The effect of intramolecular‐hydrogen bonds in the synthesis of novel imidates from a 13‐membered dioxadithia crown ether diester

The synthesis and structural properties of three novel imidates, 11,13‐bis‐(2‐amino‐ethylimino)‐1,10‐dioxa‐4,7‐dithiacyclotridecane ( 2 ), 11,13‐bis‐(3‐aminopropylimino)‐1,10‐dioxa‐4,7‐dithiacyclotridecane, ( 3 ) and 2,11‐dioxa‐5,8‐dithia‐13,16,19,22‐tetraazabicyclo[10.10.1]tricosa‐1(22),12‐diene, ( 4 ) have been described. These compounds were synthesized by treating 1,10‐dioxa‐4,7‐dithiacyclotridecane‐11,13‐diester ( 1 ) with the appropriate diamine under N₂ and their structures have been characterised by elemental analyses, ¹H‐ and ¹³C‐nmr, ir, and mass spectral studies. Elemental analyses and spectroscopic data support the proposed imidate structures. In addition, total energy and heat of formation (Figure 2) calculated for imidates 2a‐4a and 2b‐4b by the semiempirical AM1 calculations have shown that imidates 2b‐4b having intramolecular hydrogen bonds are more stable (5‐10 kcal/mol) than compounds 2a‐4a .     

Über Halogenphenylester der Phosphorsäure

A simple method for preparing halogenphenylesters of phosphoric, phenylphosphonic and phosphorous acid from the respective acid chlorides and phenols in the presence of various nitrogen-containing catalysts is described. Contrary to other methods, these reactions give high yields, despite of steric hindrance.     

Applications involving oxidation with KBrO3: III. Rapid potentiometric methods for vanadium alone or in mixtures

A rapid and reliable method is given for the determination of vanadium based on oxidation of the V(IV) with a known excess of bromate to V(V). The unreacted oxidant as well as V(V) are subsequently reduced with sulfurous acid to V(IV). The resulting Br^?1 was potentiometrically titrated with Hg(I) using silver amalgam as the indicator electrode. The method finds application to the analysis of some binary and ternary mixtures.     

Dineodymium tritelluride,Nd2Te3

From a single‐crystal study, Nd₂Te₃ is found to be isostructural with Gd₂Te₃, crystallizing in the U₂S₃ structure type. Each of the two non‐equivalent Nd atoms is surrounded by seven Te atoms, with the polyhedra best described as a seven‐octahedron and a monocapped trigonal prism. All atoms lie on mirror planes.     

Enantioselective addition of aldehydes to amines via combined catalytic biomimetic oxidation and organocatalytic C-C bond formation

The biomimetic catalytic enantioselective addition of aldehydes to amines is reported. This was accomplished by combining biomimetic coupled catalytic aerobic oxidation of amines involving ruthenium-induced dehydrogenation and organocatalytic asymmetric Mannich reactions. The novel one-pot reactions furnished β-amino aldehyde and α-amino acid derivatives in high yields with excellent chemoselectivity and up to >99% ee.     

The preparation of perfluorinated esters of fluorine containing tertiary alcohols

The reaction of an aromatic lithium reagent, LiR, with a perfluoroacid anhydride (RfCO)₂O, in ether solution at low temperatures, produces esters of composition

in addition to the expected ketone

. Mixed esters of composition

may be prepared by starting with a ketone

and reacting with a lithium reagent LiR followed by perfluoroacid anhyride (RfCO₂O. Hydrolysis of the esters provide a convenient route to trertiary alcohols of composition Rf(R) ₂COH.     

Studies in azide chemistry. Part 13 [1]. Intermolecular insertion of azide-derived polyfluorinated aryl- and heteroaryl-nitrenes into ring CH bonds of 1,3, 5-trimethyl- and 1,3,5-trimethoxy-benzene

Thermolysis of perfluoroazidobenzene, perfluoro-4- azidotoluene, perfluoro-4-azidopyridine, 4-azido-3- chlorotrifluoropyridine, and 4-azido-3, 5-dichlorodifluoropyridine (Ar_FN₃) in the presence of a large excess ($\text{ca}$. 10 molar) of 1,3,5-trimethyl- or 1,3,5-trimethoxy-benzene (ArH) gave the diarylamines expected from nitrene ‘insertions’ at nuclear CH bonds (Ar_FN₃ + ArH→Ar_FNHAr + N₂); product yields in the cases of the perfluorinated azides are the highest ever recorded for this type of reaction. By contrast, no recognisable products were obtained when either perfluoro-(2-azido-4-isopropylpyridine) or 2-azido- 4-chlorotrifluoropyridine were decomposed thermally in 1,3,5-trimethylbenzene.     

Effects of

Effects of cetyltrimethylammonium bromide (CTABr) micelles on second-order rate constants (k(n)(obs)) for nucleophilic reactions of amines (piperidine and n-butylamine) with ionized phenyl salicylate (PS(-)) reveal a nonlinear decrease with the increase in [D(n)] (where [D(n)] = [CTABr](T) - cmc) at a constant [NaBr] and 35 degrees C. The observed data, at a constant [NaBr], fit reasonably well to a pseudophase model of micelles, and such a data fit gives kinetic parameters such as CTABr micellar binding canstant (K(S)) of PS(-). The effect of [NaBr] upon K(S) is explained with the empirical relationship K(S) = K(S)(0)/(1 + psi[NaBr]), where psi is an empirical parameter.     

Studies in azide chemistry. Part 12. One-pot conversion of 4-azidotetrafluoropyridine to 1,3,4-trifluoro-7,9-dimethyl-11H-pyrido[4,3-c]benzo[1,2]diazepine

Thermolysis of 4-azidotetrafluoropyridine in the presence of an excess of mesidine at 170 °C yields tetrafluoro-4-(2,4,6-trimethylphenylazo)- pyridine, which undergoes intramolecular dehydrofluorination $\text{in situ}$ to provide 1,3,4-trifluoro-7,9-dimethyl-11$\text{H}$-pyrido[4,3-$\text{c}$]benzo[1,2]diazepine.     

Glycosidases of turnip leaf tissues

Four myrosinase (β-thioglucosidase EC. 3.2.3.1) and seven disaccharase (β-fructofuranosidase, EC. 3.2.1.26) isoenzymes were isolated from turnip leaves. The most active enzymes were isolated in pure form. Myrosinase and disaccharase mol wt was 62.0 × 10³ and 69.5 × 10³ dalton, respectively, on the basis of gel filtration on Sephadex G-200. Myrosinase pH profile showed high activity between pH 5 and 7 with the optimum at pH 5.5. The purified enzyme was heat-stable for 60 min at 30°C with only loss of 24% of activity. Its activity is strongly inhibited (100%) by Pb²⁺, Ba²⁺, Cu²⁺ and Ca²⁺ ions, and activated (70%) by EDTA at 0.04M. The pure enzyme failed to hydrolyze amylose, glycogen, lactose, maltose, and sucrose. TheK _m andV _max values of myrosinase using sinigrin as specific substrate was 0.045 mM and 2.5 U, respectively. The maximal activity of disaccharase enzyme was obtained at pH 4–5 and 35–37°C. The enzyme was heat-stable at 30°C for 30 min with only 10% loss of its activity. Its activity is strongly activated (70–240%) by Ca²⁺, Ba²⁺, Cu²⁺, and EDTA at 0.01M. The enzyme activity is specific to the disaccharide sucrose and failed to hydrolyze other disaccharides (maltose and lactose). TheK _m andV _max of disaccharase were 0.123 mM and 3.33 U, respectively.