RESUMEN
We report a catalytic skeletal rearrangement of biphenylenes with a pendant alkyne moiety at room temperature by a cationic gold catalyst, which involves the cleavage of two bonds: the C-C bond of biphenylene and the C(sp)-C(sp2 or sp3) bond. Experimental and theoretical studies revealed that the reaction mechanism included π-activation of the alkyne, ring expansion and 1,2-carbon shift.
RESUMEN
We have developed a two- or three-step synthesis of polyaza[5]-[9]helicenes by consecutive N-H/C-H coupling with a hypervalent iodine reagent. We further evaluated their photophysical properties, and circularly polarized luminescence properties and found that glum values increase with the number of fused rings up to 2.7 × 10-2, which is the highest value among [9]helicenes.
RESUMEN
Chiral polycyclic aromatic hydrocarbons (PAHs) are expected to have unusual physical properties due to their chirality and expanded π-conjugated system. Indeed, PAHs are promising compounds as chiral recognizers and organic semiconductors. Therefore, an efficient method for the synthesis of chiral PAHs is strongly desired. In contrast to helically chiral PAHs, there are only limited examples of the enantioselective synthesis of axially chiral PAHs. Herein, we report the catalytic enantioselective synthesis of benzo[b]fluoranthene-based axially chiral PAHs in excellent yields and enantioselectivities (up to >99%, >99% ee) by regioselective cleavage of the sterically hindered C-C bond of biphenylenes. The consecutive cyclizations could provide polycyclic PAHs with two chiral axes. The obtained chiral PAHs have high ε values (up to ε = 8.9 × 104), quantum yields (up to Φ = 0.67), and circularly polarized luminescence (CPL) property (|glum| = up to 3.5 × 10-3).
RESUMEN
Silicon-tethered tetraynes possessing a 1,3-diyne moiety underwent consecutive hexadehydro- and tetradehydro-Diels-Alder reactions to give a series of fused polycyclic aromatic compounds containing a dibenzosilole skeleton. The benzene ring in the product acted as a 1,3-diene and reacted with the active alkyne as well as oxygen to provide [4 + 2] cycloadducts.
RESUMEN
An efficient method for the asymmetric synthesis of 4-imidazolidinones via an iodine-catalyzed intramolecular N-H/C(sp3)-H activation of readily available and abundant feedstocks, amino acids, and amines is described. The reaction proceeded under visible light irradiation to afford a variety of 4-imidazolidinone derivatives under mild conditions in moderate to excellent yields. Secondary and tertiary C(sp3)-H bonds were aminated, and various functional groups were tolerated.
RESUMEN
Consecutive thermal and metal-catalyzed dehydro-Diels-Alder (DDA) reactions of sulfur-tethered tetraynes, possessing a 1,3-diyne moiety, proceeded efficiently, and axial chirality was achieved for the resulting dibenzothiophenyl moieties. Chiral-rhodium catalysis realized a highly enantioselective synthesis, and transformations into bis(benzocarbazole) derivatives were also achieved.
RESUMEN
The Rh-catalyzed intramolecular reaction of 1-(2-vinylaryl)-substituted biphenylenes was used to construct a dihydrobenzo[b]fluoranthene skeleton. This transformation was achieved by regioselective C-C bond cleavage of a sterically more hindered biphenylene site by using alkene as both a directing group and a reaction moiety. Furthermore, we measured and analyzed the photophysical properties of the new multicyclic fused compounds.
RESUMEN
The Ir-catalyzed intramolecular reaction of 2',6'-diaryl-2-(hydrosilyl)biphenyls gave substituted tribenzosilepins by direct dehydrogenative C-H/Si-H coupling. This is the first example of catalytic construction of the tribenzosilepin skeleton. Enantiomerically pure tribenzosilepin was prepared by optical resolution using chiral HPLC, and its inversion barrier was calculated by measurement of rate of racemization using the Eyring kinetic equation under heating conditions.
RESUMEN
An intramolecular catalytic dearomatization of phenols via gold carbene species proceeded to provide 2-azaspiro[4.5]decan-3-ones. The use of NHC ligand and water as a co-solvent was critical for achieving high reactivity. This reaction did not require hazardous diazo compounds as carbene sources and proceeded even under air. The obtained spirocyclic product could be readily transformed into a gabapentin derivative by hydrogenation and deprotection.
RESUMEN
α-Aminoalkylation of N-arylacrylamides with amino acid derivatives was achieved by silver-catalysis in moderate to high yields. The reaction provides an efficient strategy for the synthesis of functionalized oxindoles, and is suitable for a wide range of N-arylacrylamides and amino acids, both of which are inexpensive and readily available. The oxindoles obtained were readily transformed into densely functionalized pyrroloindolines by deprotection and cyclization in one pot.
RESUMEN
Sulfur-directed sp C-S bond cleavage along with a regioselective reaction with alkynes proceeded to give (Z)-enyne sulfides in high to excellent yields. Mechanistic studies were conducted, including characterization of an intermediate. An intramolecular variant realized the construction of a dibenzodithiepin skeleton, which is a seven-membered ring with two sulfur atoms.
RESUMEN
A facile two-step synthesis of aza[7]helicenes possessing a 6-5-6-6-6-5-6 skeleton from commercially available 2,9-dichloro-1,10-phenanthroline via double amination with aniline derivatives followed by hypervalent iodine reagent-mediated intramolecular double-NH/CH couplings was developed. Single-crystal X-ray analyses of the helicenes revealed unique structures, including both a significantly twisted center and planar terminals of the skeleton. The azahelicenes show high fluorescent quantum yields (Φs) under both neutral (Φ: 0.25-0.55) and acidic conditions (Φ: up to 0.80). An enantiomerically pure aza[7]helicene showed high circularly polarized luminescence (CPL) activity under both neutral and acidic conditions (glum : up to 0.009).
RESUMEN
Recently, we reported an Ir-catalyzed formal [4 + 1] cycloaddition of biphenylenes with alkenes, which gave 9,9-disubstituted fluorenes in moderate to excellent yields. We proposed a reaction mechanism that involved the intermolecular insertion of alkenes, ß-elimination, and intramolecular insertion based on the results of experimental mechanistic studies. Herein, we further support the proposed mechanism by density functional theory calculations and explain why [4 + 1] cycloaddition proceeds rather than conventional [4 + 2] cycloaddition.
RESUMEN
The Ir-catalyzed enantioselective reaction of substituted acetanilides with ß-substituted α,ß-unsaturated esters provided chiral 3,3-disubstituted propanoates in high yield with good-to-excellent enantiomeric excess (up to 99 % ee). This transformation, initiated by sp2 C-H bond activation, is the first example of enantioselective formal C-H conjugate addition to ß-substituted α,ß-unsaturated carbonyl compounds. The starting materials are commercially available and/or readily accessible.
RESUMEN
Enantioselective cycloisomerization of 2-ethynyl-1-ferrocenylbenzene derivatives proceeded by using a chiral cationic platinum catalyst at room temperature. The intramolecular reaction gave planar-chiral naphthalene- and anthracene-fused ferrocene derivatives with high to excellent ee.
RESUMEN
An Ir-catalyzed intermolecular reaction of biphenylenes as a C4 unit with various alkenes as a C1 unit gave 9,9-disubstituted fluorenes in moderate to high yields. Preliminary mechanistic studies revealed that this formal [4 + 1] cycloaddition probably proceeds via C-C bond cleavage, alkene insertion, ß-hydrogen elimination, intramolecular alkene insertion, and then reductive elimination. An example of enantioselective reaction was also disclosed.
RESUMEN
The first catalytic and highly enantioselective synthesis of tribenzothiepin derivatives was achieved. Two types of intermolecular cycloadditions using either diphenyl-sulfide-tethered diynes or 2-phenyl sulfanylbenzene-tethered diynes with a monoalkyne successfully gave chiral multisubstituted tribenzothiepins in good to excellent eeâ values under mild conditions. The inversion energy of this saddle-shaped molecule was calculated by measurement of the racemization rate of chiral tribenzothiepins using the Eyring kinetic equation under heating conditions. The present protocol could also be used to prepare a chiral tribenzoselenepin.
RESUMEN
Ir-catalyzed sp(3) C-H alkylation of γ-butyrolactam with alkenes was used for the highly enantioselective synthesis of 5-substituted γ-lactams, which were readily converted into chiral 4-substituted γ-amino acids. A broad scope of alkenes was amenable as coupling partners, and the alkylated product using acrylate could be transformed into the key intermediate of pyrrolam A synthesis.
Asunto(s)
Aminoácidos/síntesis química , Iridio/química , Lactamas/química , Compuestos Organometálicos/química , Alquilación , Aminoácidos/química , Catálisis , Conformación Molecular , EstereoisomerismoRESUMEN
4-Substituted tryptophan derivatives and the total synthesis of cis-clavicipitic acid were achieved in reactions in which Ir-catalyzed C-H bond activation was a key step. The starting material for these reactions is asparagine, which is a cheap natural amino acid. The reductive amination step from the 4-substituted tryptophan derivative gave cis-clavicipitic acid with perfect diastereoselectivity.
Asunto(s)
Aminoácidos/química , Asparagina/química , Alcaloides de Claviceps/síntesis química , Iridio/química , Triptófano/química , Aminación , Catálisis , Alcaloides de Claviceps/química , Enlace de Hidrógeno , Estructura Molecular , EstereoisomerismoRESUMEN
Numerous natural products possess ring systems and functionality for which Hajos-Parrish ketone isomers with a transposed methyl group (termed "iso-Hajos-Parrish ketones") would be of value. However, such building blocks have not been exploited to the same degree as the more typical Hajos-Parrish hydrindane. An efficient three-step synthesis of such materials was fueled by a simple method for the rapid preparation of highly functionalized cyclopentenones, several of which are new chemical entities that would be challenging to access through other approaches. Furthermore, one iso-Hajos-Parrish ketone was converted into two distinct natural product analogues and one natural product. As one indication of the value of these new building blocks, that latter target was obtained in 10â steps, having previously been accessed in 18â steps using the Hajos-Parrish ketone.