Reversing the Pinacol coupling

14 September 2013 - Again?

benzopinacol fragmentation.PNGInteresting concept. Randomly select two chemicals from a commercial catalogue and find out what happens when you mix them. Take for example benzopinacol and n-butyllithium just as Zalibera et al. did here. What happens? Just as benzopinacol is formed from benzophenone in a pinacol coupling through a ketyl , the base makes sure benzopinacol reverts back to the ketyl. To quote the authors: "we have shown that non-ionic bases are able to reverse the pinacol coupling, inducing cleavage of the central bond in benzopinacol and producing ketyl radical anions." But hold on, in 2013 nobody has ever tried to throw a base at a pinacol product before? The discovery is too good to be true? A quick search engine investigation leaves no doubt. Screttas already in 1995 (DOI) reported that "benzopinacol undergoes decomposition by an alkoxide base to diphenyl ketyl, which decays into an equimolar mixture of benzophenone and benzhydrol". So now where is the novelty? Same reaction but with a different base or same reaction investigated with a different technique? It is not that the article does not cite other work but not as relevant work (DOI, DOI, DOI). Interesting challenge for reviewers: make sure the novelty claims made in articles actually hold up.