Very Simple One-Step Synthesis of Vinylphosphonates and Enamine Phosphonates by Direct Addition of Organolithium Reagents to 1-Alkynylphosphonates

Abstract

Direct addition of organolithium to 1-alkynylphosphonates (1) afforded vinylphosphonates and enamine phosphonates (2) in good to excellent yields. The reaction was carried out in dry THF at low temperature and proved to be completely stereoselective (syn addition). Alkyl, aryl, and haloalkyl groups were attached to the alkynyl entity, so the resulting vinylphosphonates contained various functional groups. The stereochemistry of the products as well as mechanism of the reaction were determined based on ¹H and ¹³C NMR. The synthesis of enamine phosphonates in the absence of complicated, highly expensive organometallic catalysis has not been previously reported.     

Dynamic evolution of economically preferred facilities

In a sustained development scenario, it is often the case that an investment is to be made over time in facilities that generate benefits. The benefits result from joint synergies between the facilities expressed as positive utilities specific to some subsets of facilities. As incremental budgets to finance fixed facility costs become available over time, additional facilities can be opened. The question is which facilities should be opened in order to guarantee that the overall benefit return over time is on the highest possible trajectory. This problem is common in situations such as ramping up a communication or transportation network where the facilities are hubs or service stations, or when introducing new technologies such as alternative fuels for cars and the facilities are fueling stations, or when expanding the production capacity with new machines, or when facilities are functions in a developing organization that is forced to make choices of where to invest limited funding.     

Vibrational spectroscopy for glycine adsorbed on silicon clusters: Harmonic and anharmonic calculations for models of the Si(1 0 0)-2 × 1 surface

The vibrational spectroscopy of a glycine molecule adsorbed on a silicon surface is studied computationally, using different clusters as models for the surface. Harmonic frequencies are computed using density functional theory (DFT) with the B3LYP functional. Anharmonic frequency calculations are carried out using vibrational self-consistent field (VSCF) algorithms on an improved PM3 potential energy surface. The results are compared with experiments on Glycine@Si(1 0 0)-2 × 1.

The main findings are: (1) Agreement of the computed frequencies with experiment improves with cluster size. (2) The anharmonic calculations are generally in better agreement with experiment than the harmonic ones. The improvements due to anharmonicity are most significant for hydrogenic stretching. (3) An important part of the anharmonic effects is due to anharmonic coupling between different normal modes of the system. (4) The anharmonic coupling between glycine vibrational modes is much larger than the anharmonic coupling between glycine and “phonon” (cluster) modes.

Implications of the results for surface vibrational spectroscopy are discussed.     

Tight bounds and 2-approximation algorithms for integer programs with two variables per inequality

The problem of integer programming in bounded variables, over constraints with no more than two variables in each constraint is NP-complete, even when all variables are binary. This paper deals with integer linear minimization problems inn variables subject tom linear constraints with at most two variables per inequality, and with all variables bounded between 0 andU. For such systems, a 2-approximation algorithm is presented that runs in time O(mnU ² log(Un ² m)), so it is polynomial in the input size if the upper boundU is polynomially bounded. The algorithm works by finding first a super-optimal feasible solution that consists of integer multiples of 1/2. That solution gives a tight bound on the value of the minimum. It furthermore has an identifiable subset of integer components that retain their value in an integer optimal solution of the problem. These properties are a generalization of the properties of the vertex cover problem. The algorithm described is, in particular, a 2-approximation algorithm for the problem of minimizing the total weight of true variables, among all truth assignments to the 2-satisfiability problem.This paper is dedicated to Phil Wolfe on the occasion of his 65th birthday.Research supported in part by ONR contracts N00014-88-K-0377 and N00014-91-J-1241.Research supported in part by ONR contract N00014-91-C-0026.Part of this work was done while the author was visiting the International Computer Science Institute in Berkeley, CA and DIMACS, Rutgers University, New Brunswick, NJ.     

A water-soluble and "self-assembled" polyoxometalate as a recyclable catalyst for oxidation of alcohols in water with hydrogen peroxide

We have demonstrated that a simply prepared water-soluble polyoxometalate, Na12[WZnZn2(H2O)2(ZnW9O34)2], synthesized from readily available zinc and tungsten salts in the presence of nitric acid, is an effective catalyst for selective alcohol oxidation with hydrogen peroxide in biphasic (water-alcohol) reaction media. Experiments have shown that the "self-assembled" catalyst in its mother liquor was as active as the isolated catalyst. The aqueous catalyst solution is easily separated from the water-insoluble products and can be recycled without loss in activity or selectivity.     

1H-CRAMPS Solid-State NMR and X-Ray Crystal Studies of Inclusion Complexes Formed from 3,3′-bis(9-Hydroxy-9-fluorenyl)-2,2′-binaphthyl Hosts with Acetone

The crystal structures of inclusion compounds of 3,3-bis(9-hydroxy-9-fluorenyl)-2,2-binaphthyl host (1) and its chloro (2) or bromo (3) derivatives substituted in 2,7-positions of the fluorene units with acetone guests (1A–3A) were determined by X-ray studies as well as by ¹H-CRAMPS solid-state NMR. Using this NMR technique allows identification of differently bound guest molecules due to their different chemical shifts caused by the influence of the ring current effects of the host aryl units.     

Kinetics of lactose and rhamnose oxidation over supported metal catalysts

Several mono- and bimetallic Pd, Pt, Rh and Ru supported on alumina and active carbon catalysts were characterized by CO chemisorption, nitrogen adsorption, XPS and XRD and acidity titrations were performed for active carbon supported catalysts. These catalysts were tested in oxidation of two sugars, namely lactose and rhamnose, at 60 °C and at 70 °C under slightly alkaline conditions (pH 8) with molecular oxygen. The results revealed that there is an optimum metal particle size in a range of 3-10 nm giving the highest initial TOFs for both oxidations. Furthermore, the catalytic activities and conversions were related to other catalyst properties, such as the type and amount of promoters and the presence of different phases. In situ catalyst potential measurements revealed that there is an inverse correlation between the increase of catalyst potential as a function of sugar conversion and the catalyst activity after prolonged reaction times. This method is a valuable tool for in situ characterization of catalysts correlating well with their activities.     

Photoionization dynamics of glycine adsorbed on a silicon cluster: "on-the-fly" simulations

Dynamics of glycine chemisorbed on the surface of a silicon cluster is studied for a process that involves single-photon ionization, followed by recombination with the electron after a selected time delay. The process is studied by "on-the-fly" molecular dynamics simulations, using the semiempirical parametric method number 3 (PM3) potential energy surface. The system is taken to be in the ground state prior to photoionization, and time delays from 5 to 50 fs before the recombination are considered. The time evolution is computed over 10 ps. The main findings are (1) the positive charge after ionization is initially mostly distributed on the silicon cluster. (2) After ionization the major structural changes are on the silicon cluster. These include Si-Si bond breaking and formation and hydrogen transfer between different silicon atoms. (3) The transient ionization event gives rise to dynamical behavior that depends sensitively on the ion state lifetime. Subsequent to 45 fs evolution in the charged state, the glycine molecule starts to rotate on the silicon cluster. Implications of the results to various processes that are induced by transient transition to a charged state are discussed. These include inelastic tunneling in molecular devices, photochemistry on conducting surfaces, and electron-molecule scattering.     

Highly efficient recycling of a "sandwich" type polyoxometalate oxidation catalyst using solvent resistant nanofiltration

A "sandwich" type polyoxometalate catalyst ([MeN(n-C8H17)3]12[WZn3(ZnW9O34)2]) was very efficiently recycled by nanofiltration with almost quantitative retention, using an alpha-alumina supported mesoporous gamma-alumina membrane.