Silyl-enolization-asymmetric Claisen rearrangement of 2-allyloxyindolin-3-one: enantioselective total synthesis of 3a-hydroxypyrrolo[2,3-b]indoline alkaloid alline

Asymmetric Claisen rearrangement triggered by silyl-enolization of 2-(1′-nonel-3′-yloxy)indolin-3-ones was performed in order to prepare 3-(2′-nonenyl)-3-hydroxyindolin-2-ones. Total synthesis of 3-hydroxypyrrolo[2,3-b]indoline alkaloid, (+)-alline was achieved by transformation of the allylic moiety of 3-(2′-nonenyl)-3-hydroxyindolin-2-one to amine followed by reductive cyclization.     

Synthesis of deuterium-labelled, optically active, ferroelectric liquid crystals

The synthesis of two selectively deuterium-labelled 4-(((S)-1-((S)-1-((S)-2-methylbutoxy)-1-oxopropan-2-yloxy)-1-oxopropan-2-yloxy)carbonyl)phenyl 4′-(heptyloxy)biphenyl-4-carboxylate derivatives is reported. A new preparation strategy was developed in order to optimise the yields as well as the optical purity, this property being of fundamental importance for the optical applications of this ferroelectric liquid crystal.     

Synthesis of a mitochondria-targeted spin trap using a novel Parham-type cyclization

A new cyclic nitrone spin trap, [4-(3′,3′-dibutyl-2′-oxy-3′H-isoindol-5′-yloxy)butyl]triphenylphosphonium bromide (MitoSpin), bearing a lipophilic cation has been prepared by a route that involves a novel Parham-type lithiation-cyclization of an isocyanate to give the isoindolinone core. MitoSpin accumulates in a membrane potential dependent way in energized mitochondria and its oxidation could potentially be used in the study of oxidative stress resulting from reactive oxygen species generated in mitochondria.     

New Chiral Kemp's Acid Diamides for Chiral Amine Recognition by 1 H NMR

Two Kemp's acid diamides were synthesized and applied to chiral amine recognition using ¹H NMR analysis. One derivative based on 1-(1-naphthyl)ethylamine had good chiral recognition of six amines and was useful to determine the optical purity for three amines, i.e., methylbenzylamine, 1-(1-naphthyl)ethylamine and 1- henylpropylamine,however, the cyclohexylethylamine derivative showed little discrimination for the amines studied. Together with the results for alkylamines, it was shown that aromatic structure was important for aromatic shielding anisotropy and –– interactions between host and guest. The structure of the 1-(1-naphthyl)ethylamine derivative in solution was also considered based on ¹H NMR data and computer simulation.     

Two selective fluorescent chemosensors for cadmium ions in 99% aqueous solution: the end group effect on the selectivity, DFT calculations and biological applications

Two fluorescent chemosensors for cadmium ions, 2-(2-formylquinolin-8-yloxy)-N,N-diisopropylacetamide (FQDIPA) and 2-(2-formylquinolin-8-yloxy)-N,N-diphenylacetamide (FQDPA), were first assessed in 99% aqueous solutions. The sensor FQDIPA with an end group of an aliphatic amine can recognize Cd(2+) from other metal ions more selectively and sensitively than FQDPA with that of aromatic amines, which was further demonstrated by DFT calculations that were comparable to the experimental results. It is indeed the distinction between the end groups of these chemosensors that results in the variation of the energy difference between the LUMOs and HOMOs and the interaction energies of FQDIPA·Cd(2+) and FQDPA·Cd(2+). Furthermore, the living cell image experiment could also indicate that the FQDIPA is more suitable than the FQDPA in the practical applications in biological systems.     

Synthesis of novel planar-chiral [2.2]paracyclophane derivatives as potential ligands for asymmetric catalysis

The synthesis of a variety of new 4,5-disubstituted [2.2]paracyclophane derivatives has been achieved employing different cross-coupling reactions. By this methodology, a heteroatom-variation of successful catalyst ligands was achieved, giving rise to a modular ligand system. The X-ray structure of 4-hydroxy-5-(1′-hydroxy-1′-phenylethyl)-[2.2]paracyclophane was determined to elucidate the configuration. Additionally, a diastereoselective synthesis of planar- and central-chiral 4-([2.2]paracyclophanyl)ethylamine was achieved, thus resulting in a planar- and central-chiral phenyl ethylamine analogue.     

New compounds via Mannich reaction of cytosine, paraformaldehyde and cyclic secondary amines

The Mannich reaction of cytosine, paraformaldehyde and cyclic secondary amines in the presence of acetic acid gives 5-(4′-morpholinyl)methylcytosine, 5-(1′-piperidinyl)methylcytosine, 5-(1′-pyrrolidinyl)methylcytosine, 5-(4′-methyl-1′-piperidinyl)methylcytosine, 5-(3′-methyl-1′-piperidinyl)methylcytosine and 5-(2′-methyl-1′-piperidinyl)methylcytosine. These products are quite different from those obtained via cytosine aminomethylation previously described in the literature.     

Reaction, identification, and fluorescence of aminoperfluorophenazines

Perfluorophenazine regiospecifically reacted with monoalkyl-, dialkyl-, and arylamines to afford the corresponding 2-amino-substituted derivatives. 2-(Ethylamino)- and 2-(diethylamino)perfluorophenazine reacted with another molar amount of ethylamine and diethylamine to preferentially provide the 2,7-disubstituted derivatives, respectively. Perfluoro(2,7-dimethylphenazine) was allowed to react with ethylamine to give the 1-ethylamino derivative. These regiospecific reactions were explained by the density functional theory (DFT) calculations. Perfluorophenazine reacted with ethylenediamine to afford the 2,3-cyclized and N,N′-bis(2-perfluorophenazinyl) derivatives. These amino-substituted products showed UV-vis absorption (λ_max) and fluorescence maxima (F_max) in the range of 439-536 and 524-613 nm in hexane, respectively. Some of them exhibit intense fluorescence.     

Effect of structure on thermal behaviour of epoxy resins

The paper deals with the curing behaviour of diglycidyl ether of bisphenol-A (DGEBA) using three novel multifunctional aromatic amines having phosphine oxide and amide-acid linkages. The amines were prepared by reacting tris(3-aminophenyl)phosphine oxide (TAP) with 1,2,4,5-benzenetetracarboxylic acid anhydride (P)/4,4^′-(hexafluoroisopropylidene)diphthalic acid anhydride (F)/3,3^′,4,4^′-benzophenonetetracarboxylic acid dianhydride (B). Amide-acid linkage in these amines is converted to thermally stable imide linkage during curing reaction. Curing temperatures of DGEBA were higher with phosphorylated amines than the conventional amine 4,4^′-diamino diphenyl sulphone (D). A decrease in initial decomposition temperature and higher char yields were observed when phosphorus containing amide-acid amines were used as curing agents for DGEBA.     

Synthesis and some transformations of 2-[2-isopropyl-4-(3-methylbutyl)tetrahydropyran-4-yl]-ethylamine

The condensation of 2-[2-isopropyl-4-(3-methylbutyl)tetrahydropyran-4-yl]ethylamine with aromatic aldehydes followed by reduction gave rise to secondary amines of tetrahydropyrane series. Reactions of the obtained amines with acetyl chloride, succinic and phthalic anhydrides resulted in the corresponding acetamides, succinimide, and phthalimide.     

Novel four-component route to the synthesis of spiro[indoline-3,4′-pyridine]-3′-carboxylate derivatives

An effective route to spiro[indoline-3,4′-pyridine]-3′-carboxylate derivatives is described. This involves reaction of isatin, 1-phenyl-2-(1,1,1-triphenyl-λ⁵-phosphanylidene)-1-ethanone, and benzylamine derivatives or aliphatic amines in the presence of alkyl acetoacetate (1,3-dicarbonyl compounds) in dry methanol under reflux conditions. The reactive 1:1 enaminone, which is obtained from the addition of the amine to 1,3-dicarbonyl compound, adds to the α,β-unsaturated ketone, which is formed from the reaction of isatin and 1-phenyl-2-(1,1,1-triphenyl-λ⁵-phosphanylidene)-1-ethanone, to produce the alkyl 1′-benzyl-2′-methyl-2-oxo-6′-phenyl-1′H-spiro[indoline-3,4′-pyridine]-3′-carboxylate derivatives in excellent yields.     

Inhibition of Silver Corrosion in Nitric Acid by Some Aliphatic Amines

The inhibition of silver corrosion in dilute nitric acid (0.01 M) was studied using electrochemical polarization technique in the presence of different concentrations of methylamine, ethylamine, n-propylamine, and n-butylamine. It was found that the inhibition efficiency obtained from Tafel plots improved when the inhibitor concentration and the length of the alkyl chain were increased. The inhibition efficiency increased markedly with increase the additive concentrations according to the following order: methylamine < ethylamine < n-propylamine < n-butylamine. The inhibition action of such compounds occurred by simple blocking of amines on the electrode surface through adsorption process according to Temkin adsorption isotherm. The nearly constant values of the anodic Tafel slopes indicated that the presence of such amines do not affect the mechanism of metal dissolution.     

Synthesis and asymmetric catalytic activity of (1S,1′S)-4,4′-biquinazoline-based primary amines

A series of (1S,1′S)-4,4′-biquinazoline-based primary amines were prepared from natural amino acids via a six-step reaction sequence of protection and condensation followed by key synthetic steps including chlorination, nickel(0)-mediated homocoupling, and deprotection. These novel amines were screened for the asymmetric ethylation of aryl aldehydes to yield alcohols with an (S)-configuration with enantiomeric excesses (ee) varying from 2% to 95%.     

A regioselective three-component reaction for synthesis of novel 1′H-spiro[isoindoline-1,2′-quinazoline]-3,4′(3′H)-dione derivatives

A ring opening and regioselective three-component reaction of isatoic anhydride, isatins, and aromatic or aliphatic primary amines in the presence of catalytic amount of KAl(SO₄)₂·12H₂O (alum) to yield a novel series of 1′H-spiro[isoindoline-1,2′-quinazoline]-3,4′(3′H)-dione is described.     

Michael reaction of indoles with 3-(2′-nitrovinyl)indole under solvent-free conditions and in solution. An efficient synthesis of 2,2-bis(indolyl)nitroethanes and studies on their reduction

Michael reaction of 3-(2′-nitrovinyl)indole with eight 3-unsubstituted indoles on TLC-grade silica gel furnished unsymmetrical bis(indolyl)nitroethanes in 7-12 min under microwave irradiation and in 8-14 h at rt. In contrast, the p-TsOH-catalysed reaction of the nitrovinylindole with the 3-unsubstituted and two 3-substituted indoles in solution under reflux furnished both unsymmetrical and symmetrical bis(indolyl)nitroethanes, the latter resulting from novel tandem Michael addition-elimination-Michael addition reactions. The synthesis of a 2′,3″-bis(indolyl)nitroethane, the precursor core structure of two bioactive marine metabolites, and the reduction of 2,2-bis(3′-indolyl)nitroethane to the corresponding ethylamine, isolated as its N-acetyl derivative, have been achieved. Significantly, attempted hydrolysis of three nitronates, derived from the corresponding bis(indolyl)nitroethanes, with buffered aqueous TiCl₃ has led to the first isolation of oximes (syn/anti-mixture) as the only products.     

Synthesis of pyran derivatives with mesomorphic properties

N-(4-Arylidene)-4-(3,6-dihydro-4-methyl-2H-pyran-3-yloxy)anilines and N-(4-arylidene)-4-[(5,6-dihydro-2H-pyran-4-yl)methoxy]anilines that have the properties of smectic and nematic liquid crystals were synthesized. The effect of the pyran ring and the length of the aliphatic radical on the type and thermal stability of the meso phase was elucidated.Fortieth Anniversary of the October Revolution Bashkir State University, Ufa 450074. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 897–899, July, 1991.     

Gas-phase reactions of Co+ with ethylamine: a theoretical approach to the reaction mechanisms of transition metal ions with primary amines

We report herein a comprehensive study of gas-phase reactions of Co(+) with ethylamine using density functional theory. Geometries and energies for all the stationary points involved in the reactions are investigated at the B3LYP/6-311++G(2df,2pd) level. Six different "classical" N and "nonclassical" ethyl-H attached isomers are found for the Co(+)-ethylamine complexes. The classical complexes are much more stable than the nonclassical ones, which have the complexation energies close to Co(+) complexes with small alkanes. Extensive conversions could occur readily between these encounter complexes. All conceivable reaction pathways from each encounter complex to the experimentally observed products are carefully surveyed, and the most likely reaction mechanisms are derived. Activation of the C(alpha)-H bond of ethylamine by Co(+) through both the classical and nonclassical complexes leads to not only the H2 loss but also the hydride abstraction. The loss of ethylene arises from Co(+) insertion into the polar C-N bond in the classical complexes as well as from C(beta)-H activation through the nonclassical methyl-H attached complex of Co(+)- gauche-ethylamine. CH4 only forms via C-C activation from the nonclassical complex with the metal bound to two Hs from the different carbons. Initial N-H insertion is unlikely to be important. It is the reactions of the nonclassical complexes that closely parallel with the Co(+) + alkane reactions. The theoretical work sheds new light on the title reactions and can serve as a theoretical approach to the reaction mechanisms of transition metal ions with primary amines.     

Effects of sequential replacement of -NH2 by -OH in the tripodal tetraamine tren on its acidity and metal ion coordinating properties

The preparation is described of two modified derivatives of the tripodal tetraamine tren, 2-hydroxy-N,N-bis(2-aminoethyl)ethylamine, NN(2)O222, and 2-amino-N,N-bis(2-hydroxyethyl)ethylamine, NNO(2)222, in which one and two primary amines, respectively, have been replaced with hydroxyl groups. The aqueous acid-base and metal ion (Ni2+, Cu2+, Zn2+) coordination properties of these two compounds were studied by potentiometric, spectrophotometric, and NMR titrations. Two and three acidity constants, respectively, were determined for NNO(2)222 and NN(2)O222 by potentiometry. NMR titrations proved that deprotonation of the two OH residues in NNO(2)222, and of the one in NN(2)O222, corresponded to pK(a) > 14. Acidity constants related to deprotonation of the terminal primary amine functions were similar in both NNO(2)222 and NN(2)O222 (and to those in the parent compound tren), whereas deprotonation of the tertiary ammonium N atom had a very different acidity constant in each of these three compounds. Charge repulsion, polar effects, and intramolecular hydrogen bond formation are responsible for the discrepancy. Chelated diamine metal complexes for each ligand studied depended only on the basicity of the corresponding two amines, suggesting that the hydroxyl group interacted with the metal ion very weakly in acidic or neutral solutions. The ML2+ species further deprotonated to form M(L - H)+ and M(L - 2H) complexes, in which the protons are released from the coordinated OH group. A pM vs pH correlation showed that replacing an NH2 group with a OH group in tren or NN(2)O222 makes the resulting metal complex less stable. Electronic spectra showed that the Cu(II) complexes of both NNO(2)222 and NN(2)O222 adopted a square pyramidal geometry rather than a trigonal bipyramidal geometry. The X-ray crystal structure analysis of the zinc complex [Zn(OH)(mu-NNO(2)222 - H)Zn(NNO(2)222)]2+, as its [BF4]- salt, shows a dinuclear molecule containing two zinc ions, each coordinated in a distorted trigonal bipyramid. The coordination environment at one zinc atom is composed of the four donor groups of a mono-O-deprotonated ligand NNO(2)222 and a hydroxyl ion with the central nitrogen atom of the ligand and the hydroxyl ion in equatorial positions. The oxygen atom of the deprotonated alkoxo group bridges to the second zinc atom, which is coordinated by this atom and one undeprotonated ligand NNO(2)222.     

Highly stereoselective allylic ethylation with alkoxytitanacyclopropane reagents. Synthesis of (1R/S,7R)-1,7-dimethylnonyl propanoate, the Western corn rootworm sex attractant

Allylic ethylation of 2-((E)-dodec-2-en-4-yloxy)tetrahydro-2H-pyran with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide proceeds via a S_N2′ pathway to afford (E)-3-methyltridec-4-ene with excellent syn-diastereoselecivity. This transformation is used as a key step in the synthesis of (1R/S,7R)-1,7-dimethylnonyl propanoate, the Western corn rootworm (Diabrotica virgifera virgifera) sex attractant.     

Resolution of ortho- and meta-substituted 1-phenylethylamines with isopropylidene glycerol hydrogen phthalate

The hydrogen phthalate of isopropylidene glycerol 1, previously reported as an efficient resolving agent of p-substituted 1-phenylethylamines, was also found to resolve selected o- and m-isomers. In particular, the (S)-enantiomers of 1-(2-methylphenyl)ethylamine 2, 1-(3-methylphenyl)ethylamine 3, 1-(2-chlorophenyl)ethylamine 4 and 1-(3-methoxyphenyl)ethylamine 5 were obtained in good yields and very high enantiomeric excess (e.e.) by selective crystallization of the respective salts with (S)- or (R)-1. The e.e.s of the resolved substrates were determined by chiral HPLC analysis. The (S)-configuration of (−)-3 was established according to Raban's procedure. Optical rotations of non-racemic free amines 2 and 3 are reported. The success of the resolutions presented and of the precedent ones using 1 indicate that the position of the substituent on the 1-phenylethylamine framework does not affect the resolution, showing the uncommon versatility of 1 in the resolution of monosubstituted 1-phenylethylamines.