A NOVEL SYNTHESIS OF α－ARYLSELENO－α－ACYL PHOSPHORANES AND ITS INTRAMOLECULAR WITTIG REACTION

Q-Acyl phosphoranes can readily react with areneselenium canons,which can be obtained from diaryl diselenides by oxidative reaction, to give a-arylseleno-a-acyl phosphoranes in good yields. The a-arylseleno-a-acyl phosphoranes can undergo intramolecular Wittig reaction to afforda convenient synthesis of arylselenoacetylenes.

Pentacoordinate Phosphoranes as Versatile Reagents in Fluoroalkylation Reactions

A general method for the synthesis of bench-stable bis(difluoromethyl)pentacoordinate phosphoranes has been developed.The reaction is rapid,operationally simple,and easily scalable.The pentacoordinate phosphoranes can generate both difluoromethyl radical(·CF_(2)H)and difluorocarbene(:CF_(2))intermediates.Thus,a variety of fluoroalkylation transformations havebeen achieved by·CF_(2)H,such asoxidativedifluoromethylation of electron-deficient heterocycles,nickel/photoredox dual-catalyzed difluoromethylation of aryl bromides,and photoredox difluoromethylation of alkenes,or by:CF_(2),such as gem-difluorocyclopropanation of alkenes,base-promoted difluoromethylation of heteroatom nucleophiles,Pd-catalyzed difluoromethylation of arylboronic acids,and Cu-mediated trifluoromethylation of aryl iodides(via:CF_(2) and recombined CF_(3)-).These fluoroalkylation methods have been successfully applied to late-stage fluoroalkylation of drugs and drug-like molecules.

First principles study of field effect device through van der Waals and lateral heterostructures of graphene, phosphorene and graphane

Chemical modification and vertical stacking of two-dimensional materials are promising techniques for new nanoelectronic devices. We present Density Functional Tight Binding(DFTB) calculations of a field-effect device,based on lateral and vertical heterostructures of 2D materials. The device consists of a phosphorene channel protected by graphene sheets, which work as contacts and are divided into the source and drain by local hydrogenation of graphene, which gives insulating graphane. In this device composed of only 3 layers, single sheets of graphene-graphane can work as both leads and oxide gate, while also acting as protective layers for a phosphorene channel. We show how for perfect vd W heterostructures of graphane/phosphorene/graphane and graphene/phosphorene/graphene the Schottky barrier is deeply influenced by normal electric fields, and we characterize electronic transport of such a device. Finally, we characterize phosphorene channel doping and defects, which, at very high densities in the transport direction, enables transport inside the phosphorene bandgap.

A Simple Approach to the Synthesis of 2H-1-Benzopyrans and 3H-Naphtho[2,1-b] pyran Via Intramolecular Wittig Reactiont

In the presence of K2CO3, 2-hydroxyethyltripheny phosphonium bromide (1) reacts with substituted salicylaldehyde (2) and 2-hydroxy-1 naphthaldehyde (4) at 110 ℃ in a sealed tube. The title compounds were prepared in medium yield. The ratio of bromide (1) to aldehyde derivatives was also discussed in this paper.

Synthesis of dimethyl 3-perfluoroalkyl-4-(3-oxo-2-triphenyl-phosphoranylidenbutanylidene)-pent-2-enedioate and its cyclization

The title compounds 5a-5c were prepared via the reaction of methyl 2-perfluoroalkynoates (4) with methyl 5-oxo-4-(triphenylphosphoranylidene)hex-2-enoate (3), which was obtained from the reaction of methyl propynate (2) with acetylmethylenetriphenylphosphorane (1) at -5-0 degrees C. Intramolecular elimination of Ph(3)PO took place when compound 5 was heated in aqueous methanol at 115-120 degrees C in sealed tube, yielding dimethyl 2-trifluoromethyl-4-methylisophthalate (6a) from 5a and methyl 5-acetyl-4-hydroxy-2-heptafluoropropanylbenzoate (6b) from 5b, respectively. The structures of compounds 5, 6a and 6b were confirmed by IR, MS, H-1 NMR, F-19 NMR and C-13 NMR spectroscopy and elemental analyses. Rection mechanisms for the formation of compounds 5, 6a and 6b were proposed.