RESUMO
An effective method for the synthesis of furans is developed via a tandem 1,2-acyloxy migration/intramolecular [3 + 2] cycloaddition/aromatization of enol ether-tethered propargylic esters. The reaction exhibits excellent functional group tolerance, broad substrate scope, and excellent chemoselectivity. The isolation of dihydrofuran intermediates in some cases gives more insight into the [3 + 2] cycloisomerization process.
RESUMO
A cascade hexadehydro-Diels-Alder (HDDA)/[3 + 2] cycloaddition reaction between tetrayne and N,N'-cyclic acylhydrazone is described. This strategy allows the efficient construction of fully substituted 2,3-dihydro-1H-indazole scaffolds which have insecticidal activity against the third instar larvae of Mythimna separata.
RESUMO
As an important moiety in natural products, N,O-acetal has attracted wide attention in the past few years. An efficient method to construct N,O-acetal has been developed. Using silver catalyst, cyclobutenediones were smoothly converted to the corresponding γ-aminobutenolides in the presence of formamides, in which cyclobutenediones likely proceed with a key decarbonylative [3 + 2] cycloaddition process. In this way, a series of products with varied substituents were isolated in moderate yield and fully characterized.
RESUMO
An efficient GaCl3-catalyzed direct cyanation of indoles and pyrroles using bench-stable electrophilic cyanating agent N-cyanosuccinimide was achieved and afforded 3-cyanoindoles and 2-cyanopyrroles in good yields and excellent regioselectivities. Notably, this protocol exhibited high reactivity for unprotected indoles and was applicable to a broad range of indole and pyrrole substrates.
RESUMO
A convergent synthesis of four stereoisomers of the sex pheromone of the western corn rootworm (8-methyldecan-2-yl propionate, 1) from commercially available chiral starting materials is reported. The key step was Julia-Kocienski olefination between chiral BT-sulfone and chiral aldehyde. This synthetic route provided the four stereoisomers of 1 in 24-29% total yield via a six-step sequence. The simple scale-up strategy provides a new way to achieve the asymmetric synthesis of the sex pheromone.
Assuntos
Besouros/metabolismo , Propionatos/síntese química , Atrativos Sexuais/química , Animais , Estrutura Molecular , Propionatos/química , EstereoisomerismoRESUMO
Indolines are important moieties present in various biologically significant molecules and have attracted considerable attention in synthetic chemistry. This paper describes a Heck reaction/C-H activation/amination sequence for forming indolines using di-tert-butyldiaziridinone. The reaction process likely proceeds via a pallada(II)cycle, which is converted into an indoline by oxidative addition to the diaziridinone and two subsequent C-N bond formations.
Assuntos
Aziridinas/química , Indóis/síntese química , Paládio/química , Aminação , Catálise , Ciclização , Indóis/química , OxirreduçãoRESUMO
The first asymmetric total synthesis of chuanxiongnolide L1 was achieved in 16 steps and 1.9% overall yield by employing a bioinspired chiral auxiliary strategy. The key steps involving asymmetric oxidative dearomatization of chiral amino ether and subsequent asymmetric Diels-Alder reaction of the resulting masked chiral ortho-benzoquinone were adopted.
RESUMO
A novel tandem Mannich/intramolecular aminal formation between tryptamines and salicylaldehydes was reported. This strategy provides a promising approach for the stereoselective synthesis of a range of complex fused spiroindolines, which bear a highly congested contiguous spiro quaternary center and two tertiary stereocenters, in a highly economical and effective fashion.
RESUMO
The first asymmetric total syntheses of cladosporin and isocladosporin were accomplished in 8 steps with 8% overall yield and 10 steps with 26% overall yield, respectively. The relative configuration of isocladosporin was determined via this total synthesis.
Assuntos
Isocumarinas/síntese química , Isocumarinas/química , Estrutura Molecular , EstereoisomerismoRESUMO
A concise synthesis of the tetracyclic core (ABCE rings) of daphenylline has been accomplished involving a benzobicyclo[3.3.1] lactam as the key intermediate. This bridged bicyclic intermediate was efficiently constructed via a Brønsted acid promoted intramolecular Friedel-Crafts type Michael addition of a δ-benzyl α,ß-unsaturated δ-lactam.
Assuntos
Alcaloides/química , Alcaloides/síntese química , Hidrocarbonetos Aromáticos com Pontes/química , Lactamas/química , Compostos Policíclicos/química , Ciclização , EstereoisomerismoRESUMO
A sequential process involving Boc-mediated oxidative dearomatization and inter/intramolecular Diels-Alder reaction was investigated. Based on an intermolecular Diels-Alder reaction and subsequently a radical 7-endo-trig type cyclization, the [6.6.7.5] tetracyclic core of Calyciphylline N was assembled.
Assuntos
Compostos Policíclicos , Ciclização , Oxirredução , Estresse OxidativoRESUMO
An efficient PtI(2)-catalyzed tandem reaction of arylpropargylic esters, involving 3,3-rearrangement and Nazarov reaction, has been developed to produce 3-substituted and 3,3-disubstituted indanone derivatives. This approach provided a pathway to the synthesis of indanone skeletons in natural products.
Assuntos
Química Farmacêutica/métodos , Diuréticos/síntese química , Ésteres/química , Indanos/síntese química , Catálise , Ciclização , Diuréticos/análise , Humanos , Indanos/análise , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Platina/química , EstereoisomerismoRESUMO
A platinum-catalyzed tandem reaction involving enynyl ester isomerization and subsequent intramolecular [3 + 2] cyclization has been developed. This strategy provides an efficient approach to five-, six-, or seven-membered cyclic polyfunctional compounds.
RESUMO
A concise, biomimetic total synthesis of the unprecedented terpenoid skeleton (+)-chabraol has been accomplished via 6 steps from the chiral epoxide 7, involving an intramolecular Prins double cyclization to yield the bicyclo[2.2.1] core of the natural product as the key step. The absolute configuration of natural chabranol was also designated through the first asymmetric total synthesis.
Assuntos
Mimetismo Molecular , Terpenos/síntese química , Ciclização , Espectroscopia de Ressonância Magnética , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria Infravermelho , Terpenos/químicaRESUMO
Total synthesis of caesalpinnone A was achieved in 12 steps starting from resorcinol. Key features of the synthesis include BINOL-phosphoric acid catalyzed [4 + 2] cycloaddition, trans-selective nucleophilic substitution, deallylation/oxa-Michael addition cascade, and late-stage photo-Fries rearrangement.
Assuntos
Resorcinóis/química , Estrutura Molecular , EstereoisomerismoRESUMO
An efficient method to build various multisubstituted polycyclic indoline-annulated normal to medium-size rings through dearomatization of indole via a tandem 1,2-acyloxy migration/intramolecular [3 + 2] cycloaddition process is described. The pentacyclic skeleton of strychnine could be synthesized via this tandem cycloaddition and a further Mannich reaction. This approach would provide a novel strategy to the synthesis of strychons alkaloids.
RESUMO
A novel Pd(0)-catalyzed sequential C-N bond formation process via allylic and aromatic C-H amination of α-methylstyrenes with di-tert-butyldiaziridinone, giving spirocyclic indolines in good yields, is described. Four C-N bonds and one spiro quaternary carbon are generated in a single operation.
Assuntos
Aziridinas/química , Indóis/síntese química , Paládio/química , Estirenos/química , Aminação , Catálise , Ligação de Hidrogênio , Indóis/química , Estrutura MolecularRESUMO
A concise construction of the 6/6/5 tricyclic core of Lycopodium alkaloid palhinine A (1) has been accomplished. The developed synthetic strategy featured a tandem oxidative dearomatization/intramolecular Diels-Alder reaction to construct C/D rings and an intramolecular 5-exo-trig radical cyclization to install the B ring of palhinine A (1). The developed approach paves the way for the total synthesis of palhinine A (1).
Assuntos
Alcaloides/síntese química , Alcaloides/química , Ciclização , Lycopodium/química , Estrutura Molecular , OxirreduçãoRESUMO
The first total synthesis of (-)-Przewalskin B has been accomplished with an intramolecular nucleophilic acyl substitution (INAS) reaction and an intramolecular aldol condensation as key steps.