RESUMEN
We report a perchloric acid-catalyzed heteroannulation for the synthesis of spirocyclobutanes using vinyloxyphenylbicyclobutanes with water. This metal-free reaction yields high product outputs and is consistent with the formation of a cyclobutene intermediate originating from an isomerization of a bicyclobutane.
RESUMEN
A novel chiral borinic acid (CBA), an organocatalyst possessing a binaphthyl skeleton, was designed and synthesized. The synthesis of CBA was achieved with a 72% yield in four steps starting with optically pure 1,1'-bi-2-naphthol. The asymmetric catalytic activity was investigated in the desymmetrization of meso-1,2-diol.
RESUMEN
We report the heteroannulations of bicyclobutane derivatives bearing enol ether groups in the presence of H2O under mild conditions. The reaction affords spirocyclobutanes with cyclic acetal groups via the Au-catalyzed hydration of the enol ether group and subsequent intramolecular cyclization.
RESUMEN
Migratory cycloisomerization using transition metal catalyst is useful for synthesizing substituted heterocyclic compounds. We achieved palladium-catalyzed migratory cycloisomerization of 3-o-alkynylphenoxy acrylic acid ester derivatives to give 2,3-disubstituted benzofurans. Although there are several reports of benzofuran synthesis with palladium-catalyzed migratory cycloisomerization, migratory groups are limited to allyl and propargyl groups. This report is the first example of benzofuran synthesis with palladium-catalyzed cycloisomerization of C(sp2)-O bond cleavage.
Asunto(s)
Benzofuranos , Compuestos Heterocíclicos , Paladio/química , Benzofuranos/química , CatálisisRESUMEN
A double ring expansion strategy for constructing fused 3-benzazepines is described. The oxidative ring expansion of spiroamine compounds with N-chlorosuccinimide and subsequent ring expansion of the resulting ketiminium ion intermediates with trimethylsilyldiazomethane afforded fused 3-benzazepines in a one-pot operation. Importantly, the Dolby-Weinreb enamine, which is a key synthetic intermediate for harringtonine alkaloids, cephalotaxines, can be accessed from commercial materials in only two steps using our developed method.
Asunto(s)
Alcaloides , Benzazepinas , Estructura MolecularRESUMEN
The first total synthesis of marine sesterterpenoid ansellone G (2) was accomplished. This strategy utilizes the Prins cyclization reaction of a chloro-substituted homoallyl alcohol to synthesize the hydrobenzopyran skeleton. The preintroduction of the chloro groups facilitated the functional group transformation for 2 after constructing the carbon framework. Furthermore, we also successfully synthesized phorbadione (3) by dehydrating the tertiary alcohol. The HIV latency-reversing activity of the synthesized 2, 3, and deacetylated 2 was also evaluated.
Asunto(s)
Alcoholes , CiclizaciónRESUMEN
Monoamine oxidase B (MAO-B) metabolizes monoamines such as dopamine regarding neural transmission and controls its level in the mammalian's brain. When MAO-B metabolizes dopamine abnormally, normal neurotransmission does not occur, and central nervous system disorders such as Parkinson's disease may develop. Although several MAO inhibitors have been developed, most of them have no selectivity between monoamine oxidase A (MAO-A) and MAO-B, or they work irreversibly against the enzyme. This report describes the first case of screening of N-arylated heliamine derivatives to develop novel MAO-B selective inhibitors that can be synthesized concisely by microwave-assisted Pd nanoparticle-catalyzed Buchwald-Hartwig amination. We discovered that the derivatives 4h, 4i, and 4j display inhibitory activity against MAO-B with IC50 values of 1.55, 13.5, and 5.08 µM, respectively.
RESUMEN
Dehydrohelicenes are some of the most attractive chiroptical materials with unique helical chirality. However, to our knowledge, there are no prior reports on their direct construction by asymmetric methods. In this work, sequential synthesis of aza-oxa-dehydro[7]helicenes via the electrochemical oxidative hetero-coupling of 3-hydoxycarbazoles and 2-naphthols followed by dehydrative cyclization and intramolecular C-C bond formation has been realized. In addition, an efficient enantioselective synthesis through chiral vanadium-catalyzed hetero-coupling and electrochemical oxidative transformations afforded heterodehydro[7]helicene without any racemization. The obtained dehydro[7]helicenes showed intense blue-colored circularly polarized luminescence (|glum| ≈ 2.5 × 10-3 at 433 nm). Thermodynamic and kinetic studies of the racemization barrier of heterodehydro[7]helicenes indicated significant chiral stability with ΔG> 140 kJ mol-1.
RESUMEN
Multitasking single-catalyst systems that allow multiple chemical transformations within a single reaction vessel are important for the development of eco-compatible chemistry. Here, we have developed a rhodium-catalyzed system that transforms 1-(allyloxy)-2-(cyclopropylmethyl)benzene derivatives to 2-ethyl-3-isopropylbenzofurans via double isomerization/cycloisomerization/aromatization.
RESUMEN
We have developed a one-iridium-catalyst system that transforms N-allyl-N-sulfonyl-2-(silylalkynyl)aniline derivatives, which are 1,7-enynes in which both multiple bonds have a heteroatom, to the corresponding substituted indole derivatives via isomerization/cycloisomerization/aromatization. This strategy provides an atom-economical and straightforward synthetic approach to a series of valuable indoles having vinyl and silylmethyl groups at the 2- and 3-positions.
RESUMEN
Cross-dehydrogenative coupling between 3-hydroxycarbazoles and 2-naphthols has been achieved by using a mesoporous silica-supported oxovanadium catalyst.
RESUMEN
Correction for 'Exploration of flow reaction conditions using machine-learning for enantioselective organocatalyzed Rauhut-Currier and [3+2] annulation sequence' by Masaru Kondo et al., Chem. Commun., 2020, 56, 1259-1262, DOI: 10.1039/C9CC08526B.
RESUMEN
An enantioselective oxa-Piancatelli reaction was established for the first time using a chiral vanadium(v) catalyst. The dual Brønsted and Lewis acid properties of the vanadium catalyst afforded 4-hydroxycyclopent-2-enone derivatives in up to 90% yields and with 93 : 7 enantiomeric ratios, as well as >20 : 1 diastereomeric ratios.
RESUMEN
A highly atom-economical enantioselective organocatalyzed Rauhut-Currier and [3+2] annulation sequence has been established by using a flow system. Suitable flow conditions were explored through reaction screening of multiple parameters using machine learning. Eventually, functionalized chiral spirooxindole analogues were obtained in high yield with good ee as a single diastereomer within one minute.
RESUMEN
C-H trifluoromethanesulfonyloxylation (triflation) of 1,1'-bi-2-naphthol (BINOL) derivatives has been established under mild conditions using 1,3-diiodo-5,5-dimethylhydantoin (DIH) and trifluoromethanesulfonic acid (TfOH). Up to eight TfO groups can be introduced in a single operation. The resulting highly oxidized BINOL derivatives can be successfully converted to 8,8'-dihydroxy BINOL and bisnaphthoquinone compounds. Mechanistic studies suggested that C-H triflation occurs in the form of an aromatic substitution reaction via the in situ formation of a radical cation.
RESUMEN
A method for the highly regio- and enantioselective oxidative coupling of resorcinols has been established by using dibrominated dinuclear vanadium(V) catalyst 1c under air. When resorcinols bearing an aryl substituent were applied as substrates to the coupling, axially chiral biresorcinols were obtained as single regioisomers in high yield with up to 98% ee.
RESUMEN
In this paper, the dehydrogenation of tetrahydroquinolines using oxovanadium(V) catalysts under mild conditions in water and oxygen atmosphere is described. This catalytic technology was successfully applied to a range of other structurally related N-heterocycles, and a reaction mechanism is proposed.
RESUMEN
Asymmetric oxidative coupling reactions of hydroxycarbazoles have been established using a chiral dinuclear vanadium complex. To demonstrate the utility of vanadium-catalyzed reactions, we have used them to synthesize (+)-bi-2-hydroxy-3-carbazole in three steps from cyclohexanone and commercially available aniline derivatives.
Asunto(s)
Carbazoles/química , Catálisis , Estructura Molecular , Oxidación-Reducción , Vanadio/químicaRESUMEN
An enantioselective intermolecular Rauhut-Currier (RC) reaction of nitroalkenes with ethyl allenoate has been established with quinidine-derived ß-isocupreidine. The present RC reaction afforded α-functionalized allenoates 3 in up to 94% yield with 59% enantiomeric excess (ee).
Asunto(s)
Alcadienos/química , Alquenos/química , Ésteres/química , Nitrocompuestos/química , Catálisis , Ciclización , Estructura Molecular , EstereoisomerismoRESUMEN
The first enantio- and diastereoselective Betti/intramolecular aza-Michael sequence carried out using a C3-symmetric chiral trisimidazoline organocatalyst is reported. The reaction of phenols and N-tosylimines bearing a Michael acceptor moiety afforded densely functionalized 1,3-disubstituted isoindolines bearing two stereogenic centers as single diastereomers in high yields (≤93%) and excellent enantioselectivities (≤99.9%).