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

An unprecedented reactivity of 3-sulfonylphthalide with 2-hydroxyaryl-p-quinone methides (HQMs) is reported here. A cascade of reactions starting with 1,6-addition and Dieckmann cyclization produced a diverse array of indenofurans and benzofurans in high yields, depending on the amount of base used,...

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Bibliographic Details
Published in:	Organic & biomolecular chemistry 2020-07, Vol.18 (29), p.5677-5687
Main Authors:	Basu, Pallabita, Satam, Nishikant, Namboothiri, Irishi N N
Format:	Article
Language:	eng
Subjects:	Bioactive compounds Cascade chemical reactions Chemical reactions Crystallography Lactones Natural products NMR Nuclear magnetic resonance Oxidation Quinones
Online Access:	Request full text
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Summary:	An unprecedented reactivity of 3-sulfonylphthalide with 2-hydroxyaryl-p-quinone methides (HQMs) is reported here. A cascade of reactions starting with 1,6-addition and Dieckmann cyclization produced a diverse array of indenofurans and benzofurans in high yields, depending on the amount of base used, presumably via a common 8-membered ketolactone intermediate. The indenofurans could be transformed to benzofurans in the presence of excess base via a key spiro-lactone intermediate, which could be characterized via in situ oxidation to a stable spirolactone linked quinone methide, providing crucial evidence for the mechanism of the reaction. The three diverse oxygen heterocycles synthesized by our methodology constitute the core structure of several bioactive compounds including natural products.
ISSN:	1477-0520 1477-0539