Alkylation of Aryl <i>N</i>‐(2‐Pyridylsulfonyl)aldimines with Organozinc Halides: Conciliation of Reactivity and Chemoselectivity

Esquivias, Jorge; Arrayás, Ramón Goméz; Carretero, Juan C.

doi:10.1002/ange.200703239

Cited by 11 publications

(2 citation statements)

References 63 publications

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“…Dabei werden normalerweise beide Benzylgruppen auf das Elektrophil übertragen. Kürzlich berichteten Arrayas, Carretero20a und Charette,20b dass Aryl‐ N ‐(2‐pyridylsulfonyl)aldimine und eine Cu II ‐Katalyse notwendig sind, um Zinkreagentien zu addieren. Der Zusatz von MgCl 2 ermöglicht aber eine direkte Addition von Organozinkverbindungen an N ‐Tosylimine.…”

Section: Methodsunclassified

Electrospray tandem quadrupole fragmentation of quinolone drugs and related ions. On the reversibility of water loss from protonated molecules

Neta

Godugu

Liang

et al. 2010

Rapid Comm Mass Spectrometry

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Selected reaction monitoring (SRM) of quinolone drugs showed different sensitivities in aqueous solution vs. biological extract. The authors suggested formation of two singly protonated molecules with different behavior, one undergoing loss of H(2)O and the other loss of CO(2), so that SRM transitions might depend on the ratios of these forms generated by the electrospray. These surprising results prompted us to re-examine several quinolone drugs and some simpler compounds to further elucidate the mechanisms. We find that the relative contributions of loss of H(2)O vs. loss of CO(2) in tandem mass spectrometric (MS/MS) experiments depend not only on molecular structure and collision energy, but also, in certain cases, on the cone voltage. We further find that many product ions formed by loss of H(2)O can reattach a water molecule in the collision cell, whereas ions formed by loss of CO(2) do not. Since reattachment of H(2)O can occur after water loss in the cone region and prior to selection of the precursor ion, this effect leads to the dependence of MS/MS spectra on the cone voltage used in creating the precursor ion, which explains the formerly observed effect on SRM ratios. Our results support the earlier conclusion that varying amounts of two ions of the same m/z value are responsible for problems in the analysis of these drugs, but the origin is in dehydration/rehydration reactions. Thus, SRM transitions for certain complex compounds may be comparable only when monitored under equivalent ion-forming conditions, including the voltage used in the production of the protonated molecules in the electrospray ionization (ESI) source.

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Section: Methodsunclassified

Electrospray tandem quadrupole fragmentation of quinolone drugs and related ions. On the reversibility of water loss from protonated molecules

Neta

Godugu

Liang

et al. 2010

Rapid Comm Mass Spectrometry

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“…To address the issues of the imine substrate scope and a removable protecting group, various electron-withdrawing N-substituents were examined. In 2-pyridylsulfonyl imines 49, [46] the sulfonyl residue is not as electron-withdrawing as for 2,4-dinitrobenzenesulfonyl imines, but it offers the possibility for additional activation by bidentate coordination to a Lewis acid cocatalyst.…”

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Catalytic Asymmetric Synthesis of β‐Sultams as Precursors for Taurine Derivatives

Zajac

Peters

2009

Chemistry A European J

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Beta-sultams, biologically interesting sulfonyl analogues of beta-lactams, have been prepared by an organocatalytic asymmetric formal [2+2]-cycloaddition approach of non-nucleophilic imines with alkyl sulfonyl chlorides. In the case of very electron poor N-tosyl imines derived from chloral or ethylglyoxylate, this reaction type was catalyzed by cinchona alkaloids providing the heterocycles in high yield, with good diastereoselectivity and up to 94% ee. Mechanistic investigations suggested that the product formation proceeded via a zwitterionic imine-catalyst adduct. The scope was significantly extended by 2-pyridylsulfonyl imines derived from non-activated aromatic aldehydes employing Yb(OTf)3 as Lewis acid cocatalyst. The synthetic value of the strained enantioenriched beta-sultams was demonstrated by smooth nucleophilic ring opening reactions with O-, N- and C-nucleophiles yielding a variety of acyclic beta-aminosulfonyl (taurine) derivatives (sulfonates, sulfonamides, sulfones) without racemization or epimerization.

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Palladium(II)‐Catalyzed Regioselective Direct C2 Alkenylation of Indoles and Pyrroles Assisted by the N‐(2‐Pyridyl)sulfonyl Protecting Group

2009

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Alkylation of Aryl N‐(2‐Pyridylsulfonyl)aldimines with Organozinc Halides: Conciliation of Reactivity and Chemoselectivity

Cited by 11 publications

References 63 publications

Electrospray tandem quadrupole fragmentation of quinolone drugs and related ions. On the reversibility of water loss from protonated molecules

Electrospray tandem quadrupole fragmentation of quinolone drugs and related ions. On the reversibility of water loss from protonated molecules

Catalytic Asymmetric Synthesis of β‐Sultams as Precursors for Taurine Derivatives

Palladium(II)‐Catalyzed Regioselective Direct C2 Alkenylation of Indoles and Pyrroles Assisted by the N‐(2‐Pyridyl)sulfonyl Protecting Group

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