Orthoamides by selective borohydride reduction of N,N′,N″-triacyl- and N,N′,N″-tri(alkoxycarbonyl)-guanidines

N,N′,N″-Triacylguanidines and N,N′,N″-tri(alkoxycarbonyl)guanidines were prepared and reduced with borohydride salts in a mixture of tetrahydrofuran and acetic acid to give triacyl and tri(alkoxycarbonyl) orthoamides in yields of 40–85%. However, similar reduction of N,N′,N″-tri(t-butoxycarbonyl)guanidine did not give orthoamide but the aminal di(t-butyl) methylenedicarbamate.     

Synthesis of 2-(N-arylimino-κN-methyl)pyrrolide-κN complexes of nickel

2-(N-aryliminomethyl)pyrrole precursors (2,6-R₂-C₆H₃-NCH-2-C₄H₃NH) (R = Me, IH; R = ⁱPr, IIH) were prepared and transformed into their corresponding sodium salts (Na⁺I⁻ and Na⁺II⁻) by treatment with NaH. Both salts readily react with [NiBr₂(DME)] (DME = 1,2-dimethoxyethane) to give the respective bis{2-(N-arylimino-κN-methyl)pyrrolide-κN}nickel(II) complexes (1, 2) in almost quantitative yields. The oxidative addition of IH to [Ni(COD)₂] (COD = 1,5-cyclooctadiene) results in the formation of 3, which is a mono(iminomethylpyrrolide)-η³-(cyclic-allyl)-type organonickel(II) complex. The crystal structure of compound 1 has been established by X-ray diffraction studies.     

Reactions of titanocene dihalides with N,N′,N″-chelates: Preparation,X-ray structure and characterization of bis(chloro){2,6-bis[(3,5-dimethyl)pyrazol-1-yl]pyridine}(η-peroxo)titanium(IV)

The reaction of [Ti^IV(Cp)₂Cl₂] (Cp⁻ = η⁵-C₅H₅⁻) and 2,6-bis(3,5-dimethylpyrazolyl-1-yl)pyridine (bdmpp) in Me₂CO has afforded complex [Ti^IVCl₂(O₂)(bdmpp)] (1). The complex can also be prepared from the 1:1:1 [Ti(Cp)₂Cl₂]/bdmpp/H₂O₂ reaction mixture in various solvents. Single-crystal, X-ray crystallography has revealed that the Ti^IV center is in a distorted pentagonal bipyramidal environment in both of the two, crystallographically independent molecules that are present in the asymmetric unit; the equatorial positions are occupied by the two O atoms of the side-on (η²) O₂²⁻ group and the three N-atoms of the tridentate chelate, while the two chloro ligands are on the axial positions. IR, Raman, electronic and ¹H NMR data are discussed in terms of the known structure and the coordination modes of the peroxo and bdmpp ligands.     

A facile metal-free approach to N,N′-bis(1-oxidopyrimidin-4-yl)diamines with promising biological activity

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In vitro and in vivo studies of N,N′-bis[2(2-pyridyl)-methyl]pyridine-2,6-dicarboxamide–copper(II) and rheumatoid arthritis

The thermodynamic equilibria of copper(II), zinc(II) and calcium(II) with N,N′-bis[2(2-pyridyl)-methyl]pyridine-2,6-dicarboxamide (L1) have been studied at 25 °C and an ionic strength of 0.15 mol dm⁻³. Spectroscopic studies suggest metal ion complexation promotes deprotonation and coordination of the amide nitrogens resulting in overall tetragonal coordination of Cu²⁺. Blood–plasma modelling predicts that Cu(II) competes effectively against Zn(II) and Ca(II) for L1 in vivo. Octanol–water partition coefficient studies show that Cu(II)–L1 complexes are reasonably lipophilic. However, the CuL1H₋₂ species which predominates at the physiological pH of 7.4 has poor superoxide dismutase activity. Bio-distribution experiments showed activity accumulation and retention in the body of about 50% of the injected dose for the [⁶⁴Cu]Cu(II)–L1 complex after 24 h.     

Facile rearrangement of N-(α-aminoacyl)cytidines to N-(4-cytidinyl)amino acid amides

Under near neutral and mildly basic conditions, primary N⁴-(α-aminoacyl)cytidines (4a-g) undergo a facile rearrangement to form N-(4-cytidinyl)amino acid amides (5a-g). Secondary aminoacyl derivatives rearrange with other competing pathways. Tertiary aminoacyl derivatives do not rearrange.     

Chiral N,N′-dioxide-iron(II) complexes catalyzed enantioselective oxa-Michael addition of α,β-unsaturated aldehydes

The enantioselective oxa-Michael addition reaction of 1-(4-methoxyphenyl) ethanone oxime to various α,β-unsaturated aldehydes was accomplished by using chiral N,N′-dioxide-FeSO₄·7H₂O (1:1) complex. Aromatic acid was employed as additive to increase the yield of the reaction. The corresponding adducts were obtained in moderate yields with up to 76% ee under mild conditions.     

Synthesis, characterization, and norbornene polymerization of η-benzylnickel(II) complexes of N-heterocyclic carbenes

Neutral η¹-benzylnickel carbene complexes, [Ni(η¹-CH₂C₆H₅)(IiPr)(PMe₃)(Cl)] (3) (IiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and [Ni(η¹-CH₂C₆H₅)(SIiPr)(PMe₃)(Cl)] (4) (SIiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazolin-2-ylidene), were prepared by the reaction between [Ni(η³-CH₂C₆H₅)(PMe₃)(Cl)] and an equivalent amount of the corresponding free N-heterocyclic carbene. The preparation of η³-benzylnickel carbene complexes, [Ni(η³-CH₂C₆H₅)(IiPr)(Cl)] (5) and [Ni(η³-CH₂C₆H₅)(SIiPr)(Cl)] (6) were carried out by the abstraction of PMe₃ from 3 and 4 by the treatment of B(C₆F₅)₃. The treatment of AgX on 5 and 6 produced the anion-exchanged complexes, [Ni(η³-CH₂C₆H₅)(NHC)(X)] (7, NHC = IiPr, X = O₂CCF₃; 8, NHC = IiPr, X = O₃SCF₃; 9, NHC = SIiPr, X = O₂CCF₃; 10, NHC = SIiPr, X = O₃SCF₃). The solid state structures of 3 and 10 were determined by X-ray crystallography. The η³-benzyl complexes of IiPr (5, 7, and 8) alone, in the absence of any activators such as borate and MAO, showed good catalytic activity towards the vinyl-type norbornene polymerization. The catalyst was thermally robust and the activity increases as the temperature rises to 130 °C.     

Selective C-N bond oxidation: demethylation of N-methyl group in N-arylmethyl-N-methyl-α-amino esters utilizing N-iodosuccinimide (NIS)

Demethylation of N-methyl group in N-methyl-N-arylmethyl-α-amino esters was accomplished by the oxidation of the amino group using the N-iodosuccinimide (NIS)/acetonitrile system followed by treatment with O-methylhydroxylamine hydrochloride. This combination of reagents could provide a complementary method to catalytic hydrogenolysis, which certainly cleaves N-arylmethyl groups, in organic synthesis.     

Computational study of Rh(I)-Catalyzed Cycloaddition–Fragmentation of N-cyclopropylacrylamides

Rh-catalyzed cycloaddition–fragmentation of N-cyclopropylacrylamides is an effective method to directly obtain substituted azocanes. In this transformation, the challenging step is insertion of CO and alkene into the more hindered proximal cyclopropane CC bond while avoiding competitive less hindered proximal CC activation. Given the importance of this novel strategy, we performed a density functional theory study to clarify the catalytic mechanism. The calculations confirm that cleavage of the more hindered bond is more favorable than cleavage of the less hindered bond for Rh-catalyzed (7 + 1) cycloaddition of N-cyclopropylacrylamides. Comparison between Rh-catalyzed (3 + 1 + 2) and (7 + 1) cycloaddition shows that the coordination mode with different ligand plays a crucial role in enabling different CC cleavage. The main factors responsible for the occurrence of β-hydride elimination rather than CC reductive elimination are also discussed. The kinetic preference for β-hydride elimination can be attributed to the transition state of CC reductive elimination being more distorted and forming in a much more concerted fashion than that of β-hydride elimination. Additionally, C4H elimination is disfavored owing to weaker interaction energy compared with C7H elimination by analyzing using the distortion/interaction model.     

Regioselective halogenation of pyridinium N-(benzoazynyl) aminides as a way to produce N-benzyl-α-aminobenzoazines

The halogenation of pyridinium N-(benzoazynyl) aminides with N-halosuccinimides provides a mild and regioselective method to functionalize the negatively charged diazine moiety in most cases. In some examples, however, formation of other products is explained. Finally, alkylation of the exocyclic nitrogen and reduction of the N–N bond provides a simple and straightforward strategy to obtain functionalized N-benzyl-benzoazynyl-α-amines.     

Ring Closure of N,N′:N,N′-bis(decamethylene)-1, 4-diamino-2,5-bis(10-cyanodecyloxy)benzene (IV)

Recently, β-chloro-α,β-unsaturated carbonyl compounds have become increasingly useful as intermediates in organic synthesis. For example, reactions involving a number of different cyclic β-chloro-α,β-unsaturated ketones with a variety of reagents (a malonate anion², the anion of the dithiolane derivative of ethyl glyoxalate³, zinc-silver couple in methanol⁴, dimethylsulfoxonium methylide^5,6) have produced a series of structurally diverse and potentially fruitful synthetic intermediates. The second-mentioned reagent has also been successfully reacted with a β-chloro-α,β-unsaturated ester³.     

Synthesis of substituted β-carbolines via gold(III)-catalyzed cycloisomerization of N-propargylamides

Indole-substituted N-propargylamides undergo a gold(III)-catalyzed cyclization to give oxazoles or β-carbolinones, depending on the substitution pattern at the amide nitrogen. Secondary amides furnished oxazoles via a 5-exo-dig cyclization, while tertiary indole-2-carboxamides cycloisomerized to give 2,9-dihydro-β-carbolin-1-ones upon treatment with catalytic amounts of gold(III) chloride. An optimized procedure was developed to prepare several new N-benzyl-β-carbolinones as well as the corresponding β-carbolines, which are of interest as core structures found in various natural products such as the harman, ervolanine, and lavendamycin class of alkaloids.     

Trialkyl borate assisted amination of fluorinated 1,3-diketones for synthesis of N,N′-1,2-phenylen-bis(β-aminoenones) and their Ni(II), Cu(II) and Pd(II) complexes

An effecient synthetic method for fluorinated tridentate β-aminoenones and tetradentate bis(β-aminoenones) via amination of fluorinated 1,3-diketones with o-phenylenediamine in the presence of trialkyl borates was developed. Ni(II), Cu(II) and Pd(II) complexes with tetradentate bis(β-aminoenones) were obtained. Their gaschromatographic behaviour and main fragmentation paths in the electron ionization mass spectra were described.     

Synthesis of betulonic acid S,S′-bis(carboxymethyl) dithioketal

Russian Chemical Bulletin - Betulonic acid S,S′-bis(carboxymethyl) dithioketal was obtained by condensation of betulonic and thioglycolic acids.     

Synthesis and photophysical properties of α,ω-bis(terpyridine)oligothiophenes

Four novel fully π-conjugated α,ω-bis(terpyridine)oligothiophenes characterized by NMR, IR, and HR-mass spectroscopy are presented and their electronic absorption/emission and redox properties are described based on both experiments and theoretical calculations. These compounds can be potentially utilized as building blocks for preparation of conjugated metallo-supramolecular polymers or dynamers and related functional materials.     

1-(N-Acylamino)alkyltriphenylphosphonium salts as synthetic equivalents of N-acylimines and new effective α-amidoalkylating agents

1-(N-Acylaminoalkyl)triphenylphosphonium salts 2a-f on reaction with DBU in MeCN are transformed into 1-(N-acylaminoalkyl)amidinium salts 3a-f. Amidinium salts 3d-f with a proton at the β-position undergo slow tautomerization into the corresponding enamides 6d-f. The same 1-(N-acylamino)alkyltriphenylphosphonium salts 2d-f in the presence of Hünig’s base are transformed directly into the corresponding enamides. Phosphonium salts 2, amidinium salts 3, and enamides 6 react with dialkyl malonates in the presence of DBU to give the corresponding amidoalkylation products. α-Amidoalkylation of dialkyl malonates is not observed in the presence of (i-Pr)₂EtN, yet proceeds well under these conditions with more acidic nucleophiles, for example, phthalimide or benzyl mercaptan.     

Synthesis and decarboxylation of N-acyl-α-triphenylphosphonio-α-amino acids: a new synthesis of α-(N-acylamino)alkyltriphenylphosphonium salts

4-Phosphoranylidene-5(4H)-oxazolones 1 undergo hydrolysis in THF in the presence of HBF₄ at room temperature to give N-acyl-α-triphenylphosphonioglycines 3 (R² = H) in very good yields. 4-Alkyl-4-triphenylphosphonio-5(4H)-oxazolones 2 react with water in CH₂Cl₂/THF solution without any acidic catalyst at 0-5 °C in a few days yielding N-acyl-α-triphenylphosphonio-α-amino acids 3 (R² = Me) or α-(N-acylamino)alkyltriphenylphosphonium salt 4 (R² = CH₂OMe). α-Triphenylphosphonio-α-amino acids 3, on heating up to 105-115 °C under reduced pressure (5 mmHg) or on treatment with diisopropylethylamine in CH₂Cl₂ at 20 °C undergo decarboxylation to give the corresponding α-(N-acylamino)alkyltriphenylphosphonium salts 4, usually in very good yields.     

A novel strategy toward the synthesis of N-(β-glycosyl)asparagines based on the alkylation of ethyl nitroacetate using N-(β-glycosyl)iodoacetamides

A conceptually novel strategy has been developed for the synthesis of N-(β-glycosyl)asparagine precursors in good yield by the alkylation of ethyl nitroacetate using six per-O-acetylated N-(β-glycosyl)iodoacetamides derived from mono- and disaccharides. The use of a chiral organocatalyst, N-(9-anthracenylmethyl)cinchoninium chloride (10 mol %), resulted in diastereoselective alkylation up to 64% de. Single crystal structure analysis of the purified major diastereomer of the Glc derivative revealed an absolute configuration of S at the α-carbon of the monosubstituted ethyl nitroacetate which is a precursor of the l-asparagine conjugate.     

Efficient synthesis of N-Me, N-Boc-protected α-hydrazinoacids: access to 1:1:1 [N-Me α-hydrazino/α/N-Me α-hydrazino]trimers

The preparation of optically pure N^α-Me, N^β-Boc-protected α-hydrazinoacids in large scale is described via a S_N2 protocol. These compounds were used as starting materials for the synthesis of 1:1:1 [N^α-Me α-hydrazino/α/N^α-Me α-hydrazino]trimers.