摘要:

The synthesis of a series ofC-aryl-N-[2-(hydroxymethyl)phenyl]nitrones,5(that can also exist under certain conditions as isomeric 1-hydroxy-2-aryl-1,2-dihydro-4H-3,1-benzoxazines,8), via 2-(hydroxyamino)benzyl alcohol,4, and their subsequent reactions with oxybis(diphenylborane), (Ph2B)2O, leading to the 5-(arylmethylene)-7,7-diphenyl-6,8-dioxa- 5-azonia-7-borata-5H-6,7,8,9-tetrahydrobenzocyclo-heptenes6are described. Crystals of 1-hydroxy-2- (4-methoxyphenyl)- 1,2-dihydro-4H-3,1-benzoxazine,8b, are monoclinic,a= 9.379(2),b= 10.699(2),c= 12.9392(7) Å, &bgr; = 99.916(2)°,Z= 4 (two independent molecules), space groupPa; those ofC-[4-(dimethylamino)phenyl]-N-[(2-hydroxymethyl)phenyl]nitrone,5c,are monoclinic,a= 7.687(1),b= 7.891(1),c= 11.5053(9) Å, &bgr; = 92.781(9)°,Z= 2, space groupP21; and those of 5-[4-(dimethylamino)phenylmethylene]-7,7-diphenyl-6,8-dioxa-5-azonia-7-borata-5H-6,7,8,9-tetrahydro-benzocycloheptene,6a, are monoclinic,a= 10.771(1),b= 13.1057(9),c= 16.8724(7) Å, &bgr; = 90.005(5)°,Z= 4, space groupP21/n. The structures were solved by direct methods and refined by full-matrix least-squares procedures toR(F2) = 0.120 (Rw(F2) = 0.135) for all 3149 reflections (R(F) = 0.071,Rw(F) = 0.063 for 1500 reflections withI>3 &sgr; (I)) for8bandR(F) = 0.035 and 0.036 (Rw(F) = 0.031 and 0.038) for 1071 and 3594 reflections withI>3 &sgr; (I), respectively, for5cand6a. Compound8bis the first structurally characterized 1-hydroxy-1,2-dihydro-4H-3,1-benzoxazine derivative and6afeatures a relatively rare seven-membered boron-containing heterocycle.Key words:C-aryl-N-[2-(hydroxymethyl)phenyl]nitrones, 1-hydroxy-2-aryl-1,2-dihydro-4H-3,1-benzoxazines, organoboron compounds, crystal structures

ISSN:0008-4042    

DOI:10.1139/v98-023

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Group 13 metal atoms were reacted with aromatic alkenes in a specialized metal atom reactor known as a "rotating cryostat." The nature of the intermediates formed was deduced from a GC-MS study of their hydrolysis and deuterolysis products. The product studies suggest that 2-phenylaluminacyclopropane,cis- andtrans-3,4-diphenylaluminacyclopentane, andcis- andtrans- 2,4-diphenylaluminacyclopentane are formed when Al atoms react with styrene, and 2-methyl-2-phenylaluminacyclopropane and 3,4-dimethyl-3,4-diphenylaluminacyclopentane are formed when Al atoms react with &agr; -methylstyrene. These findings are consistent with the radicals detected in the EPR spectroscopic studies of Al-alkene reaction mixtures prepared under similar conditions. Mechanisms for the formation of the organoaluminium intermediates are discussed. Analogous organogallium intermediates are formed when gallium atoms react with styrene. The reductive coupling of styrene did not occur when In and Tl atoms were used. Only trace quantities of phenylethane were detected in the hydrolyzed reaction mixture.Key words: Group 13 metal atoms, aluminium atoms, organoaluminium intermediates, metal atom reactions.

ISSN:0008-4042    

DOI:10.1139/v98-033

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A number of polydentate arylamide ligands have been prepared by coupling various acyclic tripodal or linear polyamines with derivatives of nicotinic and picolinic acids. Two synthetic procedures were utilized; tris{[(2-hydroxynicotinyl)carbonyl]-2-aminoethyl}amine (H3NICTREN) was prepared by Method A, the HOSu/DCC method, and the other arylamides in this study were prepared by Method B, the CDI method. Method A involved the reaction ofN-hydroxysuccinimide with 2-hydroxynicotinic acid (in the presence of dicyclohexylcarbodiimide (DCC) as a dehydrative coupling reagent) to form the succinimide ester, followed by reaction with TREN to yield H3NICTREN. Method B involved reaction of a carboxylic acid (2-hydroxynicotinic, 3-hydroxypicolinic, nicotinic, or picolinic acids) with carbonyldiimidazole (CDI) to form theN-acylimidazolide, followed by reaction with the amine (TREN, TAME, spermidine, or TRPN) to yield the desired arylamide. The X-ray structure of 1,1,1-tris{[(3-hydroxypicolinyl)carbonyl]-2-aminomethyl}ethane (H3PICTAME) was determined; crystals of H3PICTAME are monoclinic,a= 10.257(2),b= 15.572(3),c= 15.208(2) Å, &bgr; = 96.124(15)°,Z= 4, space groupP21/a. The structure was solved by direct methods and refined by full-matrix least-squares procedures toR= 0.041 andRw= 0.038 for 2506 reflections withI>= 3 sigma (I). In the solid state, H3PICTAME contains an extensive hydrogen-bonding network, with eight intra- and one intermolecular H-bonds per molecule; the ligand is partially preorganized for metal ion chelation. The acid dissociation constants of H3NICTREN and those of 1,1,1-tris{[(2-hydroxynicotinyl)carbonyl]-2-aminomethyl}ethane (H3NICTAME) have been determined; pKa1= 11.2 (10.68), pKa2= 10.7 (10.58), pKa3= 10.0 (9.71), and pKa4= 6.25 for H3NICTREN (H3NICTAME); the high phenolic pKa'sare consistent with the hydrogen bonding observed in the solid state.Key words: arylamide, hydrogen bonding, preorganization.

ISSN:0008-4042    

DOI:10.1139/v98-030

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The X-ray crystal structure of a derivative of the nonsteroidal anti-inflammatory drug, azapropazone, has been determined using a data set obtained from a charge-coupled device (CCD) area detector. Azapropazone itself, 5-(dimethylamino)-9-methyl-2-propyl-1H-pyrazolo[1,2-a][1,2,4]benzotriazine-1,3(2H)-dione, has previously been shown to be nonplanar, probably due to steric interactions between the pyrazolidine ring and the exocyclic dimethylamino group. The derivative studied in this work, 3-dimethylamino-7-methyl-1,2,4-benzotriazine, does not have the pyrazolidine ring and is shown here to be strictly planar. There is also a significant difference in the kinetics of restricted rotation around the bond joining the dimethylamino group to the triazine ring, as measured by NMR. Both the enthalpy and entropy of activation are quite different. For the chemical exchange of the two methyl groups in azapropazone, &Dgr;Hdouble dagger= 36 ± 0.5 kJ mol-1, and &Dgr;Sdouble dagger= -34 ± 2 J K-1. For the derivative, &Dgr;Hdouble dagger= 48 ± 0.4 kJ mol-1, and &Dgr;Sdouble dagger= -12 ± 2 J K-1. This is rationalized by assuming the equilibrium state of the derivative is planar, and this defines the potential energy curve. The ground state of azapropazone is relatively destabilized, and somewhat disordered, by the steric interaction. Therefore, azapropazone has a small barrier to surmount, and the entropy of activation should be negative.Key words: NMR, chemical exchange, entropy, barriers to rotation, crystal structure.

ISSN:0008-4042    

DOI:10.1139/v98-031

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The solvation of argon in 10 different solvents at room temperature is analysed in terms of the theoretical framework developed by Lee. In order to perform calculations, we used the approach devised by Pierotti and firmly validated by Lee's theory. The fair agreement between the experimental and the calculated values of &Dgr;G.&Dgr;H., and &Dgr;S.is carefully analysed. It proves that the excluded volume effect, due to cavity creation in the solvent, opposes the solubility process. This effect in water is exaggerated by the small size of the water molecules and is the cause of hydrophobicity. The qualitative difference between water and hydrazine with regard to the solvation enthalpy and entropy changes is rationalized on the basis of the contributions arising from the structural reorganization in the two solvents on solute insertion.Key words: hydrophobic hydration, cavity creation, structural solvent reorganization.

ISSN:0008-4042    

DOI:10.1139/v98-040

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The syntheses of two terdentate chelating agents, pyridine-2-phosphonic-6-carboxylic acid (2PP6C) and 2,6-pyridinediphosphonic acid (2,6PDPA), are described. The stepwise stability constants for the ferric complexes at 25.0°C and &mgr; = 0.100 M (KNO3) are logKML= 15.97 and logKML2= 9.50 for 2PP6C, and logKML= 20.87 and logKML2= 7.81 for 2,6PDPA. Under the same conditions the stepwise formation constants for the ferrous chelates are logKML= 8.70 and logKML2= 5.10 for 2PP6C, and logKML= 10.12 and logKML2= 5.33 for 2,6PDPA. The stabilities of the Fe(III) and Fe(II) chelates are high enough to prevent precipitation of Fe(OH)3and FeS, respectively, from solutions having pH as high as 10.0. The rates of oxidative degradation of these ligands are very slow when the iron chelates are used as redox catalysts for the oxidation of H2S to S8by air. The rates of oxidative degradation are immeasurably slow when the iron chelates are used with sodium thiosulfate as a radical scavenger.Key words: 2,6-pyridinediphosphonic acid, pyridine-2-phosphonic-6-carboxylic acid, hydrogen sulfide oxidation, oxidative degradation, nitrilotriacetic acid.

ISSN:0008-4042    

DOI:10.1139/v98-037

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Ultrasonic velocities and densities of binary aqueous solutions of isomeric butanediols were measured in the temperature range 298-318 K at 10 degree intervals over the entire composition range, and 5 degree intervals in the water-rich region. The experimental data in the dilute region, with mole fraction of water less than 0.1, was analysed to determine the partial molar volumes and adiabatic compressibilities of water at infinite dilution. The standard thermodynamic transfer functions were calculated to evaluate the environment of water at infinite dilution in these systems. From the compressibility isotherms, as a function of temperature in the water-rich region, the formation and the composition of clathrate-like structures in the liquid solutions was determined, and the nature of these structures was discussed.Key words: ultrasonic velocity, adiabatic compressibility, density, partial molar quantities, standard thermodynamic transfer functions.

ISSN:0008-4042    

DOI:10.1139/v98-032

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

3-Cyano-4-(p-tolyl)pyrido[3,2-c]cinnolin-2(1H) thione3was reacted with &agr; -halo ketones, esters, or amides to give the intermediates, S-alkylated products5b-h, respectively, which underwent intramolecular ring closure reactions with ethanolic sodium ethoxide to give thienopyridocinnolines6a-h. Pyrimidothienopyridocinnolines9and11were obtained by treatment of oxazino compound8with hydrazine hydrate and ammonium acetate. Treatment of hydrazino derivative13with acetylacetone, triethylorthoformate, carbon disulphide, ethyl chloroformate, and acetic anhydride afforded triazolopyrimidothienopyridocinnolines14-16, 18,and21,while with nitrous acid the corresponding tetrazolo compound19was produced.Key words: thienopyridocinnolines; their pyrimido, triazolopyrimido, and heteroannelated systems.

ISSN:0008-4042    

DOI:10.1139/v98-048

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Ab initio GVB(6/12)/6-31G** calculations were performed on A2X==YB2(A, B = H, F; X, Y = C, Si) to obtain the optimized geometries for planar and twisted singlet structures, and to also calculate pi bond energies (rotational barriers). The nature of C-C, Si-Si, and C-Si pi bonds has been investigated. The results show that the C-C pi bond energy (Epi(ethene) = 65.4 kcal/mol) decreases with increasing fluorine substitution. The pyramidalization at the carbon or silicon center for the twisted structures decreases the pi bond energies in the substituted ethenes and their silicon counterparts. The Si-Si (Epi(disilene) = 23.2 kcal/mol) and C-Si (Epi(silaethene) = 31.6 kcal/mol) pi bonds become much weaker. Fluorine substitution stabilizes both the diradical and the dipolar twisted singlet structures.Key words: pi bond energy, ab initio calculations, generalized valence bond, fluorine substitution, disilene, and silaethene.

ISSN:0008-4042    

DOI:10.1139/v98-041

出版商:NRC Research Press    

年代:1998

数据来源: NRC