Dihydropyridones from Formamides

T Hiyama et al (JACS, 2011, 133, (10), 3264) describe a dehydrogenative nickel catalysed reaction which results in the formation of dihydropyridones from a formamide and an acetylene..

The paper contains 13 examples with isolated yields ranging from just 23% up to an impressive >95%.

There are limitations to the reaction, such as terminal alkynes don’t work, an excess of alkyne has been used and unsymmetrical alkynes result in regioisomeric products, but notwithstanding these issues, the reaction appealed to me as an alternative route to potentially interesting heterocycles.  It is interesting to note that one equivalent of alkyne is consumed and converted to the respective cis alkene as it serves as oxidant and receives the hydrogen that is ‘released’ from the reaction.  The authors undertook some reactions with deuterated substrates to help define the possible mechanism.  This mechanism does raise the question as to whether or not a ‘sacrificial’ alkyne could be used to act as oxidant.