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Zinc gets a reaction
20 September 2007
Chemists in the UK have expanded the range of addition reactions that can be carried out with organozinc compounds.
Simon Woodward and colleagues at the University of Nottingham have shown that normally unreactive organozinc halides (RZnX) can be used as versatile reagents in asymmetric carbonyl addition chemistry. Woodward's team developed a straightforward system for the activation of RZnX in aldehyde additions using only readily-available reagents and a simple ligand.
The straightforward reaction uses only commercially available reagents and catalysts
'Normally for asymmetric carbonyl addition one uses diorganic species [ZnR2]. However, only eight of these are routinely available - which is a bit of a blow if the R-group you want to add is not one of them! The fact that over 200 organozinc halide species are commercially available seemed to us an untapped resource that deserved to be mobilised,' explained Woodward.
The researchers generated their catalyst from RZnX and a widely available aluminium-based reagent. 'The well-known functional group tolerance of organozinc halides is an additional advantage,' said Woodward. 'While other methods have been developed, these all require challenging synthetic work.'
John Brown, an expert in the catalysis of organic reactions at Oxford University, UK, welcomed the work. 'Woodward's group has discovered a method which is operationally simple and obviously useful,' he said.
Woodward agreed, noting that the reaction used only commercially available reagents and catalysts. 'We believe our work is of wide interest and will spark a quest for other systems operating on these principles,' he added.
Link to journal article
Direct asymmetric catalytic 1,2-addition of RZnX to aldehydes promoted by AlMe3 and reversal of expected stereochemistry
Jonathan Shannon, David Bernier, Daniel Rawson and Simon Woodward, Chem. Commun., 2007, 3945
Also of interest
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