Transition-metal-free mono- or dinitration of protected anilines

Abstract

An amide-assisted arene nitration is presented, and both mono- and dinitration of protected anilines could be effected by using NaNO₂ and NaNO₃ as the mono- and bisnitrating agents, respectively. This divergent synthesis is transition-metal- and acid-free, and features a broad substrate scope, low cost, and ortho–para selectivity.     

The Arrow of Time: From Universe Time-Asymmetry to Local Irreversible Processes

In several previous papers we have argued for a global and non-entropic approach to the problem of the arrow of time, according to which the “arrow” is only a metaphorical way of expressing the geometrical time-asymmetry of the universe. We have also shown that, under definite conditions, this global time-asymmetry can be transferred to local contexts as an energy flow that points to the same temporal direction all over the spacetime. The aim of this paper is to complete the global and non-entropic program by showing that our approach is able to account for irreversible local phenomena, which have been traditionally considered as the physical origin of the arrow of time.     

Trichloroisocyanuric acid-promoted thiolation of phosphites by thiols

Abstract

A simple and convenient method for the synthesis of thiophosphates by coupling of phosphites with thiols under mild conditions has been developed. The reactions were promoted by trichloroisocyanuric acid (TCCA) and were carried out at room temperature in a one-pot two-step procedure within 20?min. A variety of substrates was tolerated in this method. Notably, both aryl and alkyl thiols could afford the corresponding thiophosphates in good yields.     

Elastic constants and mechanical stability of InxAl1 − xAsySb1 − y lattice-matched to different substrates

Based on a pseudopotential approach under the virtual crystal approximation, the elastic modulus of In_xAl_1???xAs_ySb_1???y quaternaries lattice-matched to InP, GaSb and InAs substrates has been investigated. Our findings show a reasonably good accord with experiment. The dependence of the elastic features of interest on the indium concentration x shows a monotonic behaviour when In_xAl_1???xAs_ySb_1???y is lattice-matched to InP substrate. In that case, the elastic constants have larger values and the material system of interest becomes less harder and its rigidity becomes weaker. The mechanical stability criteria is verified in terms of elastic constants and shows that In_xAl_1???xAs_ySb_1???y is mechanically stable for each x and substrate being considered here. The change in indium content x and the substrate is found to have no much effect on both the Poisson ratio and machinability. The present study showed that a proper choice of the indium composition x and substrate may provide more diverse opportunities as regards the elastic modulus of In_xAl_1???xAs_ySb_1???y.     

Short Intermolecular Phosphorus…Phosphorus Distances in the Crystal Structures of Bis{Bis(Perfluoroaryl)Phosphino}Methanes

Abstract

The crystal structure of bis{bis(4-trifluoromethyltetrafluorophenyl)phosphino}-methane 2 determined by single crystal X-ray diffraction comprises pairs of molecules related by an inversion center and possessing short P???P distances. The molecular structure and the structure of the pairs are similar to those in the crystal structure of bis{bis(pentafluorophenyl)-phosphino}methane, although the packing is different. Comparison with the structures of bis(diphenylphosphino)methane and bis{bis(pentafluorophenyl)phosphine}difluoromethane suggests that intramolecular C–H???F–C interactions are the most important factor in determining the presence of the short P???P distances in the crystal structures of bis(diarylphosphino)methanes.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Microwave-assisted synthesis of α-aminophosphonates with sterically demanding α-aryl substituents

Abstract

A series of N-benzhydryl protected α-aminophosphonates with α-phenyl, α-(1-naphtyl), α-(9-anthryl) or α-(1-pyrenyl) substituents was synthesized by the Kabachnik–Fields condensation of diphenylmethylamine (benzhydrylamine), the corresponding aryl aldehyde and a dialkyl phosphite under MW irradiation. X-ray studies performed at low temperatures for a few of these α-aminophosphonates confirmed the presence of unusually short intramolecular C_α–H^δ+ ··· ^δ+H–C_peri contacts.     

Decompositions of the 3-uniform hypergraphs K(3)v into hypergraphs of a certain type

In this paper, we investigate a generalization of graph decomposition, called hypergraph decomposition. We show that a decomposition of a 3-uniform hypergraph K(3)v into a special kind of hypergraph K(3)4 - e exists if and only if v ≡ 0, 1, 2 (mod 9) and v ≥ 9.