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1.
Org Biomol Chem ; 22(6): 1299-1309, 2024 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-38259138

RESUMO

A copper-catalyzed aerobic oxidative cross-dehydrogenative coupling reaction between secondary amides and terminal alkynes has been developed. With the aid of ligands and 3 Å molecular sieves, ynamides can be efficiently synthesized at room temperature and conveniently scaled up. A legitimate mechanism involving nitrogen-centred radicals and copper trivalent intermediates has been proposed.

2.
J Org Chem ; 87(14): 9044-9055, 2022 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-35748643

RESUMO

A versatile synthesis of α-amino bisphosphonates has been achieved through one-pot interrupted Ritter-type reaction under mild conditions. The reactive Ritter intermediate nitrilium is in situ generated by treatment of nitrile with readily accessible Tf2O/HC(OR1)3, which is trapped by phosphite ester to deliver the desired product. This protocol is efficient, scalable, and well compatible with a broad scope of substrates. In addition, plentiful characteristic JP-C couplings including unusual five-bond long-range 5JP-C and 3JP-C across quaternary carbon and hetero (N) atoms were observed in 13C NMR spectra.


Assuntos
Difosfonatos , Nitrilas , Carbono/química , Nitrilas/química
3.
J Org Chem ; 86(23): 16926-16939, 2021 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-34752091

RESUMO

In this paper, we document the construction of functionalized and fused eight-membered carbocycles by the triflic anhydride-mediated cyclization of 7-enamides. Taking advantage of the high electrophilicity of the nitrilium ion intermediates, generated in situ from secondary N-(2,6-dimethyl)anilides, the nonactivated, trisubstituted alkene-nitrilium cyclization reactions proceeded smoothly to afford nonconjugated ß,γ-enimines (for fused 6/6/8 ring systems), conjugated α,ß-enimines (for 6/5/8), or fused 5/8 ring systems in good yields. When the cyclization reactions were followed by one-pot acidic hydrolysis, the reaction led directly to the corresponding α,ß-enones. For some substrates, the reaction afford an efficient access to pendent cyclic ß,γ-enimines/enones.


Assuntos
Alcenos , Ciclização
4.
J Org Chem ; 86(23): 16300-16314, 2021 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-34499513

RESUMO

Ten types of Tf2O/TTBP-mediated amide transformation reactions were investigated. The results showed that compared with pyridine derivatives 2,6-di-tert-butyl-4-methylpyridine (DTBMP) and 2-fluoropyridine (2-F-Pyr.), TTBP can serve as an alternative amide activation system for the direct transformation of both secondary and tertiary amides. For most surveyed examples, higher or comparable yields were generally obtained. In addition, Tf2O/TTBP combination was used to promote the condensation reactions of 2-(tert-butyldimethylsilyloxy)furan (TBSOF) with both tertiary and secondary amides, the one-pot reductive Bischler-Napieralski-type reaction of tertiary lactams, and Movassaghi and Hill's modern version of the Bischler-Napieralski reaction. The value of the Tf2O/TTBP-based methodology was further demonstrated by the concise and high-yielding syntheses of several natural products.


Assuntos
Amidas , Lactamas , Estrutura Molecular
5.
J Org Chem ; 86(4): 3276-3286, 2021 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-33530688

RESUMO

An efficient approach to a functionalized bicyclo[2.2.2]octan-2-one scaffold has been developed through a one-pot cascade process including amino acid involved successive Michael addition and decarboxylative-Mannich sequence. Starting from α,ß-unsaturated ketones and amino acids, a series of desired products 7a-7m and 8a-8o were obtained with moderate yields. In addition, the tandem process was reasonably explained by the results of DFT calculations.


Assuntos
Aminoácidos , Cetonas , Aminas , Catálise , Esqueleto
6.
Chem Commun (Camb) ; 55(94): 14170-14173, 2019 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-31701971

RESUMO

A zinc-catalyzed decarboxylative A3 reaction of cyclic amino acids, α,ß-unsaturated aldehydes and terminal alkynes has been developed. A series of functionalized N-heterocyclic 1,6-enynes have been successfully obtained with excellent regioselectivities through this novel approach. In addition, the utility of this straightforward process is demonstrated by the preparation of a polycyclic nitrogen-containing heterocyclic compound.

7.
Org Lett ; 21(18): 7587-7591, 2019 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-31479277

RESUMO

We report the first catalytic, enantioselective reductive bis-functionalization of common amides, which provides a facile access to a variety of 2,2-disubstituted 3-iminoindolines in good yields and with excellent enantioselectivities. The reaction conditions are quite mild and can be run on a gram scale. In this one-pot reaction, three C-C bonds, one ring, and one nitrogen-containing tetrasubstituted carbon stereocenter are created in a catalytic enantioselective manner.

8.
J Org Chem ; 84(14): 9270-9281, 2019 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-31287315

RESUMO

An efficient and mild protocol for the direct and flexible synthesis of 3-amino-1,4-diynes bearing an aza-quaternary carbon from tertiary amides and lactams has been established. The one-pot method consists of in situ activation of amides with trifluoromethanesulfonic anhydride, followed by double addition of alkynyllithium reagents at a concentration of 0.5 mol·L-1 in dichloromethane. This constitutes an extension of the method of direct reductive bisalkylation of amides that allows both employing alkynyllithium reagents as the first-addition nucleophiles and incorporating an alkynyl group as the first-introduced group.

9.
Org Lett ; 20(14): 4200-4203, 2018 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-29969900

RESUMO

The first asymmetric total synthesis of (-)-verrupyrroloindoline (20% overall yield in 6 steps) is described. The short approach was enabled by Buchwald's Cu(II)-catalyzed asymmetric conjugate reduction, DMDO-triggered one-pot four-step tandem reaction, and the first amide-selective Ir-catalyzed direct reduction of ß-carboethoxy tertiary lactam. Along with the total synthesis, the absolute configuration of natural verrupyrroloindoline was determined as 7 R,10 R,11 R.

10.
Angew Chem Int Ed Engl ; 57(32): 10352-10356, 2018 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-29924902

RESUMO

The imino-Nazarov cyclization of the polysubstituted pentan-1,4-diene-3-imines was realized. To this aim, a one-pot procedure involving reductive alkenyliminylation of α,ß-unsaturated secondary amides with potassium organotrifluoroborates, followed by acid-catalyzed imino-Nazarov cyclization of the polysubstituted pentan-1,4-diene-3-imine intermediates, was studied systematically. This mild, operationally simple, flexible, and high-yielding protocol efficiently affords polysubstituted pentan-1,4-diene-3-imines, cyclopentenimines, and α-amino cyclopentenones, which are useful scaffolds in organic synthesis. The substituent effect at the C2 position of the polysubstituted pentan-1,4-diene-3-imines was studied by means of density-functional theory calculations. Results suggested that the electron-donating group facilitates the imino-Nazarov cyclization process.

11.
Sci Rep ; 6: 28801, 2016 06 29.
Artigo em Inglês | MEDLINE | ID: mdl-27356173

RESUMO

Carbon-carbon bond formation by metal-free cross-coupling of two reactants with low reactivity represents a challenge in organic synthesis. Secondary amides and alkenes are two classes of bench-stable compounds. The low electrophilicity of the former and low nucleophilicity of the latter make the direct coupling of these two partners challenging yet highly desirable. We report herein an unprecedented intermolecular reaction of secondary amides with alkenes to afford α,ß-unsaturated ketimines or enones, which are versatile intermediates for organic synthesis and are prevalent in bioactive compounds and functional materials. Our strategy relies on the chemoselective activation of the secondary amide with trifluoromethanesulfonic anhydride (Tf2O)/2-fluoropyridine to generate a highly reactive nitrilium intermediate, which reacts efficiently with alkenes. This metal-free synthesis is characterized by its mild reaction conditions, excellent functional group tolerance and chemoselectivity, allowing the preparation of multi-functionalized compounds without using protecting groups.

12.
Angew Chem Int Ed Engl ; 55(12): 4064-8, 2016 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-26890255

RESUMO

The first total synthesis of the alkaloid (-)-haliclonin A is reported. The asymmetric synthesis relied on a novel organocatalytic asymmetric conjugate addition of nitromethane with 3-alkenyl cyclohex-2-enone to set the stereochemistry of the all-carbon quaternary stereogenic center. The synthesis also features a Pd-promoted cyclization to form the 3-azabicyclo[3,3,1]nonane core, a SmI2 -mediated intermolecular reductive coupling of enone with aldehyde to form the requisite secondary chiral alcohol, ring-closing alkene and alkyne metathesis reactions to build the two aza-macrocyclic ring systems, and an unprecedented direct transformation of enol into enone.


Assuntos
Diaminas/síntese química , Compostos Macrocíclicos/síntese química , Catálise
13.
Chem Commun (Camb) ; 52(3): 561-3, 2016 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-26538080

RESUMO

The asymmetric total synthesis of (+)-N-acetyl norloline, the putative biogenic precursor of all known loline alkaloids, has been achieved in 12 steps from commercially available (R)-glyceraldehyde acetonide. The synthesis relies on the Rassu/Casiraghi's vinylogous aldol reaction, an intramolecular oxa-heteroconjugate addition and a reductive amination to establish the four contiguous stereogenic centers and construct the strained oxygen-bridge under mild conditions.


Assuntos
Alcaloides/síntese química , Hidrocarbonetos Aromáticos com Pontes/química , Gliceraldeído/análogos & derivados , Alcaloides/química , Hidrocarbonetos Aromáticos com Pontes/síntese química , Gliceraldeído/química , Estrutura Molecular , Oxirredução
14.
J Org Chem ; 78(22): 11229-37, 2013 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-24160561

RESUMO

A novel migration-addition sequence was discovered for the reaction of enantioenriched N-tert-butanesulfinyl iminoacetate 1a with functionalized benzylzinc bromide reagents, producing tert-leucine derivatives in excellent diastereoselectivity (dr 98:2). The absolute configurations of two new chiral centers were unambiguously assigned by chemical transformations and X-ray crystallography. In addition, the regio- and diastereoselectivities of this novel reaction were both explained through the key N-sulfinamine intermediate M6 generated by the tert-butyl radical attack on the imine. Computational analysis of this reaction process, which was performed at the B3LYP/6-311++G(3df,2p)//B3LYP/6-31G*-LANL2DZ level, also supported our proposed two-stage mechanism.


Assuntos
Compostos Organometálicos/química , Compostos de Sulfônio/química , Valina/análogos & derivados , Zinco/química , Cristalografia por Raios X , Radicais Livres/síntese química , Radicais Livres/química , Leucina/análogos & derivados , Modelos Moleculares , Conformação Molecular , Teoria Quântica , Estereoisomerismo , Valina/síntese química , Valina/química
15.
Artigo em Inglês | MEDLINE | ID: mdl-24046687

RESUMO

The title compound, C13H15NO2, was obtained as a by-product in the Grignard reaction of malimide. The dihedral angle between the five-memebred ring (r.m.s. deviation = 0.005 Å) and the benzene ring is 67.20 (14)°. The benzene ring and the ethyl chain lie to the same side of the five-membered ring. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, generating C(6) chains propagating in [010].

16.
J Org Chem ; 78(1): 35-41, 2013 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-22946828

RESUMO

An efficient synthesis of the Stemona alkaloid (-)-sessilifoliamide J (1) in 12 steps and 7.7% overall yield from the known building block 8 is presented. The synthesis features the Corey lactonization reaction and a highly diastereoselective α-methylation reaction to build the spiro-lactone moiety.


Assuntos
Alcaloides/síntese química , Lactonas/síntese química , Compostos de Espiro/síntese química , Alcaloides/química , Lactonas/química , Estrutura Molecular , Compostos de Espiro/química , Stemonaceae/química , Estereoisomerismo
17.
Org Biomol Chem ; 10(32): 6504-11, 2012 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-22752071

RESUMO

We have developed a one-pot method for the direct intermolecular reductive hydroxyalkylation or alkylation of amines using lactones or esters as the hydroxyalkylating/alkylating reagents. The method is based on the in situ amidation of lactones/esters with DIBAL-H-amine complex (for primary amines) or DIBAL-H-amine hydrochloride salt complex (for secondary amines), followed by reduction of the amides with an excess of DIBAL-H. Different from the reduction of Weinreb amides with DIBAL-H where aldehydes are formed, the reduction of the in situ formed Weinreb amides yielded amines. Moreover, this method is not limited to Weinreb amides, instead, it also works for other amides in general. A plausible mechanism is suggested to account for the outcome of the reactions.


Assuntos
Aminas/química , Ésteres/química , Lactonas/química , Alquilação , Amidas/química , Hidroxilação , Estrutura Molecular , Oxirredução
18.
Chem Asian J ; 7(3): 504-18, 2012 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-22315233

RESUMO

The first enantioselective synthesis of cytotoxic natural products rigidiusculamides A (ent-21) and B (8) has been achieved by two synthetic routes. The first one is convergent based on the common intermediate 11, obtained through a high yielding SmI(2) -mediated Reformatsky-type reaction. A highly diastereoselective one-pot Dess-Martin periodinane-mediated bis-oxidation allowed the direct conversion of the diastereomeric mixture of 11 into rigidiusculamide B (8). Isolation of minor diastereomer 21, in combination with computational work, allowed us to suggest the structure of the natural rigidiusculamide A to be ent-21, as synthesized by the second route. Four diastereomers (7, ent-7, 22a, and 22b) and an enantiomer (21) of rigidiusculamide A (ent-21) have been synthesized. On the basis of literature precedents and computational work, a biosynthetic pathway for rigidiusculamides A and B was proposed to account for the opposite configuration at C-5 of those two congeners.


Assuntos
Produtos Biológicos/síntese química , Pirrolidinas/síntese química , Produtos Biológicos/química , Conformação Molecular , Pirrolidinas/química , Teoria Quântica , Estereoisomerismo
19.
Eur J Med Chem ; 46(11): 5480-6, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21955681

RESUMO

An improved four-step approach for the stereoselective synthesis of long-chain anti-2-amino-3-alkanols is described. Using this method, the syntheses of antiproliferative (antitumoral) compounds, spisulosine (ES-285, 2), clavaminols A and B (3 and 4), the deacetylated products of clavaminols H and N (7 and 8), as well as (2S,3R)-2-aminododecan-3-ol (9) and xestoaminol C (10), have been achieved in excellent diastereoselectivities. In vitro study showed that these compounds induced cell death and dose-dependently inhibited cell proliferation in human glioblastoma cell line SHG-44, indicating the anti-tumor property of this series of compounds.


Assuntos
Álcoois/síntese química , Álcoois/farmacologia , Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Técnicas de Química Sintética , Álcoois/química , Álcoois/toxicidade , Antineoplásicos/química , Antineoplásicos/toxicidade , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Humanos , Estereoisomerismo , Especificidade por Substrato
20.
Org Lett ; 13(19): 5270-3, 2011 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-21879702

RESUMO

A 10-step asymmetric synthesis of 9-epi-sessilifoliamide J (20), together with sessilifoliamide J (6), has been accomplished from the key chiral building block 11 via a threo-selective vinylogous Mannich reaction and a Ley oxidation-SmI(2)-mediated coupling lactonization. The absolute configuration of the natural sessilifoliamide J was established.


Assuntos
Compostos Heterocíclicos com 3 Anéis/síntese química , Compostos Heterocíclicos com 3 Anéis/química , Modelos Moleculares , Estrutura Molecular , Estereoisomerismo
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