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Abstract: One-pot three-component coupling of o-alkynylheteroaryl carbonyl derivatives with α,β-unsaturated Fischer carbene complexes and dimethyl acetylenedicarboxylate leading to the synthesis of heterocyclic analogues of furanophane derivatives has been explored. This involves the generation of conformationally flexible dienylazaisobenzofuran intermediate as transient intermediates, which undergo [8+2] cycloaddition reaction with dienophile. In some cases, this intermediate undergoes twofold Diels–Alder reaction to afford heterolignan derivatives in a single step. [Copyright &y& Elsevier]

One-pot, three-component synthesis of nitrogen-containing polycyclic heterocycles bearing two nitrogen atoms such as quinoxaline, quinazoline, and phenazine derivatives by the coupling of appropriate vicinal alkynylheteroaryl carbonyl derivatives with Fischer carbene complexes and dienophiles has been investigated. This involves the generation of furo[3,4-b]pyrazines, furo[3,4- d]pyrimidines, and furo[3,4-b]quinoxalines as transient intermediates, which were trapped with suitable Diels-Alder dienophiles in an inter- or intramolecular fashion. [ABSTRACT FROM AUTHOR]

Abstract: The coupling of Fischer carbene complexes with 2-alkynyl-3-pyridine carbonyl derivatives has been examined. The reaction affords furo[3,4-b]pyridine as transient intermediates; the latter undergo [4+2] cycloaddition with an electron-deficient dienophile. Acid/base-induced ring opening of the exo-cycloadducts followed by aromatization give substituted quinolines related to heterocyclic analogues of 1-arylnaphthalene lignans. An intramolecular variant of this protocol is also feasible with use of unactivated alkenyl tethers; however, the bridged cycloadducts are unisolable as they undergo spontaneous ring opening to yield alcohol. This method is also useful for the in situ generation of the furo[3,4-b]quinoline intermediate for the first time, which can be trapped with dienophiles. [Copyright &y& Elsevier]

Abstract: The reaction of Fischer carbene complex with o-alkynylpyridine carbonyl derivatives has been investigated. This involves the generation of furo[3,4-c]pyridine as transient intermediates through the coupling of o-alkynylpyridine carbonyl derivatives with carbene complex and subsequent Diels–Alder trapping with suitable dienophiles resulted in the formation of isoquinoline derivatives and the entire sequence can be run in one pot. When an olefinic tether was present, intramolecular Diels–Alder cycloaddition occurred followed by ring opening to yield tricyclic alcohols. [Copyright &y& Elsevier]