Domino Michael/aza-Wittig reaction in the diastereoselective construction of spiro[azepane-4,3′-oxindoles]

A convenient synthetic strategy for the diastereoselective assembly of spiro[azepane-4,3′-oxindoles] was developed via a Staudinger/Michael/aza-Wittig/reduction/N-deprotection reaction sequence starting from PMB-protected oxindole-substituted ethylazides. The key step of the method is a domino self-catalytic Michael/aza-Wittig reaction wherein the phosphazene moiety acts first as the catalyst and then as the reactant, resulting in the formation of a seven-membered N-heterocycle.     

Ethyl α-cyanoacrylate in the Michael reaction

Ethyl -cyanocarylate undergoes the Michael reaction with strong CH-acids (pK _a < 13) in the presence of strong basic amines such as butylamine, piperidine, and triethylamine. Only polymerization of ethyl -cyanoacrylate occurs under the same conditions with weaker CH-acids in the presence of less basic amines such as aniline, N-methylaniline, and pyridine.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2449–2452, October, 1992.     

Kinetics Studies on a Multicomponent Knoevenagel−Michael Domino Reaction by an Automated Flow Reactor

The optimization of complex chemical reaction systems is often a troublesome and time-consuming process. The application of modern technologies, including automated reactors and analytics, opens the avenue for generating large data sets on chemical reaction processes in a short period of time. In this work, an automated flow reactor is used to present detailed kinetics and mechanistic studies about an amine-catalyzed Knoevenagel−Michael domino reaction to yield tetrahydrochromene derivatives. High-performance monoliths as catalyst supports and online coupled HPLC analysis allow for time-efficient data generation. We show that the two-step multicomponent domino reaction does not follow the kinetics of consecutive reaction steps proceeding independently from each other. Instead, the starting materials of both individual reactions compete for the active sites on the heterogeneous catalyst, which lowers the rate constants of both steps. This knowledge was used to implement a more efficient experimental setup which increased the turnover numbers of the catalyst, without adjusting common reaction parameters like temperature, reaction time, and concentrations.     

Nickel-coordinated chiral enols and Michael addition intermediate stabilized by the Ni–C bond

1. Download high-res image (149KB)
2. Download full-size image

     

Michael Polanyi—pupils and crossroads—on the 125th anniversary of his birth

Michael Polanyi (1891–1976) was a Hungarian-born British physician turned physical chemist turned philosopher. His milestone epistemological treatise Personal Knowledge followed his substantial discoveries in adsorption studies, X-ray crystallography, materials science, and the mechanism of chemical reactions. Michael Polanyi was one of the last polymaths and his teachings impacted the world views of other outstanding contributors to twentieth century science and culture.     

Catalytic phosphorylation of polyfluoroalkanols. 17. Synthesis and the stereochemistry of tris(α-trifluoromethylbenzyl) phosphates

Catalytic phosphorylation of -trifluoromethylbenzyl alcohols with POCl₃ taken in a ratio of 3 : 1 under particular temperature conditions afforded predominantly symmetrical tris(-trifluoromethylbenzyl) phosphates. The latter were obtained as mixtures of two diastereomers with a statistical ratio of the components.     

Cu(I)- and Cu(II)-catalyzed cyclo- and Michael addition reactions of unsaturated β-ketoesters

The α-alkylidene β-ketoesters 2-carbethoxycyclopentenone (1a) and ethyl 2-benzoylacrylate (1b) react with 1,2-dimethylbutadiene (2) (Diels-Alder), N-benzyl-N-(cyclohexylethynyl)-4-methylbenzenesulfonamide (3) (Ficini reaction), ethynyl(phenyl)sulfane (4) ([2 + 2] cycloaddition), and 1,2,5-trimethyl-1H-pyrrole (5) (Michael addition) in the presence of copper(I) (6) or copper(II) triflate (7) (1-2 mol %) in dichloromethane. This convenient protocol converts 1a and 1b to the corresponding cycloaddition (8-10) or Michael addition (11) products in good yields after reaction times of 0.5-3 h without requiring purified solvents or inert gas atmosphere.     

Long-range spin–spin interactions in the 13C-n.m.r. spectra of the nickel(II) complex of the Schiff base of (S)-N-benzylproline (2-benzoylphenyl)amide and glycine. Quantum-chemical calculations and possible donation of electron density from the π-system of the benzyl group to nickel

Long-range [ ⁿ J(¹³C, ¹³C), ⁿ J(¹⁵N, ¹⁵N) and ⁿ J(¹⁵N, ¹³C)] interactions in the ¹³C-n.m.r. spectra of CDCl₃ solutions of selectively labeled nickel(II) complexes of the Schiff base derived from (S)-N-benzylproline (2-benzoylphenyl)amide and glycine provide experimental evidence for the necessity of the donation of electron density from the -system of the benzyl ring to the nickel orbitals. No such interactions were observed in (²H)DMSO solutions, where the complex exists in a different conformation.     

Combination of the Claisen-Schmidt reaction,the Michael addition,and the Hantzsch reaction in the synthesis of 2,6′-bis-aryl-3,4′-bipyridines

Russian Chemical Bulletin - Pyridine-3-carbaldehyde reacted with 1-(aryl)ethan-1-ones to give 1,5-diaryl-3-(pyridin-3-yl)pentane-1,5-diones, which were further converted to...     

New Light on the Alchemical Writings of Michael Sendivogius (1566–1636)

The Polish alchemist Michael Sendivogius is best known for the influential Novum lumen chymicum, a work composed of three separate texts. Sendivogius's authorship was questioned in the mid-seventeenth century, and these reservations are still held by some modern historians. On the other hand, other early modern and modern readers not only accepted his authorship of all three texts, but also ascribed as many as eleven texts to him. This paper discusses the key works published under the anagrammatised name of Sendivogius with the aim of resolving the authorship question. Newly discovered evidence makes it possible to trace the circumstances leading to the publication of these works in much greater detail than previously, and to present new arguments affirming Sendivogius's authorship. In the Tractatus de sulphure, Sendivogius promised to write another two treatises, which readers sought to identify and (in some cases) to write themselves. This paper sets out, and rejects, the arguments for including them in the corpus of genuine Sendivogian writings.     

M. S. Tswett and the discovery of chromatography II: Completion of the development of chromatography (1903–1910)

Summary In this, the second part of our review we continue the discussion of the activities of M. S. Tswett related to the development of chromatography. We shall deal here with his activities in Warsaw from 1903 onwards, resulting in his fundamental twin papers of 1906 and his book of 1910, summarizing all his activities related to the investigation of plant pigments and to the development of chromatography. Finally, a few special questions related to Tswett's work shall be discussed.For Part I, seeChromatographia 35, 223 (1993). References are numbered through.     

Molecular dynamics simulations for CO(2) absorption spectra. I. Line broadening and the far wing of the ν(3) infrared band

Classical molecular dynamics simulations (CMDS) have been carried out for gaseous CO(2) starting from the intermolecular potential energy surface. Through calculations for a large number of molecules treated as rigid rotors, various autocorrelation functions (ACFs) are obtained together with probabilities of rotational changes. Those used in the present paper are the ACFs of the center of mass velocity and of the molecular orientation, and the conditional probability of a change of the angular speed. They enable calculations, respectively, of the mass diffusion coefficient, of the infrared (dipolar) band shape including the wings, and of individual line-broadening coefficients. It is shown that these calculations, free of any adjustable parameter, lead to good agreement with measured values. This is expected from previous studies for the mass diffusion coefficient and line-broadening coefficients, but it is, to our knowledge, the first demonstration of the interest of CMDS for the prediction of band wings. The present results thus open promising perspectives for the theoretical treatment of the difficult problem of far wings profiles.