Utilization of methanol for condensation interrupted chemoselective transfer hydrogenation of CC, CO, and CN bonds under low catalyst loading

Sau, Anirban; Mahapatra, Divya; Dey, Sadhan; Panja, Dibyajyoti; Saha, Saghnik; Kundu, Sabuj

doi:10.1039/d3qo00308f

“…The selective transfer hydrogenation of C=C bond in α, β‐unsaturated carbonyl compounds to corresponding saturated ketones using methanol poses significant challenges due to the higher activation barrier for methanol dehydrogenation along with possibilities of other side reactions such as formation of the allylic alcohol or α‐methylated alcohols or α‐methylated ketones (Scheme 1a) [37–41] . Till date, only complexes with the expensive Rh III , Ir III and Ru II were reported for the similar transformation using methanol (Scheme 1b) [42–45] . Hence, developing an inexpensive 3d‐metal based catalytic system for the similar transformation can have great potential in terms of practical applicability towards sustainable synthesis.…”

Section: Introductionmentioning

confidence: 99%

Selective Transfer Hydrogenation of C=O and Conjugated C=C Bonds Using An NHC‐Based Pincer (CNC)Mn^I Complex in Methanol**

Mandal,

Ganguli,

Pradhan

et al. 2023

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Base metal catalyzed transfer hydrogenation reactions using methanol is highly challenging. Employing a single N-heterocyclic carbene (NHC)-based pincer (CNC)Mn I complex, chemoselective single and double transfer hydrogenation of α, βunsaturated ketones to saturated ketones or alcohols by utilizing methanol as the hydrogen source is disclosed. The protocol was tolerant towards the selective transfer hydrogenation of C=C or C=O bonds in the presence of several other reducible functional groups and led to the synthesis of several biologically relevant molecules and natural products. Notably, this is the first report of a Mn-catalyzed transfer hydrogenation of carbonyl groups with methanol. Several control experiments, kinetic studies, Hammett studies, and density functional theory (DFT) calculations were carried out to understand the mechanistic details of this catalytic process.

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Photoredox‐Catalyzed [3+2] annulation of Aromatic Amides with Olefins via Iminium Intermediates

Tang,

Yao,

Yu

et al. 2024

Angewandte Chemie

0

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Despite the preliminary success of transition metal‐catalyzed [3+2] annulation of amides with olefins, the corresponding radical‐type [3+2] annulation remains a laborious challenge. Herein we report the first photoredox‐catalyzed radical‐type [3+2] annulation of aromatic amides with olefins. We established an approach to generate unprecedented iminium radicals by reducing the oxyiminium intermediates, formed in situ from corresponding amides with Tf2O, via photoredox catalysis. The [3+2] annulation was achieved via stepwise radical process, instead of forming linear products via other pathways as previously reported. This annulation protocol exhibits excellent functional group tolerance, and a diversity of substrates are united under the photoredox conditions, affording iminium products that can be in situ diversified into 1‐indanones, enamines and amines. Mechanistic investigations indicate reduction of the oxyiminium intermediate to the iminium radicals by excited‐state of the photocatalyst initiates the catalytic cycle.

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Photoredox‐Catalyzed [3+2] annulation of Aromatic Amides with Olefins via Iminium Intermediates

Tang,

Yao,

Yu

et al. 2024

Angew Chem Int Ed

0

View full text Add to dashboard Cite

Despite the preliminary success of transition metal‐catalyzed [3+2] annulation of amides with olefins, the corresponding radical‐type [3+2] annulation remains a laborious challenge. Herein we report the first photoredox‐catalyzed radical‐type [3+2] annulation of aromatic amides with olefins. We established an approach to generate unprecedented iminium radicals by reducing the oxyiminium intermediates, formed in situ from corresponding amides with Tf2O, via photoredox catalysis. The [3+2] annulation was achieved via stepwise radical process, instead of forming linear products via other pathways as previously reported. This annulation protocol exhibits excellent functional group tolerance, and a diversity of substrates are united under the photoredox conditions, affording iminium products that can be in situ diversified into 1‐indanones, enamines and amines. Mechanistic investigations indicate reduction of the oxyiminium intermediate to the iminium radicals by excited‐state of the photocatalyst initiates the catalytic cycle.

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Utilization of methanol for condensation interrupted chemoselective transfer hydrogenation of CC, CO, and CN bonds under low catalyst loading

Abstract: Selective transfer hydrogenation (TH) of unsaturated molecules using methanol is challenging as the in situ generated formaldehyde is prone to react with the active methylene (C-methylation) or amine (N-methylation) core...

Cited by 9 publications

References 57 publications

Selective Transfer Hydrogenation of C=O and Conjugated C=C Bonds Using An NHC‐Based Pincer (CNC)Mn^I Complex in Methanol**

Selective Transfer Hydrogenation of C=O and Conjugated C=C Bonds Using An NHC‐Based Pincer (CNC)Mn^I Complex in Methanol**

Photoredox‐Catalyzed [3+2] annulation of Aromatic Amides with Olefins via Iminium Intermediates

Photoredox‐Catalyzed [3+2] annulation of Aromatic Amides with Olefins via Iminium Intermediates

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Utilization of methanol for condensation interrupted chemoselective transfer hydrogenation of CC, CO, and CN bonds under low catalyst loading

Abstract: Selective transfer hydrogenation (TH) of unsaturated molecules using methanol is challenging as the in situ generated formaldehyde is prone to react with the active methylene (C-methylation) or amine (N-methylation) core...

Cited by 9 publications

References 57 publications

Selective Transfer Hydrogenation of C=O and Conjugated C=C Bonds Using An NHC‐Based Pincer (CNC)MnI Complex in Methanol**

Selective Transfer Hydrogenation of C=O and Conjugated C=C Bonds Using An NHC‐Based Pincer (CNC)MnI Complex in Methanol**

Photoredox‐Catalyzed [3+2] annulation of Aromatic Amides with Olefins via Iminium Intermediates

Photoredox‐Catalyzed [3+2] annulation of Aromatic Amides with Olefins via Iminium Intermediates

Contact Info

Product

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Selective Transfer Hydrogenation of C=O and Conjugated C=C Bonds Using An NHC‐Based Pincer (CNC)Mn^I Complex in Methanol**

Selective Transfer Hydrogenation of C=O and Conjugated C=C Bonds Using An NHC‐Based Pincer (CNC)Mn^I Complex in Methanol**