In vitro antimicrobial-activity studies on the mixed ligand complexes of Hg(II) with 8-hydroxyquinoline and salicylic acids

A series of mixed ligand complexes of Hg(II) with the general formula Hg (OX) (SA) (where OX: 8-hydroxyquinoline, SA: salicylic, 5-chloro-, 3,5-dibromo, 3,5-diiodo, 3,5-dinitro, acetyl thiosalicylic acids) are isolated in pure state and characterised by elemental analysis and infrared data. The low molar conductance of the complexes in dimethylformamide indicates non-electrolyte nature. The antimicrobial activity of these complexes against various bacteria and fungi is studied which indicates that in several cases, the mixed ligand complexes possess fairly highly antimicrobial activity than the binary mercury-oxinate. The lipophilic tendency of these complexes and its influence on the antimicrobial activity is critically examined. A probable mechanism for the toxic action of these complexes against various organisms is discussed.     

Copper catalyzed access to functionalized oxazoles from oximes via carbenoids

An operationally simple, economical and straightforward synthesis of diverse oxazoles from oximes possessing a vicinal carbonyl group has been achieved by treatment of the latter with terminal diazo compounds like ethyl/benzyl diazoacetate and diazoacetophenone (which act as carbenoids) in one pot. At least two reducible functional groups (two ester groups or cyano?+?ester) are simultaneously introduced in one step. This reaction involves expulsion of a molecule each of N₂ and water only as byproducts under copper catalysis. The structure of one of these oxazoles is confirmed by X-ray crystallography. Both the ester groups in the oxazole product could be reduced to alcohol moieties by using NaBH₄/EtOH.     

The onset of convection in a viscoelastic liquid saturated anisotropic porous layer

The linear stability of a viscoelastic liquid saturated horizontal anisotropic porous layer heated from below and cooled from above is investigated by considering the Oldroyd type liquid. A generalized Darcy model, which takes into account the viscoelastic properties, the mechanical and thermal anisotropy is employed as momentum equation. The critical Rayleigh number, wavenumber, for stationary and oscillatory states and frequency of oscillation are determined analytically. It is shown that oscillatory instabilities can set in before stationary modes are exhibited. The effect of the viscoelastic parameter, the mechanical and thermal anisotropy parameters and specific heat ratio on the linear stability of the system is analyzed and presented graphically.     

Oxidative bromination of ketones using ammonium bromide and oxone®

A highly efficient, environmentally safe and economic method for selective α-monobromination of aralkyl, cyclic, acyclic, 1,3-diketones and β-keto esters and α,α-dibromination of 1,3-diketones and β-keto esters without catalyst is reported using ammonium bromide as a bromine source and oxone® as an oxidant. The reaction proceeds at ambient temperature and yields range from moderate to excellent. Bromination of unsymmetrical ketones takes place at the less substituted α-position predominantly. Aromatisation of tetralones is also carried out with this reagent system.     

Intermediate statistics as a consequence of deformed algebra

We present a formulation of deformed oscillator algebra which leads to intermediate statistics as a continuous interpolation between Bose-Einstein and Fermi-Dirac statistics. It is deduced that a generalized permutation or exchange symmetry leads to the introduction of the basic number and it is then established that this in turn leads to the deformed algebra of oscillators. We obtain the mean occupation number describing the particles obeying intermediate statistics which thus establishes the interpolating statistics and describe boson-like and fermion-like particles obeying intermediate statistics. We also obtain an expression for the mean occupation number in terms of an infinite continued fraction, thus clarifying successive approximations.     

Enantiomeric Separation of Moxifloxacin and Its (R,R)-Isomer by Ligand-Exchange Chiral Chromatography

A new stereospecific LC method for the separation and quantification of moxifloxacin and its (R,R)-enantiomer in bulk drug was developed and validated by ligand-exchange liquid chromatography on a reversed phase column using aqueous mobile phase containing the chiral reagent l-isoleucine-Cu(II). The UV detector was operated at 293 nm. The flow rate of mobile phase was set at 0.9 mL min^?1. The achiral ODS column offers good separation of the two enantiomers in less than 20 min. The test concentration was 1,000 μg mL^?1 in the mobile phase. This method was capable of detecting the (R,R)-enantiomer of moxifloxacin up to 0.1 μg mL^?1 for a 20 μL injection volume. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. There was no interference of degradants with the (R,R)-enantiomer in the developed method. The developed chiral RP-LC method was validated with respect to linearity, accuracy, precision and robustness. The percentage recovery for the (R,R)-enantiomer in bulk drug samples ranged from 98.1 to 104.4%. The test solution was found to be stable in the mobile phase for 48 h after preparation.     

Palladium-catalyzed coupling of allenylphosphonates, phenylallenes, and allenyl esters: remarkable salt effect and routes to novel benzofurans and isocoumarins

Coupling reactions of allenylphosphonates (OCH(2)CMe(2)CH(2)O)P(O)CH=C=CRR' [R, R' = H (1a), R = H, R' = Me (1b), R = R' = Me (1c)] with aryl iodides, iodophenol, and iodobenzoic acid in the presence of palladium(II) acetate are investigated and compared with those of phenylallenes PhCH=C=CR2 [R = H (2a), Me (2b)] and allenyl esters EtO(2)CCH=C=CR(2) [R = H (2c), Me (2d)]. While 1b and 1c couple with different stereochemical outcomes using PhI in the presence of Pd(OAc)(2)/PPh(3)/K(2)CO(3) to give phenyl-substituted 1,3-butadienes, 1a does not undergo coupling but isomerizes to the acetylene (OCH(2)CMe(2)CH(2)O)P(O)CCMe (7). In the reaction of 1c with PhI, use of K(2)CO(3) affords the butadiene (Z)-(OCH(2)CMe(2)CH(2)O)P(O)CH=C(Ph)-C(Me)=CH(2) (12); in contrast, the use of Ag(2)CO(3) leads to the allene (OCH(2)CMe(2)CH(2)O)P(O)C(Ph)=C=CMe(2) (20), showing that these bases differ very significantly in their roles. The reaction of 1a with PhI or PhB(OH)2 in (t)he presence of Pd(OAc)2/CsF/DMF leads mainly to (E)-(OCH(2)CMe(2)CH(2)O)P(O)CH=C(Me)Ph (21) and (OCH(2)CMe(2)CH(2)O)P(O)CH2-C(Ph)=CH(2) (22) and is thus a net 1,2-addition of Ph-H. Compound 1b reacts with iodophenol in the presence of Pd(OAc)(2)/PPh(3)/K(2)CO(3) to give a benzofuran that has a structure different from that obtained by using 1c under similar conditions. Treatment of 1a with iodophenol/Pd(OAc)(2)/CsF/DMF also gives a benzofuran whose structure is different from that obtained by using 2a under similar conditions. In the reaction with 2-iodobenzoic acid, 1a and 2c afford one type of isocoumarin, while 1b,c and 2a,b give a second type of isocoumarin. The structures of key compounds are established by X-ray crystallography. Utility of the phosphonate products in the Horner-Wadsworth-Emmons reaction is demonstrated.     

Further characterization of Mitsunobu-type intermediates in the reaction of dialkyl azodicarboxylates with P(III) compounds

Structural characterization of compounds analogous to the proposed intermediates in the Mitsunobu esterification process is achieved by the combined use of NMR spectroscopy and X-ray diffractometric studies. The results show that compounds (t-BuNH)P(mu-N-t-Bu)(2)P[(N-t-Bu)(N-(CO(2)R)-N(H)(CO(2)R))] [R = Et (11), i-Pr (12)], obtained by treating [(t-Bu-NH)P-mu-N-t-Bu](2) (10) with diethylazodicarboxylate (DEAD) or diisopropylazodicarboxylate (DIAD), respectively, have a structure with the NH proton residing between the two nitrogen atoms ((P)N(t-Bu) and (P)N-N(CO(2)Et)); this is the tautomeric form of the expected betaine (t-BuNH)P(mu-N-t-Bu)(2)P(+)[(NH-t-Bu)(N-(CO(2)R)-N(-)(CO(2)R)]. Treatment of ClP(mu-N-t-Bu)(2)P[(N-t-Bu){N-(CO(2)-i-Pr)-N(H)(CO(2)-i-Pr)] (6) with 2,6-dicholorophenol affords (2,6-Cl(2)-C(6)H(3)-O)P(mu-N-t-Bu)(2)P(+)[(NH-t-Bu){N[(CO(2)i-Pr)(HNCO(2)i-Pr)]}](Cl(-))(2,6-Cl(2)-C(6)H(3)-OH) (14) that has a structure similar to that of (CF(3)CH(2)O)P(mu-N-t-Bu)(2)P(+)[(NH-t-Bu){N[(CO(2)i-Pr)(HNCO(2)i-Pr)]}](Cl(-)) (13), but with an additional hydrogen bonded phenol. Both of these have the protonated betaine structure analogous to that of Ph(3)P(+)N(CO(2)R)NH(CO(2)R)(R'CO(2))(-) (2) proposed in the Mitsunobu esterification. Two other compounds, (ArO)P(mu-N-t-Bu)(2)P(+)(NH-t-Bu){N(CO(2)i-Pr)(HNCO(2)i-Pr)}(Cl(-)) [Ar = 2,6-Me(2)C(6)H(3)O- (15) and 2-Me-6-t-Bu-C(6)H(3)-O- (16)], are also prepared by the same route. Although NMR tube reactions of 11 or 12 with tetrachlorocatechol, catechol, 2,2'-biphenol, and phenol revealed significant changes in the (31)P NMR spectra, attempted isolation of these products was not successful. On the basis of (31)P NMR spectra, the phosphonium salt structure (t-BuNH)P(mu-N-t-Bu)(2)P(+)[(HN-t-Bu){N-(CO(2)R)-N(H)(CO(2)R)](ArO(-)) is proposed for these. The weakly acidic propan-2-ol or water did not react with 11 or 12. Treatment of 12 with carboxylic acids/ p-toluenesulfonic acid gave the products (t-BuNH)P(mu-N-t-Bu)(2)P(+)[(HN-t-Bu){N-(CO(2)-i-Pr)-N(H)(CO(2)-i-Pr)](ArCO(2)(-)) [Ar = Ph (18), 4-Cl-C(6)H(4)CH(2) (19), 4-Br-C(6)H(4) (20), 4-NO(2)-C(6)H(4) (21)] and (t-BuNH)P(mu-N-t-Bu)(2)P(+)[(HN-t-Bu){N-(CO(2)-i-Pr)-N(H)(CO(2)-i-Pr)](4-CH(3)-C(6)H(4)SO(3)(-)) (22) that have essentially the same structure as 2. Compound 18 has additional stabilization by hydrogen bonding, as revealed by X-ray structure determination. Finally it is shown that the in situ generated (t-BuNH)P(mu-N-t-Bu)(2)P(+)[(HN-t-Bu){N-(CO(2)Et)-N(H)(CO(2)Et)](4-NO(2)-C(6)H(4)CO(2)(-)) can also effect Mitsunobu esterification. A comparison of the Ph(3)P-DIAD system with the analogous synthetically useful Ph(3)P-dimethyl acetylenedicarboxylate (DMAD) system is made.     

Synthesis and spectral investigations of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of new polydentate ligands containing a 1,8-naphthyridine moiety

2-(o-Hydroxyphenyl)-1,8-naphthyridine (HN), 2-(4-hydroxy-6-methylpyran-2-one-3-yl)-1,8-naphthyridine (HMPN) and 2-(benzimidazol-2-yl)-1,8-naphthyridine(BN) react with acetates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) to yield metal ion complexes of definite composition. These compounds were characterized by elemental analyses, molar conductivity, magnetic susceptibility measurements, thermal studies, IR, UV-visible, NMR and mass spectral investigations. The complexes are found to have the formulae [M(HN)2(H2O)2], [M(HMPN)2(H2O)2] and [M(BN)2(OAc)2], respectively.