Structure and Spectroscopic Insights for CH3PCO Isomers: A High-Level Quantum Chemical Study.

The exploration of phosphorus-bearing species stands as a prolific field in current astrochemical research, particularly within the context of prebiotic chemistry. Herein, we have employed high-level quantum chemistry methodologies to predict the structure and spectroscopic properties of isomers composed of a methyl group and three P, C, and O atoms. We have computed relative and dissociation energies, as well as rotational, rovibrational, and torsional parameters using the B2PLYPD3 functional and the explicitly correlated coupled cluster CCSD(T)-F12b method. Based upon our study, all the isomers exhibit a bent heavy atom skeleton with CH3PCO being the most stable structure, regardless of the level theory employed. Following in energy, we found four high-energy isomers, namely, CH3OCP, CH3CPO, CH3COP, and CH3OPC. The computed adiabatic dissociation energies support the stability of all [CH3, P, C, O] isomers against fragmentation into CH3 and [P, C, O]. Torsional barrier heights associated with the methyl internal rotation for each structure have been computed to evaluate the occurrence of possible A-E splittings in the rotational spectra. For the most stable isomer, CH3PCO, we found a V3 barrier of 82 cm-1, which is slightly larger than that obtained experimentally for the N-counterpart, CH3NCO, yet still very low. Therefore, the analysis of its rotational spectrum can be anticipated as a challenging task owing to the effect of the CH3 internal rotation. The complete set of spectroscopic constants and transition frequencies reported here for the most stable isomer, CH3PCO, is intended to facilitate eventual laboratory searches.

Economic Cost of the Waste of Anti-inflammatory and Analgesic Drugs in Mexico City.

Anti-inflammatory and analgesic medications (AAMs) are widely used in Mexico and the rest of the world. Their excessive acquisition can lead to waste, representing an unnecessary expense for families and the public health system. The aim of this study was to estimate the economic cost of the waste of unused AAMs collected by the National System for the Collection of Residues of Containers and Medications (SINGREM, the acronym in Spanish) in Mexico City during 2019. Data from SINGREM on discarded AAMs in Mexico City were classified by the type and quantity of drug, pharmaceutical dosage form, origin, dose, and the complete or incomplete condition of the package. The unitary cost for each medication was based on public tenders of the Mexican Social Security Institute (IMSS) for the public sector and the prices in large drug store franchises for the private sector. A decision-making model was constructed to appraise the total cost of discarded AAMs. The economic cost of the 48924 units of discarded AAMs in SINGREM containers in Mexico City during 2019 was approx. USD$143500, of which over USD$127000 corresponded to the private health sector. The current findings evidence an enormous accumulation of unneeded or expired AAMs in Mexico City. According to the present data, the cost of such waste is substantial. The estimated cost was 8-fold higher for discarded medications originating from the private versus the public healthcare sector. It is important to implement measures to prevent this waste and increase awareness of the consequences of inadequate drug disposal.

Construcción de una escala de autoeficacia para comunicación oral y escrita dentro de entornos laborales en futuros egresados / Construction of a self-efficacy scale for oral and written communication in work environments in future graduates

Resumen El mercado laboral requiere de futuros trabajadores con buen desarrollo de competencias transversales como la Comunicación Oral y Escrita para el trabajo. Relacionado con esto, la categoría de auto-eficacia es relevante, pues constituye un factor decisivo para que un individuo logre sus metas, siendo entonces necesario evaluarla para dicha competencia en futuros egresados. Con este fin se diseñó, validó y evaluó la confiabilidad de una escala (n=443). Para la de validez de contenido se utilizó el método CVI y para la consistencia interna el método de división por mitades así como el coeficiente alfa de Cronbach. Finalmente se aplicó un análisis factorial para la validez de constructo. Se obtuvieron niveles altos de CVI (0.87) y consistencia interna (R=0.97, α=0.95) así como cuatro factores que explican el 66 % de la varianza total. Concluyendo que el instrumento es válido y confiable para medir auto-eficacia para la comunicación oral y escrita en entornos laborales en futuros egresados.

Abstract The labor market needs future workers with adequate levels of transversal skills such as Oral and Written Communication for the job. In this regard, the category of self-efficacy becomes relevant, since it constitutes a decisive factor for an individual to achieve his goals, being then necessary to evaluate this competence in future graduates. To this end, a scale was designed, validated and evaluated for reliability (n=443). For content validity the CVI method was used and for internal consistency the method of division by halves was used as well as Cronbach's alpha coefficient. Finally, a factor analysis was applied for construct validity. High levels of CVI (0.87) and internal consistency (R=0.97, α=0.95) were obtained, as well as four factors that explain 66% of the total variance. We conclude that the instrument is valid and reliable to measure self-efficacy for oral and written communication in work environments in future graduates.

Triphenyltin derivatives of sulfanylcarboxylic esters.

The reaction of 3-(aryl)-2-sulfanylpropenoic acids [H2xspa; x: p=3-phenyl-, f=3-(2-furyl)-, t=3-(2-thienyl)-] with methanol or ethanol gave the corresponding methyl (Hxspme) or ethyl (Hxspee) esters. The reaction of these esters (HL) with triphenyltin(IV) hydroxide gave compounds of the type [SnPh3L], which were isolated and characterized as solids by elemental analysis, IR spectroscopy and mass spectrometry and in solution by multinuclear (1H, 13C and 119Sn) NMR spectroscopy. The structures of [SnPh3(pspme)], [SnPh3(fspme)] and [SnPh3(fspee)] were determined by X-ray diffractometry and the antimicrobial activity against E. coli, S. aureus, B. subtilis, P. aeruginosa, Resistant P. aeruginosa (a strain resistant to 'carbapenem'), and C. albicans was tested and the in vitro cytotoxic activity against the HeLa-229, A2780 and A2780cis cell lines was determined for all compounds.

Halogen-abstraction reactions from chloromethane and bromomethane molecules by alkaline-earth monocations.

The reactions, in the gas phase, between alkali-earth monocations (Mg(+), Ca(+), Sr(+), Ba(+)) and CH3X (X = Cl, Br) have been theoretically studied. The stationary points on the potential energy surfaces were characterized at the Density Functional Theory level on the framework of the mPW1K functional with the QZVPP Ahlrichs's basis sets. A complementary kinetics study has also been performed using conventional/variational microcanonical transition state theory. In the reactions of Mg(+) with either chloro- or bromomethane the transition structure lies in energy clearly above the reactants rendering thermal activation of CH3Cl or CH3Br extremely improbable. The remaining reactions are exothermic and barrierless processes; thus carbon-halogen bonds in chloro- or bromomethane can be activated by calcium, strontium or barium monocations to obtain the metal halogen cation and the methyl radical. The Mulliken population analysis for the stationary points of the potential energy surfaces supports a "harpoon"-like mechanism for the halogen-atom abstraction processes. An analysis of the bonding situation for the stationary points on the potential energy surface has also been performed in the framework of the quantum theory of atoms in molecules.

Mono and dinuclear phosphinegold(I) sulfanylcarboxylates: influence of nuclearity and substitution of PPh3 for PEt3 on cytotoxicity.

Gold complexes of the type [Au(PEt3)(Hxspa)] were prepared by reacting triethylphosphinegold(I) chloride in ethanol/water (8:1) with the 3-(aryl)-2-sulfanylpropenoic acids H2xspa [x=p=3-phenyl-; f=3-(2-furyl)-; t=3-(2-thienyl)-; py=3-(2-pyridyl); Clp=3-(2-Chlorophenyl)-; -o-mp=3-(2-methoxyphenyl)-; -p-mp=3-(4-methoxyphenyl)-; -o-hp=3-(2-hydroxyphenyl)-; -p-hp=3-(4-hydroxyphenyl)-; -diBr-o-hp=3-(3,5-dibromo-2-hidroxyphenyl-); spa=2-sulfanylpropenoato] or 2-cyclopentylidene-2-sulfanylacetic acid (H2cpa) and KOH in a 1:1:1 mole ratio. The compounds were characterized by IR spectroscopy and FAB mass spectrometry and by (1)H, (13)C and (31)P NMR spectroscopy. The in vitro antitumor activity of these and of the previously described dinuclear [(AuPEt3)2(xspa)] complexes against the HeLa-229, A2780 and A2780cis cell lines was determined and compared with those of the analogous PPh3 complexes. The results show that the substitution of the PPh3 ligand by PEt3 is particularly effective in increasing the cytotoxicity of the dinuclear [(AuPR3)2(xspa)] complexes, giving rise to compounds that are significantly more active than cisplatin against the aforementioned cell lines. In addition, and as a preliminary test for nephrotoxicity, the cytotoxicity of the most active compounds against the normal renal LCC-PK1 cell line was evaluated and compared with that of cisplatin.

Heteronuclear gold(I)-silver(I) sulfanylcarboxylates: Synthesis, structure and cytotoxic activity against cancer cell lines.

Heteronuclear complexes of the type [AgAu(PPh3)2(xspa)] [H2xspa=3-(aryl)-2-sulfanylpropenoic acids; (x=3-phenyl-; 3-(2-chlorophenyl)-; 3-(o-methoxyphenyl)-; 3-(p-methoxyphenyl)-; 3-(p-hydroxyphenyl)-; 3-(2-furyl)-; 3-(2-thienyl)-; spa=2-sulfanylpropenoate)] were prepared by reacting the appropriate [Au(PPh3)(Hxspa)] precursor with Ag(PPh3)NO3. The compounds were characterized by spectroscopic methods, (IR; (1)H, (13)C and (31)P NMR) and mass spectrometry and the structures of the phenyl and p-methoxyphenyl derivatives were determined by X-ray diffraction. The in vitro antitumor activity against the HeLa-229, A2780 and A2780cis cell lines was determined and compared with that of cisplatin and the equivalent homonuclear gold(I) complexes.

Kinetics studies of the reactions of main fourth-period monocations (Ga+, Ge+, As+, and Se+) with methyl fluoride.

Thermodynamics and kinetics theoretical studies on the gas-phase reactions of fluoromethane with main fourth-period monocations (Ga(+), Ge(+), As(+), and Se(+)) have been carried out. Density functional theory (in particular mPW1K functional) was employed in the description of the potential energy surfaces, and refinement of the energies were done at the CCSD(T) level. The reaction rate constants were estimated using variational/conventional microcanonical transition state theory. From a thermodynamic viewpoint, the fluorine abstraction product is predicted for Ga(+) and Ge(+), whereas for As(+) and Se(+) the elimination product, MCH2(+) (M = As, Se) + HF, is the preferred one. Nevertheless, the most favorable channel for the reactions of CH3F with Ga(+) and Se(+) cations present a net activation barrier. In the case of Ga(+), the reaction proceeds via an addition channel forming the adduct complex, CH3FGa(+), whereas for Se(+) no reaction is found, in agreement with the experiments. The predicted reaction rate constants are in reasonable good agreement with the experimental values available. Apart from the harpoon-like mechanism, our results suggest that an oxidative addition mechanism seems to play a relevant role.

A novel hexanuclear silver(I) cluster containing a regular Ag6 ring with short Ag-Ag distances and an argentophilic interaction.

The hexanuclear complex [HQ][Ag(p-mpspa)] (H2-p-mpspa = 3-(4-methoxyphenyl)-2-sulfanylpropenoic acid) was prepared by reacting the precursor [Ag(H-p-mpspa)] with diisopropylamine (Q). The complex was characterized by spectroscopic techniques and the structure was solved by a single crystal X-ray diffraction study. The crystal contains hydrogen-bonded diisopropylammonium cations and [Ag6(p-mpspa)6](6-) anions that are based on a regular Ag6 ring with each S-donor atom of the sulfanylcarboxylate ligand bridging two Ag atoms. The Ag-Ag bond distances, 2.8036(6) Å, are very short and suggest a closed shell d(10)···d(10) argentophilic interaction. To analyze the relative role of this interaction and that of the S-bridging atom the anionic [Ag6(p-mpspa)6](6-) moiety has been studied theoretically at the Hartree-Fock (HF) and 2(nd) order Møller-Plesset perturbation theory (MP2) levels on a very simple [Ag6(SH)6] A model system. A large model system [Ag6(p-mpspa)6](6-)B has also been studied by applying the ONIOM (QM/MM) approach using HF/UFF and MP2/UFF combinations as levels of theory. The six experimentally observed Ag(I)···Ag(I) supported interactions are reproduced when dispersion-type interactions are considered in the theory levels MP2 and ONIOM MP2/UFF for models A and B, respectively. The use of HF and ONIOM HF/UFF levels led to a similar hexanuclear structure but displayed a large hexagonal disposition without argentophilic contacts for both models A and B. The steric hindrance exerted by the ligands did not preclude the formation of argentophilic interactions, as observed experimentally.

Reactivity of first-row transition metal monocations (Sc+, Ti+, V+, Zn+) with methyl fluoride: a computational study.

The gas-phase reactivity of methyl fluoride with selected first-row transition metal monocations (Sc(+), Ti(+), V(+), and Zn(+)) has been theoretically investigated. Our thermochemical and kinetics study shows that early transition-metal cations exhibit a much more active chemistry than the latest transition metal monocation Zn(+). The strong C-F bond in methyl fluorine can be activated by scandium, titanium, and vanadium monocations yielding the metal fluorine cation, MF(+). However, the rate efficiencies vary dramatically along the period 0.73 (Sc), 0.91 (Ti), and 0.028 (V) in agreement with the experimental observation. The kinetics results show the relative importance of the entrance and exit channels, apart from the "inner" bottleneck, to control the global rate constant of these reactions. At the mPW1K/QZVPP level our computed kglobal (at 295 K), 1.99 × 10(-9) cm(3) molecule(-1) s(-1) (Sc(+)), 1.29 × 10(-9) cm(3) molecule(-1) s(-1) (Ti(+)), and 3.46 × 10(-10) cm(3) molecule(-1) s(-1) (V(+)) are in good agreement with the experimental data at the same temperature. For the reaction of Zn(+) and CH3F our predicted value for kouter, at 295 K, 3.79 × 10(-9) cm(3) molecule(-1) s(-1), is in accordance with the capture rate constant. Our study suggests that consideration of the lowest excited states for Ti(+) and V(+) is mandatory to reach agreement between calculations and experimental measurements.

Ruthenium(IV)-catalyzed isomerization of the C=C bond of o-allylic substrates: a theoretical and experimental study.

A general mechanism to rationalize Ru(IV) -catalyzed isomerization of the C=C bond in O-allylic substrates is proposed. Calculations supporting the proposed mechanism were performed at the MPWB1K/6-311+G(d,p)+SDD level of theory. All experimental observations in different solvents (water and THF) and under different pH conditions (neutral and basic) can be interpreted in terms of the new mechanism. Theoretical analysis of the transformation from precatalyst to catalyst led to structural identification of the active species in different media. The experimentally observed induction period is related to the magnitudes of the energy barriers computed for that process. The theoretical energy profile for the catalytic cycle requires application of relatively high temperatures, as is experimentally observed. Participation of a water molecule in the reaction coordinate is mechanistically essential when the reaction is carried out in aqueous medium. The new mechanistic proposal helped to develop a new experimental procedure for isomerization of allyl ethers to 1-propenyl ethers under neutral aqueous conditions. This process is an unique example of efficient and selective catalytic isomerization of allyl ethers in aqueous medium.

BCl3-mediated ene reaction of sulfur dioxide and unfunctionalized alkenes.

The first ene reactions of SO(2) and unfunctionalized alkenes are reported. Calculations suggest that the endergonic ene reactions of SO(2) with alkenes can be used to generate beta,gamma-unsaturated sulfinyl and sulfonyl compounds. Indeed, in the presence of one equivalent of BCl(3), the unstable sulfinic acid form stable sulfinic acid.BCl(3) complexes that can be reacted in situ with NCS to generate corresponding sulfonyl chlorides, or with a base to generate corresponding sulfinates. The latter can be reacted with electrophiles to generate sulfones, or with silyl chloride to form beta,gamma-unsaturated silyl sulfinates. The sulfinic acid.BCl(3) complexes can be reacted with ethers that act as oxygen nucleophiles to produce corresponding sulfinic esters. Thus one-pot, three-component synthesis of beta,gamma-unsaturated sulfonamides, sulfinyl esters and sulfones have been developed starting from alkenes and sulfur dioxide (reagent and solvent).

Interaction of Pb2+, PbMe22+ and PbPh22+ with 3-(phenyl)-2-sulfanylpropenoic acid: a coordinative and toxicological approach.

We investigated the reaction of Pb(2+), PbMe(2)(2+) and PbPh(2)(2+) with 3-(phenyl)-2-sulfanylpropenoic acid (H(2)pspa) to give the complexes [Pb(pspa)], [PbMe(2)(pspa)], [PbPh(2)(pspa)], [HQ](2)[Pb(pspa)(2)] and [HQ[(2)[PbPh(2)(pspa)(2)] (HQ=diisopropylammonium), which were characterized by IR and NMR ((1)H, (13)C and (207)Pb) spectroscopy and by fast atom bombardment (FAB) spectrometry. The structures of [PbMe(2)(pspa)], [PbPh(2)(pspa)], [PbPh(2)(pspa)(dmso)].dmso and [HQ[(2)[PbPh(2)(pspa)(2)] are interesting examples of unexplored Pb coordination kernels and supramolecular association. Pig renal proximal tubule LLC-PK1 culture cells were used to determine in vitro the effect of the pretreatment with H(2)pspa (alone or combined with vitamin B(6)) and [HQ](2)[Zn(pspa)(2)] on the cytotoxicity of PbMe(2)(2+) and PbPh(2)(2+) by comparing the results with those of meso-2,3-dimercaptosuccinic acid (dmsa). The results show that the cell viability was scarcely affected by these agents. The ability of these reagents to decorporate lead was investigated in vivo by analysing the lead levels in the liver, kidney, brain and blood. In the case of the dimethyl derivative, and under certain protocols, undesirable effects such as an increase in brain and liver lead levels were detected. These increases were not detected when the diphenyl derivative was assayed but in this case a positive effect was not identified either. The blood lead levels also increased in the case of the dimethyl derivative and the activity of delta-ALAD was significantly recovered upon treatment with vitamin B(6) or H(2)pspa; neither the blood lead levels nor the delta-ALAD activity was modified in the case of the diphenyl derivative.

Dinuclear triphenylphosphinegold(I) sulfanylcarboxylates: Synthesis, structure and cytotoxic activity against cancer cell lines.

Compounds of the type [(AuPPh(3))(2)(xspa)]; H(2)xspa [x:p=3-phenyl-, f=3-(2-furyl)-, t=3-(2-thienyl)-, -o-py=3-(2-pyridyl)-, Clp=3-(2-chlorophenyl)-, -o-mp=3-(2-methoxyphenyl)-, -p-mp=3-(4-methoxyphenyl)-, -o-hp=3-(2-hydroxyphenyl)-, -p-hp=3-(4-hydroxyphenyl)-, -diBr-o-hp=3-(3,5-dibromo-2-hydroxyphenyl)-; spa=2-sulfanyl propenoato] were synthesized and characterized by IR and NMR ((1)H, (13)C and (31)P) spectroscopy and by FAB mass spectrometry. The structures of [(AuPPh(3))(2)(Clpspa)], [(AuPPh(3))(2)(o-hpspa)], [(AuPPh(3))(2)(p-hpspa)].MeOH and [(AuPPh(3))(2)(diBr-o-hpspa)].2Me(2)CO show the dinuclear nature of the complexes with the two gold atoms, one of which is also O-bonded to an O atom of the carboxylate group, bonded to the S atom. The in vitro antitumor activities against the HeLa-229, A2780 and A2780cis cell lines were determined and the compounds were found to be highly effective, in particular against the A2780cis cell line, with eight of the nine compounds having IC(50) values better than that of cisplatin. This behavior is indicative of a high ability to circumvent the cellular resistance to this drug.

Canonical variational transition-state theory study of the CF3CHFCH2F + OH reaction.

Variational transition-state theory rate constants with multidimensional tunneling contributions using the small curvature method have been calculated for the CF(3)CHFCH(2)F (HFC-245eb) + OH reaction over a temperature range from 200 to 800 K. The mPW1B95-41.0 hybrid functional, parametrized by Albu and Swaminathan to generate theoretical rate constants nearly identical to the experimental values for the CH(3)F + OH reaction, has been used in conjunction with the 6-31+G(d,p) basis set to explore the potential energy surface of the title reaction. The functional provides results within the limits of chemical accuracy, supporting the conclusions about transferability of a previous study on the CF(3)CH(2)CH(3) + OH reaction. Fourteen different reaction channels have been explored, all of them with significant contributions to the global rate constants.

Interactions of diorganolead(IV) with 3-(2-thienyl)-2-sulfanylpropenoic acid and/or thiamine: chemical and in vitro and in vivo toxicological results.

The reactions of PbR(2)(OAc)(2) (R = Me, Ph) with 3-(2-thienyl)-2-sulfanylpropenoic acid (H(2)tspa) in methanol or ethanol afforded complexes [PbR(2)(tspa)] that electrospray ionization-mass spectrometry (ESI-MS) and IR data suggest are polymeric. X-ray studies showed that [PbPh(2)(tspa)(dmso)] x dmso, crystallized from a solution of [PbPh(2)(tspa)] in dmso, is dimeric, and that [HQ](2)[PbPh(2)(tspa)(2)] (Q = diisopropylamine), obtained after removal of [PbPh(2)(tspa)] from a reaction including Q, contains the monomeric anion [PbPh(2)(tspa)(2)](2-). In the solid state the lead atoms are O,S-chelated by the tspa(2-) ligands in all these products, and in the latter two have distorted octahedral coordination environments. NMR data suggest that tspa(2-) remains coordinated to PbR(2)(2+) in solution in dmso. Neither thiamine nor thiamine diphosphate reacted with PbMe(2)(NO(3))(2) in D(2)O. Prior addition of H(2)tspa protected LLC-PK1 renal proximal tubule cells against PbMe(2)(NO(3))(2); thiamine had no statistically significant effect by itself, but greatly potentiated the action of H(2)tspa. Administration of either H(2)tspa or thiamine to male albino Sprague-Dawley rats dosed 30 min previously with PbMe(2)(NO(3))(2) was associated with reduced inhibition of delta-ALAD by the organolead compound, and with lower lead levels in kidney and brain, but joint administration of both H(2)tspa and thiamine only lowered lead concentration in the kidney.

Gas-phase reaction between calcium monocation and fluoromethane: Analysis of the potential energy hypersurface and kinetics calculations.

The gas-phase reaction between calcium monocation and fluoromethane: Ca(+)+CH(3)F-->CaF(+)+CH(3) was theoretically analyzed. The potential energy hypersurface was explored by using density functional theory methodology with different functionals and Pople's, Dunning's, Ahlrichs', and Stuttgart-Dresden basis sets. Kinetics calculations (energy and total angular momentum resolved microcanonical variational/conventional theory) were accomplished. The theoretically predicted range for the global kinetic rate constant values at 295 K (7.2x10(-11)-5.9x10(-10) cm(3) molecule(-1) s(-1)) agrees reasonably well with the experimental value at the same temperature [(2.6+/-0.8)x10(-10) cm(3) molecule(-1) s(-1)]. Explicit consideration of a two transition state model, where the formation of a weakly bounded prereactive complex is preceded by an outer transition state (entrance channel) and followed by an inner transition state connecting with a second intermediate that finally leads to products, is mandatory. Experimental observations on the correlation, or lack of correlation, between reaction rate constants and second ionization energies of the metal might well be rationalized in terms of this two transition state model.

Synthesis, structure and cytotoxicity studies of diisopropylammonium and triethylammonium salts of triphenylphosphinegold(I) sulfanylcarboxylates.

Compounds of the type [HQ][Au(PPh(3))(xspa)] and [HP][Au(PPh(3))(xspa)] {HQ=diisopropylammonium; HP=triethylammonium; H(2)xspa=3-aryl-2-sulfanylpropenoic acids [x: p=3-phenyl-, f=3-(2-furyl)-, t=3-(2-thienyl)-, -o-py=3-(2-pyridyl)-, Clp=3-(2-chlorophenyl)-, -o-mp=3-(2-methoxyphenyl)-, -p-mp=3-(4-methoxyphenyl)-, -o-hp=3-(2-hydroxyphenyl)-, -p-hp=3-(4-hydroxyphenyl)-, diBr-o-hp=3-(3,5-dibromo-2-hydroxyphenyl]} were synthesized and characterized by IR and NMR ((1)H, (13)C and (31)P) spectroscopy and by FAB mass spectrometry. The structures of [HQ][Au(PPh(3))(Clpspa)] and [HQ][Au(PPh(3))(-o-mpspa)] show that the crystal contains hydrogen-bonded diisopropylammonium cations and [Au(PPh(3))(xspa)](-) anions. The anions in the two compounds have different structures, with the carboxylate group either coordinated or not coordinated to the gold atom, respectively. The in vitro antitumour activities against the HeLa-229, A2780 and A2780cis cell lines were determined for all complexes. The diisopropylammonium derivatives were generally found to be more active, in particular against the A2780cis cell line, and showed a high ability to circumvent the cellular resistance to cisplatin.

Desulfinylation of prop-2-enesulfinic acid: experimental results and mechanistic theoretical analysis.

The potential energy surfaces of the desulfinylation of prop-2-enesulfinic acid (13) in CH(2)Cl(2) solution at -15 degrees C have been explored by quantum calculations and analyzed with kinetic data obtained for the reaction in absence or presence of additives. Monomeric 13 adopts a preferred conformation with gauche S=O/sigma(C(1)-C(2) bond pairs and the O-H bond pointing toward C(3). It equilibrates with the more stable dimer (13)(2) (at -15 degrees C) formed by two O-H...O=S hydrogen bonds and in which the S=O/sigmaC(1)-C(2) are gauche also, but the SOH moieties are antiperiplanar with respect to sigma(C(1)-C(2)). Dimer (13)(2) undergoes desulfinylation into propene + SO(2) + 13 following a one-step, concerted mechanism. The preferred transition state is a six-membered, chairlike transition structure (C...S elongation and S-O...H...C(3) hydrogen transfer occur in concert) in which the S=O/sigma(C(1)-C(2)) bonds are gauche (S=O adopt pseudoaxial positions). There are at least 48 transition states, each one defining a different pathway, all with similar calculated free energies (DeltaG(double dagger) = 25.3-28.6 kcal/mol), which makes the bimolecular (autocatalyzed) retro-ene elimination of SO(2) competing (entropy factor) with a monomolecular process for which the transition state (calculated DeltaG(double dagger) = 24.3 kcal/mol) implies only one molecule of sulfinic acid. This agrees with the experimental rate law of the reaction which is first order in the concentration of dimer (13)(2). SO(2), CF(3)COOH, and BF(3) x Me(2)O do not catalyze the reaction. In the presence of an excess of BF(3) x Me(2)O the desulfinylation is completely inhibited due to the formation of a stable tetramolecular complex of type (CH(2)=CHCH(2)SO(2)H x BF(3))(2) (18), for which quantum calculations show that the S=O/sigma(C(1)-C(2)) bonds are antiperiplanar whereas the S-OH/sigma(C(1)-C(2)) bonds are gauche. Independently of the additive, the retro-ene eliminations of SO(2) are calculated to be concerted and have transition states adopting six-membered cyclic structures in which S=O and sigma(C(1)-C(2)) are gauche, the S=O interacting with the additive. Preliminary experiments suggested that the thermodynamically unfavored ene reaction of SO(2) with propene can occur at low temperature using 1 equiv of BF(3).