New Strategy for the Synthesis of Phosphonyl Pyrazoles

Phosphonyl hydrazones react with DMF/POC1₃ to afford 3-phosphonyl pyrazoles. Phosphonyl methylene hydrazones react with DMF/POC1₃ to provide 4-phosphonyl pyrazoles. 5-Phosphonyl pyrazoles are obtained from the reaction of phosphonyl chlorovinylaldehydes with phenylhydrazine.     

Synthesis of Fluorinated Cyclobutenes Based on β‑Polyfluoroalkyl β‐Keto Sulfones,Sulfamides, and Phosphonates

β‐Polyfluoroalkyl β‐keto sulfones, sulfamides, and phosphonates react under mild conditions with dimethyl acetylenedicarboxylate and triphenyl phosphine to yield via the intramolecular Wittig reaction, correspondingly, 4‐sulfonyl‐ (4‐sul‐famoyl‐) (4‐phosphonyl‐) 3‐(polyfluoroalkyl)cyclobut‐2‐ene‐1,2‐dicarboxylates.     

Synthesis of 4‐phosphonyl‐1,3‐dithioles and 1,3‐dithiolanes via the Bu3P‐CS2 adduct

New one‐pot syntheses of 2‐arylidene‐4‐phosphonyl‐1,3‐dithioles or 1,3‐dithiolanes were realized by reaction of the tributylphosphine‐carbon disulfide adduct with phosphonyl alkynes or phosphonyl alkenes and aldehydes in moderate yields. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:633–637, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10053     

New isomeric N‐substituted hydrazones of 2‐, 3‐ and 4‐pyridinecarboxaldehydes and methyl‐3‐pyridylketone

Twelve compounds unknown in the literature N‐(E)‐2‐stilbenyloxymethylenecarbonyl substituted hydrazones of 2‐, 3‐ and 4‐pyridinecarboxaldehydes, as well as methyl‐3‐pyridylketone have been prepared. The stereochemical behavior of these compounds in dimethyl‐d₆ sulfoxide solution has been studied by ¹H NMR technique. The E geometrical isomers and cis/trans amide conformers have been found for N‐substituted hydrazones 1–12. EI induced mass spectral fragmentation of these compounds were also investigated. The data obtained create the basis for distinguishing isomers.     

A convenient synthesis of substituted pyrazolidines and azaproline derivatives through highly regio- and diastereoselective reduction of 2-pyrazolines

The synthesis of substituted N-acetyl- and N-aroyl-2-pyrazolines via intramolecular Michael addition of alpha,beta-unsaturated hydrazones generated through olefination of phosphinyl and phosphonyl hydrazones with carbonyl compounds is reported. The regioselective reduction of the C-N double bond in these 2-pyrazolines using Superhydride (Et3BHLi) gives pirazolidine derivatives with excellent levels of cis-diastereoselectivity. These 2-pyrazolines can also be obtained in one-pot reaction from allenes, hydrazides, and aldehydes; and pyrazolidines, after reduction, from allenes, hydrazides, and aldehydes. This synthetic route was developed to provide a new approach to substituted azaproline derivatives in a diastereoselective fashion.     

Reactions of methyl 2‐(benzyloxycarbonyl)amino‐3‐dimethylaminopropenoate and related compounds with hydrazines. Regiospecific synthesis of 1‐substituted‐4‐amino‐substituted‐1H‐pyrazol‐5‐(2H)‐ones

In this paper the regiospecific transformations of methyl 2‐(benzyloxycarbonyl)amino‐3‐dimethylaminopropenoate ( 1 ) with hydrazine, alkyl‐, aryl‐ and heteroaryl‐substituted hydrazines via the corresponding hydrazones 12‐16 into pyrazoles 17‐25 are described. Heteroaryl‐substitued hydrazones 13‐16 afforded by oxidation with bromine or lead tetraacetate the corresponding substituted (1,2,4‐triazolo[4,3‐b]pyridazin‐3‐yl)glycinates 27‐30 . Alkyl 2‐(2,2‐disubstituted‐1‐ethenyl)amino‐3‐dimethylaminopropenoates 31‐33 gave with hydrazines alkyl 2‐[2,2‐(disubstituted)ethenyl]amino‐3‐heteroarylhydrazonopropanoates 40‐48 and 2‐alkyl 2,3‐bis((hetero)arylhydrazono)propanoates 51‐55 .     

Synthesis of 2‐alkyl‐4,5‐aryl‐2H‐[1λ6,2,3,6]‐thiatriazine‐1,1‐dioxides

Sulphamoyl chlorides and chlorosulphonyl isocyanate react with monosubstituted hydrazones and alkylhydrazonates to sulphamoyl hydrazones and sulphamoyl hydrazonates respectively. Reaction of benzil monoalkylhydrazones with chlorosulphonyl isocyanate results in formation of 2‐alkyl‐4,5‐aryl‐2H‐ [1λ⁶,2,3,6]‐thiatriazine‐1,1‐dioxides.     

General approach for regioselective synthesis of fused phosphono substituted‐oxadiazines

A series of fused 1,3,4‐oxadiazines were regioselectively prepared in reasonable yields as major products from the reactions of the corresponding α‐carbonyl hydrazones with tetraethyl 1,3‐dithietane‐2,4‐diylidene‐bis(cyanomethylphosphonate) (1) . Side products were also observed wherein the dimeric products 8 or 17 and/or different types of N‐heterocycles such as pyrazole 24 or pyridazines 28 or 29 were isolated and identified. A comparative study on the chemistry of 1 toward α‐aminonitrile 30 is also described. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:196–204, 2000     

Intramolecular catalysis of aminolysis of phosphorus heterocycles incorporating an α‐aminoamide moiety. III. Synthesis of 2‐oxo or 2‐thioxo 1,3‐disulfonyl‐1,3,2‐diazaphospholidines and reactions with amines and alcohols

A series of 2‐oxo or 2‐thioxo 1,3‐disulfonyl‐1,3,2‐diazaphospholidines 4 was prepared by condensation of phosphonyl dichlorides 2 with bis‐N,N'‐sulfonylethylenediamines 1 in pyridine. Complete aminolysis or alcoholysis of heterocycles 4 took place with regeneration of sulfonyldiamines 1 . These reactions are very sensitive to steric hindrance, and hydrolysis is generally favoured over aminolysis. The results are discussed in terms of mechanisms of phosphorylation.     

Extending the Scope of the B(C6F5)3‐Catalyzed CN Bond Reduction: Hydrogenation of Oxime Ethers and Hydrazones

The B(C₆F₅)₃‐catalyzed hydrogenation is applied to aldoxime triisopropylsilyl ethers and hydrazones bearing an easily removable phthaloyl protective group. The C?N reduction of aldehyde‐derived substrates (oxime ethers and hydrazones) is enabled by using 1,4‐dioxane as the solvent known to participate as the Lewis‐basic component in FLP‐type heterolytic dihydrogen splitting. More basic ketone‐derived hydrazones act as Lewis bases themselves in the FLP‐type dihydrogen activation and are therefore successfully hydrogenated in nondonating toluene. The difference in reactivity between aldehyde‐ and ketone‐derived substrates is also reflected in the required catalyst loading and dihydrogen pressure.     

Facile synthesis of 3‐substituted [1,2,4]triazino[3,4‐f]purine‐4,6,8‐trione derivatives

A new synthetic route to build the [1,2,4]triazino[3,4‐ f]purine nucleus is described. The novel [1,2,4]‐triazino[3,4‐ f]purine‐4,6,8(l H,7 H,9 H)‐trione derivatives were obtained by condensation of 8‐hydrazinotheophylline with appropriate glyoxylic acids via the intermediate hydrazones.     

Miscibility and morphologies of poly(arylene ether phenyl phosphine oxide/sulfone) copolymer/vinyl ester resin mixtures and their cured networks

Nonreactive bisphenol A‐based poly(arylene ether triphenyl phosphine oxide/diphenyl sulfone) statistical copolymers and a poly(arylene ether triphenyl phosphine oxide) homopolymer, each having a number‐average molecular weight of about 20 kg/mol, were synthesized and solution‐blended with a commercial dimethacrylate vinyl ester resin. Free‐radical cured systems produced morphologies that were a function of both the amount of phosphonyl groups and the weight percentage of the copolymers. For example, highly hydrogen‐bonded poly(arylene ether phenyl phosphine oxide) homopolymer/vinyl ester resin mixtures were homogeneous in all proportions both before and after the formation of networks. Copolymers containing low amounts (≤30 mol %) of the phosphonyl groups displayed phase separation either before or during cure. The phase‐separated cured materials generally had phase‐inverted morphologies, such as a continuous thermoplastic copolymer phase and a particulate, discontinuous vinyl ester network phase, except for systems containing a very low copolymer content. The resin modified with a copolymer containing 30 mol % phosphine oxide comonomer showed improved fracture toughness, suggesting the importance of both phase separation and good adhesion between the thermoplastic polymer and the crosslinked vinyl ester filler phase. The results suggested that the copolymers with high amounts of phosphine oxide should be good candidates for interphase sizing materials between a vinyl ester matrix and high‐modulus carbon fibers for advanced composite systems. Copolymers with low amounts of phosphonyl groups can produce tough, vinyl ester‐reinforced plastics. The char yield increases with the concentration of bisphenol A poly(arylene ether phosphine oxide) content, suggesting enhanced fire resistance. The incorporation of thermoplastic copolymers sustains a high glass‐transition temperature but does not significantly affect the thermal degradation onset temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2409–2421, 2000     

Isomerization/recyclization of some 5‐ethoxycarbonyl‐pyrimidines

This communication reports on the investigation of a new recyclization conversion of a pyrimidine ring, which can be referred to as C? C recyclization. In this reaction the nucleophile cleaves the pyrimidine ring at the N(3)‐C(4) bond, and following rotation around the single C(5)‐C(6) bond the new cyclization takes place. This type of recyclization has general applicability, and takes place upon alkali treatment of substituted 4‐methyl‐5‐ethoxycarbonyl‐ and 4‐amino‐5‐ethoxycarbonyl‐pyrimidines (1) which are transformed respectively to 4‐hydroxy‐5‐acetyl‐ and 4‐hydroxy‐5‐carbamoylpyrimidines (2). The obtained pyrimidyl‐ketones can be readily converted to their hydrazones 7‐12.     

Pyridazine derivatives and related compounds,part 8: Synthesis of different heterocycles from 3‐hydrazinopyridazine

The reaction of 3‐hydrazino‐4,5,6‐triphenylpyridazine 1 with phenylisothiocyanate in ethanol gave thiocarbamoylhydrazine 2 while in butanol gave triazolo[4,3‐b]pyridazinethione 3 . Reaction of 1 with ethyl chloroformate gave ethoxycar‐ bamoylhydrazinopyridazine 5 which upon heating it furnished triazolopyridazine 6 . Also, the reaction of 1 with chloroacetylchloride gave triazolopyridazine 7 . Reaction of 1 with a number of aromatic aldehydes, D ‐glucose, and pyruvic acid gave the corresponding hydrazones 9,11 . Oxidative cyclization of 9a,b gave triazolo[4,3‐b]pyridazine 10a,b . On the other hand, reactions of 1 with diethyl oxalate, ethyl acetoacetate, acetylacetone, ethyl cyanoacetate, diacetyl, and with phthalic anhydride are also reported. © 2005 Wiley Periodicals, Inc. 16:278–284, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20110     

New many fold 1,2,3‐selenadiazole aromatic derivatives

The many fold aromatic ketones 2a‐d are versatile compounds for the synthesis of the many fold 1,2,3‐selenadiazole aromatic derivatives 5a‐d . The preparation starts with the reaction between the many fold bromomethylene benzene derivatives 1a‐d and 4‐hydroxyacetophenone, which are transformed through the reaction with semicarbazide hydrochloride or ethylhydrazine carboxylate into the corresponding semicarbazones derivatives 3a‐d or hydrazones 4a‐d . The reaction with selenium dioxide leads to regiospecific ring closure of semicarbazones or hydrazones to give the many fold 1,2,3‐selenadiazole aromatic derivatives in high yield.     

N‐Trifluoromethyl Hydrazines,Indoles and Their Derivatives

Reported herein is the first efficient strategy to synthesize a broad range of unsymmetrical N‐CF₃ hydrazines, which served as platform to unlock numerous currently inaccessible derivatives, such as tri‐ and tetra‐substituted N‐CF₃ hydrazines, hydrazones, sulfonyl hydrazines, and valuable N‐CF₃ indoles. These compounds proved to be remarkably robust, being compatible with acids, bases, and a wide range of synthetic manipulations. The feasibility of RN(CF₃)‐NH₂ to function as a directing group in C?H functionalization is also showcased.     

A “quasi‐flexible” automatic docking processing for studying stereoselective recognition mechanisms. Part I. Protocol validation

The main purpose of this work is the development and validation of a general scheme based on a systematic and automatic “quasi‐flexible” docking approach for studying stereoselective recognition mechanisms. To achieve our goals we explore the conformational and configurational space for small‐ or medium‐size flexible molecules in a systematic way, seeking a method that is both reasonably accurate and relatively fast from the computational point of view. In particular, we have developed a general computational protocol for the global molecular interaction evaluation (“Glob‐MolInE”) to efficiently explore the orientational and conformational space of flexible selectors and selectands used in modern chiral high‐performance liquid chromatography (HPLC); the enantioselective binding of the selector (S)‐N‐(3,5‐dinitrobenzoyl)‐leucine‐ n‐propylamide (S)‐ 1 towards the selectand N‐(2‐naphthyl)‐alanine methyl ester 2 has been studied; the global minimum obtained for the homochiral associate [S( 1 )/S( 2 )] (Pop. >99%) is very close (RMS≃0.20) to the crystallographically determined structure. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 515–530, 2000     

The Reaction of Phosphorus Decasulfide with some Hydrazides and their Hydrazones: New Route for Construction of Four‐membered,Five‐membered,and Six‐membered Phosphorus Heterocycles

Reaction of some selected benzoic acid hydrazides 1a – c with phosphorus decasulfide P₄S₁₀ in dry pyridine afforded some novel pyridine solvate of 1,3,4,2‐thiadiazaphospholes 2a – c . Similarly, treatment of their corresponding hydrazones 3a – c toward phosphorus decasulfide under the same reaction conditions gave the corresponding thio‐analog 4 and 1,3,2‐benzoxazaphosphinine and benzodiazaphosphinine pyridine solvates 5a,b , respectively. Treatment of (thio)semicarbazides and their corresponding (thio)semicarbazones with phosphorus decasulfide in dry pyridine yielded the novel 1,2,4,3‐triazaphospholidines 6a,b , and 1,3,2‐diazaphosphetidines 8a,b , respectively. Moreover, cyclization of (thio)carbohydrazides and their mono‐ (thio)carbohydrazones with phosphorus decasulfide produced 1,2,4,3‐triazaphospholidines 9a,b and 11a,b , respectively. The structures of these products were confirmed from analytical and spectral data.     

Transformation of 1,2,3‐Thiadiazolyl Hydrazones as Method for Preparation of 1,2,3‐Triazolo[5,1‐b][1,3,4]thiadiazines

The transformation of 1,2,3‐thiadiazolyl hydrazones of aldehydes and ketones including Dimroth rearrangement giving 1‐alkylidenamino‐5‐mercapto‐1,2,3‐triazoles, alkylation of mercapto group of these heterocyclic compounds by α‐bromoacetophenones and cyclization giving 6,7‐dihydro‐5H‐[1,2,3]triazolo[5,1‐b ][1,3,4]thiadizines have been investigated. It was shown that the reaction for hydrazones of acetophenones and benzoaldehydes is diastereoselective. Triazolothiadiazine spiro derivatives were prepared with transformation of hydrazones of cyclic ketones.     

Organophotocatalytic Generation of N‐ and O‐Centred Radicals Enables Aerobic Oxyamination and Dioxygenation of Alkenes

A cooperative TEMPO and photoredox catalytic strategy was applied for the first time to the direct conversion of N?H and O?H bonds into N‐ and O‐centred radicals, enabling a general and selective oxidative radical oxyamination and dioxygenation of various β,γ‐unsaturated hydrazones and oximes. In the reaction, O₂ was employed not only as a terminal oxidant but also as the oxygen source. This protocol provided efficient access to the synthesis of various synthetically and biologically important pyrazoline, pyridazine and isoxazoline derivatives under metal‐free and mild reaction conditions. Mechanistic studies revealed that the cooperative organophotocatalytic system functions through two single‐electron‐transfer (SET) processes.