Substituted pyridines occur widely in nature and have high biological activity leading to their prevalence in both the agrochemical and pharmaceutical industries. The aza-Diels-Alder reaction of 2-azabutadienes has provided an alternative pathway to pyridines avoiding the use of multiple electron-withdrawing groups and limited substitution patterns that many classical methods suffer from. However, the requirement for organic azides and generation of stoichiometric phosphine oxide waste in the preparation of 2-azabutadienes via aza-Wittig reaction has prevented its wider uptake. We recently described a organocatalytic azide-free aza-Wittig reaction utilising a phosphine oxide catalyst and isocyanate precursors. This has now been extended to the intermolecular aza-Wittig reaction using vinyl isocyanates to give 2-azabutadienes and dienophiles added to give substituted pyridines in a one-pot fashion.

Pyridine synthesis: A modular, catalytic approach

243rd National Meeting (2012)

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