Visible-Light-Induced Acetalization of Aldehydes with Alcohols

Hong, Yi; Niu, Linbin; Wang, Shengchun; Liu, Tianyi; Singh, Atul K.; Lei, Aiwen

doi:10.1021/acs.orglett.6b03403

Cited by 74 publications

(40 citation statements)

References 42 publications

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“…On the basis of above experiments (Table S1, entries 23-25, (see Supporting Information) and Scheme 3) and some literature reports, [36,37,39] a plausible mechanistic pathway is sketched in Scheme 4. According to this, initially, rose bengal (RB) is excited from its ground state to excited state (RB*) under irradiation of compact 20 W white LED bulb.…”

Section: Full Papermentioning

confidence: 82%

Visible‐Light Mediated Photooxidative Synthesis of α‐Keto Amides

2019

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Photocatalytic amidation of α-keto aldehydes is herein investigated. This transformation was achieved using rose bengal as photocatalyst at room temperature under ambient air and under irradiation of a 20 W white LED bulb. The method is mild, efficient and environmentally benign. This photocatalytic method is compatible with different unsubstituted and substituted α-keto aldehydes having electron-withdrawing or -donating groups, secondary amines, cyclic or acyclic, and primary aliphatic amines. Mechanistic studies reveal that the reaction proceeds via oxidative quenching of the photocatalyst.

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Section: Full Papermentioning

confidence: 82%

Visible‐Light Mediated Photooxidative Synthesis of α‐Keto Amides

2019

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“…19 In that work, a single electron transfer to the thiol was proposed, 19 while in the Eosin-catalyzed process, an energy transfer mechanism was proposed. 15 Following the literature, a variety of solvents were then studied and the quenching of the catalyst presented similar behaviour, so an energy transfer pathway is hinted. 20 This is in accordance with literature evidence that concurs that an electron transfer event is highly unlikely to happen [E ox,thiox = +1.69 V, E red,thiox = −1.62 V, E ox,PhCHO = +2.71 V, E red,PhCHO = −1.93 V].…”

Section: Resultsmentioning

confidence: 99%

Photo-organocatalytic synthesis of acetals from aldehydes

2019

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“…Indeed, these approaches have inherent limitations such as handling of corrosive acid catalyst, high temperature, longer reaction time, and limited substrates scope. In recent times, various catalytic methods including organocatalysts,– photo‐redox catalysts,– and heterogeneous catalysts– and transition‐metal catalysis have been reported in replacement of highly acidic conditions. Nevertheless, these methods require high catalyst loading and harsh reaction conditions.…”

Section: Methodsmentioning

confidence: 99%

Nickel‐Catalyzed Chemoselective Acetalization of Aldehydes With Alcohols under Neutral Conditions

Subaramanian

Landge

Mondal

et al. 2019

Chemistry An Asian Journal

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Am olecularly defined Ni II -complex catalyzing the chemoselective acetalization of aldehydes with alcohols under neutralc onditions is reported. The reactioni s general, efficient and showedawide substrate scope (including aliphatic aldehydes)a sw ell as excellent functional group tolerance. Reusability of the present nickel catalyst is also demonstrated.Development of new catalytic approaches, in particular,c atalysts based on cheap,e arth-abundant, non-precious metalsf or sustainable chemical synthesis is the key motivation in contemporary science. The carbonyl compounds such as aldehydes and ketones are the most significant functional groups in organic synthesis owing to their ubiquitous, andv ersatile reactivity.I nt he multi-stepo rganic transformations,ag reen protocol for the protection or maskingo fc arbonyl compounds that operate under neutralc onditions is highly required. In this regard, acetalization reaction using widespread alcohols hasa ttracted much interest. Acetals serve as an excellent protective group of carbonyl compounds [1] as well as they found various applicationsi nt he synthesis of chiral auxiliaries, steroids, flavoring agents, and pharmaceutical moieties. [2][3][4] In general, acetalization involves the condensation of carbonyl compounds with alcoholic substrates in the presence of Brçnsted/Lewis acid, mineral acid, or base catalysts. [5] However, these protocols often requireatoxic orthoformate as an alcohol source (for acetalization). Indeed,t hese approaches have inherentl imitations such as handling of corrosivea cid catalyst, high temperature, longer reaction time, and limited substrates scope. In recent times, variousc atalytic methods including or-ganocatalysts, [6a-f] photo-redox catalysts, [7a-c] and heterogeneous catalysts [8a-c] and transition-metal catalysis [9] have been reportedi nr eplacement of highly acidic conditions. Nevertheless, these methods require high catalystl oading and harsh reaction conditions.Recently,L yons et al. reported the acetalization of aldehydes in the presence of tropylium salt as organo-Lewisa cidc atalyst using triethyl orthoformate as alcohol source.T his methodr equiresh eating condition, longerr eactiont ime, and an excess amount of Na 2 SO 4 as the dehydrating agent for the cyclic acetalization. [10] Hudnall and co-workers reported antimony(V) catalyzed acetalization of aldehydesi nt he presence of as toichiometrica mount of either triethoxymethane or triethoxysilane, and the products can be purified by distillation processw hich limits the scope of this protocol for thermally stable substrates. [11] However, both of these methods require as toichiometric amount of toxic triethylo rthoformates and triethylo rthoformate/silicate, respectively.T hus, it would be of interest to develop as imple and eco-benign catalystt hat works under neutral and mild reaction conditions and avoid the use of toxic orthoformates. Here, we report am olecularly defined nickel(II) complex catalyzed acetalization of aldehydes using widespread alcohols. The re...

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Visible-Light-Induced Acetalization of Aldehydes with Alcohols

Cited by 74 publications

References 42 publications

Visible‐Light Mediated Photooxidative Synthesis of α‐Keto Amides

Visible‐Light Mediated Photooxidative Synthesis of α‐Keto Amides

Photo-organocatalytic synthesis of acetals from aldehydes

Nickel‐Catalyzed Chemoselective Acetalization of Aldehydes With Alcohols under Neutral Conditions

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