Concise synthesis of the bioactive natural polyhydroxynaphthoate parvinaphthol B via Hauser-Kraus annulation

Assembly of multicyclic isoquinoline scaffolds from pyridines: formal total synthesis of fredericamycin A

The construction of an isoquinoline skeleton typically starts with benzene derivatives as substrates with the assistance of acids or transition metals. Disclosed here is a concise approach to prepare isoquinoline analogues by starting with pyridines to react with β-ethoxy α,β-unsaturated carbonyl compounds under basic conditions. Multiple substitution patterns and a relatively large number of functional groups (including those sensitive to acidic conditions) can be tolerated in our method. In particular, our protocol allows for efficient access to tricyclic isoquinolines found in hundreds of natural products with interesting bioactivities. The efficiency and operational simplicity of introducing structural complexity into the isoquinoline frameworks can likely enable the collective synthesis of a large set of natural products. Here we show that fredericamycin A could be obtained via a short route by using our isoquinoline synthesis as a key step.

A concise approach for rapid assembly of multicyclic isoquinoline scaffolds from pyridines and β-ethoxy α,β-unsaturated carbonyl compounds was developed, which enabled the formal total synthesis of fredericamycin A.

Annulations with Butenolides and Phthalides: New Entries to Isocoumarins, 3,4-Dihydroisocoumarins, and Benzofurans

The reactions of the anions of butenolides and substituted phthalides with sorbate esters and mono-epoxy sorbate esters furnish isocoumarins, 3,4-dihydroisocoumarins, and benzofurans. The yields range from 41% to 71%.

Synthesis of indenofurans, benzofurans and spiro-lactones via Hauser–Kraus annulation involving 1,6-addition of phthalide to quinone methides

Base mediated 1,6-addition–Dieckmann cyclization of phthalide with quinone methide leads to oxygen heterocycles such as indenofurans, spiro-lactones and benzofurans through a cascade of rearrangements involving multiple ring opening and ring closure.

Synthesis of Spiro- and Fused Heterocycles via (4+4) Annulation of Sulfonylphthalide with o-Hydroxystyrenyl Derivatives

An expedient one-pot protocol for the synthesis of functionalized benzofuran containing fused and spiro-heterocycles has been accomplished by the modified Hauser-Kraus (HK) annulation of sulfonylphthalide with o-hydroxychalcones and o-hydroxynitrostyrylisoxazoles. The multicascade process involves Michael addition, Dieckmann cyclization, and a series of cyclizations, eliminations, and rearrangements to deliver the fused and spiro-heterocyclic products. An unusual transformation of fused indenofuran to naphthoquinone, the classical HK adduct, unraveled a novel pathway for the synthesis unsymmetrical naphthoquinones.