Rates of N-methylation of azoles with methyl iodide and dimethyl sulphate

1973 ◽  
Vol 26 (9) ◽  
pp. 1949 ◽  
Author(s):  
LW Deady
Keyword(s):  
Methyl Iodide ◽  
Dimethyl Sulphate ◽  
Inductive Effect ◽  
Reaction Rates ◽  
Dimethyl Sulphoxide ◽  
The Other

The rates of quaternization of various azoles and their benzo derivatives with dimethyl sulphate, and with methyl iodide in dimethyl sulphoxide, are reported. Reaction rates are controlled mainly by the inductive effect of the other hetero atom and there is a good correlation between rate of quaternization and basicity of the azole.

Rates of N-methylation of N-methylpyrazole, isothiazole and isoxazole and their 2,1- and 1,2-benzologues

1974 ◽  
Vol 27 (6) ◽  
pp. 1221 ◽  
Author(s):  
M Davis ◽  
LW Deady ◽  
E Homfeld
Keyword(s):  
Methyl Iodide ◽  
Dimethyl Sulphate ◽  
Dimethyl Sulphoxide ◽  
New Compounds

The rates of quaternization of N-methylpyrazole, isothiazole and isoxazole and of their 2,l- and 1,2-benzologues with methyl iodide in dimethyl sulphoxide and with dimethyl sulphate are reported. All compounds quaternized at 33� and a number of new compounds were isolated. The order of reactivity in each series is NMe > S > O. Benzofusion was shown to be rate-diminishing with one exception. 2,l-Benzisoxazole reacted faster than did isoxazole and the reason for this behaviour is discussed.

Lithiation of bridgehead positions in 3,6-bridged piperazine-2,5-diones

1982 ◽  
Vol 35 (11) ◽  
pp. 2289 ◽  
Author(s):  
FW Eastwood ◽  
D Gunawardana ◽  
GT Wernert
Keyword(s):  
Carbonyl Group ◽  
Methyl Iodide ◽  
Methyl Ether ◽  
Sodium Methoxide ◽  
Inductive Effect ◽  
Amide Nitrogen

2,5-Dimethyl-2,5 diazabicyclo[2,2,2]octane-3,6-dione can be lithiated at the 1,4 (bridgehead) positions with 2 equiv. of t-butyllithium at -78� and deuterated with D2O (Do, 11.2; Dl, 56.1 ; D2, 30.1%). With butyllithium and methyl iodide the 1,2,5-trimethyl and 1,2,4,5-tetramethyl derivatives are obtained. Treatment of dimethyl 2,6-diaminoheptanedioate dihydrochloride with sodium methoxide in boiling butanol gives 6,8-diazabicyclo[3,2,2]nonane-7,9-dione in 62% yield. N-Methylation of this compound yields 6,8-dimethyl-6,8-diazabicyclo[3,2,2]nonane-7,9-dione which can similarly be lithiated at the 1,5 (bridgehead) positions and deuterated with D2O (Do, 5.6; Dl, 70.8; D2, 23.6%). Lithiation with butyllithium and reaction with methyl iodide, benzyl iodide or bromomethyl methyl ether gives mono-and di-alkylated products at the 1,5-positions. The ability to lithiate the bridgehead positions in these compounds is attributed primarily to a combination of the inductive effect of the carbonyl group and dipole stabilization by the amide nitrogen.

scholarly journals The preparation of some fused isothiazole derivatives

1985 ◽  
Vol 63 (4) ◽  
pp. 882-886 ◽  
Author(s):  
David M. McKinnon ◽  
K. Ann Duncan ◽  
Aileen M. McKinnon ◽  
Perry A. Spevack
Keyword(s):  
Methyl Iodide ◽  
The Other ◽  
Methylation Product

The treatment of di(2-amino-5-methylphenyl)methane with N-sulfinylmethanesulfonamide gives two materials, 3-(2-amino-5-methylphenyl)-5-methyl-2,1-benzisothiazole and what appears to be its tautomer, a 2,1-benzisothiazolo[2,3-b]-2,1-benzisothiazole derivative. Reaction of the former with methyl iodide gives mono-, di-, and trimethyl derivatives. The second of these also possesses the symmetrical 2,1-benzisothiazolo[2,3-b]-2,1-benztsothiazole structure. The structure of the other methylation product and of the acetylation products are discussed. Some 1,2-dithiol-3-ylidene-2-pyridylmethanes were made by condensation of 3-alkylthio-1,2-dithiolium salts with methyl 2-pyridylacetate. These demonstrate little sulphur–nitrogen interaction. 3-Methylthio-4-phenyl-1,2-dithiolium iodide reacts anomalously with methyl 2-pyridylacetate to form a quinolizinethione. 1,2-Benzisothiazolo[2,3-a]pyridintum triiodide was made by iodine oxidation of 2-(2-mercaptophenylpyridine).

Unsteady convective diffusion with interphase mass transfer

1973 ◽  
Vol 333 (1592) ◽  
pp. 115-132 ◽  
Keyword(s):  
Dispersion Model ◽  
Reaction Rates ◽  
The Other ◽  
Time Dependent ◽  
Transport Systems ◽  
Exchange Coefficient ◽  
Dispersion Coefficients ◽  
Interfacial Transport ◽  
Order Of Magnitude ◽  
Proper Values

The theory of miscible dispersion is extended to interphase transport systems. As a specific example miscible dispersion in laminar flow in a tube in the presence of interfacial transport due to an irreversible first-order reaction at the wall is analysed by an exact procedure. A new exact dispersion model which accounts for dispersion with interphase transport is derived from first principles. The new concept of an ‘exchange coefficient’ arises naturally. This coefficient depends strongly on the rate of interfacial transport. Such transport also affects the convection and dispersion coefficients significantly. A general expression is derived which shows clearly the time-dependent nature of the coefficients in the dispersion model. The complete time-dependent expression for the exchange coefficient is obtained explicitly and is independent of the velocity distribution in the flow; however, it does depend on the initial solute distribution. Because of the complexity of the problem only asymptotic large-time evaluations are made for the convection and dispersion coefficients, but these are sufficient to give useful physical insight into the nature of the problem. When the rate of the wall reaction approaches zero the exchange coefficient also approaches zero and the other two coefficients approach their proper values in the absence of interfacial transport. At the other extreme of rapid wall reaction rates, the convection coefficient is more than 50 % larger than its value in the absence of interfacial transport and the dispersion coefficient is an order of magnitude smaller than that for zero interphase transport.

scholarly journals Interaction of solvents with membranal and soluble potassium ion-dependent enzymes

1970 ◽  
Vol 116 (1) ◽  
pp. 49-54 ◽  
Author(s):  
M. Mayer ◽  
Y. Avi-Dor
Keyword(s):  
Enzyme Activity ◽  
Pyruvate Kinase ◽  
Solvent Effects ◽  
Adenosine Triphosphatase ◽  
The State ◽  
Dimethyl Sulphoxide ◽  
The Other ◽  
Enzyme Structure ◽  
Wide Range ◽  
Muscle Pyruvate Kinase

The effects of dimethyl sulphoxide and glycerol on ox brain microsomal Na++K+-stimulated adenosine triphosphatase (EC 3.6.1.3), K+-stimulated p-nitrophenyl phosphatase and K+-dependent muscle pyruvate kinase (EC 2.7.1.40) were studied. Dimethyl sulphoxide at concentrations below 20% (v/v) was found to stimulate the p-nitrophenyl phosphatase and pyruvate kinase by increasing their affinity for K+ but to inhibit the Na++K+-stimulated adenosine triphosphatase. The latter enzyme activity was also inhibited by glycerol, which like dimethyl sulphoxide, stimulated the K+-activated p-nitrophenyl phosphatase at a wide range of concentrations. The solvent effects were promptly reversed by dilution. Similarity was found between glycerol and dimethyl sulphoxide, on one hand, and ATP, on the other, in their stimulatory effect and their ability to increase the ouabain- and oligomycin-sensitivity of the K+-stimulated p-nitrophenyl phosphatase. However, only the solvents, not the ATP, increased the binding of K+ by the microsomes. From the above findings it is suggested that solvents may act on K+-dependent enzymes by altering the state of solvation of the activating cation as well as by changing the enzyme structure.

The mechanisms of α-H and proton transfers of glycine induced by Mg2+

2015 ◽  
Vol 14 (02) ◽  
pp. 1550008
Author(s):  
Qing Zhang ◽  
Xiang-Jun Meng
Keyword(s):  
Energy Barrier ◽  
Inductive Effect ◽  
Covalent Bond ◽  
Electron Cloud ◽  
Chemical Activity ◽  
The Other ◽  
Single Bond ◽  
Substitution Reactions ◽  
Neutral Complex ◽  
Proton Transfers

A MP2/6-31++G(d,p)//B3LYP/6-31++G(d,p) method was used to investigate the mechanisms of α- H and proton transfers of glycine induced by Mg 2+. Eight complexes were obtained, six of which were neutral and the other two were zwitterionic. Among them, the zwitterion with a binding energy of 159.4 kcal/mol was the most stable structure. Conformation transformations of the complexes caused by the rotation of single bond and the transfers of α- H and proton were completed via seven transition states. The inductive effect of Mg 2+ made the electron cloud of glycine deviate to Mg 2+, which activated the covalent bond involving the transferred proton. The neutral complex can be turned into the zwitterionic one by the transfers of both carboxyl hydrogen and α- H , and the energy barrier of each reaction was less than 9.2 kcal/mol. After the transfer of α- H , a delocalized π bond was formed in glycine skeleton and the α- C atom took 0.19 positive charges. So the chemical activity of the glycine enhanced, and glycine was readily available for addition and nucleophilic substitution reactions. The path from the most stable glycine conformer G1 to the zwitterionic conformation I is G1 → G1–G3 → G3 → G3–G4 → G4 → G2–G4 → G2 → VI → I–VI → I, and the highest energy barrier of this path is 9.2 kcal/mol.

Preservation of viable flexibacteria at low temperatures

1970 ◽  
Vol 16 (6) ◽  
pp. 441-444 ◽  
Author(s):  
Annika Sanfilippo ◽  
Ralph A. Lewin
Keyword(s):  
Liquid Nitrogen ◽  
Low Temperatures ◽  
Extreme Temperature ◽  
Dimethyl Sulphoxide ◽  
The Other

Most of the 28 species (91 strains) of flexibacteria tested without additives survived after freezing in liquid nitrogen (−196 °C): they included all six Microscilla spp., all three Cytophaga spp., both of the Herpetosiphon spp. tested, Flexithrix dorotheae, and seven (most strains) of the eight species of Flexibacter spp. All but 2 of the 19 strains of Saprospira grandis, but neither of the two other tested species of Saprospira, survived freezing to −196° without additives.Incorporation of 10% glycerol before freezing permitted survival of three of the sensitive strains of Flexibacter (F. aurantiacus copepodarum, F. flexilis iolanthae, and F. giganteus), but adversely affected two other species (F. elegans and F. ruber). Incorporation of 10% dimethyl sulphoxide (DMSO) had some similar effects. Freezing to −196° with glycerol conserved viable cultures of all 19 S. grandis strains, of S. toviformis, and of 2 of the 3 strains of S. thermalis.A less extreme temperature was less satisfactory. Stored at −22°, some or all strains of 6 species died out in less than 1 week; most strains of 12 others died after a few weeks; and 7 species survived for at least 21 weeks. (The other three were not tested.)

METHYLATION OF SUGAR DITHIOACETALS: V. D-MANNOSE DIETHYL DITHIOACETAL

1963 ◽  
Vol 41 (10) ◽  
pp. 2500-2503 ◽  
Author(s):  
G. G. S. Dutton ◽  
Y. Tanaka
Keyword(s):  
Methyl Iodide ◽  
Silver Oxide ◽  
The Other ◽  
Partial Methylation

Partial methylation of D-mannose diethyl dithioacetal in tetrahydrofuran with methyl iodide and silver oxide yielded 2-, 3-, and 6-O-methyl-D-mannose in the ratio of 12:1:1, respectively. The major component, 2-O-methyl-D-mannose, was characterized as the phenyl-hydrazone and the other isomers identified by electrophoresis. The Mg values of these mono-O-methyl ethers were recorded.

The Mills-Nixon effect. IV. Base-catalysed cleavage of Trimethylsilyl-veratrol, -1,3-benzodioxole and -1,4-benzodioxan derivatives

1974 ◽  
Vol 27 (4) ◽  
pp. 895 ◽  
Author(s):  
LJ Brocklehurst ◽  
KE Richards ◽  
GJ Wright
Keyword(s):  
Sodium Hydroxide ◽  
Dimethyl Sulphoxide ◽  
The Other ◽  
Ring Junction

The rates of cleavage for 4-trimethylsilyl-veratrol, 5-trimethylsilyl-1,3-benzodioxole and 6-trimethyl- silyl-1,4-benzodioxan have been measured at 30�C in 1 : 9 water-dimethyl sulphoxide containing sodium hydroxide. The benzodioxole derivative is more reactive than the other two substrates; this enhanced reactivity arises from hybridization changes enforced on the ring junction carbons by the strained dioxole ring.

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