Synthesis of azahomosteroid ring system through intramolecular [4+2] cycloaddition of in situ generated azaisobenzofuran intermediates

Azahomosteroid ring systems were synthesized through two-component coupling of γ,δ-unsaturated Fischer carbene complexes with o-alkynylheteroaryl carbonyl derivatives. The reaction occurs through the formation of azaisobenzofuran as transient intermediate; the latter undergoes a subsequent Diels–Alder cycloaddition reaction with in-built dienophile with high regio- and stereoselectivity.