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N-Heterocyclic carbene-catalyzed oxidative [3 + 2] annulation of dioxindoles and enals: cross coupling of homoenolate and enolate † † Electronic supplementary information (ESI) available: Experimental procedures and compound characterizations (PDF). CCDC 1041425 ( 3fb ). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc04135c Click here for additional data file. Click here for additional data file.

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ABSTRACT

The N-heterocyclic carbene-catalyzed oxidative [3 + 2] annulation of dioxindole and enals was developed, giving the corresponding spirocyclic oxindole-γ-lactones in good yields with high to excellent diastereo- and enantioselectivities. The challenging aliphatic enals worked effectively using this strategy. The oxidative cross coupling of homoenolate and enolate via single electron transfer was proposed as the key step for the reaction.

No MeSH data available.


Ruled out pathway A by control experiments.
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sch2: Ruled out pathway A by control experiments.

Mentions: A series of control experiments were carried out to clarify the possible reaction pathways (Schemes 2–4). Pathway A, involving the oxidation of dioxindole to isatin followed by annulation with enals was ruled out by the control experiment in which the oxidation of dioxindole 2a′ under the reaction conditions gave only a trace amount of isatin but a majority amount of isatide via homocoupling of the radical of dioxindole (Scheme 2, reaction a).14,15 The formation of isatide was found to be not reversible (Scheme 2, reaction b).


N-Heterocyclic carbene-catalyzed oxidative [3 + 2] annulation of dioxindoles and enals: cross coupling of homoenolate and enolate † † Electronic supplementary information (ESI) available: Experimental procedures and compound characterizations (PDF). CCDC 1041425 ( 3fb ). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc04135c Click here for additional data file. Click here for additional data file.
Ruled out pathway A by control experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384455&req=5

sch2: Ruled out pathway A by control experiments.
Mentions: A series of control experiments were carried out to clarify the possible reaction pathways (Schemes 2–4). Pathway A, involving the oxidation of dioxindole to isatin followed by annulation with enals was ruled out by the control experiment in which the oxidation of dioxindole 2a′ under the reaction conditions gave only a trace amount of isatin but a majority amount of isatide via homocoupling of the radical of dioxindole (Scheme 2, reaction a).14,15 The formation of isatide was found to be not reversible (Scheme 2, reaction b).

View Article: PubMed Central - PubMed

ABSTRACT

The N-heterocyclic carbene-catalyzed oxidative [3 + 2] annulation of dioxindole and enals was developed, giving the corresponding spirocyclic oxindole-γ-lactones in good yields with high to excellent diastereo- and enantioselectivities. The challenging aliphatic enals worked effectively using this strategy. The oxidative cross coupling of homoenolate and enolate via single electron transfer was proposed as the key step for the reaction.

No MeSH data available.