Wetting hysteresis induces effective unidirectional water transport through a fluctuating nanochannel

We propose a water pump that actively transports water molecules through nanochannels. Spatially asymmetric thermal fluctuations imposed on the channel radius cause unidirectional water flow without osmotic pressure, which can be attributed to hysteresis in the cyclic transition between the wetting/drying states. We show that the water transport depends on fluctuations, such as white, Brownian, and pink noises. Because of the high-frequency components in white noise, fast switching of open and close states inhibits channel wetting. Conversely, pink and Brownian noises generate high-pass filtered net flow. Brownian fluctuation leads to a faster water transport rate, whereas pink noise has a higher capability to overcome osmotic pressure in the opposite direction. A trade-off relationship exists between the resonant frequency of the fluctuation and the flow amplification. The proposed pump can be considered as an analogy for the reversed Carnot cycle, which is the upper limit on the energy conversion efficiency

Formation of anti-Bredt-type azabicyclo[4.2.0]octene frameworks through photochemical intramolecular [2+2] cycloaddition between indole and a distal double bond of allene

Irradiation of 1-(penta-3,4-dienoyl)indole derivatives in the presence of an aromatic ketone by a high-pressure mercury lamp through Pyrex glass gave two types of cyclized products stereoselectively in high combined yields. The major product was a tetracyclic indoline derivative containing anti-Bredt-type azabicyclo[4.2.0]octene moiety produced via photo [2+2] cycloaddition between indole and a distal double bond of allene, accompanied by a small amount of proximal [2+2] adduct. Among a range of aromatic ketones screened, 3 ',4 '-methylenedioxyacetophenone was found to sensitize the substrate most effectively

Intramolecular [2+2] Cycloaddition of Isocarbostyrils Catalyzed by an Iridium Visible-Light Photocatalyst

Irradiation on N-(omega-alkenyl)isocarbostyrils in the presence of an iridium photocatalyst by LEDs emitting 455 nm light gave the corresponding cyclobutane-fused benzo[b]quinolizine derivatives stereoselectively in high yields. Loading 1 mol % of the catalyst was enough to obtain high yields of the products in convenient reaction time in many cases. The reaction likely proceeds through stepwise [2 + 2] cycloaddition via a triplet biradical intermediate

Oxidative Generation of 1-Nitroalkyl Radicals and Their Addition Reaction to Olefins

1-Nitroalkyl radicals are generated by oxidation of potassium salt of 1-aci-nitroalkanes with ammonium hexanitratocerate(IV). When the oxidation is carried out in the presence of electron-rich olefins, such as silyl enol ethers, intermolecular addition of the radicals onto the olefins proceeds to afford β-nitro ketones, which are further converted to α,β-unsaturated ketones in high yield. Stereoselective construction of fused ring systems is achieved by intramolecular addition of 1-nitroalkyl radicals

Stereoselective construction of cycloheptene-fused indoline frameworks through photosensitised formal [5+2] cycloaddition

Irradiation of 1-acylindole derivatives that possess a vinylcyclopropane moiety at the end of the acyl side chain by a high-pressure mercury lamp through Pyrex glass under sensitization of an aromatic ketone gave the corresponding cyclised products stereoselectively in high yields. The distribution of the products was highly dependent on the substituents on the cyclopropane ring. In the case of a simple cyclopropane, the product was a mixture of ring-expanded cycloheptene-fused indoline and all -cis-fused cyclopropylcyclobutane-fused indoline through [2 + 2] cycloaddition, while cycloheptene-fused indolines were predominantly produced via formal [5 + 2] cyclisation in the case of substituted cyclopropanes. In particular, the product selectivity was substantially high in the case of silylcyclopropane

Photosensitized Intramolecular [2+2] Cycloaddition of 1H-Pyrrolo[2,3-b]pyridines Enabled by the Assistance of Lewis Acids

The [2+2] photocycloaddition of alkenyl-tethered 1H-pyrrolo[2,3-b]pyridine derivatives sensitized with 3',4'-dimethoxyacetophenone under irradiation by a high-pressure mercury lamp through Pyrex glass was dramatically accelerated by the addition of Lewis acids, preferably Mg(OTf)(2), to give the products stereoselectively in high yields. The reaction without a Lewis acid gave only small amounts of the [2+2] cycloaddition products. Conformational fixation of the substrates by coordination with a Lewis acid was presumed to facilitate the cycloaddition

Generation of α-Nitroalkyl Radicals by Oxidation of Nitronate Anions with Cerium(IV) Ammonium Nitrate and Their Addition Reaction to Electron-Rich Olefins

α-Nitroalkyl radicals are generated by oxidation of nitronate anions with cerium(IV) ammonium nitrate. When the reactions are carried out in the presence of electron-rich olefins, such as silyl enol ethers, intermolecular addition of the radicals proceeds to afford β-nitroketones, which are further converted to α,β-unsaturated ketones in good yield

Stereoselective preparation of methylenecyclobutane-fused angular tetracyclic spiroindolines via photosensitized intramolecular [2+2] cycloaddition with allene

Irradiation of 3-(hexa-4,5-dienyl)indole derivatives in the presence of 3',4'-dimethoxyacetophenone by a high-pressure mercury lamp through Pyrex glass gave the corresponding [2+2] cycloaddition products stereoselectively in high yields. The major product was a methylenecyclobutane-fused angular tetracyclic spiroindoline derivative produced by the [2+2] cycloaddition through a parallel orientation. The minor product was a hexahydromethanocarbazole derivative through a crossed orientation. Electron-withdrawing substituents, such as acyl or alkoxycarbonyl, on the indole nitrogen were suitable for this reaction. (C) 2019 Elsevier Ltd. All rights reserved

Isomerization-Asymmetric Hydrogenation Sequence Converting Racemic beta-Ylidenecycloalkanols into Stereocontrolled beta-Substituted Cycloalkanols Using a Ru Catalytic System with Dual Roles

Racemic beta-ylidenecycloalkanols were transformed into the cis-beta-substituted cycloalkanols with high enantio- and diastereoselectivities through an isomerization-asymmetric hydrogenation sequence with the (4,4 '-bi-1,3-benzodioxole)-5,5 '-diylbis[di(3,5-xylyl)phosphine (DM-Segphos)/2-dimethylamino-1-phenylethylamine (DMAPEN)-ruthenium(II) catalyst; such transformation hardly proceeded by single-step asymmetric hydrogenation. The reaction was usually carried out with a substrate-to-catalyst molar ratio of 500 under 4 to 10 atm of H-2 to afford the products in cis/trans ratio up to 99:1 and 98% ee. Mechanistic experiments suggested that this catalytic system reversibly formed two reactive species, types (I) and (II), through a ruthenacyclic amide intermediate. The amide complex and allylic alcohol reacted to afford the allylic alkoxide complex with partial or full removal of diamine (type (I)), and this type (I) complex catalyzed isomerization of the allylic alcohols into the racemic alpha-substituted ketones. The RuH2 complex with chelation of diamine (type (II)) formed by reaction of the amide complex and hydrogen promoted asymmetric hydrogenation of racemic alpha-substituted ketone into the stereocontrolled beta-substituted cycloalkanols through dynamic kinetic resolution

Generation of Radical Species from Cyclohexane-1,2-dione and the Reaction with Olefins : Preparation of 4,5-Dihydro-7(6H)-benzofuranone Derivatives

Oxidation of cyclohexane-1,2-dione with ammonium hexanitratocerate(IV) (CAN) generates 2,3-dioxocyclohexyl radical, which reacts with electron-rich olefins to afford the corresponding addition products. The adducts thus generated are converted to 4,5-dihydro-7(6H)-benzofuranone by acid treatment. In addition to cyclohexane-1,2-dione, radical species are also generated from cyclopentane-1,2-dione and cycloheptane-1,2-dione