BARAC - yet another strain-promoted copper-free click chemistry

Believe it or not, this one is called BARAC. 

Click chemistry is certainly not "done". This time, instead of electronic properties, Bertozzi group looked at the strain energy by introducing some level of double bond nature into the octyne ring structure. The choice was amide bond which displays well-known partial double bond nature (C=N). "Brushing against the line between stability and reactivity without crossing it", this is another beautiful example of "rational design" in physical organic chemistry. "Gratifying", The click reaction rate was superior, 12-fold faster than DIFO the difluoro-version. The group then evaluated BARAC derivatives in their "traditional" cell glycobiology imaging where cell surface carries glycan azide. It demonstrates superior performance than DIFO and DIBO. Modular and scalable synthesis of BARAC offers more opportunities and wider applications of this new copper-free click chemistry. 

Champagne finished, time to work on the next click chemistry.

Journal of the American Chemical Society, 2010, DOI 10.1021/ja100014q