Barton-Zard reaction

The Barton-Zard reaction , named after the chemists Derek Barton and Samir Zard , is a name reaction from the field of organic chemistry and was first described in 1985. The Barton-Zard reaction enables the preparation of pyrrole derivatives from isocyanides and nitroalkenes .

Overview reaction

The Barton-Zard reaction is a condensation reaction in which an isocyanide is reacted with a nitroalkene to form 2-substituted pyrroles . The reaction takes place in a strongly basic medium.

The substituents at positions 3 and 4 depend on the nitroalkene used and are variable.

Reaction mechanism

The following reaction mechanism is described in the literature:

The isocyanide 1 is first deprotonated by a strong base so that the nitroalkene 2 can be added via a Michael addition . The heterocycle 3 is then formed through ring closure . After a proton exchange, the nitro group is eliminated . The pyrrole 4 is finally formed by a 1,3 proton shift .

Individual evidence

1. ↑ Derek HR Barton and Samir Z. Zard: A new synthesis of pyrroles from nitroalkenes In: J. Chem. Soc., Chem. Commun. . 1985, pp. 1098-1100, doi: 10.1039 / C39850001098 .
2. ↑ ^{a b} Derek HR Barton, Jocelyne Kervagoret and Samir Z. Zard: A useful synthesis of pyrroles from nitroolefins In: Tetrahedron . 1990, pp. 7587-7598, doi: 10.1016 / S0040-4020 (01) 89069-4 .
3. ^ Zerong Wang: Comprehensive Organic Name Reactions and Reagents , Wiley, 2009, ISBN 978-0-471-70450-8 , pp. 254-257.
4. ↑ Jie Jack Li: Heterocyclic Chemistry in Drug Discovery , Wiley, 2013, ISBN 978-1-118-14890-7 , pp. 43-44.