Event Details

Join Lancaster's Chemistry Department for an enlightening seminar delivered by Professor Ann Marie O’Donoghue of Durham University on the synthesis of stable carbenes such as Nitron.

Abstract

Our research is focused on the synthesis, mechanistic evaluation and applications of stable carbenes as organo- and biocatalysts. As part of this work, we recently reported the unusual rearrangement of a C(3)-anilino-1,2,4-triazolium ion, commonly known as Nitron, to new C(3)-amido and anilino Blattertype organic radicals.

These stable benzotriazinyl organic radicals have seen successful application as switchable signal enhancement agents for NMR spectroscopy. Prior to this work, only the synthesis of the parent Nitron was reported, which we used to access radical derivatives with simple alkyl substituents. Nitron exists in both zwitterionic and N-heterocyclic carbene (NHC) tautomeric forms.

In the first part of the talk, we report a new improved synthetic route to Nitron, which permits access to a broader range of C(3)-anilino-1,2,4-triazolium derivatives encompassing both strong electron donating and withdrawing substituents. The range of Nitron derivatives were evaluated in the Nitron to Blatter radical rearrangement, with radical formation proving to be dependent on the zwitterion to carbene equilibrium position (KT). Determination of NH and C(3)-H pKas enabled access to KT values

for zwitterion-NHC tautomerization (KT). In the second part of the talk, we will report our recent results on the synthesis, mechanistic evaluation and applications of 1,2,4-triazolium mimics of Vitamin B1 (thiamine) as non-native co-factors for biocatalysis.