Max Koenig

A general method for preparing diphosphiranes

Abstract Diphosphiranes 3a - 3f are obtained by action of diazo derivatives and carbenes on the trans-diphosphene 1 . The structures are elucidated by spectroscopic methods. In all cases the cycloaddition reaction is stereoselective.

Ring opening of diphosphiranes leading to 1,3-diphosphaallene

Abstract The 3,3-dihalogeno-1,2-diphosphiranes 1(a–b) and its photochemical isomers, the 2,3-dihalogeno-diphosphapropenes 8(a–b) lead to the 1,3-diphosphaallene 4 by action the methyllithium. The anionic ring opening mechanism appears most likely.

Spirophosphoranylation d'α-aminoacides—I : Preparation et tautomerie1

Resume Une vingtaine de spirophosphoranes nouveaux (Tableaux 1 et 2) ont ete prepares en faisant reagir les &alpha-aminoacides sur des composes du phosphore tricoordine possedant un groupement partant convenable. Dans le cas du compose 1i , un equilibre chaǐne-cycle P III P v a ete mis en evidence.

Spirophosphoranes a liaison P-OH. Synthese, tautomerie

Abstract Spirophosphoranes with a P-OH bond have been prepared as free acid (compound 5c), triethylammonium salts (compounds 2c–6c), or adducts 1 1 with DMF (compounds 5c and 6c). The ionic feature of triethylammonium salts of compounds 1c–6c, shows that these Spirophosphoranes are relatively strong Bronsteds acids. Tautomeric equilibrium phosphoric ester—phosphorane with a P-OH bond [Scheme 9), shown in many cases, has been studied by means of 31PN, MRspectroscopy. Influence of factors ruling this equilibrium is analysed. Some elements of dynamic stereochemistry are examined.

Nem method of obtaining a stable diphosphirane

Abstract The stable monomer diphosphirane 2 is produced by the reaction of the diazomethane on the diphosphene 1 .

Role of Base Catalysts upon the Pudovik Reaction : Unexpected Synthesis of 1,2-Dihydropyridine Phosphonate Derivatives

Abstract The role of base catalysts (CsNaX zeolite, hydrotalcite, triethylamine and pyridine derivatives) upon the regioselectivity of the Pudovik reaction is studied. The unexpected synthesis of stable 1,2-dihydropyridine phosphonate derivatives via a one-pot addition reaction under mild conditions is described.

Alkylation of phosphine PH3 generated from red phosphorus

Abstract The generation of phosphine PH 3 by alkaline hydrolysis of red phosphorus is realized. The subsequent alkylation of PH 3 by terminal alkenes and alkynes in basic media leading to the corresponding aliphatic and vinylic phosphine derivatives can occur by two-steps or one-pot reaction by a Michael-like reaction mechanism.

Laser irradiation of a diphosphene: evidence for the first cis–trans isomerization

Low temperature laser irradiation of trans-diphosphene (1), followed using u.v., and 31P and 1H n.m.r. spectroscopy, gives an equilibrium between (1) and the unstable cis-isomer (2): the activation free energy of the (2)→(1) reaction is 20.3 kcal mol–1(1 kcal = 4.18 kJ).

Zirconocyclisation: Access to new racemic (di) phosphines☆

Abstract The bis-allylic 1 and the bis-propargylic 6 derivatives react with the zirconocene “ZrCp2” and lead, after electrophilic addition, to the corresponding chiral trans heterocyclopentanes (MSi,Ge,P) 3–5 and bis-methylenecyclopentanes 8. New chiral diphosphine 9 is obtained starting from the intermediate complex 2 or the functionalized heterocyclopentane 4.

Isomerisation de composes du phosphore hexacoordine optiquement actifs : mise en evidence d'un processus irregulier

Abstract The synthesis, with asymmetric induction, of chiral hexacovalent phosphorus anions, allows a polarimetric kinetic study of epimerization or racemization mechanism of these compounds which is shown to be irregular (acid catalyzed).