The diels-alder approach to musk odor type arenes

The readily accesible 2-halogeno-1-trimethylsilyloxy-1,3-butadienes react smoothly with dimethyl acetylenedicarboxylate to afford 4-halophthalic esters. One of these cycloadducts was subsequently converted into heterocyclic analogues of phantolide like musk fragrances.     

Synthesis of diphenylcarbazoles as cytotoxic DNA binding agents

We report the synthesis of a series of novel diphenylcarbazoles designed to interact with DNA. The compounds bearing two or three dimethylaminoalkyloxy side chains were found to bind much more tightly to DNA, preferentially at AT-rich sites, than the corresponding hydroxy compounds. The DNA binding compounds exhibit potent cytotoxic activity toward P388 leukemia cells. The 3,6-diphenylcarbazole thus represent an interesting scaffold to develop antitumor agents interacting with nucleic acids.     

Factors influencing C-ON bond homolysis in alkoxyamines: unexpected behavior of SG1 (N-(2-methyl-2-propyl)- N-(1-diethylphosphono-2,2-dimethylpropyl)-N-oxyl)-based alkoxyamines

Alkoxyamines and persistent nitroxides are important regulators of nitroxide-mediated radical polymerization (NMP). Since the polymerization time decreases with the increasing equilibrium constant K (k(d)/k(c)), i.e., the increasing rate constant k(d) of the homolysis of the C-ON bond between the polymer chain and the nitroxide moiety, the factors influencing the cleavage rate constants are of considerable interest. SG1-based alkoxyamines have turned out to be the most potent alkoxyamine family to use for NMP of various monomers. Therefore, it is of high interest to determine the factors which make SG1 derivatives better regulators than TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl) derivatives. Contrary to what we had observed with TEMPO derivatives, we observed two relationships for the plot E(a) vs BDE(C-H), one for the nonpolar released alkyl radicals (E(a) (kJ/mol) = -133.0 + 0.72BDE) and the other one for the polar released alkyl radicals (E(a) (kJ/mol) = -137.0 + 0.69BDE). However, for both families (SG1 and TEMPO derivatives), the rate constants k(d) of the C-ON bond homolysis were correlated to the cleavage temperature T(c) (log(k(d)(s(-)(1))) = 1.51 - 0.058T(c)). Such correlations should help to design new alkoxyamines to use as regulators and to improve the tuning of NMP experiments.     

Tetrathiophosphoric acid tri(1-phenylethyl) ester and1-phenylethyl-diphenylphosphinodithioate as controlled radical polymerization agents

Polystyrene and polystyrene-b-polyvinylacetate have been prepared in presence of either tetrathiophosphoric acidtri(1-phenylethyl) ester 1 or 1-phenylethyl-diphenylphosphinodithioate 2 under radical conditions. From kinetic studies performed with or without 1 or 2, it was shown that the polymerization presents the criteria of living/controlled polymerization.     

Sound focusing in rooms: the time-reversal approach

New perspectives in audible range acoustics, such as virtual sound space creation and active noise control, rely on the ability of the rendering system to recreate precisely a desired sound field. This ability to control sound in a given volume of a room is directly linked to the capacity to focus acoustical energy both in space and time. However, sound focusing in rooms remains a complicated problem, essentially because of the multiple reflections on obstacles and walls occurring during propagation. In this paper, the technique of time-reversal focusing, well known in ultrasound, is experimentally applied to audible range acoustics. Compared to classical focusing techniques such as delay law focusing, time reversal appears to considerably improve quality of both temporal and spatial focusing. This so-called super-resolution phenomenon is due to the ability of time reversal to take into account all of the different sound paths between the emitting antenna and the focal point, thus creating an adaptive spatial and temporal matched filter for the considered propagation medium. Experiments emphasize the strong robustness of time-reversal focusing towards small modifications in the medium, such as people in motion or temperature variations. Sound focusing through walls using the time-reversal approach is also experimentally demonstrated.     

Open 3-manifolds whose fundamental groups have infinite center, and a torus theorem for 3-orbifolds

Our main result is a characterization of open Seifert fibered -manifolds in terms of the fundamental group and large-scale geometric properties of a triangulation. As an application, we extend the Seifert Fiber Space Theorem and the Torus Theorem to a class of -orbifolds.

     

On four-dimensionals-cobordisms,II

Partially supported by NSF grants.     

A versatile synthesis of 2‐amino‐4H‐pyrido[1,2‐a][1,3,5]triazin‐4‐ones from 2‐aminopyridines

The quasi‐one pot synthesis of new 2‐aminopyrido[1,2‐a][1,3,5]triazin‐4‐ones starting from 2‐amino‐pyridine and 2‐aminopicolines is herein described in order to obtain a library of cyclic guanidines.