant. No metal, base, or other additives were needed.

Organoboron complexes having aggregation- and crystalization-induced emission properties are presented. The series of boron diiminates were synthesized and the emission behaviors of the synthesized compounds were investigated. Finally, it was found that s

Cumulative evidence strongly supports that glycogen synthase kinase-3 (GSK-3) is a pathogenic molecule when it is up-dysregulated, emerging as an important therapeutic target in severe unmet human diseases. GSK-3 specific inhibitors might be promising effective drugs for the treatment of devastating pathologies such as neurodegenerative diseases, stroke, and mood disorders. As GSK-3 has the ability to phosphorylate primed substrates, small molecules able to bind to this site should be perfect drug candidates, able to partially block the activity of the enzyme over some specific substrates. Here, we report substituted 5-imino-1,2,4-thiadiazoles as the first small molecules able to inhibit GSK-3 in a substrate competitive manner. These compounds are cell permeable, able to decrease inflammatory activation and to selectively differentiate neural stem cells. Overall, 5-imino-1,2,4-thiadiazoles are presented here as new molecules able to decrease neuronal cell death and to increase endogenous neurogenesis blocking the GSK-3 substrate site

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.

Some bicyclic C-fused chlorinated tetrahydrofuro[3,2-c]azetidin-2-ones were prepared by a fairly general route involving Staudinger reaction of allylic/propargylic imidates with dichloroketene followed by highly diastereoselective CuCl/PMDETA-catalyzed 5-

A wide variety of substituted quinazolin-4(3H)-ones were prepared in 63-91% yields by the palladium-catalyzed cyclocarbonylation of o-iodoanilines with imidoyl chlorides and carbon monoxide. The reaction is believed to proceed via in situ formation of an amidine, followed by oxidative addition, CO insertion, and intramolecular cyclization to give the substituted quinazolin-4(3H)-ones.

Disclosed is a process for preparing a compound of formula A - N=C(D)(B), from a compound of formula A-N=C(E)(B) and a compound of formula D-M using an iron catalyst, where the process has is represented by Equation (I).

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-NM

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%).

Catalysts for the living; polymerization of α-olefins are phenoxyketimine compounds with titanium centers. The phenoxyketimine compounds are prepared by Friedel Crafts acylation of a phenol with imidoyl chloride in the presence of a Lewis acid to form phe

A number of 2,3,5-substituted [1,2,4]thiadiazole analogues of SCH-202676 (N-(2,3-diphenyl-[1,2,4]thiadiazole-5(2H)-ylidene)methanamine, 7a) were synthesized and tested as potential allosteric modulators of adenosine receptors. All compounds were capable of displacing the binding of the radiolabeled agonist [3H]CCPA to human A1 adenosine receptors, whereas modest and varying effects were observed on the binding of [3H]DPCPX, a radiolabeled antagonist for this receptor subtype. Four compounds, 7a (SCH-202676), 7k (LUF5792), 71 (LUF5794), and 8e (LUF5789), were selected for more detailed characterization. They all proved allosteric inhibitors of agonist binding, with 7k being most potent, whereas their effects on antagonist binding were more ambiguous. Subsequently, experiments were done on human adenosine A2A and A3 receptors. Compounds 7a and 7l displayed peculiar displacement characteristics of both radiolabeled agonist and antagonist binding to A2A receptors, whereas 7a showed some activity on A3 receptors.

We report on new families of non-metallocene metal precatalysts for olefin polymerization with titanium, zirconium, vanadium and nickel as the active metal sites. The novel ligand design concept is based on iminohydroxamic acids and their derivatives as the principal chelating units. Various anionic and neutral [N,O] and [N,N] ligand systems are easily accessible by a modular synthetic sequence of imidoyl chlorides with substituted hydroxylamines or hydrazines, respectively. Steric protection of the metal coordination site, a necessary requirement for suppression of chain termination pathways of non-metallocene catalysts, is brought about by bulky aryl substituents on the imino nitrogen atoms. Crystal structures of some of the hydroxamato ligands reveal interesting intermolecular hydrogen-bridged structures, whereas in the solid-state structure of one titanium precatalyst a five-membered chelate was observed, in line with the design principle of these systems. Preliminary ethylene polymerization studies with methylaluminoxane-activated metal complexes (M = Ti, Zr, V, Ni) show that the most active systems are [N,O]NiBr2 catalysts containing neutral O-alkyl iminohydroxamate ligands. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Several 1-aryl-2-phenyl-4-piperidino-4-thioalkyl-1,3-diazabuta-1,3-dienes were prepared by the treatment of N-arylimino isothiocyanate with piperidine followed by S-alkylation with alkyl iodides in the presence of dry acetone and potassium hydroxide. The

Nitrilium ions Ar-C≡N+-Ar′ have been studied by laser flash photolysis in aqueous solutions containing 20% acetonitrile. The cations were generated by photoheterolysis of benzimidate esters Ar-CZ=N-Ar′ (Z = -OC6H4-4-CN) with 4-cyanophenoxide as the photochemical leaving group. Rate constants for the reaction with water (kw), azide ion (kaz) and hydroxide (kOH) were measured. The cation Ph-C≡N+-Ph is only 50-fold shorter lived in water compared to Ph-C≡N+-iPr (2); thus the effect of replacing an N-alkyl group with N-phenyl is modest. These two cations are also shown to have similar lifetimes to iminium analogs, e.g. Ph-CH=N+ (Me)-Ph. Thus, addition of water to analogous sp and sp2 hybridized systems occurs at a similar rate, and the increased steric access to the nitrilium plays at most a modest role. For the series where substituents in Ar′ were varied with Ar equal to phenyl, the Hammett plot for log kw correlated with σ, with ρ = - 1.4. For the series where Ar was varied, the data correlated much better with σ+, although ρ+ was only -0.6. This remarkably small effect of substituents in Ar constrasts with the effects seen in benzylic carbocations, but is consistent with the nitrilium structure, with most of the positive charge located on the nitrogen. Rate constant ratios kaz:kw, including the N-alkylnitrilium ion 2, are constant at ～104, with values of kaz well below the diffusion limit, even for the most reactive nitrilium ions. This is very different behaviour from that of carbocations and arylnitrenium ions of similar lifetimes in water. For these cations the rate constants kaz would be at or at least approaching the diffusion limit.

A new group of 6-and 7-substituted compounds of 4-amino-2-phenylquinazoline were synthesized by reaction of N-arylbenzimidoyl chlorides with cyanamide in the presence of TiCl4. The products were identified by spectroscopic methods, their dissoc

Two new heterocyclic thiophosphoryl chlorides (2), derivatives of 1,3,2-benzodiazaphosphole, are synthesized. The reaction of respective thiophosphoryl chlorides (1) and (2) with AlCl3 affords dimeric heterocyclic diphosphonium dications 3and 4

The asymmetric aza-Claisen rearrangement of (E)-3-alkyl-2-propenyl N- [4-trifluoromethyl)phenyl]benzimidates was catalyzed by a homochiral cationic palladium(II) complex generated from PdCl2{(S)-2-(2- diphenylphosphino)phenyl-4-benzyloxazoline}

The synthesis of the hitherto unreported 1-alkyl-1,4-dihydro-4-(ethylimino or arylimino)-3-quinoline-carboxylates is described. The method utilises a 2-halogeno-benzenecarboximidoyl chloride for C-imidoylation of an ethyl 3-alkylamino-2-butenoate or 2-pro

Imidoyl chlorides, obtained by common methods from a wide range of aromatic mono- and diamides, are smoothly converted to the corresponding tetrazoles in high yields by treatment with NaN3 under phase-transfer conditions.

The reaction of substituted N-phenylbenzimidoyl chlorides with N,N-dimethylcyanamide in the presence of titanium tetrachloride has yielded seven 4-(N,N-dimethylamino)-2-arylquinazolines substituted on the phenyl ring with electron donating or withdrawing groups. pKa values have been determined for these compounds and analyzed in conjunction with the Hammertt σ constants to observe the influence of these phenyl substituents upon the basicity of 4-(N,N-dimemylamino)-2-arylquinazolines. The σ value, single crystal X-ray analysis and 15N-nmr spectra give evidence about the preferential site of protonation in such systems.

The reaction of N-phenylimidoyl chlorides (2) with cyanamide and N,N-dimethylcyanamide (4) was studied.At the first stage, linear products like 1-amino-1-chloro-3,5-diphenyl-2,4-diaza-1,3-butadienes (6) were obtained.They underwent cyclization to 4-aminoq

Reaction of 5-aryltetrazoles with N-arylbenzimidoyl chlorides in a methylene chloride-water two-phase system in the presence of tetrabutylammonium bromide or 2,3-diphenyl-5-butyltetrazolium bromide results in the formation of isomeric 1-imidoyl- and 2-imidoyl-5-aryltetrazoles, which are converted to 3H-1,3,4-benzotriazepines upon heating in toluene, m-xylene, or dioxane.

Dialkyltrichloromethylphosphines; diphenyltrichloro-methylphosphine; P-chloro-dialkyl-dichloromethylenephosphoranes; P-chloro-diphenyl-dichloromethylenephophorane; phosphonium salt; chlorination; dehydration; condensation.

2-N-Benzoyl-N-phenylamino-2-oxo-5,5-dimethyl-1,3,2-dioxaphosphorinane (3a) undergoes rearrangement to (2-oxo-5,5-dimethyl-1,3,2-dioxaphosphorinanyl) (N-phenyliminobenzoyl)oxide (4a). This transformation is shown to be catalysed by electrophilic reagents such as benzoyl chloride, trimethylsilyl chloride, p-toluenesulphonyl chloride.

The oxidation of 1,5-diphenyl-3-alkylformazanes by potassium permanganate in methylene chloride (chloroform)-water two-phase systems is a convenient method for the preparation of 2,3-diphenyl-5-alkyltetrazolium salts.The 2,3-diphenyl-5-alkyltetrazolium salts can be used as catalysts for interphase transfer in reactions proceeding in organic solvent-water two-phase systems, with a neutral or acid aqueous phase.The catalytic activity of 2,3-diphenyl-5-alkyltetrazolium salts increases with increase in the length of the alkyl substituent in the 5-position of the tetrazole ring.

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Known methods were developed to give convenient general procedures for preparing N-acyl-N'-mono- and -N',N'-disubstituted thioureas from acid chlorides, and related N-imidoyl thioureas from imidoyl chlorides.In the products from three acid chlorides and ammonium thiocyanate the acyl isothiocyanates did not appear to be accompained by the isomeric thiocyanates.Treatment of N-(anilino)benzylidene-N',N'-disubstituted thioures with chloroacetone in the presence of triethylamine leads to 5-acetyl-4-phenyl-2-(N,N-disubstituted amino)thiazoles.In contrast, the corresponding N-benzoyl thioureas form only small amounts of these compounds; the main products are the 5-benzoyl-4-methyl isomers, and this unexpected outcome requires a revision of the literature.It is thought that formation of the 5-benzoyl-4-methylthiazoles involves N-C(4) fission of a cyclic intermediate to give an open-chain intermediate in which nucleophilic attack can occur at either the acetyl or the benzoyl group.One of the latter intermediates was generated directly from 2-acetyl-2-bromoacetophenone and N-methyl-N-phenylthiourea, and found to give the 5-benzoyl-4-methyl- and 5-acetyl-4-phenyl-thiazoles as the major and minor products, respectively.

Palladium(0), palladium(II), rhodium(I), and iridium(I) complexes catalyze the rearrangement of allyl imidates to allyl amides under mild conditions.The palladium(II) catalysis is characterized by exclusive regioselectivity and high steroeselectivity whereas the palladium(0), rhodium(I), and iridium(I) catalysts generally give both the and rearrangement products and although the palladium(0) catalyst can give high stereoselectivity, the rhodium(I) and iridium(I) catalysts are nonstereoselective.After a series of experiments using chiral substrates and substrates with specific deuterium labels, the mechanisms of these catalytic reactions have been elucidated.The palladium(II) catalysis is proposed to proceed via cyclic carbonium ion intermediates, and the mechanism resembles the thermal uncatalyzed Claisen rearrangement path.The palladium(0) catalysis is a form of catalytic allylation involving oxidative addition followed by nucleophilic attack on a ?-allyl intermediate.The mechansim of the rhodium(I) and iridium(I) catalysis was not as fully investigated as the others, but it appears to involve carbonium ion intermediates formed by cleavage of the allyl-oxygen bond.

1-(2-Nitrophenyl)-5-phenyltetrazole (5b) decomposes when heated to give nitrogen, carbon dioxide, and 2-phenylbenzotriazole (6) in high yield.This new molecular rearrangement proceeds via 2-nitrophenyl(phenyl)carbodi-imide (8).Other precursors of this carbodi-imide, i.e. oxadiazolone (10), oxadiazolethione (11), oxathiadiazole 2-oxide (12), and the aminimide (16), and carbodi-imide itself, all give 2-phenylbenzotriazole (6) on thermolysis, the last three in high yield.This reaction is general for diarylcarbodi-imides with an ortho nitro group, and their precursors, and it provides a useful new route to 2-arylbenzotriazoles.A sequence of electrocyclic ring closing and opening reactions (Scheme 5) is proposed as the mechanism of this process.The key intermediate, 2-phenyl-1,2,4-benzotriazin-3-one 1-oxide (19) has been isolated from a careful thermolysis of (12) in toluene; in solution it is in reversible equlibrium with the ring-opened form (20).This new nitro-carbodi-imide group interaction has been extended to the more stable nitrobiphenyl(phenyl)carbodi-imide (25) and nitronaphthyl(phenyl)carbodi-imide (24) which, on flash vacuum pyrolysis, give benzimidazophenanthridine (29) and benzindazole 1-oxide (32) respectively, in new rearrangements.