Bernard Deschamps

Factors controlling the regioselectivity of additions to α-enones—III: Reactions of 3-aryl α-enones with phosphorylated anions

Abstract Reaction of phosphonoester 2 and phosphononitrile 3 with chalcone and p -methoxychaleone in THF-t-BuOK at room temperature gives only the product resulting from Cue5fbC double bond attack. The same reagents with benzalacetone lead to mixture of products resulting from Cue5fbC double bond and carbonyl attack, though phosphine oxide 4 gives only the products of Cue5fbC attack. Dypnone gives products of carbonyl attack with 3 and does not react with 2 . These results are discussed in terms of perturbation theory: C 4 attack increases with delocalization of the reagents negative charge and lowering of the α-enone LUMO level.

Factors controlling the regioselectivity of additions to α-enones—IV: Reactions of 3-alkyl and alicyclic α-enones with phosphorylated anions

Abstract Reaction of phosphonoester ( 2 ) and phosphononitrile ( 3 ) with 3-alkyl or alieyclic α-enones in THF—t-BuOK gives different products resulting mainly from primary Cue5fbC double bond attack. The reaction is very fast, compared with 3-aryl substituted analogs. These results are interpreted in terms of a transition state for which deconjugation (π energy loss due to hybridization change of reagent) has to be taken into account in addition to HOMO-LUMO interactions. A 3,3-disubstituted α-enone reacts slowly with phosphonitrile ( 3 ) at the carbonyl carbon, Cue5fbC double bond attack being inhibited by steric hindrance. These results indicate the limitation of perturbation theory which only applies with certainty for very early transition states.

Synthesis of 1-chlorophosphirenes in the coordination sphere of tungsten

Abstract Upon treatment with AlCl3, 1-β-chloroethylphosphirene P-W(CO) 5 complexes lose ethylene and yield the corresponding 1-chlorophosphirene complexes.

Factors controlling the regioselectivity of additions to α-enones—VII: Influence of lithium cation on phosphonitriles reactions

Abstract Reaction of phosphononitrile 2 with a series of a-enones in THF- n -BuLi gives different results according to the enone nature. C 4 -disubstituted enones are attacked at the carbonyl carbon; phenones and cyclopentenone are attacked at the double bond (except dypnone); benzalacetone, 3-penten-2-one and cyclo-hexenone give mixtures of C 2 and C 4 substituted products. Electrophilic assistance by complexation of the lithium cation by α-enone can be shown except for phenones.

Conversion directe des phospholes en dihydro-6,7 phosphepines dans la sphere de coordination du tungstene

Abstract In the presence of AlCl 3 , [1-β-chloroethyl-3,4-dimethylphosphole]pentacarbonyltungsten( 1 ) rearranges into [1-chloro-3,4-dimethyl-6,7-dihydrophosphepin]pentacarbonyltungsten ( 3 ).

Criteres d'evaluation de la position de l'etat de transition dans les additions conjuguees

Abstract The conjugate addition of substituted aryacetonitrile anions to α-enones implies a reagent-like transition state; it is insensitive to conjugation loss but slightly sensitive to steric factors.

STABILISATION DES CYCLOPENTADIENYL-HALOGENOPHOSPHINES PAR COMPLEXATION SUR LE PHOSPHORE

Abstract Several halocyclopentadienylphosphines CpPCl2, Cp2PBr and CpP(Ph)Cl (1–3) have been made by low temperature reaction of cyclopentadienylthallium with the appropriate halophosphines and stabilized by P-complexation with W(CO)5. In the complexes thus obtained, the phosphorus atom is connected with the sp3 carbon of the cyclopentadienyl ring but the molecules are not fluxional at room temperature probably because of the steric bulk of the phosphorus substituents. The [4 + 2] cycloadducts of [CpPCl2]W(CO)5 with N-phenyl maleimide 5 and dimethyl acetylenedicarboxylate 6 are also described. Plusieurs halogenocyclopentadienylphosphines: CpCl2, Cp2PBr et CpP(Ph)Cl (1–3), ont ete obtenues par reaction a basse temperature du cyclopentadienylthallium sur les halogenophosphines appropriees et stabilisees par complexation du phosphore avec le groupement W(CO)5. Dans les complexes ainsi obtenus, le phosphore est connecte au carbone sp3 du cycle cyclopentadienyle mais les molecules ne sont pas fluxionnelles pro...

2,3-Diphenylphosphirenepentacarbonyltungsten Complex: Synthesis and Reactivity

Abstract 2-3-Diphenylphosphirenepentacarbonyltungsten complex 1 is prepared using the following scheme :