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Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp 2 C – H and sp 3 C – H bonds

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ABSTRACT

The synthesis of a variety of 2-oxindoles bearing an all-carbon quaternary center at the pseudo benzylic position has been achieved via a ‘transition-metal-free’ intramolecular dehydrogenative coupling (IDC). The construction of 2-oxindole moieties was carried out through formation of carbon–carbon bonds using KOt-Bu-catalyzed one pot C-alkylation of β-N-arylamido esters with alkyl halides followed by a dehydrogenative coupling. Experimental evidences indicated toward a radical-mediated path for this reaction.

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Synthesis of spirocyclic product through IDC The synthesis of 14 as per method A has been reproduced from reference [46]. Conditions A: KOt-Bu, iodine; conditions B: KOt-Bu, NIS.
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C3: Synthesis of spirocyclic product through IDC The synthesis of 14 as per method A has been reproduced from reference [46]. Conditions A: KOt-Bu, iodine; conditions B: KOt-Bu, NIS.

Mentions: Our synthetic methodology was further explored in the construction of spiro-fused oxindole ring systems (Scheme 3). The spiro-fused oxindoles such as coerulescine (15a) [68–72], horsfiline (15b) [73], and elacomine (16), are prevalently found in a huge number of indole-based alkaloids having analgesic properties. Our oxidative methodology offered us a direct access to the core structures of these alkaloids under the optimized IDC conditions in high yields (Scheme 3).


Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp 2 C – H and sp 3 C – H bonds
Synthesis of spirocyclic product through IDC The synthesis of 14 as per method A has been reproduced from reference [46]. Conditions A: KOt-Bu, iodine; conditions B: KOt-Bu, NIS.
© Copyright Policy - Beilstein
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4979638&req=5

C3: Synthesis of spirocyclic product through IDC The synthesis of 14 as per method A has been reproduced from reference [46]. Conditions A: KOt-Bu, iodine; conditions B: KOt-Bu, NIS.
Mentions: Our synthetic methodology was further explored in the construction of spiro-fused oxindole ring systems (Scheme 3). The spiro-fused oxindoles such as coerulescine (15a) [68–72], horsfiline (15b) [73], and elacomine (16), are prevalently found in a huge number of indole-based alkaloids having analgesic properties. Our oxidative methodology offered us a direct access to the core structures of these alkaloids under the optimized IDC conditions in high yields (Scheme 3).

View Article: PubMed Central - HTML - PubMed

ABSTRACT

The synthesis of a variety of 2-oxindoles bearing an all-carbon quaternary center at the pseudo benzylic position has been achieved via a ‘transition-metal-free’ intramolecular dehydrogenative coupling (IDC). The construction of 2-oxindole moieties was carried out through formation of carbon–carbon bonds using KOt-Bu-catalyzed one pot C-alkylation of β-N-arylamido esters with alkyl halides followed by a dehydrogenative coupling. Experimental evidences indicated toward a radical-mediated path for this reaction.

No MeSH data available.


Related in: MedlinePlus