tri-n-butyltin hydride-mediated radical reaction of a 2-iodobenzamide: Formation of an unexpected carbon-tin bond

Leonardo S. Santos. Instituto de Química de Recursos Naturales, Universidad de Talca, P.O. Box 747, Talca - Chile.The tri-n-butyltin hydride-mediated reaction of methyl 2,3-di-O-benzyl-4-O-trans-cinnamyl -6-deoxy-6-(2-iodobenzoylamino)-a-D-galactopyranoside afforded an unexpected aryltributyltin compound. The structure of this new tetraorganotin(IV) product has been elucidated by 1H, 13C NMR spectroscopy, COSY and HMQC experiments and electrospray ionization mass spectrometry (ESI-MS). The formation of this new compound via a radical coupling reaction and a radical addition-elimination process is discusse

The Proton-bound Dimer Of Acetone [2]

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Electrospray ionization mass spectrometric characterization of key Te(IV) cationic intermediates for the addition of TeCl4 to alkynes

Leonardo Silva Santos. Universidad de Talca, Instituto de Química de Recursos Naturales, P.O. Box 747, Talca, Chile.Tellurium tetrachloride adds to alkynes via two pathways: a concerted syn-addition that yields Z-tri- and -tetrasubstituted alkenes or an anti-addition that yields E-alkenes. The mechanistic aspects of these divergent pathways for TeCl4 addition to alkynes have been investigated by on-line electrospray ionization (tandem) mass spectrometry (ESI-MS(/MS)). Via ESI-MS(/MS), we have been able to intercept and characterize the active electrophile TeCl in tetrahydrofuran (THF) solutions of TeCl4, as well as its THF complex and several TeClx(OH) derivatives. For the first time, also, key Te(IV) cationic intermediates of the electrophilic addition of TeCl4 to alkynes were captured for gas-phase MS investigation. The detailed structural data of cyclic tellurane intermediates intercepted herein seems to provide insights into the coordinative behavior of the Te(IV) atom and its mode of action towards biological targets. Copyright © 2007 John Wiley & Sons, Ltd

The mechanism of the stille reaction investigated by electrospray ionization mass spectrometry

Leonardo Silva Santos. Universidad de Talca, Instituto de Química de Recursos Naturales, P.O. Box 747, Talca, Chile.On-line monitoring of Stille reactions was performed via direct infusion electrospray ionization mass spectrometry (ESI-MS) and its tandem version (ESI-MS/MS). When operated in the positive ion mode, ESI(+)-MS was able to transfer, directly from solution to the gas phase, the species involved in all main steps of a Stille reaction, that is, the catalytically active palladium species Pd(PPh3)2, in its molecular ion form as well as the key cationic Pd(II) intermediates, including cyclic IPd-(CH2CH)Sn species. When searching for anionic species, ESI(-)-MS monitoring showed I- as the only anion detectable in the reaction medium. A detailed catalytic cycle for a Stille reaction was elaborated in which reaction intermediates and the previously elusive catalytically active Pd(0) species are shown in association with the respective ionic species intercepted by ESI-MS and further characterized by ESI-MS/MS

Varietal discrimination of Chilean wines by direct injection mass spectrometry analysis combined with multivariate statistics

Reprint Address: Laurie, VF (reprint author), Univ Talca, Sch Agr Sci, 2 Norte 685, Talca, Chile.A simple, direct injection, electrospray ionization Fourier transform mass spectrometry (ESI FT-MS) method, in combination with multivariate statistics, was used for the characterization and sorting of Chilean wines. 47 commercial red wines labelled as Cabernet Sauvignon, Carmenere, Syrah, and Pinot noir, and 25 white wines of the varieties Chardonnay and Sauvignon blanc were diluted, directly infused into the mass spectrometer, and analyzed in negative ion mode. The signature ions used for statistical analyses were manually filtered out from the signals with m/z ratios over 10%. The results of principal component analysis allowed a good sorting of white wines, but not so in the case of reds. The main three principal components explained 96.82% and 85.65% of the variance for white and red wines, respectively. Instead, linear discriminant analysis, allowed the correct discrimination of 100.00% of white and 95.74% of red samples. The validation of these results using the leave-one-out cross-validation method gave lower percentages of correct classification (76.00% and 61.70% of white and red samples respectively), suggesting that some of the wine samples analyzed might have been blends of more than one variety. Consequently, ESI FT-MS direct injection analysis of wines can be used for sample discrimination, but requires a stronger mathematical model built with spectral information of pure and blended samples before improving the percentages of classification. (C) 2011 Elsevier Ltd. All rights reserved

The Mechanism Of Tröger's Base Formation Probed By Electrospray Ionization Mass Spectrometry

(Chemical Equation Presented) Using direct infusion electrospray ionization mass and tandem mass spectrometric experiments [ESI-MS(/MS)], we have performed on-line monitoring of some reactions used to form Tröger's bases. Key intermediates, either as cationic species or as protonated forms of neutral species, have been intercepted and characterized. The role of urotropine as the methylene source in these reactions has also been accessed. Reaction pathways shown by ESI-MS(/MS) have been probed by gas-phase ion/molecule reactions, and an expanded mechanism for Tröger's base formation based on the mass spectrometric data has been elaborated. © 2007 American Chemical Society.721140484054Tröger, J., (1887) J. Prakt. Chem, 36, p. 225Valík, M., Strongin, R.M., Král, V., (2005) Supramol. Chem, 17, p. 347. , For a recent review, see(1992) Fascinating Molecules in Organic Chemistry, pp. 237-249. , Vögtle, F, Ed, John Wiley: New YorkPrelog, V., Wieland, P., (1944) Helv. Chim. 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Transient intermediates of the Tebbe reagent intercepted and characterized by atmospheric pressure chemical ionization mass spectrometry

Santos, L.S. Laboratory of Asymmetric Synthesis, Instituto de Química de Recursos Naturales, Universidad de Talca, P.O. Box 747, Talca, Chile

Unexpected Synthesis Of Conformationally Restricted Analogues Of γ-amino Butyric Acid (gaba): Mechanism Elucidation By Electrospray Ionization Mass Spectrometry

(Chemical Equation Presented). From previous results with lower homologues, dehydroiodination of the three alkenyl-β-enamino esters 3a-c was expected to provide six-membered N-heterocyclic products. The reactions of 3a-c with triethylamine are found to lead, however, to the unexpected stereoselective synthesis of the trisubstituted cyclopentane derivatives 4a-c, as confirmed by IR and NMR spectroscopy. Cyclopentanes 4a-c bear two chiral centers and a γ-amino ester moiety, and are therefore conformationally restricted analogues of γ-amino butyric acid (GABA), which is the major inhibitory neurotransmitter in the central nervous system. Use of electrospray ionization mass (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) allowed the key iminium ion intermediates 5a-c+, as well as the protonated molecules of both the reactant and final products, [3a-c + H]+ and [4a-c + H] +, to be intercepted and structurally characterized. From these findings a mechanism for this unexpected but synthetically attractive and efficient stereoselective reaction is proposed.701110114Krogsgaard-Larsen, P., (1988) Med. Res. Rev., 8, p. 27Andersen, K.E., Sorensen, J.L., Lau, J., Lundt, B.F., Petersen, H., Huusfeldt, P.O., Suzdak, P.D., Swedberg, M.D.B., (2001) J. Med. Chem., 44, p. 2152Moglioni, A.G., Brousse, B.N., Álvarez-Larena, A., Moltrasio, G.Y., Ortuño, R.M., (2002) Tetrahedron: Asymmetry, 13, p. 451Carpes, M.J., Correia, C.R.D., (2002) Tetrahedron Lett., 43, p. 741Dumond, Y.R., Montchamp, J.L., (2002) J. Organomet. Chem., 653, p. 252Ito, H., Omodera, K., Takigawa, Y., Taguchi, T., (2002) Org. Lett., 4, p. 1499Aitken, R.A., Karodia, N., Massil, T., Young, R.J., (2002) J. Chem. Soc., Perkin Trans. 1, p. 533Blay, G., Fernàndez, I., Monje, B., Pedro, J.R., (2004) Tetrahedron, 60, p. 165Eberlin, M.N., Kascheres, C., (1988) J. Org. Chem., 53, p. 2084Augusti, R., Eberlin, M.N., Kascheres, C., (1995) J. Heterocycl. Chem., 32, p. 1355Augusti, R., Kascheres, C., (1993) J. Org. Chem., 58, p. 7079Fustero, S., Torre, M.G., Jofre, V., Carlón, R.P., Navarro, A., Fuentes, A.S., Carrió, J.S., (1998) J. Org. Chem., 63, p. 8825Gilchrist, T.L., (1998) J. Chem. Soc., Perkin Trans. 1, p. 615Ferraz, H.M.C., Pereira, F.L.C., (2004) Quim. Nova, 27, p. 89Kascheres, C.M., (2003) J. Braz. Chem. Soc., 14, p. 945Elassar, A.Z.A., El-Khair, A.A., (2003) Tetrahedron, 59, p. 8463Melo, J.O.F., Ratton, P.M., Augusti, R., Donnici, C.L., (2004) Synthetic Commun., 34, p. 369Ferraz, H.M.C., Oliveira, E.O., Payret-Arrúa, M.E., Brandt, C.A., (1995) J. Org. Chem., 60, p. 7357Ferraz, H.M.C., Pereira, F.L.C., Leite, F.S., Nunes, M.R.S., Payret-Arrúa, M.E., (1999) Tetrahedron, 55, p. 10915Triggle, D.J., Langs, D.A., Janis, R.A., (1989) Med. Res. Rev., 9, p. 123Triggle, D.J., Janis, R.A., (1987) Annu. Rev. Pharmacol. Toxicol., 27, p. 347Elmslie, K.S., (2004) J. Neurosci. Res., 75, p. 733Stout, D.M., Meyers, A.I., (1982) Chem. Rev., 82, p. 233Sausins, A., Duburs, G., (1988) Heterocycles, 27, p. 291Goldman, S., Stoltefuss, J., (1991) Angew. Chem., Int. Ed. Engl., 30, p. 1559Whitehouse, C.M., Dreyer, R.N., Yamashita, M., Fenn, J.B., (1985) Anal. Chem., 57, p. 675Fenn, J.B., Mann, M., Meng, C.K., Wong, S.F., Whitehouse, C.M., (1989) Science, 246, p. 64Cole, R.B., (1997) Electrospray Ionization Mass Spectroscopy, , John Wiley & Sons, Inc.: New YorkCooks, R.G., Zhang, D.X., Koch, K.J., Gozzo, F.C., Eberlin, M.N., (2001) Anal. Chem., 73, p. 3646Gozzo, F.C., Santos, L.S., Augusti, R., Consorti, C.S., Dupont, J., Eberlin, M.N., (2004) Chem. Eur. J., 10, p. 6187Koch, K.J., Gozzo, F.C., Nanita, S.C., Takats, Z., Eberlin, M.N., Cooks, R.G., (2002) Angew. Chem., Int. Ed., 41, p. 1721Santos, L.S., Pavam, C.H., Almeida, W.P., Coelho, F., Eberlin, M.N., (2004) Angew. Chem., Int. Ed., 43, p. 4330Raminelli, C., Prechtl, M.H.G., Santos, L.S., Eberlin, M.N., Comasseto, J.V., (2004) Organometallics, 23, p. 3990Domingos, J.B., Longhinotti, E., Brandão, T.A.S., Bunton, C.A., Santos, L.S., Eberlin, M.N., Nome, F., (2004) J. Org. Chem., 69, p. 6024Meyer, S., Metzger, J.O., (2003) Anal. Bioanal. Chem., 377, p. 1108Meyer, S., Koch, R., Metzger, J.O., (2003) Angew. Chem., Int. Ed., 42, p. 4700Meurer, E.C., Santos, L.S., Pilli, R.A., Eberlin, M.N., (2003) Org. Lett., 5, p. 1391Griep-Raming, J., Meyer, S., Bruhn, T., Metzger, J.O., (2002) Angew. Chem., 114, p. 2863Hilderling, C., Adlhart, C., Chen, P., (1998) Angew. Chem., Int. Ed., 37, p. 2685Chen, P., (2003) Angew. Chem., Int. Ed., 42, p. 2832Tomazela, D.M., Gozzo, F.C., Ebeling, G., Dupont, J., Eberlin, M.N., (2004) Inorg. Chim. Acta, 357, p. 2349Neto, B.A.S., Ebeling, G., Gonçalves, R.S., Gozzo, F.C., Eberlin, M.N., Dupont, J., (2004) Synthesis, p. 1155Pereira, R.M.S., Paula, V.I., Buffon, R., Tomazela, D.M., Eberlin, M.N., (2004) Inorg. Chim. Acta, 357, p. 2100Ferraz, H.M.C., Sano, M.K., Nunes, M.R.S., Bianco, G.G., (2002) J. Org. Chem., 67, p. 412