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Thermal Hetero-Diels-Alder Reaction of Benzocyclobutenones with Isatins To Form 2-Oxindole Spirolactones.

ABSTRACT: Benzocyclobutenones 1a-1g undergo cycloreversion at 150 °C in m-xylene solvent to form transient ?-oxo-ortho-quinodimethanes or "ortho-quinoid ketene methides", which engage in intermolecular [4+2] cycloadditions with isatins 2a-2f to form 2-oxindole spirolactones 3a-3l. This process tolerates an array of different functional groups and substitution patterns, and is applicable to unprotected isatins 2b-2f bearing free NH-functionalities. The superior performance of isatins compared to other carbonyl based dienophiles was demonstrated and rationalized with the aid of quantum chemical calculations.

SUBMITTER: Wurm T

PROVIDER: S-EPMC5757836 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Thermal Hetero-Diels-Alder Reaction of Benzocyclobutenones with Isatins To Form 2-Oxindole Spirolactones.

Wurm Thomas T Turnbull Ben W H BWH Ambler Brett R BR Krische Michael J MJ

The Journal of organic chemistry 20171122 24

Benzocyclobutenones 1a-1g undergo cycloreversion at 150 °C in m-xylene solvent to form transient α-oxo-ortho-quinodimethanes or "ortho-quinoid ketene methides", which engage in intermolecular [4+2] cycloadditions with isatins 2a-2f to form 2-oxindole spirolactones 3a-3l. This process tolerates an array of different functional groups and substitution patterns, and is applicable to unprotected isatins 2b-2f bearing free NH-functionalities. The superior performance of isatins compared to other carb ...[more]

PMID: 29164878

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