Reactivite des derives organomanganeux—VIII : Préparation de cétones par acylation d'organomanganeux. Influence de la nature de l'agent acylant,des solvants et des ligands

The influence of the nature of acylating reagents, solvents and ligands on the preparation of ketones by acylation of organomanganous reagents is studied. Thus acid chlorides in ether, symmetrical acid anhydrides in ether or THF and mixed carboxylic-carbonic anhydrides (R'COOCOOEt) in ether are compared, they lead to the corresponding ketones with good or excellent yields. Some problems of reproductibility are encountered and discussed when mixed anhydrides R'COOCOOEt are used in THF. The addition of a great variety of cosolvents (e.g. C₆H₆, AcOEt, CO₃Et₂, CH₂CN, CH₂CL₂, . .) to the reaction mixture before addition of the acylating reagent does not affect the yield of ketones. In comparison the complexation of organomanganous reagents by several ligands (e.g. Me₂S or Ph₃P) has no subsequent effect on their acylation. The main limitation for the choice of solvents or ligands is the use of amino derivatives which generally lead to a very low yield of ketones (e.g. C₅H₅N, TMEDA, Et₃N) or unreproducible yields (e.g. HMPA). Two applications of these studies are described:The stabilization of s or t-alkyl manganous derivatives by complexation which leads to the best yield of the corresponding ketonesThe use of a cosolvent in order to increase the yield when mixed anhydrides R'COOCOOEt are used in THF.     

Etude d'un modele d'induction asymetrique: Les oxazolidines α,β-insaturees issues de l'ephedrine

Various oxazolidines were prepared from ephedrine. It was shown that their formation is not general, the reaction is not always stereoselective and can lead to isomerization of the double bond of α,β-unsaturated aldehydes. Some of these oxazolidines were used in stereoselective preparation of β-alkyl aldehydes.     

Regioselectivite de la reaction des dialkyl cuprates de magnesium sur des aldehydes α,β-ethyleniques

Various magnesium organocuprates give conjugative addition products with α,β-ethylenic aldehydes, and even with acrolein. The enolates may be trapped with bromine or trimethylsilyl chloride.     

Synthèse stéréospécifique récurrente de structures apparentées à celle de l'hormone juvénile de Hyalophora cecropia

A stereospecific synthesis of Hyalophora cecropia juvenile hormone analogs is proposed. The three double bonds are obtained successively by addition of an alkyl copper reagent to the apporpriate 1-alkyne.     

Organomanganese (II) Reagents: V1: Organomanganous Chlorides as a New Reagent for Ketone Synthesis via Mixed or Symmetrical Anhydrides

We have recently described an efficient preparation of ketones (or esters) from organomanganous iodides (RMnI) and acid chlorides² (or chloro-carbonates³). The scope of this reaction is very large and RMnI is often superior to other organometallics. However, the major limitations of this reaction are^2b:     

Substitutions nucleophiles d'olefines fluorees—II

The nucleophilic substitution of compounds ACFCFCl (ARO, RS) proceeds by addition-elimination. The observed regioselectivity depends upon the nature of A. The stereospecificity is explained by steric hindrance in the transition state of the elimination step. Butyllithium also promotes a lithium—chlorine exchange.     

Substitution reactions of dicyclooctatetraeneiron. A simple route to zerovalent iron—organophosphorus compounds

Fe(cot)₂ (cot = cyclooctatetraene) reacts with certain phosphines and phosphites to give Fe(cot)L₃ compounds in good yield. Reaction of Fe(cot)₂ with Ph₂PCH₂CH₂PPh₂ under N₂ gives a complex containing coordinated dinitrogen, which is converted into Fe(cot)(Ph₂PCH₂CH₂PPh₂)(CO) on reaction with CO or formate esters.     

Carbonatation de divers organocuivreux

Various saturated, α- or β- ethylenic, or arylic organocopper compounds have been carboxylated under conditions very similar to those used with vinyl-copper compounds. We discuss the positive influence of a catalytic amount of triethyl phosphite, whereas the use of a stoichiometric quantity, or the presence of metallic halides, decreases the yields of insertion. Carboxylic acids are obtained with excellent yields.