Class Of Reactive Intermediates Research Articles

Mass spectrometry studies of nitrene anions.

Nitrene anions are a class of reactive intermediates that provide a means for studying the corresponding neutral molecules via electron photodetachment spectroscopy and photoelectron spectroscopy. The added electron makes it possible for protected nitrene anions to be manipulated by external electric and magnetic fields of a mass spectrometer. Nitrene anions also display their own unique reactivities as reagents, which have been investigated using ion/molecule reactions. Mass spectrometry of negative ions has thereby provided information on the electronic states, reactivities, and thermochemical properties of nitrene intermediates. This review also includes a discussion of condensed-phase nitrene anions.

Cover Picture: One Century of Aryne Chemistry (Angew. Chem. Int. Ed. 5/2003)

A century of aryne chemistry has not dampened the interest in this class of reactive intermediates. The cover picture shows the structure of a calicheamicin–DNA complex, the “warhead” of which is a cyclic enediyne unit (highlighted). The biological activity of the enediyne cytostatics is based on the depicted Bergman cyclization of the enediyne to a didehydrobenzene biradical. More about these short‐lived species is given by Sander et al. on pp. 502 ff.

Carbohydrate Chemistry of the Anomeric Carbon-Sulfur Bond

Abstract Aryl and alkyl S-glycosides and sulfones are ideal precursors of three classes of reactive intermediates : anomeric carbenium, anion, and radical, and thus play a remarkable role in carbohydrate chemistry of the anomeric carbon atom. Reported reactions will include: - A conceptually novel glycosylation reaction based on the activation of thioglycosides by a one electron -transfer reagent - Uses of a novel class of glycosyl donors: anomeric S-xanthates of 2-azido sugars. - Selective synthesis of α and β C-glycosides using anomeric reductive lithiation or reductive samariation of phenyl S-glycosides or sulfones. - Convenient synthesis of substituted pyranoid glycals - Expeditious synthesis of C-disaccharides by Sml2 induced intramolecular coupling reaction of tethered glycosyl phenyl sulfone and exomethylene sugar.

Carbohydrate Chemistry of the Anomeric Carbon-Sulfur Bond

Abstract Aryl and alkyl S-glycosides and sulfones are ideal precursors of three classes of reactive intermediates : anomeric carbenium, anion, and radical, and thus play a remarkable role in carbohydrate chemistry of the anomeric carbon atom. Reported reactions will include: - A conceptually novel glycosylation reaction based on the activation of thioglycosides by a one electron -transfer reagent - Uses of a novel class of glycosyl donors: anomeric S-xanthates of 2-azido sugars. - Selective synthesis of α and β C-glycosides using anomeric reductive lithiation or reductive samariation of phenyl S-glycosides or sulfones. - Convenient synthesis of substituted pyranoid glycals - Expeditious synthesis of C-disaccharides by Sml2 induced intramolecular coupling reaction of tethered glycosyl phenyl sulfone and exomethylene sugar.

Benzo[a]pyrene bay-region sulfonates, a novel class of reactive intermediates

The mutagenicity of 7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) toward Salmonella typhimurium strain TA98 is enhanced by over 1.5-fold by the addition of 1-10 mM sulfite to the incubations. Sulfite itself is neither mutagenic nor toxic to the bacteria under these conditions. Analysis of anti-BPDE-derived products from these bacterial incubations demonstrates that, in addition to the expected hydrolysis products of the epoxide, novel more polar metabolites are produced. These same more polar compounds are produced by the addition of anti-BPDE to buffered aqueous solutions of sulfite. The major product of this reaction has been characterized by UV/visible and fluorescence spectroscopy, NI-FAB mass spectrometry, and proton NMR spectroscopy and is identified as 7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene-10-sulfonate (BPT-10-sulfonate). This derivative is formed by the nucleophilic addition of sulfite to the 9,10-oxirane ring of anti-BPDE. This product is easily differentiated both spectrally and chromatographically from the isomeric 7,8,10-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene-9-sulfonate reported from the attack of the sulfite anion radical on the activated aliphatic double bond of 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) [Curtis et al. (1988) Carcinogenesis 9, 2015]. The nucleophilic trapping of diol epoxides by water or thiols is assumed to represent a detoxication of this class of mutagen. In contrast, the extensive conversion of anti-BPDE to BPT-10-sulfonate in the bacterial incubations correlates with a marked enhancement of resultant mutagenicity. Further support for a key role of BPT-10 sulfonate in the enhancement of anti-BPDE mutagenicity is provided by our findings on the reactivity of this compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonaromatic diazonium ions

Nonbenzenoid diazonium ions comprise a class of reactive intermediates of increasing significance. They can be generated under stable ion conditions, observed spectroscopically, and studied chemically. Synthetic applications have been extended from aliphatic to a variety of heterosubstituted diazonium ions. Even the parent diazonium ion, HN+2 (protonated dinitrogen), can now be studied in solution.

Organic ion radical chemistry

This paper will briefly introduce ion radicals as a relatively new class of reactive intermediates.