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One-Pot Synthesis of Highly Substituted N-Fused Heteroaromatic Bicycles from Azole Aldehydes
- Outlaw, Victor
K., d’Andrea, Felipe B., Townsend, Craig A.
- Organic letters 2015 v.17 no.8 pp. 1822-1825
- Lewis acids, aldehydes, alkylation, chemical structure, indolizines, pyridines, synthesis
- An efficient route to substituted N-fused aromatic heterocycles, including indolizines, imidazo[1,2-a]pyridines, and imidazo[1,5-a]pyridines from azole aldehydes, is reported. Wittig olefination of the aldehydes with fumaronitrile and triethylphosphine affords predominantly E-alkenes that undergo rapid cyclization upon treatment with a mild base. Substituent control of the 1-, 2-, and 3-positions of the resulting heteroaromatic bicycles is shown. Alternatively, the isolable E-alkene undergoes selective alkylation with electrophiles, followed by in situ annulation to indolizines additionally substituted at the 6-position.