No abstract

On-surface Ullmann coupling reaction of aryl chlorides has been achieved on Cu(111), Ag(111), and Au(111), and the mechanism has been investigated on the single molecule level using scanning tunneling microscopy and density functional theory. The different reactivity of the aryl halides was utilized to design a stepwise on-surface synthesis, which affords a zigzag template and then converts to 2D porous networks.

A series of symmetrical and unsymmetrical stilbenes bearing two or more strong electron-withdrawing groups were oxidatively cleaved to the corresponding aldehydes in high yield by electrocatalytic anodic oxidation in aqueous acetonitrile employing a new high oxidation potential triphenylamine electrocatalyst. The oxidations apparently involve the corresponding 1,2-diols, which are also converted to aldehydes in high yield under the same conditions.

The efficiency of Ullmann reaction of aryl chlorides on an Au(111) surface has been substantially increased by using dosed Cu as a catalyst. The different reactivity of aryl bromides and aryl chlorides has been exploited to design a programmed, on-surface synthesis to form 2D covalent organic frameworks.

No abstract

A fructose-derived diacetate ketone has been shown to be an effective catalyst for asymmetric epoxidation. High ee's have been obtained for a variety of trans-and trisubstituted olefins including electron-deficient α,β-unsaturated esters as well as certain cis-olefins.Chiral ketones of various structures have been extensively investigated for asymmetric epoxidation of olefins in a number of laboratories. 1 In our studies, we have found that fructosederived ketone 1 provides high ee's for a wide variety of trans-and trisubstituted olefins, 2 and oxazolidinone ketone 2 can give high ee's for olefins which had not been effective with ketone 1, including various cis-olefins, 3a,c,d,e,g,k,l styrenes, 3b,c,d,f and certain trisubstituted 3h,j and tetrasubstituted olefins. 3i,j In our efforts to expand the substrate scope, we have reported that ketone 3a is an effective epoxidation catalyst for a variety of electron-deficient α,β-unsaturated esters. 4 Replacing the fused ketal of 1 with more electron-withdrawing diacetates significantly enhances the ketone's reactivity and possibly reduces the Baeyer-Villiger decomposition. Herein we wish to report our detailed studies on epoxidations with ketone 3a and its related analogues.Email: yian@lamar.colostate.edu. Ketone 3a can be synthesized from ketone 1 in two steps by selective deketalization with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) 5 and subsequent acetylation with Ac 2 O and catalytic amount (2 mol%) of DMAP (Scheme 1). 4 Ketone 3a is highly electrophilic and can easily form a hydrate with water. 6 With this method, ketone 3a can be obtained largely in ketone form by avoiding moisture. The β-acetate of ketone 3a is prone to elimination to form an enone. To minimize this elimination, it is crucial to use only a small amount of DMAP (ca. 2 mol%) and to carefully control the reaction time in the acetylation step. Nevertheless, it was found that the resulting enone was barely active and had little impact on the asymmetric epoxidation. Alternatively, ketone 3a can be readily prepared in hydrate form from ketone 1 by one pot deketalization and acetylation with ZnCl 2 , AcOH, and Ac 2 O in water (Scheme 2). 7,8,9 However, if ketone 3a is desired, it can be obtained from 3a·H 2 O by simply dissolving 3a·H 2 O in solvents such as EtOAc and stirring with Na 2 SO 4 overnight at rt, followed by filtration and concentration or by passing 3a·H 2 O through a short column of SiO 2 . In CDCl 3 , the hydrate gradually converted into the ketone as judged by 1 H NMR (25% ketone at 10 min, 50% ketone at 30 min, 67% ketone at 1 h, 90% ketone at 2 h, 100% ketone at 11 h). In CD 3 CN-D 2 O (1.5:1, v/v), ca. 21% of the ketone was formed from the hydrate at 1 h (ca. 22% at 7 h). When the ketone was subjected to the same solvent mixture, ca. 26% of the ketone remained at 1 h (ca. 25% at 7 h). It appears that a similar amount of the ketone was present at around 1 h regardless of whether the ketone or its hydrate was used. Similar conversions and ee's were also obtained for the e...

No abstract

Microglial inflammation leads to the upregulation of proinflammatory cytokine and proinflammatory enzyme expression, resulting in inflammation‐induced neuronal cell apoptosis. Ketamine, an anesthetic mostly used in critical patients, has been reported to possess neuroprotective effects. However, the potential mechanism is still not well understood. In the present study, we investigated how ketamine attenuates lipopolysaccharide (LPS)‐mediated BV2 cell inflammation. LPS upregulated proinflammatory cytokine and proinflammatory enzyme expression, increased NF‐κB phosphorylation and nuclear translocation, and augmented calcium (Ca2+)/calmodulin‐dependent protein kinase II (CaMK II) phosphorylation and Ca2+ levels in BV2 cells. Ketamine could reverse these LPS‐induced effects. Furthermore, AP5, an inhibitor of NMDA receptors, inhibited LPS‐induced inflammatory effects in BV2 cells, which was similar to the effects of ketamine. Moreover, these effects of ketamine against LPS‐mediated inflammation in BV2 cells could be reversed by D‐serine, an activator of NMDA receptors. The present study suggests that ketamine, by inhibiting NMDA receptors, attenuating Ca2+ levels, and inhibiting CaMK II phosphorylation, NF‐κB phosphorylation and nuclear translocation, may ameliorate LPS‐mediated inflammation in BV2 cells.