Synthesis and hydrolysis of substituted imidazolinium salts. Behaviour of the degradation products on varying pH

Reaction of l-alkyl-2,3-diarylimidazolinium iodides 1a-i with alkaline solutions afforded N'-alkyl-N-aroyl-N-arylethylenediamines 2a-i. Compounds 2 are stable under acid conditions but in neutral or alkaline media rearrange giving N-alkyl-N-aroyl-N-arylethylenediamines 3a-i. Treating compounds 3 with concentrated acids reverse reaction 3 → 2 takes place. Kinetic studies were performed on this intramolecular N → N' aroyl transfer over the H_o-pH range ?0.9 to 2.30. Compounds 3 undergo acyl transfer to give 2 by a mechanism which involves a change in the rate determining step from formation to catalysed decomposition of a heterocyclic intermediate I ²⁺ on going from H_o to pH values. The existence of maxima in the pH rate profile allowed to determine apparent pK_a values of the imidazolidine intermediates which gave good correlation with Hammett sigma values. Stability of these heterocycles was also predicted by determination of thermodynamic parameters.     

Ring opening reaction of 1,2-diaryl-3-methyl-1,4,5,6-tetrahydropyrimidinium salts with metal hydride complexes

The reaction of a series of 1,2-diaryl-3-methyl-1,4,5,6-tetrahydropyrimidinium iodides 1 with reducing agents acting by hydride ion transfer was studied. With excellent yields alkaline borohydrides readily reacted to form N'-aryl-N-benzyl-N-methyltrimethylenediamines 3 by reductive cleavage of the intermediate hexahydropyrimidine 2 . Ring opening is explained by the formation of a stabilized iminium ion, which also accounts for the cyclic aminal 2 hydrolysis observed in alcoholic solution after gradual addition of borohydride. Reactions with lithium aluminum hydride or with borane failed to render satisfactory results due to insolubility of the salt in solvents commonly employed. Comparisons are made with the behaviour of 1H-4,5-dihydroimidazolium salts which were studied in an earlier paper.     

Synthesis of 5H-imidazo[5,1-a]isoindole: Photocyclization of N,N′ -bis(o-chlorobenzyl)imidazolium chloride and N-(o-chlorobenzyl)imidazole

A N-heterocyclic compound containing two hetero atoms, imidazo[5,1-a]isoindole, was synthesized in 40% yield by the intramolecular photocyclization of N,N'-bis(o-chlorobenzyl)imidazolium salts 1 in water (neutral or pH ～4) or of N-(o-chlorobenzyl)imidazole 2 , in aqueous acid (pH ?4). However, the photocyclized compound 3 was not formed effectively in basic aqueous solution (3 equivalents of sodium hydroxide or pyridine) or in acetonitrile by the photochemical reaction of N,N'-bis(o-chlorobenzyl)imidazolium salts 1 or N-(o-chlorobenzyl)imidazole (2).     

The synthesis of 3-[(dimethylamino)(2-phenyl-5-oxo-2-oxazolinyl-idene-4)methyl]imidazo[1,2-x]azines and related compounds,intermediates in the formation of azaaplysinopsin derivatives

4-(2-Bromo-1-dimethylaminoethylidene)-2-phenyl-5(4H)-oxazolone ( 5 ) reacts with N,N-dimethyl-N'-heteroarylformamidines 7 to form imidazoazine derivatives 9 with the oxazolone ring connected through a conjugated double bond to the fused imidazole system at position 3. Compounds 9 were transformed with sodium methoxide in methanol into 2-benzoylamino-3-dimethylamino-3-imidazoazinylpropenoates 10 , while by treatment with hydrochloric acid in methanol, 3-(benzoylaminoacetyl)imidazoazines 12 were formed. The synthesis of compounds 9 represents a facile route to intermediates in the synthesis of azaaplysinopsin and related systems.     

Study of substituted aryldiazonium salts and their crown ethers complexes by XPS

The complexes of fourteen substituted aryldiazonium salts RC₆H₄N₂+BF₄^? (R?H, p-CH₃, p-NO₂, p-I, p-Cl, p-F, m-Br, m-Cl. m-CH₃, o-CH₃, o-OCH₃, o-NO₂, o-Br, o-Cl) with crown ethers 18-C-6 (1) and dibenzo-24-c-8 (2) have been studied by XPS. The results show that the chemical shifts of α-N1s and β-N1s of substituted aryldiazonium salts are closely related to the induction and conjugation effects of R groups. It is interesting to note that charge transfer(β-N→O) take place upon complexation of substituted aryldiazonium salts with crown ethers. Therefore the decrease of binding energy of crown ether oxygen may be used as a measurement of the stabilities of these complexes.     

Paradoxes in Thermal Stability of the Liquid-Crystal Phase of Phenylpropargyl Phenyl Ethers: I. Synthesis and Mesogenic Properties of Phenylpropargyl Phenyl Ethers

The ethers PhCCCH₂OC₆H₃RR' were prepared in 51-83% yields by reactions of phenylpropargyl tosylate in alkaline solution with appropriate p- and o-substituted phenols. Below are given R, R', and the ranges of existence of the nematic mesophase (°C): p-I, H, 104-137; p-Cl, H, 65-117; p-F, H, 33-53; p-OMe, H, 79-120; H, H, 44-115; p-(Me)₃C, H, 74-82; p-COOH, H; p-NO₂, H, 77-96; o-NO₂, H, 83-139; o-CHO, H, 75-115; p-Br, o-NO₂, 95-132; p-Cl, o-NO₂, 71-123; p-F, o-NO₂, 79-120; o-Cl, H, none; p-COOPr, H, none; and p-COOPh, H, 116-134. In contrast to the traditional views, the presence of the o-nitro group enhances, rather than distorts, the thermal stability of the mesophase. The stability increases in parallel with the -R effect of the o-substituent.     

NMR study of products of thermal transformation of substituted N-aryl-o-quinoneimines

Products of thermal transformation of substituted N-aryl-o-quinoneimines were studied using NMR spectroscopy. The formation of 4aH-phenoxazine, which was further dimerized by the Diels—Alder reaction, was established.     

The reactions of some pyraiiylideneiminium salts with amines. II

The iminium salt, N,N-dimethyl-N-[2-(2-phenyl-4H-l-benzopyran-4-ylidene)ethylidene] imin-ium perchlorate ( 3 ), reacts with secondary amines by exchanging the dimethylimino group for the added amine. Primary amines also reacted with 3 in the same manner. The bis iminium salts, N,N,N',N'-tetramethyl-N,N'-[2-(2-phenyl-4H-l-benzopyran-4-ylidene)-1,3-propanediylidene]-bis(immium perclilorate) ( 4 ) and the corresponding thiapyran derivative ( 5 ), react with ammonia to give 5-dimethylamino-2-phenyl-5H-1-benzopyrano[3,4-c]pyridine ( 10 ) and the thia analog 11 . The reactions of 4 and 5 with primary amines give 3-alkyl-5-dimethylamino-2-phenyl-5H-l-beiizopyrano[3,4-c]pyridinium perclilorate salts or the corresponding thiapyrano compounds. Compounds 4 and 5 react with secondary amines by exchanging the dimethylimino groups with the secondary amine and addition of the amine at the 2-position of the pyran or thiapyran ring.     

Sulfur as hydrogen‐bond acceptor in cocrystals of 2‐thio‐modified thymine

Doubly and triply hydrogen‐bonded supramolecular synthons are of particular interest for the rational design of crystal and cocrystal structures in crystal engineering since they show a high robustness due to their high stability and good reliability. The compound 5‐methyl‐2‐thiouracil (2‐thiothymine) contains an ADA hydrogen‐bonding site (A = acceptor and D = donor) if the S atom is considered as an acceptor. We report herein the results of cocrystallization experiments with the coformers 2,4‐diaminopyrimidine, 2,4‐diamino‐6‐phenyl‐1,3,5‐triazine, 6‐amino‐3H‐isocytosine and melamine, which contain complementary DAD hydrogen‐bonding sites and, therefore, should be capable of forming a mixed ADA–DAD N—H…S/N—H…N/N—H…O synthon (denoted synthon 3s_{N·S;N·N;N·O}), consisting of three different hydrogen bonds with 5‐methyl‐2‐thiouracil. The experiments yielded one cocrystal and five solvated cocrystals, namely 5‐methyl‐2‐thiouracil–2,4‐diaminopyrimidine (1/2), C₅H₆N₂OS·2C₄H₆N₄, (I), 5‐methyl‐2‐thiouracil–2,4‐diaminopyrimidine–N,N‐dimethylformamide (2/2/1), 2C₅H₆N₂OS·2C₄H₆N₄·C₃H₇NO, (II), 5‐methyl‐2‐thiouracil–2,4‐diamino‐6‐phenyl‐1,3,5‐triazine–N,N‐dimethylformamide (2/2/1), 2C₅H₆N₂OS·2C₉H₉N₅·C₃H₇NO, (III), 5‐methyl‐2‐thiouracil–6‐amino‐3H‐isocytosine–N,N‐dimethylformamide (2/2/1), (IV), 2C₅H₆N₂OS·2C₄H₆N₄O·C₃H₇NO, (IV), 5‐methyl‐2‐thiouracil–6‐amino‐3H‐isocytosine–N,N‐dimethylacetamide (2/2/1), 2C₅H₆N₂OS·2C₄H₆N₄O·C₄H₉NO, (V), and 5‐methyl‐2‐thiouracil–melamine (3/2), 3C₅H₆N₂OS·2C₃H₆N₆, (VI). Synthon 3s_{N·S;N·N;N·O} was formed in three structures in which two‐dimensional hydrogen‐bonded networks are observed, while doubly hydrogen‐bonded interactions were formed instead in the remaining three cocrystals whereby three‐dimensional networks are preferred. As desired, the S atoms are involved in hydrogen‐bonding interactions in all six structures, thus illustrating the ability of sulfur to act as a hydrogen‐bond acceptor and, therefore, its value for application in crystal engineering.     

Nucleophilic addition to substituted 1H-4,5-dihydroimidazolium salts

1H-4,5-Dihydroimidazolium salts 1 react readily with nucleophilic reagents originating cyclic products which may be stable or become transformed into acyclic compounds maintaining the structural ethylenediamine unit. With methylmagnesium iodide compound 1e affords the expected imidazolidine, but in the case of substituted 1-aryl-3-methyl-2-phenyl salts 1b-d the N-aryl-N′-methylethylenediamines 3b-d and acetophenone ( 4 ) were isolated, the process representing the transfer of the C-2 unit to a nucleophilic carbon. With alkaline cyanides salts 1 react efficiently affording α,α-diaminonitriles 5 . In these compounds the cyano group may be readily substituted by nucleophiles (hydroxyl anion, species with nucleophilic carbon and reagents that act by hydride ion transfer), in a way similar to the salts but with better yields.     

Steric impediment of alkyl groups in the nitrosation of alkylureas

The oxygenation constants and thermodynamic parameters (ΔH^o, ΔS^o) of a series of novel Co(II) dihydroxamic acids containing a central functional group (-OCH₃) CoL¹∼CoL⁶ were measured, their catalytic performance in the oxidation of p-xylene to p-toluic acid (PTA) were examined. The influence of` ligand structure, the substituents (X = Cl, OCH₃ and Y = H, CH₃, Cl) of the aromatic rings and added alkaline cations on the O₂-binding capabilities and catalytic oxidation activities were investigated.     

Model Complexes for Ureases: A Dinickel(II) Complex with a Novel Asymmetric Ligand and Comparative Kinetic Studies on Catalytically Active Zinc,Cobalt, and Nickel Complexes

The dinuclear nickel(II) complex of the asymmetric ligand 1‐[N,N‐bis(2‐pyridylmethyl)amino]‐3‐[2‐(3,5dimethyl‐1H‐pyrazol‐1‐yl)ethoxy]‐2‐hydroxypropane (HL1) was prepared as a model for the active site of urease. The novel complex [Ni₂(L1)(MeCOO)(ClO₄)(EtOH)₂](ClO₄) · 0.5 Et₂O ( 1 ) crystallizes in the triclinic space group P 1 with a = 11.639(2) Å, b = 12.571(3) Å, c = 16.341(3) Å, α = 92.29°, β = 106.54°, and γ = 113.73°. The nickel ions (c.n. 6) are bridged by the alkoxy donor substituent of the ligand and an acetate anion. The dinuclear nickel(II), cobalt(II), and zinc(II) complexes of the ligands 1‐[N,N‐bis(2‐benzimidazolylmethyl)amino]‐3‐[2‐(3,5‐dimethyl‐1 H‐pyrazol‐1‐yl)ethoxy]‐2‐hydroxypropane (HL2), N‐methyl‐N,N',N'‐tris(2‐benzimidazolylmethyl)‐2‐hydroxy‐1,3‐diaminopropane (HL3), and N,N,N',N'‐tetrakis(2‐benzimidazolylmethyl)‐2‐hydroxy‐1,3‐diaminopropane (HL4) were investigated for their activity towards the hydrolysis of the test substrate p‐nitrophenyl acetate (npa) in ethanol‐water (1 : 1). The second‐order rate constants for the cleavage of npa were determined for all complexes. The profile of the pH dependence indicates that a hydroxide initially binds to the metal ion. The bound nucleophile subsequently attacks the test substrate. The results are discussed in terms of a refined model for the structure activity relationships of the dinuclear active site of urease.     

Addition Reactions of Me3SiCN with Aldehydes Catalyzed by Aluminum Complexes Containing in their Coordination Sphere O,S, and N Ligands

The reaction of one equivalent of LAlH₂ ( 1 ; L=HC(CMeNAr)₂, Ar=2,6‐iPr₂C₆H₃, β‐diketiminate ligand) with two equivalents of 2‐mercapto‐4,6‐dimethylpyrimidine hydrate resulted in LAl[(μ‐S)(m‐C₄N₂H)(CH₂)₂]₂ ( 2 ) in good yield. Similarly, when N‐2‐pyridylsalicylideneamine, N‐(2,6‐diisopropylphenyl)salicylaldimine, and ethyl 3‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐2‐carboxylate were used as starting materials, the corresponding products LAl[(μ‐O)(o‐C₆H₄)CN(C₅NH₄)]₂ ( 3 ), LAlH[(μ‐O)(o‐C₄H₄)CN(2,6‐iPr₂C₆H₃)] ( 4 ), and LAl[(μ‐NH)(o‐C₈SH₈)(COOC₂H₅)]₂ ( 5 ) were isolated. Compounds 2 – 5 were characterized by ¹H and ¹³C NMR spectroscopy as well as by single‐crystal X‐ray structural analysis. Surprisingly, compounds 2 – 5 exhibit good catalytic activity in addition reactions of aldehydes with trimethylsilyl cyanide (TMSCN).     

Substituted 2,3-dihydro-4(1H)quinazoIinones, 2

Details are given for the reaction of isatoic anhydrides with different primary aromatic amines to give several new N-aryl-o-aminobenzamides. The latter were annulated with a variety of dialkyl and alkyl aryl ketones to give 2,3-dihydro-4(1H)quinazolinones. Several novel and efficient procedures for effecting the cyclization are described.     

Novel aluminium compounds derived from Schiff bases: Synthesis,characterization and catalytic performance in hydroboration

Seven novel aluminium complexes supported by Schiff base ligands derived from o‐diaminobenzene or o‐aminothiophenol were synthesized and characterized. The reactions of AlMe₃ with L¹ (N,N′‐bis(benzylidine)‐o‐phenylenediamine) and L² (N,N′‐bis(2‐thienylmethylene)‐o‐phenylenediamine) gave the complexes L¹AlMe₃ ( 1 ) and L²AlMe₂ ( 2 ), respectively, which involved two types of reaction mechanisms: one was proton transfer and ring closure, and the other was alkyl transfer. Complexes L³AlMe₂ (HL³ = 4‐chlorobenzylidene‐o‐aminothiophenol) ( 3 ), L⁴AlMe₂ (HL⁴ = 2‐thiophenecarboxaldehyde‐o‐aminothiophenol) ( 4 ), L³AlH(NMe₃) ( 5 ), L⁴AlH(NMe₃) ( 6 ) and L⁵AlH(NMe₃) (HL⁵ = 4‐methylbenzylidene‐o‐aminothiophenol) ( 7 ) were prepared by reacting HL^3–5 with equimolar AlMe₃ or H₃Al?NMe₃, respectively. Compounds 3 – 7 feature an organic–inorganic hybrid containing CNAlSC five‐membered ring. All complexes were characterized using ¹H NMR and ¹³C NMR spectroscopy, X‐ray crystal structure analysis and elemental analysis. The efficient catalytic performances of 1 – 7 for the hydroboration of carbonyl groups were investigated, with compound 4 exhibiting the highest catalytic activity among all the complexes.     

Efficient dehydration of primary amides to nitriles catalyzed by phosphorus-chalcogen chelated iron hydrides

A series of phosphorus-chalcogen chelated hydrido iron (II) complexes 1–7 , (o-(R'₂P)-p-R-C₆H₄Y)FeH (PMe₃)₃ ( 1 : R = H, R' = Ph, Y = O; 2 : R = Me, R' = Ph, Y = O; 3 : R = H, R' = ⁱPr, Y = O; 4 : R = Me, R' = ⁱPr, Y = O; 5 : R = H, R' = Ph, Y = S; 6 : R = Me, R' = Ph, Y = S; 7 : R = H, R' = Ph, Y = Se), were synthesized. The catalytic performances of 1–7 for dehydration of amides to nitriles were explored by comparing three factors: (1) different chalcogen coordination atoms Y; (2) R' group of the phosphine moiety; (3) R substituent group at the phenyl ring. It is confirmed that 5 with S as coordination atom has the best catalytic activity and 7 with Se as coordination atom has the poorest catalytic activity among complexes 1 , 5 and 7 . Electron-rich complex 4 is the best catalyst among the seven complexes and the dehydration reaction was completed by using 2 mol% catalyst loading at 60 °C with 24 hr in the presence of (EtO)₃SiH in THF. Catalyst 4 has good tolerance to many functional groups. Among the seven iron complexes, new complexes 3 and 4 were obtained via the O-H bond activation of the preligands o-ⁱPr₂P(C₆H₄)OH and o-ⁱPr₂P-p-Me-(C₆H₄)OH by Fe(PMe₃)₄. Both 3 and 4 were characterized by spectroscopic methods and X-ray diffraction analysis. The catalytic mechanism was experimentally studied and also proposed.     

Synthesis of novel 5‐aryl‐1H‐tetrazoles

In this study phenylselenocyanate and some of its derivatives (o‐Cl, p‐Cl, p‐Br, o‐NO₂, p‐NO₂, o‐CH₃, p‐CH₃, o‐COOH, p‐COOH, p‐OCH₃ substituted) were synthesized ( 3a–3j ). The synthesized compounds were converted to 5‐aryl‐1H‐tetrazole ( 4a–4j ), by Et₃N ċ HCl‐NaN₃ in toluene, which are a new series of phenylselanyl‐1H‐tetrazoles. The structure of all the presently synthesized compounds were confirmed using spectroscopic methods (FTIR, ¹H NMR, MS). © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:255–258, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20293     

Anil-Synthese. 15. Mitteilung. Über die Herstellung von heterocyclisch substituierten Stilbenyl-Derivaten des 2H-1,2,3-Triazols

Preparation of heterocyclic substituted stilbenyl derivatives of 2H-1,2,3-triazole Schiff's bases derived from 2- and 4-(p-formylphenyl)-2H-1,2,3-triazoles and o- or p-chloroaniline are reacted with various p-tolyl substitued aromatic heterocycles in the presence of dimethylformamide and potassium hydroxide or potassium t-butoxide to yield the corresponding heterocyclic substituted stilbenes (“Anilsynthesis”). In order to avoid opening of the 2H-1,2,3-triazole ring, the reaction is carried out without external heating. In many cases an improvement in yield is obtained by irradiation with UV. light at the beginning of the reaction.     

A simple aza wittig-mediated pyrimidine annulation reaction

Treatment of heterocyclic o-aminonitriles and o-aminoesters 1a-5a with dibromotriphenylphosphorane gives iminophosphoranes 1b-5b which undergo a facile aza-Wittig reaction at room temperature with phenyl isocyanate to provide the carbodiimides 1c-5c . Treatment of the latter intermediates with ammonia leads to intramolecular ring closure of the initially formed guanidines to provide the fused 4-aminopyrimidines and 4(3H)-pyrimidinones 1d-Sd .     

New Synthesis and Reactions of Ethyl 5‐amino‐4‐cyano‐1‐phenyl‐1H‐pyrazole‐3‐carboxylate

Synthesis of ethyl 5‐amino‐4‐cyano‐1‐phenyl‐1H‐pyrazole‐3‐carboxylate 5 has been achieved via abnormal Beckmann rearrangement of o‐chloroaldehyde 1 . Reaction of o‐aminocarbonitrile 5 with concentrated H₂SO₄ furnished expected o‐aminocarboxamide pyrazole 6 . Key intermediates o‐aminocarbonitrile 5 and o‐aminocarboxamide 6 were successfully utilized for the synthesis of pyrazolopyrimidine derivatives. The replacement of Cl in o‐chlorocarbonitrile 3 with secondary amine furnished new synthon 13 , which was further used for the synthesis of polysubstituted heterocycles. The obtained new products were well characterized by IR, ¹H and ¹³C NMR, and mass spectra.