Magnetic Resonance Imaging is perhaps the most important and prominent technique in diagnostic clinical medicine and biomedical research. Its success and development as an imaging technique has been aided by the characteristics of contrast agents that enhance signal intensities and improve specificity. Gadolinium(iii) remains the dominant starting material for contrast agent design but other lanthanide ions (and other oxidation states i.e. +2) are also being increasingly investigated as alternatives to gadolinium(III) within laboratory conditions. This critical review provides a concise summary of the MRI-active gadolinium(III) complexes to date--their pros and cons, an outline of contrast agents based on other lanthanide ions (e.g. europium, dysprosium), and directs the reader to newer, more speculative areas of lanthanide-containing contrast agent design.

Enantiopure bromonium ions may be generated from enantiopure bromohydrins and derivatives, they can be trapped with an in situ nucleophile to give enantiomerically pure products.

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Intermediates O 0190The Generation and Trapping of Enantiopure Bromonium Ions. -Treatment of tosylates (V) and (VIII) with TiCl 4 affords a mixture of enantiomerically pure bromochlorides (VI) and (VII) in the same product ratio via an enantiopure bromonium ion. -(BRADDOCK*, D. C.; HERMITAGE, S. A.; KWOK, L.; POUWER, R.; REDMOND, J. M.; WHITE, A. J. P.; Chem. Commun. (Cambridge) 2009, 9, 1082-1084; Dep. Chem., Imp. Coll. London, London SW4 2AY, UK; Eng.) -R. Staver 29-038