A palladium‐catalyzed N−H/B−H double activation of 1,2‐dihydro‐1,2‐benzazaborines proceeded via cycloaddition with vinyl ethylene carbonate to produce polycyclic oxazaborolidines in 31–96 % yield. ...The key step in this process is the release of molecular hydrogen from a borate intermediate. Using a SPINOL‐derived phosphoramidite as a chiral ligand, chiral oxazaborolidines were synthesized in good to high yields with excellent enantioselectivity (up to 95 % ee). The vinyl group of the resulting oxazaborolidine underwent metathesis, Heck reaction, and Wacker oxidation without affecting the oxazaborolidine framework.
Catalytic N−H/B−H double activation of 1,2‐azaborines has been demonstrated. A wide variety of 1,2‐azaborines underwent cycloaddition with vinylethylene carbonate through N−H/B−H bond cleavage to produce unique polycyclic oxazaborolidines under mild conditions. Furthermore, highly enantioselective direct functionalization of 1,2‐azaborines afforded chiral tricyclic oxazaborolidines.
The Mizoroki–Heck reaction is one of the most efficient methods for alkenylation of aryl, vinyl, and alkyl halides. Given its innate nature, this protocol requires the employment of compounds ...possessing a halogen atom at the site of functionalization. However, the accessibility of organic molecules possessing a halogen atom at a particular site in aliphatic systems is extremely limited. Thus, a protocol that allows a Heck reaction to occur at a specific nonfunctionalized C(sp3)−H site is desirable. Reported here is a radical relay Heck reaction which allows selective remote alkenylation of aliphatic alcohols at unactivated β‐, γ‐, and δ‐C(sp3)−H sites. The use of an easily installed/removed Si‐based auxiliary enables selective I‐atom/radical translocation events at remote C−H sites followed by the Heck reaction. Notably, the reaction proceeds smoothly under mild visible‐light‐mediated conditions at room temperature, producing highly modifiable and valuable alkenol products from readily available alcohols feedstocks.
A selective Heck reaction at β‐, γ‐, and δ‐C(sp3)−H sites of aliphatic alcohols has been developed. The radical hydrogen‐atom transfer/I‐atom translocation process, combined with the palladium‐catalyzed Heck reaction, allows selective remote alkenylation at unactivated C(sp3)−H sites under mild visible‐light‐induced conditions at room temperature. Neither exogenous oxidants nor photosensitizers are necessary.
A direct functionalization of unsubstituted isoxazole (1) was achieved by generation of 4‐isoxazolyl anion species (3). An efficient 4‐iodination of isoxazole and halogen–metal exchange reaction ...using a turbo Grignard reagent (iPrMgCl⋅ LiCl) were essential for the generation of 3, which reacted with various electrophiles to give 4‐functionalized isoxazoles in good to high yields. Isoxazolyl boronate, boronic acid, and stannane were also synthesized as useful building blocks from 1. The current methods enabled us to synthesize multi‐functionalized isoxazoles by introducing each substituent into the desired positions. Furthermore, total synthesis of triumferol, which was isolated from Triumfetta rhomboidea, was achieved from 1 in only three steps.
Taking position: Preparation of a 4‐isoxazolyl anion species from 4‐iodoisoxazole using iPrMgCl⋅LiCl enabled introduction of a wide variety of functional groups into the 4‐position of the isoxazole ring in good to excellent yields. This approach provides various isoxazolyl metal species which can be used for multifunctionalization of isoxazoles. The step‐by‐step synthesis of 3,4,5‐trisubstituted isoxazoles was achieved by using the this 4‐isoxazolyl anion method.
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•Suzuki-Miyaura cross-coupling of 3,4-substituted 5-bromoisoxazoles at C5 position.•Use of bulky phosphine ligands increase the yields of trisubstituted isoxazoles.•Formation of ...ketone 4 is suppressed under the optimized conditions.
The Suzuki-Miyaura cross-coupling of 3,4-disubstituted 5-bromoisoxazoles 1 at the C5 position has successfully proceeded in the presence of Pd2(dba)3 and P(t-Bu)3·HBF4 catalysts to give the corresponding trisubstituted isoxazoles 3 in good to high yields while suppressing the formation of ketone 4 as a byproduct. The use of bulky phosphine ligand P(t-Bu)3·HBF4 is essential for the current transformation, and the formation of ketone 4, which was a major product in the previous report, was able to be suppressed under the current conditions.
The nitrogen‐heteroatom single bonds of 1,2‐azoles and isoxazolines underwent methylene insertion in the presence of CH2I2 (6 equiv.) and diethylzinc (3 equiv.) to produce a wide variety of the ...ring‐expanded six‐membered heterocycles. Density functional theory calculations suggest that the methylene insertion proceeds via cleavage of nitrogen‐heteroatom single bonds followed by ring closure.
Methylene insertions of a zinc carbenoid into nitrogen‐heteroatom single bonds of 1,2‐azoles and cyclic oximes are demonstrated. The reaction produces a wide variety of six‐membered heterocycles from easily preparable substrates. Furthermore, density functional theory calculations reveal the reaction mechanism, where cleavage of nitrogen‐heteroatom single bonds and following ring‐closure are essential for the ring‐expansion.
Intramolecular electrophilic aromatic substitution (SEAr) reaction at the 5-position of isoxazoles was achieved. The electron-donating heteroatoms (N and O) at the 4-position of isoxazoles, which can ...be readily prepared based on our originally developed synthetic procedure, and a cationic gold(I) catalyst are essential for the intramolecular SEAr reaction to synthesize isoxazole-containing fused heterocycles. Structurally diverse isoxazolopyridines 6 and isoxazolopyrans 9, including base-labile 3-unsubstituted derivatives, were synthesized in good to high yields. The addition of N-phenylbenzaldimine as a hydrogen acceptor improved yields in the synthesis of isoxazolopyridines. Furthermore, synthesis of the tetracyclic fused ring system 12 was achieved by tandem cyclization from the corresponding diyne 11.
Nesidiocoris tenuis
(Reuter) (Hemiptera: Miridae) is a zoophytophagous predator that feeds on plants as well as prey. Several non-crop host plant species have been used to maintain this mirid as a ...biological control agent in different crop systems. To evaluate the benefit of these non-crop host plants on biological control services, data on the life-history traits of
N. tenuis
on these plants are important as fundamental information. Herein, we studied the demographic growth parameters of
N. tenuis
reared on three alternative non-crop host plants (
Cleome hassleriana
Chod., Brassicales: Cleomaceae;
Verbena
×
hybrida
Voss, Lamiales: Verbenaceae; and
Sesamum indicum
L., Lamiales: Pedaliaceae) and one crop plant (tomato) in the absence of prey under laboratory conditions (25 ± 1 °C, 16:8 h L:D). The estimated intrinsic rate of increase in each plant was significantly greater in the following order:
S. indicum
(0.094) >
C. hassleriana
(0.074) > tomato (−0.002) >
Verbena
×
hybrida
(−0.060). The results indicated that
C. hassleriana
and
S. indicum
were able to fully support the development and reproduction of
N. tenuis
with nutrients derived from only its plant tissues, whereas
Verbena
×
hybrida
and tomato were not. Our findings revealed that
C. hassleriana
is a promising resource for the conservation or mass rearing of
N. tenuis
besides
S. indicum
.
A novel sp3 carbon‐rich tricyclic 3D scaffold‐based peptide mimetic compound library was constructed to target protein‐protein interactions. Tricyclic framework 7 was synthesized from ...9‐azabicyclo3,3,1nonan‐3‐one (11) via a gold(I)‐catalyzed Conia‐ene reaction. The electron‐donating group on the pendant alkyne of cyclization precursor 12 b–e was the key to forming 6‐endo‐dig cyclized product 7 with complete regioselectivity. Using the synthetic strategy for regioselective construction of bridged tricyclic framework 7, a diazatricyclododecene 3D‐scaffold 8 a, which enables the introduction of substituents into the scaffold to mimic amino acid side chains, was designed and synthesized. The peptide mimetics 21 a–u were synthesized via step‐by‐step installation of three substituents on diazatricyclododecene scaffold 8 a. Compounds 21 a–h were synthesized as α‐helix peptide mimics of hydrophobic ZZxxZ and ZxxZZ sequences (Z=Leu or Phe) and subjected to cell‐based assays: antiproliferative activity, HIF‐1 transcriptional activity which is considered to affect cancer malignancy, and antiviral activity against rabies virus. Compound 21 a showed the strongest inhibitory activity of HIF‐1 transcriptional activity (IC50=4.1±0.8 μM), whereas compounds 21 a–g showed antiviral activity with IC50 values of 4.2–12.4 μM, suggesting that the 3D‐scaffold 8 a has potential as a versatile peptide mimic skeleton.
Three‐dimensional (3D) scaffolds have the potential to provide unique bioactivity, which cannot be achieved by conventional flat aromatic ring‐based compounds. (Di)Azatricyclododecene scaffold with a bridged tricyclic system was developed and applied to design peptidomimetics with a 3D scaffold. The designed peptidomimetics showed inhibition of HIF transcription activity and antiviral activity toward rabies virus, both of which α‐helix peptide mediated interaction play a pivotal role.
Water-soluble pteroyl-
-dodecaborate conjugates (PBCs 1-4), were developed as folate receptor (FRα) targeting boron carriers for boron neutron capture therapy (BNCT). PBCs 1-4 had adequately low ...cytotoxicity with IC
values in the range of 1~3 mM toward selected human cancer cells, low enough to use as BNCT boron agents. PBCs 1-3 showed significant cell uptake by FRα positive cells, especially U87MG glioblastoma cells, although the accumulation of PBC 4 was low compared with PBCs 1-3 and L-4-boronophenylalanine (L-BPA). The cellular uptake of PBC 1 and PBC 3 by HeLa cells was arrested by increasing the concentration of folate in the medium, indicating that the major uptake mechanisms of PBC 1-3 are primarily through FRα receptor-mediated endocytosis.
A directing/protecting‐group‐free synthesis of 1,3,4,5‐tetraaryl‐substituted pyrazoles was achieved through four transition metal‐catalyzed direct arylations. Various pyrazoles with four different ...aryl rings were obtained using readily available reagents from an unsubstituted pyrazole. Two aryl‐substituted pyrazoles showed intense violet fluorescence, high quantum yields (Φf=0.68, 0.64), and large Stokes shifts (19000, 15200 cm−1).
Free from direction: A new approach has been developed for the preparation of tetraaryl‐substituted pyrazoles without the need for directing or protecting groups. This was achieved by means of four transition‐metal‐catalyzed arylations. Various pyrazoles with four different aryl rings were obtained from an unsubstituted pyrazole. Two aryl‐substituted pyrazoles showed intense violet fluorescence, high quantum yields (Φf=0.68, 0.64), and large Stokes shifts (19000, 15200 cm−1).
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