Dearomative C2-borylation of indoles.
Ayesha Begum1, Manjur O Akram1, Caleb D Martin1
1Department of Chemistry and Biochemistry, Baylor University, One Bear Place #97348, Waco, Texas 76798, USA. caleb_d_martin@baylor.edu.
Dalton Transactions (Cambridge, England : 2003)
|March 20, 2025
Summary
We developed a new metal- and base-free method for indole borylation. This approach uses a novel electrophilic borylating reagent under mild conditions, simplifying indole functionalization.
Area of Science:
- Organic Chemistry
- Catalysis
- Synthetic Methodology
Background:
- Dearomative borylation of indoles is synthetically challenging.
- Existing methods often require transition metal catalysts, strong bases, or harsh reaction conditions, limiting their scope and applicability.
Purpose of the Study:
- To develop a novel, metal- and base-free method for the direct C2-borylation of indoles.
- To introduce a new electrophilic borylating reagent for efficient indole functionalization under mild conditions.
Main Methods:
- Utilized bis(1-methyl-ortho-carboranyl)borane as an electrophilic borylating reagent.
- Conducted the C2-borylation of indoles under metal- and base-free conditions.
- Employed mild reaction conditions to promote the desired transformation.
Main Results:
- Achieved metal- and base-free C2-borylation of indoles.
- Successfully generated borylated indolenium species.
- Demonstrated the efficacy of the novel borylating reagent under mild conditions.
Conclusions:
- The reported method offers a facile and mild alternative for the dearomative C2-borylation of indoles.
- This new strategy avoids the need for transition metals and strong bases, expanding synthetic possibilities.
- The use of bis(1-methyl-ortho-carboranyl)borane provides an efficient route to valuable borylated indole derivatives.
More Related Videos
Related Concept Videos
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
5.7K
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the...
5.7K
01:29Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
4.6K
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.
4.6K
02:36Regioselectivity and Stereochemistry of Hydroboration
8.0K
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...
8.0K
02:33Stereoisomerism of Cyclic Compounds
8.6K
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
8.6K
01:28Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
3.7K
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
3.7K
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
2.1K
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
2.1K