This review article gives an update on the metal‐free photocatalyzed and photocatalyzed‐free α‐C−... more This review article gives an update on the metal‐free photocatalyzed and photocatalyzed‐free α‐C−H functionalizations of tertiary amines promoted by visible light. C−H activation is one of the easiest and step‐economic strategies to functionalize the α‐C−H bond of tertiary amines. Various important nitrogen heterocycles having biological significance can be synthesized using α‐C−H functionalization of tertiary amines. In addition to thermal reactions, many such reactions have been reported using visible light as it is abundant, renewable and green alternative for organic transformations. However, the high price of transition metal photocatalyst prevents its use. In contrast, organic photocatalysts are inexpensive, environment friendly and easy to handle. Therefore, visible‐light‐promoted metal‐free photoredox catalysis (or photocatalyst‐free reactions) is being used recently. Although several research articles have been published in this area, no review articles have been reported recently. Here, we have discussed the reactions from the year 2011 to till date with concise discussion about their plausible mechanisms. We believe that the content of this review will guide the readers to develop more such visible‐light‐promoted reactions using metal‐free photocatalysts or avoiding catalysts if possible.
European Journal of Organic Chemistry, Jul 19, 2023
A novel I2‐DMSO‐mediated cascade cyclization approach for synthesizing 2‐hydroxy‐pyrrol‐3(2H)‐one... more A novel I2‐DMSO‐mediated cascade cyclization approach for synthesizing 2‐hydroxy‐pyrrol‐3(2H)‐one scaffold from readily accessible β‐ketosulfoxonium ylides and β‐enaminone derivatives has been developed. Under metal‐free and mild conditions, this cascade transformation facilitates the formation of one C−C bond and one C−N bond in a single reaction vessel, exhibiting a wide range of functional group compatibility. In addition, this method added an active hydroxyl group to a quaternary carbon center.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract Here we disclose an iodine- tert -butylhydroperoxide promoted intramolecular sp 3 C–H ox... more Abstract Here we disclose an iodine- tert -butylhydroperoxide promoted intramolecular sp 3 C–H oxygenation α- to tertiary amine for the synthesis of 1,3-oxazines. The reaction is metal-free, atom economic, high yielding and proceeds within a short time under heating at 130 °C in DMF solvent. A variety of Betti bases of naphthol and phenol having cyclic as well as acyclic tert -amine moieties are employed as the starting materials. The Betti bases of naphthol produce single diastereomer of oxazine, whereas phenolic Betti bases give diastereomeric mixture. The mechanistic investigation suggests the non-radical pathway involving “I + ” as the active catalytic species. The method gives excellent yield on multigram scale reaction.
Here we report a metal‐free iodine/tert‐butyl hydroperoxide mediated reaction of N‐substituted in... more Here we report a metal‐free iodine/tert‐butyl hydroperoxide mediated reaction of N‐substituted indoles with dimethylformamide (DMF) / dimethylacetamide (DMA). The reaction produces bis‐ and tris(indolyl)methanes (BIMs and TIMs), in which DMF/DMA provides the methylene (of BIMs) and methine carbons (of TIMs). We have established different optimized conditions for their synthesis. Iodine (10 mol %) with TBHP (in decane, 1.0 equivalent) in DMF/DMA at 130 °C is required for the BIMs synthesis, whereas iodine (20 mol %) with TBHP (in water, 3.0 equivalent) in DMF‐H2O or DMA‐H2O (9:1) is needed for the TIMs. This methodology could be used to synthesize a variety of BIMs and TIMs. We believe, this is the first report of their metal‐free synthesis through C−H functionalization using one carbon source. The use of inexpensive, metal‐free and environmentally benign catalyst made the method handy.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
A recent review on the α-C–H functionalization of tertiary amines using low-cost and benign I2 or... more A recent review on the α-C–H functionalization of tertiary amines using low-cost and benign I2 or its derivatives.
This review presents the construction of C–X bonds (X = O/N/S) by using intramolecular C–H functi... more This review presents the construction of C–X bonds (X = O/N/S) by using intramolecular C–H functionalization for the synthesis of heterocyclic compounds.
Visible-light-promoted reactions have proven to be a decent strategy for the synthesis of complex... more Visible-light-promoted reactions have proven to be a decent strategy for the synthesis of complex molecules.
A copper-catalyzed benzoylation/formylation of naphthols and phenols via oxidative deamination of... more A copper-catalyzed benzoylation/formylation of naphthols and phenols via oxidative deamination of Betti bases.
This review article gives an update on the metal‐free photocatalyzed and photocatalyzed‐free α‐C−... more This review article gives an update on the metal‐free photocatalyzed and photocatalyzed‐free α‐C−H functionalizations of tertiary amines promoted by visible light. C−H activation is one of the easiest and step‐economic strategies to functionalize the α‐C−H bond of tertiary amines. Various important nitrogen heterocycles having biological significance can be synthesized using α‐C−H functionalization of tertiary amines. In addition to thermal reactions, many such reactions have been reported using visible light as it is abundant, renewable and green alternative for organic transformations. However, the high price of transition metal photocatalyst prevents its use. In contrast, organic photocatalysts are inexpensive, environment friendly and easy to handle. Therefore, visible‐light‐promoted metal‐free photoredox catalysis (or photocatalyst‐free reactions) is being used recently. Although several research articles have been published in this area, no review articles have been reported recently. Here, we have discussed the reactions from the year 2011 to till date with concise discussion about their plausible mechanisms. We believe that the content of this review will guide the readers to develop more such visible‐light‐promoted reactions using metal‐free photocatalysts or avoiding catalysts if possible.
European Journal of Organic Chemistry, Jul 19, 2023
A novel I2‐DMSO‐mediated cascade cyclization approach for synthesizing 2‐hydroxy‐pyrrol‐3(2H)‐one... more A novel I2‐DMSO‐mediated cascade cyclization approach for synthesizing 2‐hydroxy‐pyrrol‐3(2H)‐one scaffold from readily accessible β‐ketosulfoxonium ylides and β‐enaminone derivatives has been developed. Under metal‐free and mild conditions, this cascade transformation facilitates the formation of one C−C bond and one C−N bond in a single reaction vessel, exhibiting a wide range of functional group compatibility. In addition, this method added an active hydroxyl group to a quaternary carbon center.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract Here we disclose an iodine- tert -butylhydroperoxide promoted intramolecular sp 3 C–H ox... more Abstract Here we disclose an iodine- tert -butylhydroperoxide promoted intramolecular sp 3 C–H oxygenation α- to tertiary amine for the synthesis of 1,3-oxazines. The reaction is metal-free, atom economic, high yielding and proceeds within a short time under heating at 130 °C in DMF solvent. A variety of Betti bases of naphthol and phenol having cyclic as well as acyclic tert -amine moieties are employed as the starting materials. The Betti bases of naphthol produce single diastereomer of oxazine, whereas phenolic Betti bases give diastereomeric mixture. The mechanistic investigation suggests the non-radical pathway involving “I + ” as the active catalytic species. The method gives excellent yield on multigram scale reaction.
Here we report a metal‐free iodine/tert‐butyl hydroperoxide mediated reaction of N‐substituted in... more Here we report a metal‐free iodine/tert‐butyl hydroperoxide mediated reaction of N‐substituted indoles with dimethylformamide (DMF) / dimethylacetamide (DMA). The reaction produces bis‐ and tris(indolyl)methanes (BIMs and TIMs), in which DMF/DMA provides the methylene (of BIMs) and methine carbons (of TIMs). We have established different optimized conditions for their synthesis. Iodine (10 mol %) with TBHP (in decane, 1.0 equivalent) in DMF/DMA at 130 °C is required for the BIMs synthesis, whereas iodine (20 mol %) with TBHP (in water, 3.0 equivalent) in DMF‐H2O or DMA‐H2O (9:1) is needed for the TIMs. This methodology could be used to synthesize a variety of BIMs and TIMs. We believe, this is the first report of their metal‐free synthesis through C−H functionalization using one carbon source. The use of inexpensive, metal‐free and environmentally benign catalyst made the method handy.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
A recent review on the α-C–H functionalization of tertiary amines using low-cost and benign I2 or... more A recent review on the α-C–H functionalization of tertiary amines using low-cost and benign I2 or its derivatives.
This review presents the construction of C–X bonds (X = O/N/S) by using intramolecular C–H functi... more This review presents the construction of C–X bonds (X = O/N/S) by using intramolecular C–H functionalization for the synthesis of heterocyclic compounds.
Visible-light-promoted reactions have proven to be a decent strategy for the synthesis of complex... more Visible-light-promoted reactions have proven to be a decent strategy for the synthesis of complex molecules.
A copper-catalyzed benzoylation/formylation of naphthols and phenols via oxidative deamination of... more A copper-catalyzed benzoylation/formylation of naphthols and phenols via oxidative deamination of Betti bases.
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Papers by Paran Jyoti Borpatra