Henry Rzepa's Blog Chemistry with a twist

December 11, 2010

Janus mechanisms (the past and the future): Reactions of the diazonium cation.

Janus was the mythological Roman god depicted as having two heads facing opposite directions, looking simultaneously into the past and the future. Some of the most ancient (i.e. 19th century) known reactions can be considered part of a chemical mythology; perhaps it is time for a Janus-like look into their future.

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May 26, 2010

Anatomy of an asymmetric reaction. The Strecker synthesis, part 2.

In the first part of the post on this topic, I described how an asymmetric sulfoxide could be prepared as a pure enantiomer using a chiral oxygen transfer reagent. In the second part, we now need to deliver a different group, cyano, to a specific face of the previously prepared sulfoxide-imine. The sulfoxide is now acting as a chiral auxilliary, and helps direct the delivery of the cyanide group to specifically one face of the imine rather than the other. After removal of the aluminum carrier for the cyano group and hydrolysis of the cyano group to a carboxylic acid group, we end up with an enantiomerically pure amino acid.

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