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This account describes the development of novel dearomatization reactions of phenols using transition-metal-catalyzed ipso-Friedel-Crafts-type processes. In general, phenols function as O-nucleophiles in transition-metal-catalyzed allylic substitution reactions, providing the corresponding aryl ethers. We found that, however, an intramolecular ipso-Friedel-Crafts allylic alkylation of phenols proceeded smoothly in the presence of a palladium catalyst, producing various spiro[4.5]cyclohexadienone derivatives. This finding led us to launch detailed investigations into this type of reaction. Pd-catalyzed intramolecular Friedel-Crafts allylic alkylation of phenols was next examined to synthesize 10-vinyl 9,10-dihydrophenanthrene derivatives. This reaction was successfully extended to a catalytic asymmetric process. We also developed a novel synthetic method for spiro[5.5]cyclohexadienones based on a Pd-catalyzed intramolecular ipso-Friedel-Crafts-type addition of phenols to ç3-propargylpalladium(II) intermediates. Mechanistic studies revealed that the present reaction proceeds through a rearomatization-assisted oxidative addition. Moreover, a Au-catalyzed intramolecular ipso-Friedel-Crafts alkenylation of phenols with a terminal alkyne is discussed. [ABSTRACT FROM AUTHOR]

We have developed a novel method for synthesizing trisubstituted cyclopropane derivatives by a palladium-catalyzed intramolecular allylic alkylation of ƒ¿-aryl esters. By using ƒ¿-aryl ƒ¿-(methoxycarbonyl) ƒÁ-vinyl ƒÁ-lactones as substrates, decarboxylative formation of ƒÎ- allylpalladium(II) intermediates followed by an intramolecular allylic alkylation of the ester enolates proceeded in the presence of 5 mol% of a palladium catalyst, producing 1-aryl-1-(methoxycarbonyl)-2-vinylcyclopropanes in good to excellent yields and high diastereoselectivities. The relative configuration of the major isomer was determined by transforming the product into a known intermediate of milnacipran synthesis. When we extended our method to asymmetric catalysis, we obtained methyl (1S,2S)-1-phenyl-2-vinylcyclopropanecarboxylate in up to 55% ee by using (S)-[2Œ-(diphenylmethoxy)-1,1Œ-binaphthalen-2- yl](diphenyl)phosphine as a chiral monodentate phosphorus ligand. [ABSTRACT FROM AUTHOR]

We developed a novel method of synthesizing nitrogen-containing fused-polycyclic compounds using tyramine derivatives as substrates. The method is based on the dearomatization of phenols via an intramolecular ipso-Friedel-Crafts allenylation and sequential bond-forming-cleavage reactions initiated by the construction of an indole skeleton. Structurally diverse fused-heterocycles were produced in reaction sequences requiring only a few steps. [ABSTRACT FROM AUTHOR]

Homogeneous chiral nickel-bisphosphine complexes catalyze the asymmetric hydrogenation of α-amino-β-keto ester hydrochlorides through dynamic kinetic resolution to efficiently afford anti-β-hydroxy-α-amino esters with high diastereo- and enantioselectivities. [ABSTRACT FROM AUTHOR]

This study evaluates the challenges of powder removal inside surface-based lattice structures that have been fabricated by the polymer-powder-based additive manufacturing (AM) process. The natural flow adaptations of plant cells' morphology and perforation that allow water and minerals easy transport have been bio-mimicked for ease of powder flow during post-processing powder removal. Vessel-shaped and supportless lattice structures with ventilations have been designed, followed by a Computational fluid dynamics (CFD) simulation. This is to study the fluid flow pattern and turbulence inside the lattice structures. The designed lattice structures were 3d printed with polyamide 12 (PA-12) material by HP-MJF 4200 powder bed technology. They were followed by powder removal using a pressurised air gun and computerised tomography (CT-scan) to observe the regions of trapped powder inside the lattice structures. The uni-axial compression tests were conducted to observe the effect of ventilation on the mechanical properties of the lattice structures. [ABSTRACT FROM AUTHOR]

Aziridines are an important class of synthetic intermediates that are widely used in the synthesis of useful compounds and intermediates found in pharmaceuticals, natural products, and other functional materials. Several compounds with the aziridine ring system exhibit significant biological activity as well. Consequently, the synthesis of aziridines has been the focus of intense research over the last two decades. Despite numerous successful methods, no review article exclusively on Enone aziridination has been published to date. Therefore, the up‐to‐date developments in the synthesis of aziridines from enones, which are convenient synthetic precursors, by nucleophilic addition reactions are described with advantages, limitations, and mechanistic pathways. [ABSTRACT FROM AUTHOR]

The article presents a study conducted by Yasumasa Hamada and Takayuki Shiori, researchers from Naguya, Japan, regarding the recent progress of the synthesis of biologically active marine cyclic peptides and depsipeptides of natural products. It investigates on the constituents of marine organisms that will provide new cyclic peptides and depsipeptides having active structures and biological activities.

A novel platinum-catalyzed cascade cyclization reaction was developed by intramolecular Friedel-Crafts-type C−H coupling of aniline derivatives with a propargyl carbonate unit-allylic amination sequence. Treatment of various propargyl carbonates tethered to meta-aniline derivatives with a Pt(dba)3/DPEphos catalyst system afforded the corresponding 3,4-fused tricyclic 3-alkylidene indolines in 42-99 % yield, which were transformed into 3,4-fused indole derivatives by reaction with trifluoroacetic acid. The reaction products exhibited antiproliferative activities against cancer cells, but not normal cells, revealing the potential usefulness of this reaction for medicinal chemistry. [ABSTRACT FROM AUTHOR]

Gephyrotoxin 287C, a bioactive alkaloid bearing a perhydropyrrolo[1,2- a]quinoline skeleton with five stereocenters, is an attractive target for synthetic organic chemistry. We achieved an enantioselective total synthesis of (+)-gephyrotoxin 287C, for which the key steps were palladium-catalyzed asymmetric allylic amination using a chiral diaminophosphine oxide (DIAPHOX) preligand, diastereoselective intramolecular Mannich reaction, and tin tetrachloride-catalyzed diastereoselective conjugate addition/protonation. [ABSTRACT FROM AUTHOR]

Herein we report an enantioselective synthesis of (R)-Sumanirole wherein an organocatalytic asymmetric aziridination of 2-nitrocinnamaldehyde was the key step. [ABSTRACT FROM AUTHOR]

We have developed a novel synthetic method to furnish spiro[4.5]cyclohexadienones using an gold-catalyzed carbocyclization of phenols with a terminal alkyne via an intramolecular ipso-Friedel-Crafts alkenylation. Using 2-5 mol% of gold catalyst, 1 equiv. of methanesulfonic acid, and 1 equiv. of 2,6-di- tert-butylpyridine, a variety of spiro[4.5]cyclohexadienone derivatives with an exo-cyclic olefin unit was obtained in good to excellent yields. The divergent synthesis of dihydronaphthalene derivatives was also examined based on the newly developed gold catalysis. [ABSTRACT FROM AUTHOR]

We have succeeded in the highly diastereoselective synthesis of cyclobutane-fused multi-cyclic compounds using a scandium-catalyzed cascade cyclization. Using 3-10 mol% of scandium(III) triflate [Sc(OTf)3], various cyclobutane-fused tetrahydroquinoline derivatives as well as its chromane, thiochromane, and tetrahydronaphthalene analogues were obtained in good to excellent yields. Derivatizations of the reaction products, as well as the plausible reaction mechanism, are also discussed. [ABSTRACT FROM AUTHOR]

This review describes our recent works on the diastereo- and enantioselective synthesis of anti-β-hydroxy-α-amino acid esters using transition-metal-chiral-bisphosphine catalysts. A variety of transition metals, namely ruthenium ( Ru), rhodium ( Rh), iridium ( Ir), and nickel ( Ni), in combination with chiral bisphosphines, worked well as catalysts for the direct anti-selective asymmetric hydrogenation of α-amino-β-keto ester hydrochlorides, yielding anti-β-hydroxy-α-amino acid esters via dynamic kinetic resolution ( DKR) in excellent yields and diastereo- and enantioselectivities. The Ru-catalyzed asymmetric hydrogenation of α-amino-β-ketoesters via DKR is the first example of generating anti-β-hydroxy-α-amino acids. Complexes of iridium and axially chiral bisphosphines catalyze an efficient asymmetric hydrogenation of α-amino-β-keto ester hydrochlorides via dynamic kinetic resolution. A homogeneous Ni-chiral-bisphosphine complex also catalyzes an efficient asymmetric hydrogenation of α-amino-β-keto ester hydrochlorides in an anti-selective manner. As a related process, the asymmetric hydrogenation of the configurationally stable substituted α-aminoketones using a Ni catalyst via DKR is also described. [ABSTRACT FROM AUTHOR]

A novel and efficient synthetic method for functionalized spiro[4.5]cyclohexadienones was developed based on the palladium-catalyzed sequential process: Heck insertion to an allene-intramolecular ipso-Friedel-Crafts allylic alkylation cascade. Using 5 mol% of palladium catalyst, a wide variety of spirocycles was obtained in good to excellent yields. The developed cascade process was also applicable to the synthesis of tetrahydronaphthalene derivatives. [ABSTRACT FROM AUTHOR]

Inspiroation: A novel synthesis of spirocycles based on a palladium‐catalyzed intramolecular ipso‐Friedel–Crafts alkylation of phenols (see scheme; dba=dibenzylideneacetone) and indoles is described. Mechanistic studies show that the reaction proceeds through an unprecedented rearomatization‐assisted oxidative addition. [ABSTRACT FROM AUTHOR]

A novel method of the enantioselective synthesis of 2-substituted hexahydroquinolin-4-ones is described. The method relies on a Pd-catalyzed asymmetric allylic amination using a chiral diaminophosphine oxide (DIAPHOX) preligand and diastereoselective intramolecular Mannich reaction. The developed synthetic method could be applied to the catalytic asymmetric synthesis of (+)-2-epi-cis-195A. [ABSTRACT FROM AUTHOR]

Highly enantioselective L-thiaproline catalyzed α-aminoxylation of aldehydes in the presence of water and tetrabutylammonium bromide followed by in situreduction to afford the respective α-aminoxy alcohols has been developed in good to high yields (74–88%) and excellent enantioselectivities (93–>99%). [ABSTRACT FROM AUTHOR]