Reaction Of Hydrazones Research Articles

Unusual fluorescence and sol–gel transition properties of a pyridine-based polymeric gel formed via the hydrazone reaction

A polymeric gel via the hydrazone reaction was prepared.

Control of the mechanical strength of a bipyridine-based polymeric gel from linear nanofibre to helix with a chiral dopant.

A mixture of building blocks 1 and 2 having hydrazine moieties and aldehyde moieties, respectively, formed a gel by a hydrazone reaction in the absence and presence of cyclohexane diamines as chiral dopants and Fe(2+). In particular, the mechanical strength of the helical gel prepared from 1 and 2 in the presence of a chiral dopant and Fe(2+) was ca. 10-fold stronger as compared to that of the gel prepared from the building blocks 1 and 2 without a chiral dopant and Fe(2+). The improved mechanical strength was attributed to the formation of a helix. The results indicate that the mechanical strength of gels obtained by hydrazone reaction could be controlled by a chiral dopant and Fe(2+).

Efficient synthesis of 2-acylquinolines based on an aza-vinylogous Povarov reaction

The aza-vinylogous Povarov reaction between α-ketoimines and α,β-unsaturated dimethylhydrazones in the presence of indium trichloride affords 2-acyl-4-alkyl-4-dimethylhydrazonomethyl-1,2,3,4-tetrahydroquinolines with good cis/trans diastereoselectivities. These compounds were readily transformed into highly substituted 2-acylquinolines using a two-reaction sequence involving the oxidative generation of a C-4 nitrile group, followed by its elimination under thermal conditions. Alternatively, a one-pot protocol based on the reaction of hydrazones with magnesium monoperoxyphthalate hexahydrate in refluxing methanol afforded the target 2-acylquinolines in good to excellent yields. This methodology was also extended to the preparation of 2-arylquinolines.

ChemInform Abstract: Exploring the Chemistry of Furans: Synthesis of Functionalized Bis(furan‐2‐yl)methanes and 1,6‐Dihydropyridazines.

AbstractHetero‐Diels‐Alder reactions of hydrazones or oximes with furylmethanes give annulated pyridazines and oxazines, respectively, which are easily transformed into the title compounds.

ChemInform Abstract: Palladium‐Catalyzed One‐Pot Reaction of Hydrazones, Dihaloarenes, and Organoboron Reagents: Synthesis and Cytotoxic Activity of 1,1‐Diarylethylene Derivatives.

A new three-component assembly reaction between N-tosylhydrazones, dihalogenated arenes, and boronic acids or boronate esters was developed, producing highly substituted 1,1-diarylethylenes in good yields. The two C–C bonds formed through this coupling have been catalyzed by a single Pd-catalyst in a one-pot fashion. It is noted that the one-pot pinacol boronate cross-coupling reaction generally provides products in high yields, offers an expansive substrate scope, and can address a broad range of aryl, styrene, vinyl, and heterocyclic olefinic targets. The scope of this one-pot coupling has been also extended to the synthesis of the 1,1-diarylethylene skeleton of the natural product ratanhine. The new compounds were evaluated for their cytotoxic activity, and this allowed the identification of compound 4ab that exhibits excellent antiproliferative activity in the nanomolar concentration range against HCT116 cancer cell lines.

Palladium-Catalyzed One-Pot Reaction of Hydrazones, Dihaloarenes, and Organoboron Reagents: Synthesis and Cytotoxic Activity of 1,1-Diarylethylene Derivatives.

A new three-component assembly reaction between N-tosylhydrazones, dihalogenated arenes, and boronic acids or boronate esters was developed, producing highly substituted 1,1-diarylethylenes in good yields. The two C-C bonds formed through this coupling have been catalyzed by a single Pd-catalyst in a one-pot fashion. It is noted that the one-pot pinacol boronate cross-coupling reaction generally provides products in high yields, offers an expansive substrate scope, and can address a broad range of aryl, styrene, vinyl, and heterocyclic olefinic targets. The scope of this one-pot coupling has been also extended to the synthesis of the 1,1-diarylethylene skeleton of the natural product ratanhine. The new compounds were evaluated for their cytotoxic activity, and this allowed the identification of compound 4ab that exhibits excellent antiproliferative activity in the nanomolar concentration range against HCT116 cancer cell lines.

ChemInform Abstract: Reaction of Hydrazones Derived from Active Methylene Compounds with Vilsmeier—Haack Reagent.

AbstractHydrazones with sulfone, ester, nitrile, triphenylphosphonium, and phthalimide moieties are evaluated.

ChemInform Abstract: Copper‐Catalyzed Aerobic Oxidative Transformation of Ketone‐Derived N‐Tosyl Hydrazones: An Entry to Alkynes.

A novel strategy involving Cu-catalyzed oxidative transformation of ketone-derived hydrazone moiety to various synthetic valuable internal alkynes and diynes has been developed. This method features inexpensive metal catalyst, green oxidant, good functional group tolerance, high regioselectivity and readily available starting materials. Oxidative deprotonation reactions were carried out to form internal alkynes and symmetrical diynes. Cross-coupling reactions of hydrazones with halides and terminal alkynes were performed to afford functionalized alkynes and unsymmetrical conjugated diynes. A mechanism proceeding through a Cu-carbene intermediate is proposed for the CC triple bond formation.

Reaction of hydrazones derived from electron-deficient ketones with Vilsmeier-Haack reagent

Abstract Reaction of hydrazones derived from ketones bearing an acceptor substituent adjacent to the carbonyl group (α,α,α-trifluoroacetone and ethyl pyruvate) with Vilsmeier-Haack reagent was studied. In most cases, the method allows for regioselective preparation of 1,3-disubstituted pyrazole-4-carbaldehydes – the products of initial C-electrophilic attack, although in one case, the product resulting from concurrent N- and C-attacks of the electrophile at the hydrazone moiety is observed. Under analogous conditions, the reaction of N-arylhydrazone derived from butanedione leads to the formation of 3-chloro-3-(1-arylpyrazol-3-yl)acrylaldehyde – the product of double formylation at both ketone and hydrazone moieties of the starting material.

Copper‐Catalyzed Aerobic Oxidative Transformation of Ketone‐Derived N‐Tosyl Hydrazones: An Entry to Alkynes

AbstractA novel strategy involving Cu‐catalyzed oxidative transformation of ketone‐derived hydrazone moiety to various synthetic valuable internal alkynes and diynes has been developed. This method features inexpensive metal catalyst, green oxidant, good functional group tolerance, high regioselectivity and readily available starting materials. Oxidative deprotonation reactions were carried out to form internal alkynes and symmetrical diynes. Cross‐coupling reactions of hydrazones with halides and terminal alkynes were performed to afford functionalized alkynes and unsymmetrical conjugated diynes. A mechanism proceeding through a Cu‐carbene intermediate is proposed for the CC triple bond formation.

Copper-catalyzed aerobic oxidative transformation of ketone-derived N-tosyl hydrazones: an entry to alkynes.

A novel strategy involving Cu-catalyzed oxidative transformation of ketone-derived hydrazone moiety to various synthetic valuable internal alkynes and diynes has been developed. This method features inexpensive metal catalyst, green oxidant, good functional group tolerance, high regioselectivity and readily available starting materials. Oxidative deprotonation reactions were carried out to form internal alkynes and symmetrical diynes. Cross-coupling reactions of hydrazones with halides and terminal alkynes were performed to afford functionalized alkynes and unsymmetrical conjugated diynes. A mechanism proceeding through a Cu-carbene intermediate is proposed for the CC triple bond formation.

Reaction of hydrazones derived from active methylene compounds with Vilsmeier–Haack reagent

Reaction of hydrazones derived from active methylene compounds with the Vilsmeier–Haack reagent was studied. Compounds with sulfone, ester, nitrile, triphenylphosphonium, and phthalimide moieties were evaluated. It was found that electron-withdrawing and steric effects provided by the substituent at α position strongly influenced the regioselectivity of the reaction. Increasing mesomeric electron-withdrawing effect of this group favors the formation of functionalized 1,3,4-trisubstituted pyrazoles as compared to 1,3-disubstituted pyrazole-4-carbaldehydes. On the contrary, enhanced steric hindrance and lowered electron-withdrawing effect shift the balance toward 1,3-disubstituted pyrazole-4-carbaldehydes. Other factors such as substituent at the nitrogen atom of the hydrazone, as well as reagent ratio, can affect the outcome of the reaction dramatically, so that in certain cases acyclic products are obtained.

Facile Access to 1H‐Indazoles through Iodobenzene‐Catalyzed C–H Amination under Mild, Transition‐Metal‐Free Conditions

AbstractThe transition‐metal‐ and halogen‐free synthesis of N‐aryl‐substituted 1H‐indazole and derivatives was accomplished on the basis of the iodobenzene‐catalyzed intramolecular C–H amination of hydrazones under mild conditions. Reactions of hydrazones derived from ketones and hydrazines with a catalytic amount of iodobenzene in the presence of Oxone as an oxidant in trifluoroacetic acid took place to afford 1H‐indazoles in moderate to good yields. A plausible reaction mechanism was described on the basis of the control experiments.

Pd-Catalyzed Cross-Coupling Reactions of Hydrazones: Regioselective Synthesis of Highly Branched Dienes

The regioselective formation of highly branched dienes is a challenging task. Design and exploration of alternative working models to achieve such a regioselectivity to accomplish highly branched dienes is considered to be a historical advancement of Heck reaction to construct branched dienes. On the basis of the utility of carbene transfer reactions, in the reaction of hydrazones with Pd(II) under oxidative conditions, we envisioned obtaining a Pd-bis-carbene complex with α-hydrogens, which can lead to branched dienes. Herein, we report a novel Pd-catalyzed selective coupling reaction of hydrazones in the presence of t-BuOLi and benzoquinone to form the corresponding branched dienes. The utility of the Pd catalyst for the cross-coupling reactions for synthesizing branched conjugated dienes is rare. The reaction is very versatile and compatible with a variety of functional groups and is useful in synthesizing heterocyclic molecules. We anticipate that this Pd-catalyzed cross-coupling reaction will open new avenues for synthesizing useful compounds.

Regioselective Synthesis of 4‐Nitro‐ or 4‐Chloro‐Tetrasubstituted Pyrazoles from Hydrazones and β‐Halo‐β‐nitrostyrenes

AbstractWe report an acid‐catalyzed cycloaddition reaction of hydrazones with β‐bromo‐ or β‐chloro‐β‐nitrostyrenes for the regioselective synthesis of 4‐nitro‐ or 4‐chloro‐tetrasubstituted pyrazoles. Arising from a common 4‐halo‐4‐nitropyrazolidine intermediate, the identity of the pyrazole product formed is dependent on the relative leaving group abilities of the halo and nitro substituents.

ChemInform Abstract: Tuning Catalysts to Tune the Products: Phosphine‐Catalyzed Aza‐Michael Addition Reaction of Hydrazones with Allenoates.

AbstractA new phosphine‐catalyzed aza‐Michael β‐addition reaction between hydrazones and allenoates is developed.

ChemInform Abstract: Catalytic Three‐Component One‐Pot Reaction of Hydrazones, Dihaloarenes, and Amines.

AbstractThe present new method allows efficient sequential C—C bond formation and intermolecular C—N cross‐coupling to afford 1,2‐diaryl ethylene derivatives of biological interest.

ChemInform Abstract: Palladium Catalyzed Coupling of Tosylhydrazones with Aryl and Heteroaryl Halides in the Absence of External Ligands: Synthesis of Substituted Olefins.

Palladium catalyzed cross-coupling reaction of hydrazones with aryl halides in the absence of external ligand is reported. The versatility of this coupling reaction is demonstrated in showcasing the selectivity of coupling reaction in the presence of hydroxyl and amine functional groups. This method allows synthesizing a variety of heterocyclic compounds, which are difficult to access from other traditional methods and are not synthesized by employing similar coupling reactions. Application of the present methodology is validated in tandem reaction of ketones to the corresponding substituted olefins in a single pot experiment.

Tuning Catalysts to Tune the Products: Phosphine‐Catalyzed Aza‐Michael Addition Reaction of Hydrazones with Allenoates

A new tunable phosphine-catalyzed aza-Michael β-addition reaction between allenoates and various hydrazones has been developed. These reactions are most-efficiently promoted by a catalytic amount of phosphine catalysts. These atom-economical reactions are operationally simple and their corresponding adducts can been achieved in high yields and high selectivity under mild reaction conditions. Further studies revealed that different phosphine catalyst can produce different adducts from the same starting materials.

Catalytic Three-Component One-Pot Reaction of Hydrazones, Dihaloarenes, and Amines

A new three-component assembly reaction between N-tosylhydrazones, dihalogenated arenes, and various primary and secondary amines was devised, producing nitrogen-containing 1,1'-diarylethylenes in good yields. The two C-C and C-N bonds formed through this coupling have been catalyzed by a single Pd-catalyst in a one-pot fashion.