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1.
Org Lett ; 26(27): 5752-5757, 2024 Jul 12.
Article in English | MEDLINE | ID: mdl-38949643

ABSTRACT

A new self-cyclopropanation of 1,3-diphenylpropane-1,3-dione, leading to tetrasubstituted cyclopropane containing three contiguous stereogenic centers with high stereoselectivity, has been achieved through violet-light-emitting diode-irradiated photocatalysis, featuring both cycloaddition and a distinctive rearrangement. Diverging from conventional cyclopropanation pathways, this reaction yields a tetrasubstituted cyclopropane through unprecedented rearrangement and cascade reactions.

2.
Org Biomol Chem ; 22(19): 3799-3842, 2024 May 15.
Article in English | MEDLINE | ID: mdl-38651982

ABSTRACT

Tetrabutylammonium decatungstate (TBADT) has recently emerged as an intriguing photocatalyst under visible-light or near-visible-light irradiation in a wide range of organic reactions that were previously not conceivable. Given its ability to absorb visible light and excellent effectiveness in activating unactivated chemical bonds, it is a promising addition to traditional photocatalysts. This review covers some of the contemporary developments in visible-light or near-visible-light photocatalysis reactions enabled by the TBADT catalyst to 2023, with the contents organized by reaction type.

3.
Org Biomol Chem ; 21(47): 9330-9336, 2023 Dec 06.
Article in English | MEDLINE | ID: mdl-37987508

ABSTRACT

A new thioxanthone-based photocatalyst with a [2.2]paracyclophane skeleton and planar chirality has been developed. The catalyst has been successfully applied in the visible light-mediated enantioselective aza Paternò-Büchi reactions of quinoxalinone and styrenes to produce azetidines. The structures of the catalyst derivatives were unequivocally determined by their single crystal X-ray crystallography analysis.

4.
Org Biomol Chem ; 21(20): 4200-4205, 2023 May 24.
Article in English | MEDLINE | ID: mdl-37132457

ABSTRACT

A series of iridoids, including iridomyrmecin A, B, C', D', (-)-isoiridomyrmecin, (+)-7-epi-boschnialactone, and the inside-yohimbine analogues have been synthesized from readily available, naturally occurring (-)-citronellal via the key step reaction of metathesis, organocatalysis, and subsequent transformations, such as reduction, lactonization, alkylation, Pictet-Spengler reaction and lactamization. Notably, the use of DBU as an additive in the organocatalytic intramolecular Michael reaction of an aldehyde ester with Jørgensen-Hayashi catalysts resulted in better stereoselectivity than the conditions using acetic acid as an additive. The structures of three products have been unequivocally established with single-crystal X-ray crystallographic analyses.

5.
Org Lett ; 24(28): 5155-5160, 2022 Jul 22.
Article in English | MEDLINE | ID: mdl-35802069

ABSTRACT

An intriguing stereoselective visible-light photocatalysis of dihydroquinoxalinone derivatives has been realized via cyclization with or without the solvolysis cascade. The reactions provided the polycyclic ring structures with efficient formation of multiple bonds and with high stereoselectivity. X-ray crystallography unequivocally determined the structures of five polycyclic products.

6.
Org Lett ; 24(18): 3353-3357, 2022 05 13.
Article in English | MEDLINE | ID: mdl-35499378

ABSTRACT

First total synthesis of ulodione A has been achieved via the key-step reactions of DIPEA-promoted dialkytion of 1,3-cyclopentadione with a bromonitroolefin and DABCO promoted/catalytic semipinacol-like ring-expansion rearrangement, with regioselective transformation of the nitrocyclohexane intermediates to their cyclopentenone counterparts via a sequence of reactions in a one-pot operation. Structures of six products were unequivocally established by X-ray crystallography.


Subject(s)
Piperazines , Alkylation , Catalysis , Molecular Structure
7.
Org Biomol Chem ; 20(16): 3292-3302, 2022 04 20.
Article in English | MEDLINE | ID: mdl-35388394

ABSTRACT

Using a visible-light photoredox catalysis strategy with household decorative blue LEDs and the additives Et3N and DIPEA, as well as the subsequent hydrolysis sequence, a mild one-pot process for the direct transformation of nitroalkanes to the corresponding ketones and aldehydes, constituting a Nef-like reaction, has been developed. It is worth noting that by using an appropriate photocatalyst (e.g., [Ir(dtbbpy)(ppy)2]PF6) and the extra additive Et3N with the combination of DIPEA and Mg(ClO4)2 in i-PrOH (instead of CH3CN), the transformation of nitroalkanes to the corresponding oximes, rather than nitrones, can be markedly more effective. The oximes can then be hydrolyzed to ketones by reaction with CuCl2·2H2O in a pH 7 buffer solution. This process is appealing because of the benefits of efficient conversion, mild conditions, high yields, and general applicability to compounds with a wide range of labile functional groups.


Subject(s)
Aldehydes , Ketones , Aldehydes/chemistry , Alkanes , Catalysis , Hydrolysis , Ketones/chemistry , Molecular Structure , Nitro Compounds/chemistry , Oximes/chemistry
8.
Org Lett ; 23(12): 4688-4693, 2021 06 18.
Article in English | MEDLINE | ID: mdl-34048266

ABSTRACT

The organocatalytic α-alkylation of vinylogous carbonyl compounds to hydroxynitroolefins for the synthesis of hemiacetals was realized with excellent enantioselectivities and in high yields. High diastereoselectivity (up to >20:1) has been accomplished with the addition of Et3N. The α- and γ-alkylation of vinylogous ketone against nitroolefins displayed high but opposite facial selectivities. Transformation of the hemiacetal products to other polycyclic compounds, including the euroticin B analog, has been demonstrated.

9.
Org Biomol Chem ; 18(32): 6247-6252, 2020 08 19.
Article in English | MEDLINE | ID: mdl-32735638

ABSTRACT

Incorporation of water has been revealed to successfully facilitate visible-light photoredox catalysis of indole leading to increased production of C2-quaternary indolinone. The water-promoted photoreaction of indole under catalyst-free conditions by a household compact fluorescence light was also demonstrated. The antiproliferative activity of the synthesized indolinones was evaluated against three human cancer cell lines.


Subject(s)
Antineoplastic Agents/pharmacology , Indoles/pharmacology , Light , Water/chemistry , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Catalysis , Cell Line, Tumor , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Humans , Indoles/chemical synthesis , Indoles/chemistry , Molecular Structure , Oxidation-Reduction , Photochemical Processes , Structure-Activity Relationship
10.
Org Biomol Chem ; 2020 May 27.
Article in English | MEDLINE | ID: mdl-32458948

ABSTRACT

Enantioselective photoreaction has been a synthetic challenge for decades. With the continuous development of modern visible light photocatalysis and asymmetric catalysis, remarkable advances have been achieved through the synergistic action of these catalytic reactions, allowing the construction of various enantiomerically enriched molecules that were once inaccessible using photocatalytic reactions. This review presents some of the contemporary developments in enantioselective visible-light photocatalysis reactions, covering the period from 2008 to March 2020, with the contents classified by catalysis type.

11.
Org Lett ; 22(1): 62-67, 2020 01 03.
Article in English | MEDLINE | ID: mdl-31829018

ABSTRACT

New types of organocatalytic 1,2-rearrangements, which resemble the Smiles-like or semi-pinacol-like rearrangement, of Michael adducts of 1,3-dicarbonyl-2-alkyl compounds and nitroalkenes have been realized. Unlike the well-known conjugate addition, the reaction affords the 1-phenyl-1-nitroalkanes via unprecedented rearrangement and cascade reactions. Structures of the appropriate products were unambiguously characterized by X-ray crystallography.

12.
Org Lett ; 21(19): 7750-7754, 2019 10 04.
Article in English | MEDLINE | ID: mdl-31513414

ABSTRACT

A mild and convenient process for direct transformation of nitroalkanes to the corresponding nitriles was developed using a visible-light photoredox catalysis strategy with household decorative blue LEDs and the additives of Et3N and DIPIBA (or DIPEA). Application of the process in secondary nitroalkanes bearing a ß-alcohol resulted in a domino process of the retro-Henry reaction and the subsequent acetalization, aldol, cyanohydrin, and ring-contraction reactions with stereoselectivities. The photocatalytic reaction was demonstrated by a continuous flow method.

13.
ACS Omega ; 4(1): 655-667, 2019 Jan 31.
Article in English | MEDLINE | ID: mdl-31459355

ABSTRACT

An enantioselective domino Michael-Michael reaction of nitroolefins and 2-nitro-3-arylacrylates has been established, which provided a series of spirocyclopentane oxindoles with four consecutive stereocenters including quaternary α-nitro esters with good yields (up to 73%) and excellent enantioselectivities (up to 97% ee). The reaction was realized and optimized with the aid of a chiral squaramide-amine catalyst. The structures of 11 products were confirmed by single-crystal X-ray diffraction analysis.

14.
J Org Chem ; 84(18): 12138-12147, 2019 09 20.
Article in English | MEDLINE | ID: mdl-31291725

ABSTRACT

An efficient and one-pot method has been developed for the enantioselective synthesis of pentacyclic indole derivatives with the yohimbane skeleton via a sequence of asymmetric Michael-Michael-Mannich-reduction-amidation-Bischler-Napieralski-reduction reactions with a high diastereoselectivity and high enantioselectivities (up to >99% ee). The seven-step reaction sequence, which generates five bonds and five stereocenters, can be conducted with a pot-economic synthetic strategy and one-pot operation in good yields. The structure and absolute stereochemistry of two products were confirmed by X-ray crystallography analysis.

15.
Org Lett ; 20(24): 7835-7839, 2018 12 21.
Article in English | MEDLINE | ID: mdl-30525690

ABSTRACT

The first regioselective, diastereoselective, and enantioselective organocatalyzed Michael-Michael cascade of vinylogous ketone enolates and nitroalkenes for the construction of fully substituted cyclobutanes is achieved by the deployment of the appropriate chiral squaramide catalyst and the pertinent substituent on the substrate. The domino reaction provided cyclobutanes with four contiguous stereocenters, including a quaternary center in good yields with diastereomeric ratio of >20:1 and with enantioselectivities of mostly up to 98% enantiomeric excess (ee). The structures and the absolute configurations of the adducts were confirmed by single-crystal X-ray crystallographic analyses of the appropriate products.

16.
Bioorg Chem ; 81: 504-511, 2018 12.
Article in English | MEDLINE | ID: mdl-30245232

ABSTRACT

The nuclear factor-κB (NF-κB) plays an important role in inflammatory and immune responses. Aberrant NF-κB signaling is implicated in multiple disorders, including cancer. Targeting the regulatory scaffold subunit IκB kinase γ (IKKγ/NEMO) as therapeutic interventions could be promising due to its specific involvement in canonical NF-κB activation without interfering with non-canonical signaling. In this study, the use of unnatural amino acid substituted IKKß with unique photophysical activity to sense water environment changes upon interaction with NEMO provides a powerful in vitro screening platform that would greatly facilitate the identification of compounds having the potential to disrupt IKKß-NEMO interaction, and thus specifically modulate the canonical NF-κB pathway. We then utilized a competitive binding platform to screen the binding ability of a number of potential molecules being synthesized. Our results suggest that a lead compound (-)-PDC-099 is a potent agent with ascertained potency to disrupt IKKß-NEMO complex for modulating NF-κB canonical pathway.


Subject(s)
Drug Evaluation, Preclinical/methods , Fluorescent Dyes/chemistry , I-kappa B Kinase/metabolism , Peptides/chemistry , Protein Interaction Maps/drug effects , Tryptophan/analogs & derivatives , Aza Compounds/chemistry , Aza Compounds/metabolism , Fluorescent Dyes/metabolism , Humans , I-kappa B Kinase/antagonists & inhibitors , I-kappa B Kinase/chemistry , Models, Molecular , Peptides/metabolism , Tryptophan/metabolism
17.
RSC Adv ; 8(35): 19580-19584, 2018 May 25.
Article in English | MEDLINE | ID: mdl-35540997

ABSTRACT

A convenient photocatalyzed oxidative coupling reaction of 4-alkyl-3,4-dihydroquinoxalin-2(1H)-one and its derivatives with a variety of nucleophiles was developed with a ruthenium photoredox catalyst and oxygen under a household compact fluorescent light. With a slower reaction rate, the cross coupling transformation can be achieved in the absence of an external photocatalyst with a similar isolated yield. An application to the synthesis of natural product cephalandole A was also demonstrated.

18.
Org Lett ; 19(22): 6112-6115, 2017 11 17.
Article in English | MEDLINE | ID: mdl-29090937

ABSTRACT

An organocatalyzed enantioselective Michael-Michael-Michael-aldol cascade reaction for the construction of cyclopentane fused spirooxindoles was achieved. The domino reaction provided the spirooxindoles with six contiguous stereocenters including a quaternary center in good yields (55-64%) with excellent enantioselectivities (up to >99% ee). Enantioselective Michael-Michael-Michael-aldol condensation-aromatization reactions of an isomeric product were observed.

19.
J Org Chem ; 82(23): 12840-12848, 2017 12 01.
Article in English | MEDLINE | ID: mdl-29065686

ABSTRACT

A domino reaction with the organocatalytic enantioselective Michael-acetalization-Henry reaction of 2-hydroxynitrostyrene and 5-oxohexanal was developed for the synthesis of hexahydro-6H-benzo[c]chromenones with four consecutive stereogenic centers and high enantioselectivity (up to >99% ee). The transformation of a NaBH4-reduced adduct to the aflatoxin system via the Nef-cyclization process was achieved by the assistant of ZnBr2.


Subject(s)
Acetals/chemistry , Aflatoxins/chemistry , Chromones/chemistry , Hydroxy Acids/chemistry , Nitro Compounds/chemistry , Styrene/chemistry , Catalysis , Molecular Structure , Organic Chemicals , Stereoisomerism
20.
Org Lett ; 19(13): 3494-3497, 2017 07 07.
Article in English | MEDLINE | ID: mdl-28608693

ABSTRACT

An efficient method has been developed for the enantioselective synthesis of the aflatoxin system with multiple stereocenters via a sequence of organocatalytic Michael-acetalization-reduction-Nef reactions that proceed with high enantioselectivities (90-99% ee). The one-pot reaction sequence provides a facile entry to the aflatoxin system, including dihydroaflatoxin D2, which includes a formal total synthesis of aflatoxin B2. The first total synthesis of (-)- and (+)-microminutinin was also achieved via this protocol.


Subject(s)
Aflatoxins/chemistry , Catalysis , Molecular Structure , Stereoisomerism
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