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1.
Org Lett ; 24(41): 7527-7532, 2022 Oct 21.
Article in English | MEDLINE | ID: mdl-36207146

ABSTRACT

A Ni(II)/bisoxazoline-catalyzed asymmetric dearomative [3+2] cycloaddition of substituted purines with donor-acceptor oxiranes was developed. This reaction, which proceeds via highly chemoselective C-C bond cleavage of the oxiranes, accesses chiral purino[3,2-c]oxazole compounds (≤99% ee after enrichment via crystallization). The electronic effects of the purine ring determine the reactivity of the substrate. The general applicability of this method was illustrated by gram-scale synthesis, the diverse transformations of the product, and the promising biological activities of selected derivatives.


Subject(s)
Epoxy Compounds , Oxazoles , Cycloaddition Reaction , Epoxy Compounds/chemistry , Oxazoles/chemistry , Stereoisomerism , Catalysis , Ethylene Oxide , Purines/chemistry
2.
J Org Chem ; 87(21): 14284-14298, 2022 11 04.
Article in English | MEDLINE | ID: mdl-36240155

ABSTRACT

A Pd/phase-transfer catalyst cooperatively catalyzed domino Heck/allylation reaction is first reported, which represents interesting substrate-dependent regioselectivity. Under the same conditions, Ts-protected N-(2-iodophenyl)allenamides produced only linear allylation products, while Cbz, Ac, or Boc-protected N-(2-iodophenyl)allenamides and N-(2-iodobenzoyl)allenamides with various compounds generated branch allylation products with an exocylic C═C bond and two vicinal stereocenters. Up-scale syntheses and diverse fused cyclization transformations of products were then carried out. The enantioselective version for the domino process was studied.


Subject(s)
Carbon , Palladium , Palladium/chemistry , Molecular Structure , Cyclization , Catalysis , Organic Chemicals
3.
Org Lett ; 24(23): 4212-4217, 2022 Jun 17.
Article in English | MEDLINE | ID: mdl-35666666

ABSTRACT

A palladium-catalyzed domino Heck/decarboxylative alkynylation reaction of trisubstituted alkenes or enamines is reported. For two different types of substrates, the current domino reaction employing different solvents and bases led to 3,3-disubstituted oxindoles and hydropyrimidinyl spirooxindoles containing vicinal quaternary and tertiary stereocenters in moderate to good yields, respectively. The general applicability of this method was shown by gram-scale syntheses and diverse transformations of the reaction products. The enantioselective version for this domino process was also studied.

4.
Org Lett ; 24(23): 4234-4239, 2022 06 17.
Article in English | MEDLINE | ID: mdl-35658480

ABSTRACT

Described herein is an efficient strategy for assembling a new library of functionalized polycyclic purinium salts with a wide range of anions through RhIII-catalyzed C-H activation/annulation of 6-arylpurine nucleosides with alkynes under mild reaction conditions. The resulting products displayed tunable photoluminescence covering most of the visible spectrum. Mechanistic insights delineated the rhodium catalyst's mode of action. A purinoisoquinolinium-coordinated rhodium(I) sandwich complex was well characterized and identified as the key intermediate.


Subject(s)
Rhodium , Alkynes , Catalysis , Nucleosides , Salts
5.
Org Lett ; 24(21): 3861-3866, 2022 06 03.
Article in English | MEDLINE | ID: mdl-35604128

ABSTRACT

Bifunctional chiral tridentate bis(pyrroloimidazolone)pyridine (PyBPI) ligands have been designed, synthesized, and applied in an asymmetric Michael addition. With a 0.05 mol % PyBPI-Co(II) complex, ß,γ-unsaturated α-keto esters reacted with 4-hydroxycoumarin to give the adducts in 93-99% yields and 90-97% ee. Experiments and DFT calculations supported the dual activation manner, in which the tridentate ligand coordinated with Co(II) to activate the keto ester, and the hydroxyl and carbonyl groups in PyBPI interacted with 4-hydroxycoumarin via two different H bonds.


Subject(s)
4-Hydroxycoumarins , Cobalt , Catalysis , Esters , Hydrogen Bonding , Ligands , Stereoisomerism
6.
J Org Chem ; 87(9): 6161-6178, 2022 05 06.
Article in English | MEDLINE | ID: mdl-35438486

ABSTRACT

An electrochemical approach to promote the ortho-C-H alkylation of (hetero)arenes via rhodium catalysis under mild conditions is described. This approach features mild conditions with high levels of regio- and monoselectivity that tolerate a variety of aromatic and heteroaromatic groups and offers a widely applicable method for late-stage diversification of complex molecular architectures including tryptophan, estrone, diazepam, nucleosides, and nucleotides. Alkyl boronic acids and esters and alkyl trifluoroborates are demonstrated as suitable coupling partners. The isolation of key rhodium intermediates and mechanistic studies provided strong support for a rhodium(III/IV or V) regime.


Subject(s)
Rhodium , Alkylation , Catalysis , Electrochemistry , Nucleosides , Nucleotides , Rhodium/chemistry
7.
Org Lett ; 23(20): 7865-7872, 2021 Oct 15.
Article in English | MEDLINE | ID: mdl-34582193

ABSTRACT

A palladium-catalyzed enantioselective Heck cyclization/dearomatization cascade via capturing the cyclized Heck π-allylpalladium intermediate by ß-naphthols is reported, which provides a new strategy for the construction of chiral indole-terpenoid frameworks. This method affords indole-functionalized ß-naphthalenone compounds bearing an all-carbon-substituted quaternary chiral center in excellent yields (up to 92%) and enantioselectivities (up to 94% ee). In addition, the utility of this method is showcased by the gram-scale syntheses and diverse transformations of the dearomatized products.

8.
Chem Commun (Camb) ; 57(37): 4552-4555, 2021 May 06.
Article in English | MEDLINE | ID: mdl-33956013

ABSTRACT

The first ring-opening of D-A oxiranes with N-heteroaromatics in a chemoselective C-C bond cleavage manner was achieved. In the presence of 5 mol% of Y(OTf)3 as the catalyst, diverse N-heteroaromatics, including benzotriazoles, purines, substituted benzimidazole, imidazole and pyrazole, reacted well with various D-A oxiranes, providing acyclic nucleoside analogues containing a N-glycosidic bond in up to 97% yield and up to >95 : 5 regioselectivity. Through simple transformation, the Ganciclovir analogue could also be obtained.

9.
Org Lett ; 23(4): 1209-1215, 2021 02 19.
Article in English | MEDLINE | ID: mdl-33538167

ABSTRACT

Electrochemically driven, Cp*Ir(III)-catalyzed regioselective annulative couplings of benzoic acids with alkynes have been established herein. The combination of iridium catalyst and electricity not only circumvents the need for stoichiometric amount of chemical oxidant, but also ensures broad reaction compatibility with a wide array of sterically and electronically diverse substrates. This electrochemical approach represents a sustainable strategy as an ideal alternative and supplement to the oxidative annulations methodology to be engaged in the synthesis of isocoumarin derivatives.

10.
Org Lett ; 23(1): 81-86, 2021 01 01.
Article in English | MEDLINE | ID: mdl-33332122

ABSTRACT

A generally useful Ni(II)/trisoxazoline-catalyzed asymmetric sulfa-Michael/Aldol cascade reaction is introduced to access chiral 3-amine-tetrahydrothiophene derivatives containing a quaternary stereocenter (32 examples, up to 93% yield, > 20:1 dr and 92% ee). Moreover, the novel strategy offers an efficient and convenient approach to construct chiral thionucleoside analogues.

11.
Chem Commun (Camb) ; 56(78): 11649-11652, 2020 Oct 01.
Article in English | MEDLINE | ID: mdl-33000801

ABSTRACT

A highly enantioselective cyclopropanation to synthesize pyrimidine-substituted diester D-A cyclopropanes is reported. Various N1-vinylpyrimidines react well with phenyliodonium ylides, delivering chiral cyclopropanes in up to 97% yield with up to 99% ee. Through simple [3+2] annulation with benzaldehyde or ethyl glyoxylate, different chiral pyrimidine nucleoside analogues with a sugar ring could be obtained.

12.
J Am Chem Soc ; 142(45): 19226-19238, 2020 11 11.
Article in English | MEDLINE | ID: mdl-33119307

ABSTRACT

A novel concept that conversion of chiral 2-substituted DMAP into its DMAP-N-oxide could significantly enhance the catalytic activity and still be used as an acyl transfer catalyst is presented. A new type of chiral 2-substituted DMAP-N-oxides, derived from l-prolinamides, has been rationally designed, facilely synthesized, and applied in the dynamic kinetic resolution of azlactones. Using simple MeOH as the nucleophile, various l-amino acid derivatives were produced in high yields (up to 98% yield) and enantioselectivities (up to 96% ee). Furthermore, α-deuterium labeled l-phenylalanine derivative was also obtained. Experiments and DFT calculations revealed that in 2-substituted DMAP-N-oxide, the oxygen atom acted as the nucleophilic site and the N-H bond functioned as the H-bond donor. High enantioselectivity of the reaction was governed by steric factors, and the addition of benzoic acid reduced the activation energy by participating in the construction of a H-bond bridge. The theoretical chemical study indicated that only when attack directions of the chiral catalyst were fully considered could the correct calculation results be obtained. This work paves the way for the utilization of the C2 position of the pyridine ring and the development of chiral 2-substituted DMAP-N-oxides as efficient acyl transfer catalysts.


Subject(s)
Aminopyridines/chemistry , Lactones/chemistry , Oxides/chemistry , Aminopyridines/chemical synthesis , Catalysis , Hydrogen Bonding , Kinetics , Molecular Conformation , Phenylalanine/analogs & derivatives , Phenylalanine/chemical synthesis , Stereoisomerism , Thermodynamics
13.
Org Lett ; 22(1): 164-167, 2020 01 03.
Article in English | MEDLINE | ID: mdl-31868372

ABSTRACT

A straight synthetic approach to fused polycyclic tropane scaffold formation through an asymmetric dearomatization cycloaddition process of 2-nitrobenzofurans with cyclic azomethine ylides was successfully developed. In the presence of a chiral copper complex, derived from Cu(OAc)2 and a diphosphine ligand, a series of fused polycyclic tropane derivatives were obtained in high yields (75-91%) with excellent enantioselectivities (90-98%). The utility of this method was showcased by the facile transformation of product.

14.
Chem Commun (Camb) ; 55(90): 13550-13553, 2019 Nov 07.
Article in English | MEDLINE | ID: mdl-31650142

ABSTRACT

A highly efficient Pd-catalyzed asymmetric formal [3+2] cycloaddition using α-N-heterocyclic acrylates to react with vinyl epoxides has been achieved for the first time to access chiral functionalized tetrahydrofuran skeletons (34 examples, up to 93% yield, >20 : 1 dr and 99% ee). Meanwhile, using a palladium/(S,S)-tBu-FOXAP catalyst or a palladium/(R)-Segphos catalyst, purine or pyrimidine isonucleoside analogs are constructed in high yields and stereoselectivity, respectively. The commercial availability of the catalysts, broad substrate scope and easy transformation of the products make this methodology an attractive method in asymmetric synthesis.

15.
Chem Commun (Camb) ; 55(62): 9144-9147, 2019 Aug 11.
Article in English | MEDLINE | ID: mdl-31304482

ABSTRACT

The phosphine-catalyzed asymmetric dearomative [3+2] cycloaddition of 2-nitrobenzofurans with aldehyde-derived Morita-Baylis-Hillman (MBH) carbonates or allenoate was developed. The reaction with MBH carbonates resulted in a series of cyclopentabenzofurans containing three contiguous stereocenters with good to high yields, diastereoselectivities and enantioselectivities. The use of allenoate also gave the target product with moderate enantioselectivity.

16.
Org Lett ; 21(9): 2998-3002, 2019 05 03.
Article in English | MEDLINE | ID: mdl-30939024

ABSTRACT

An asymmetric transfer hydrogenation via dynamic kinetic resolution of a broad range of rac- α-(purin-9-yl)cyclopentones was first developed. A series of cis-ß-(purin-9-yl)cyclopentanols were obtained with up to 97% yield, >20/1 dr, and >99% ee. This also provides an efficient synthetic route to a variety of chiral carbocyclic nucleosides.


Subject(s)
Ketones/chemistry , Nucleosides/chemical synthesis , Purines/chemistry , Catalysis , Coordination Complexes/chemistry , Hydrogenation , Kinetics , Ruthenium/chemistry , Stereoisomerism
17.
Chem Commun (Camb) ; 55(11): 1580-1583, 2019 Jan 31.
Article in English | MEDLINE | ID: mdl-30652697

ABSTRACT

The Yb(OTf)3-catalyzed [3+2] cycloaddition of donor-acceptor cyclopropanes with thiourea offers an efficient route to diverse 2-amino-4,5-dihydrothiophenes (up to 92% yield), in which optically active 2-amino-dihydrothiophenes can be produced from enantiomerically pure cyclopropanes. Thiourea, which is an odorless and cheap reagent, provides a C[double bond, length as m-dash]S double bond, serves as an amino source, and functions as a decarbalkoxylation reagent in this reaction. Preliminary mechanistic studies demonstrate that the reaction undergoes a sequential [3+2] cycloaddition/deamination/decarboxylation process.

18.
Angew Chem Int Ed Engl ; 58(9): 2839-2843, 2019 02 25.
Article in English | MEDLINE | ID: mdl-30653794

ABSTRACT

A DMAP-N-oxide, featuring an α-amino acid as the chiral source, was developed, synthesized and applied in asymmetric Steglich rearrangement. A series of O-acylated azlactones afforded C-acylated azlactones possessing a quaternary stereocenter in high yields (up to 97 % yield) and excellent enantioselectivities (up to 97 % ee). Compared to the widespread use of pyridine nitrogen, which serves as the nucleophilic site in the asymmetric acyl transfer reaction, we discovered that chiral DMAP-N-oxides, in which the oxygen now acts as the nucleophilic site, are efficient acyl transfer catalysts. Our finding might open a new door for the development of chiral DMAP-N-oxides for asymmetric acyl transfer reactions.

19.
Chem Commun (Camb) ; 55(4): 553-556, 2019 Jan 03.
Article in English | MEDLINE | ID: mdl-30556555

ABSTRACT

Intermolecular asymmetric dearomative 1,3-dipolar cycloaddition of 2-nitrobenzofurans with azomethine ylides was enabled by using a chiral Cu(i)/(S,Sp)-iPr-Phosferrox catalyst. As a result, a series of highly stereoselective chiral [2,3]-fused hydrobenzofurans possessing four contiguous stereogenic centers were obtained with good to high yields, diastereoselectivities and enantioselectivities. The reaction has broad substrate scope tolerating various functional groups.

20.
Org Lett ; 20(24): 8026-8029, 2018 12 21.
Article in English | MEDLINE | ID: mdl-30525701

ABSTRACT

A Sc(OTf)3-catalyzed dearomative [3 + 2] cycloaddition of benzazoles with donor-acceptor oxiranes through chemoselective C-C bond cleavage of oxiranes was developed under mild conditions. This reaction provides an efficient method to construct benzazolo[3,2- c]oxazole compounds in good yields and with high diastereoselectivity. The reaction has a general substrate scope, and the donor-acceptor oxiranes with electron-donating and electron-withdrawing groups on the aromatic ring afforded the desired cycloadducts.

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