Thursday, October 30, 2008

Cool Three-In-One Reaction

ResearchBlogging.orgSince I teach sophomore organic chemistry, I'm always interested to see new research that involves basic organic reactions that I cover in class.  A new reaction using alkynyl halides produces alkynyl epoxides in a one pot procedure as a result of three different reactions.  At first glance, this looks like a complicated reaction, but everything involved is routinely taught in standard organic chem classes.  And it works well, this example gave 92% yield.

In a recent paper Trofimov, Chernyak and Gevorgyan describe their work with this reaction.  They report that it works quite well for aromatic ketones with a tertiary alpha-hydrogen, while other ketones give mixtures of products.  

The reaction starts with a deprotonation of the ketone to form the enolate, which performs nucleophilic attack on the alkynyl Bromine.  To a beginning student of organic chemistry this might look like a strange version of bromine, but mechanistically it is similar to brominating with Br2.  Next, the alkynyl anion attacks the carbonyl carbon.  This produces a halohydrin that simply closes to form the final epoxide product.  Pretty slick - three reactions all in one go.

Alexander Trofimov, Natalia Chernyak, Vladimir Gevorgyan (2008). Dual Role of Alkynyl Halides in One-Step Synthesis of Alkynyl Epoxides Journal of the American Chemical Society, 130 (41), 13538-13539 DOI: 10.1021/ja806178r

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