Mixed Amide Research Articles

Conformationally Rigid Diamide Complexes of Zirconium: Electron Deficient Analogues of Cp2Zr

Zirconium complexes bearing a pyridine−diamide ligand [2,6-(RNCH2)2NC5H3]2- (R = 2,6-diisopropylphenyl, 2,6-diethylphenyl (BDEP), 2,6-dimethylphenyl) have been synthesized. The mixed amide complexes [2,6-(RNCH2)2NC5H3]Zr(NMe2)2 are prepared in high yield from [2,6-(RHNCH2)2NC5H3] and Zr(NMe2)4. The mixed amides react with excess ClSiMe3 to afford the dichlorides [2,6-(RNCH2)2NC5H3]ZrCl2 in nearly quantitative yield. Dimethyl complexes are prepared from [2,6-(RNCH2)2NC5H3]ZrCl2 and 2 equiv of MeMgBr. A single-crystal X-ray diffraction study of (BDEP)ZrMe2 revealed a distorted trigonal bipyramid structure with the amides occupying the axial positions. The frontier orbitals of a model of the fragment (BDEP)Zr are very similar the those of Cp2Zr, suggesting that complexes bearing the pyridine−diamide ligand may behave as sources of Cp2Zr.

Predictions of Secondary Structure using Statistical Analyses of Electronic and Vibrational Circular Dichroism and Fourier Transform Infrared Spectra of Proteins in H 2O

Vibrational circular dichroism (VCD) and Fourier transform IR (FTIR) methods for prediction of protein secondary structure are systematically compared using selective regression analysis. VCD and FTIR spectra over the amide I and II bands of 23 proteins dissolved in H 2O were analyzed using the principal component method of factor analysis (PC/FA) and regression fits to fractional components (FC) of secondary structure. Predictive capability was determined by computing structures for proteins sequentially left out of the regression. All possible combinations of PC/FA spectral parameters (coefficients) were used to form a full set of restricted multiple regressions (RMR) of PC/FA coefficients with FC values, both independently for each spectral data set as well as for the VCD and FTIR sets grouped together and with similarly obtained electronic CD (ECD) data. The distribution of predictive error for a set of the best RMR relationships that use a given number of spectral coefficients was used to select the optimal prediction algorithm. Minimum predictive error resulted for a small subset (three to six) of spectral coefficients, which is consistent with our earlier findings using VCD measured for proteins in 2H 2O and ECD data. Subtracting the average absorption spectrum from all the training set FTIR spectra before analysis yields more variance in the FTIR band shape and improves the predictive ability of the best PC/FA RMR to near that for the VCD. Both methods (FTIR and VCD) using data for proteins in H 2O are somewhat better predictors than amide I′ (in 2H 2O) VCD alone and, for helix, worse than ECD alone. Combining FTIR and VCD data did not dramatically change the prediction results. Predictions are improved by combining both with ECD data, indicating that the improvement is due to using their very different structural sensitivities. The coupled H 2O-based spectral analyses and the mixed amide I′ + II VCD plus ECD analysis are comparable for the helix and sheet components, indicating that partial deuteration is not a major source of prediction error.

A novel technique for the preparation of secondary fatty amides

AbstractA low‐temperature synthesis of fatty alkanolamides, fatty diamides and fatty aralkylamides directly from triglycerides and primary amines provides essentially quantitative yields of the various products. The reactions run to completion in 3–12 h at temperatures of 50–60°C, approximately 100°C lower than employed in present conventional practice. The amines are used in excess and serve as solvent, reagent and, perhaps, as catalyst. The amides were characterized by melting point and spectroscopic (infrared and nuclear magnetic resonance) methods. If the mixed amides produced from the various natural triglyceride mixtures of fats and oils are acceptable products, this synthetic method provides these products in satisfactory quality while conserving energy and avoiding the intermediate production of free fatty acids or their esters.

Metalation of Hantzsch esters and mixed amide esters: a general route to C-2 functionalized 1,4-dihydropyridines

1,4-Dihydropyridine (Hantzsch) diesters 3a-e readily undergo metalation at the C-2 methyl (vinylogous ester) position on treatment with alkyllithium bases. The resulting anion intermediates can be treated with electrophilic reagents to afford 1,4-dihydropyridine products that have been chemically elaborated at the C-2 methyl position. The methodology permits a variety of electrophilic functionalities to be regiospecifically introduced at the C-2 methyl position of 1,4-dihydropyridines. Deuterium distribution studies with mixed dihydropyridine amide esters 20a and 20b having nonequivalent C-2 and C-6 methyl groups indicate specific metalation occurs at the C-2 methyl (vinylogous ester) position.Tri- and tertaanion formaion is also possible at both vinylogous methyl and NH positions when the metalation reactions are performed with excess equivalents of n-BuLi or s-BuLi bases

The effect of amino acids and amides on the regulation of nitrate uptake by wheat seedlings

Abstract Wheat plants grown hydroponically increased their nitrate uptake rate more than two‐fold after three days of N starvation. Exogenously supplied amino acids and amides had no effect on the nitrate uptake rate of plants well nourished in N. After three days of N starvation, however, some of the amino acids and amides supplied to plants inhibited up to 50% of the nitrate uptake rate. The most effective inhibitor was aspartic acid. Asparagine, glutamine or phenylalanine did not show any inhibitory effect. The percentage of inhibition was not increased by increasing the amino acid concentration, nor did the addition of mixed amino acids and amides increase the inhibition exerted by one amino acid alone. During the three days of N starvation, there was a decrease in the concentration of endogenous amino acids in the roots, but not all amino acids decreased their concentration at the same rate. It is suggested that the endogenous levels of some amino acids may repress the nitrate uptake system in plants...

Mixed amide thiolate complexes of zinc with low coordination number at the metal atom

AbstractThree different thiophenoles 2,4,6‐(CF3)3C6H2SH (4), 2,4,6‐(iPr)3C6H2SH (5), and 2,6‐(Me3Si)2C6H3SH (6) with bulky sub‐stituents in ortho position were treated with Zn[N(SiMe3)2]2 (7) in a non‐coordinating solvent like CH2Cl2 or toluene to yield mixed amide thiolate zinc complexes Zn2[N(SiMe3)2]{S[2,4,6‐(CF)3C6H2]}3 (8), Zn3[N(SiMe3)2]2{S[2,4,6‐(iPr)3C6H2]}4 (9), and Zn2{S[2,6‐(Me3Si)2C6H3]}4 (10), respectively. These compounds comprise low‐coordinated zinc atoms. Initially, the reactions were performed in a 1:1 ratio of the reactants. However, in no reaction the expected {Zn[N(SiMe3)2](SR)}x (X = 1,2,3…) species were obtained but compounds which are richer in thiolate substituents (SR/NR2 > 1) even if a large excess of amide 7 was used. Distinct from these, the reaction between 7 and 2,6‐(iPr)2C6H3OH (14) in a 1:1 ratio afforded indeed dimer Zn2[N(SiMe3)2]2{O[2,6‐(iPr)2C6H3]}2 (15). The molecular structures of 8, 9, 10, and 15 in the crystal are elucidated by X‐ray structural analyses and compared with proposed structures in solution based on multinuclear NMR experiments.

Cosulfation of fatty acid alkanolamides and lower molecular weight alcohols

Abstract and SummaryThe process for the sulfation of tallow isopropanolamide or of a 50:50 mixture of tallow diglycolamide and isopropanolamide with chlorosulfonic acid was studied. The major obstacle to complete and uniform sulfation was the high viscosity of the sulfation mix. This could be overcome most advantageously by cosulfation with lower molecular weight alcohols, preferably isopropanol. The most fluid reaction mix and product were prepared from the mixed amides. No chlorinated solvent is required for such cosulfations.

Synthesis and NMR spectea of compounds containing the=P(S)-N-P=group

1. Mixed amides of dimethyl thiophosphoric acid and trivalent phosphorus acids were produced. 2. The NMR spectra of H1 and P31 of the synthesized compounds were recorded, and the dependence of the constant of the spin-spin interaction between phosphorus nuclei in the geminal system PIV-N-PIII on the electron-donor capacity of substituents at PIII was determined.

P?-d? Interaction in amides of phosphorous acid

1. pπ-dπ conjugation in the ethyleneamides of phosphorous acid is confirmed by the rapid inversion of the nitrogen atom in these compounds as shown by PMR data. 2. The absence of peaks due to amine and oxygenous fragments in the mass spectra of amides and esters of phosphorous acid is explained by pπ-dπ conjugation. It follows from the mass spectra of the mixed amides and amidoesters that the stabilization of the fragments due to pπ-dπ conjugation decreases upon going from the dimethylamides to the ethylamides.

Kinetics of the aminolysis of hydrogenated tallow by allylamine and other primary amines in methanol

AbstractKinetics of the aminolysis of hydrogenated tallow by allylamine in methanol solution under sodium methoxide catalysis was studied at several temperatures (60 to 90C) and catalyst concentrations. Under the experimental conditions the triglycerides were rapidly converted to the mixed methyl esters, which slowly reacted with the amine to produce the mixed amides. At constant catalyst concentration, disappearance of triglyceride was found to be first order in triglyceride and in amine. Because rate was found to be directly proportional to catalyst concentration, the experimental over‐all rate was 蜢d[Triglyceride]/dt=k3[Triglyceride] [Amine] [RO蜢], and k3 was 2.022 kg2 mole蜢2 hr蜢1. A mechanism proposed by Bunnett and Davis for ester aminolysis involving an ester‐amine complex formed in a rapid pre‐transition‐state equilibrium is consistent with thermodynamic terms which reconcile a large negative entropy of activation (蜢44.17 cal deg蜢1 equivalent蜢1) and relatively small energy of activation (11.60 kcal equivalent蜢1). Relative rate constants at 70C under sodium‐methoxide catalysis for the aminolysis of hydrogenated tallow by a variety of structurally different primary amines agreed, in general, with those found by others for the ethylene glycol‐catalyzed reaction of methyl acetate with the same amines at 25C. However, monoethanolamine reacted nineteen times faster than predicted, which suggested a mechanism involving initial attack by the alkoxy anion of the ethanolamine in the rate detering step, followed by rapid, base‐catalyzed, acyl acyl oxygen‐to‐nitrogen (O薔N) migration. The velocity constants and thermodynamic constants reported enable prediction of the time required for specific yields under a variety of experimental conditions.

Phosphorylation of formamide

1. Mixed amides of formic and dialkyl hydrogen phosphites (dialkyl formylphosphoramidites) (alkyl=C2H5; i-C3H7; i-C4H9) were synthesized by the reaction of formamide or N-ethylformamide with dialkyl phosphorochloridites. 2. The formation of unsubstituted dialkyl formylphosphoramidites in this reaction passes through the stage of the formation of a pyrophosphorous ester and its reaction with formamide. 3. In the reaction of diethyl phosphorochloridate with formamide or substituted formamide the latter is dehydrated, and as a result of subsequent reactions tetraethyl pyrophosphate is formed. Diisopropyl phosphorochloridite reacts with formanilide analogously, and the final reaction product is the pyrophosphorous ester. 4. The reactions of some dialkyl ethylformylphosphoramidites with sulfur, nitrogen dioxide, and chloral were investigated. As a result of these reactions, the following compounds were obtained: O,O-dialkyl ethylformylphosphoramidothioates (alkyl=i-C3H7; i-C3H9), diisobutyl ethylformylphosphoramidate, and alkyl 2, 2-dichlorovinyl ethylformylphosphoramidates (alkyl=C2H5; i-C3H7; C4H9).

Nitrogenous derivatives of cyclic fatty acids

AbstractA number of nitrogenous derivatives of cyclized acids derived from C‐18, triene‐containing fatty acid sources, were prepared. Mixed amides (mp 33C), nitriles (fp 蜢25C), and amines (fp 蜢34C), prepared from the hydrogenated cyclic acids, have uniquely low mp for fat‐derived substances of their mol wt. Compatibility with synthetic resins and solubility in organic solvents of the mixed amides are high compared to common fatty‐amide mixtures. The nitriles and morpholides are compatible with polyvinyl chloride and may have potential as plasticizers for it. The hydrogenated cyclic fatty acid amines have an approximate fp of 蜢34C. The diethanolamides, ethenoxylated amides, and quaternary amines were prepared and their surface‐active properties compared with similar fat‐derived substances.