Divergent Asymmetric Synthesis of Chiral Spiroheterocycles through Pd-Catalyzed Enantio- and Diastereoselective [3 + 2] Spiroannulation.

The palladium-catalyzed divergent asymmetric synthesis of chiral spiro-furanindoline derivatives is described. The zwitterionic alkoxy π-allyl Pd(II) intermediate, generated catalytically from vinyl ethylene carbonate (VEC), could undergo ligand-controlled enantio- and diastereoselective dipolar [3 + 2] spiroannulation with indole-based azadienes to afford the optically active spiro-furanindolines embedding an all-carbon quaternary stereocenter in high yields (up to 99%) with good to excellent stereoselectivities (up to 99% ee and up to >94:6 dr).

Agrobacterium-Mediated Capsicum annuum Gene Editing in Two Cultivars, Hot Pepper CM334 and Bell Pepper Dempsey.

Peppers (Capsicum annuum L.) are the most widespread and cultivated species of Solanaceae in subtropical and temperate countries. These vegetables are economically attractive worldwide. Although whole-genome sequences of peppers and genome-editing tools are currently available, the precision editing of peppers is still in its infancy because of the lack of a stable pepper transformation method. Here, we employed three Agrobacterium tumefaciens strains-AGL1, EHA101, and GV3101-to investigate which Agrobacterium strain could be used for pepper transformation. Hot pepper CM334 and bell pepper Dempsey were chosen in this study. Agrobacterium tumefaciens GV3101 induced the highest number of calli in cv. Dempsey. All three strains generated similar numbers of calli for cv. CM334. We optimized a suitable concentration of phosphinothricin (PPT) to select a CRISPR/Cas9 binary vector (pBAtC) for both pepper types. Finally, we screened transformed calli for PPT resistance (1 and 5 mg/L PPT for cv. CM334 and Dempsey, respectively). These selected calli showed different indel frequencies from the non-transformed calli. However, the primary indel pattern was consistent with a 1-bp deletion at the target locus of the C. annuumMLO gene (CaMLO2). These results demonstrate the different sensitivity between cv. CM334 and Dempsey to A. tumefaciens-mediated callus induction, and a differential selection pressure of PPT via pBAtC binary vector.

Optical Analysis of Hole Patterned Ag Nanoparticle Structure.

A structure with periodic sub-wavelength nanohole patterns interacts with incident light and causes extraordinary optical transmission (EOT), with metal nanoparticles leading to localized surface plasmon resonance (LSPR) phenomena. To explore the effects of metal nanoparticles (NPs), optical analysis is performed for metal NP layers with periodic hole patterns. Investigation of Ag NP arrangements and comparisons with metal film structures are presented. Ag NP structures with different hole configuration are explored. Also, the effects of increasing light incident angle are investigated for metal NP structures where EOT peak at 460 nm wavelength is observed. Moreover, electric field distributions at each transmittance peak wavelengths and optical noise are analyzed. As a result, optical characteristics of metal NP structures are obtained and differences in resonance at each wavelength are highlighted.

Synergistic Dual Transition Metal Catalysis.

Synergistic catalysis, a type of plural catalysis which utilizes at least two different catalysts to enable a reaction between two separately activated substrates, has unlocked a plethora of previously unattainable transformations and novel chemical reactivity. Despite the appreciable utility of synergistic catalysis, specific examples involving two transition metals have been limited, as ensuring a judicious choice of reaction parameters to prevent deactivation of catalysts, undesirable monocatalytic event(s) leading to side products, or premature termination and other potentially troublesome outcomes present a formidable challenge. Excluding those driven by photocatalytic mechanisms, this review will highlight the reported examples of reactions that make use of two simultaneous catalytic cycles driven by two transition metal catalysts.

Rh(II)/Mg(OtBu)2-Catalyzed Tandem One-Pot Synthesis of 1,4-Oxazepines and 1,4-Oxazines from N-Sulfonyl-1,2,3-triazoles and Glycidols.

A novel, one-pot route for the synthesis of nonaromatic ring-fused 1,4-oxazepines and 1,4-oxazines has been developed. The reaction features a sequential rhodium(II)-catalyzed reaction of N-sulfonyl-1,2,3-triazoles with glycidols, followed by a regioselective Lewis acid Mg(OtBu)2-catalyzed intramolecular ring-opening reaction. It has been found that the regioselectivity in the epoxide ring-opening was largely determined by the substituents on the glycidols. Thus, substituted glycidols (R2 ≠ H) afforded seven-membered oxazepine derivatives selectively, while unsubstituted glycidols (R2 = H) afforded six-membered oxazine derivatives. Plausible reaction pathways are elucidated and supported by experiments with several glycidols bearing different substituents around the epoxide functionality.

Synthesis of α-methylene-δ-oxo-γ-amino esters via Rh(ii)-catalyzed coupling of 1-sulfonyl-1,2,3-triazoles with Morita-Baylis-Hillman adducts.

A rhodium(ii)-catalyzed coupling of 1-sulfonyl-1,2,3-triazoles, prepared from 1-alkynes and sulfonyl azides, with Morita-Baylis-Hillman (MBH) adducts afforded highly functionalized α-methylene-δ-oxo-γ-amino esters in excellent yields with broad functional group tolerance. This transformation can also be successfully accomplished as a multicomponent all-in-one-pot reaction of 1-alkynes, sulfonyl azides and MBH adducts in the presence of Cu(i) and Rh(ii) catalysts.

Pd-Catalyzed Aminocarbonylation of the Blaise Reaction Intermediate: One-Pot Synthesis of (Z)-3-Methyleneisoindolin-1-ones from Nitriles.

A highly efficient method for the one-pot synthesis of stereocontrolled (Z)-3-methyleneisoindolin-1-ones was developed starting from 2-bromoarylnitriles via tandem sequential reaction with a Reformatsky reagent (Blaise reaction), followed by Pd-catalyzed intramolecular aminocarbonylation with carbon monoxide at 1 atm pressure. It has been found that the conformational flexibility of the bisphophine ligand is of great importance to the success of this tandem aminocarbonylation reaction.

Cu(I)/Rh(II)-Catalyzed Tandem Convergent Multicomponent Reaction for the Regio- and Stereocontrolled Synthesis of γ-Oxo-ß-amino Esters.

The first example of a highly regio- and stereoselective catalytic method for the three-component one-pot synthesis of highly functionalized α-vinylated γ-oxo-ß-amino esters is disclosed. In this catalytic triad, the Cu(I)-catalyst selectively catalyzes the cycloaddition of the 1-alkyne and sulfonyl azide first resulting in the corresponding 1-sulfonyl-1,2,3-triazole. An α-imino Rh(II)-carbene is generated from an open-chain α-imino diazo of the triazole, and this species reacts with γ-hydroxy α,ß-unsaturated esters to form allylic (Z)-amino vinyl ethers. Rapid deconjugative [3,3]-sigmatropic rearrangement affords the α-vinyl γ-oxo-ß-amino esters in high yields with high levels of diastereoselectivity.

From triazoles to imidazolines through the sequential N-H insertion of α-imino rhodium-carbenes into ß-enamino esters/enamine-imine tautomerization/conjugate addition cascade.

A rhodium(II)-catalyzed denitrogenative coupling of N-sulfonyl-1,2,3-triazoles with ambiphilic ß-enamino esters affords 2,5-dihydro-1H-imidazoles (3-imidazolines) with broad functional group tolerance. Mechanistic studies using a deuterium-labeled triazole suggest that the reaction proceeds in a cascade through the N-H insertion of an α-imino rhodium-carbene, followed by enamine-imine tautomerization and conjugate addition. Moreover, the reaction proceeds with high diastereoselectivity for α-substituted ß-enamino esters (R(3) = Me, Ph) to give a single diastereomer.

DMF as a source of oxygen and aminomethine: stereoselective 1,2-insertion of rhodium(II) azavinyl carbenes into the C═O bond of formamides for the synthesis of cis-diamino enones.

A new catalytic reaction in which all the atoms of a formamide are incorporated into the product through a formal stereoselective 1,2-insertion of rhodium(II) azavinyl carbenes, generated in situ from readily available N-sulfonylated 1,2,3-triazoles, into the C═O bond of DMF and other N,N-disubstituted formamides to afford cis-diamino enones is described.

Insight into the origin of the positive effects of imidazolium salt on electrocatalytic activity: ionic carbon nanotubes as metal-free electrocatalysts for oxygen reduction reaction.

We report remarkable metal-free electrocatalytic activities of the imidazolium salt-functionalized ionic multi-walled carbon nanotubes (IM-f-MWCNTs) in the oxygen reduction reaction (ORR). The electrocatalytic activity can be attributed to the induced polarization of the π-electrons of CNTs, thus accelerating interfacial electron transfer. The zwitterionic MWCNTs functionalized with poly(vinylimidazolium sulfonate) have a more positive surface charge and exhibit a better electrocatalytic activity than the poly(vinylbutylimidazolium chloride)-functionalized MWCNTs. The IM-f-MWCNTs showed better fuel selectivity than the commercial Pt/C electrocatalyst.

High-density assembly of gold nanoparticles with zwitterionic carbon nanotubes and their electrocatalytic activity in oxygen reduction reaction.

Gold nanoparticles (AuNPs) were assembled with high density onto multi-walled carbon nanotubes, which were functionalized with zwitterionic poly(imidazoliumsulfonate). The AuNP/zwitterionic CNT hybrids exhibited decent electrocatalytic activity in oxygen reduction reaction as the AuNP-based catalysts.