Chiral ion-dipole complexes

This volume seeks in a small way to bridge the wide gap between organic chemistry in the gas and condensed phases. The same types of chiral ion-dipole complexes that form as intermediates of solvolysis may be generated in the gas phase by allowing neutral molecules to cluster with chiral cations. The reactions of these chiral clusters have been characterized in exquisite detail by mass spectrometry. The results of this work are summarized by Maurizio Speranza in a chapter that is notable for its breadth and thoroughness of coverage. This presentation leaves the distinct impression that further breakthroughs on the problems discussed await us in the near future. 

Enantioselective self-assembling of amino acids 209 Host-guest inclusion complexes 213 Reactivity of chiral ion-dipole complexes 233... 

The development of mass spectrometric techniques, such as fast atom bombardment mass spectrometry (FAB-MS), ° ° Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), ° and tandem mass spectrometry (MS"), ° allowed enantiodiscrimination of chiral ion-dipole complexes the gas phase. These techniques and others will be illustrated in detail in the next Section 3. 

Hydro gen-deuterium exchange in chiral ion—dipole complexes. The rates of gas phase H/D exchange reactions are most conveniently measured in a FT-ICR cell in which the ions can be trapped for extended periods of time in the presence of a fixed... 

Stereospecific nucleophilic substitution in chiral ion—dipole complexes. Chiral molecules can be discriminated in the Cl source of a CIMS instmment by specific ion-molecule reactions induced by chiral reagent gas. This method has been applied with success to distinguish between enantiomeric and diastereomeric forms of menthols ((lR,2S,5R)-(— )-14, (lS,2R,5S)-(+)-14, and (lR,2R,5S)-(—)-14 in Scheme 11) through the nucleophilic displacement of their hydroxyl group by (5)-2-amino-l-butanol Self-protonation of As... 

High-pressure reactions in chiral ion-dipole complexes... 

A. Filippi, M. Speranza, Gas-phase activation and reaction dynamics of chiral ion-dipole complexes. Chem. Eur. J. 9, 5274—5282 (2003)... 

Azomethine ylides are very important 1,3-dipoles, and they are usually used to react with alkenes leading to the formation of the highly substituted pyrrolidine derivatives [17]. A novel and practical process for the 1,3-dipolar cycloaddition of azomethine ylides with alkenes had been reported by j0rgensen and coworkers [18]. They proposed that a dipol-chiral base ion pair would be generated between a-imino ester-metal complex and a cinchona alkaloid, and subsequent cycloaddition with dipolarophile would take place in a stereoselective manner (Scheme 10.13). 

The optical activity in valence excitations of chiral metal complexes has been effectively treated using the model of an achiral chromophore (metal ion) in a chiral environment (ligands) and this model appears also appropriate for XAS in view of the core nature of the initial orbital state. The zero-order electric and magnetic transition moments arise from different transitions and must be mixed by some chiral environmental potential (V ). Considering the case of a lanthanide ion, and taking tihe electric dipole transitions for the Z.2,3 edge as Ip—Kj), a first-order perturbation expression for the rotational strength looks like ... 

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