Michel Franck-Neumann

Stabilisation de molecules hyperactives par complexation: Le formyl-2 butadiene fer-tricarbonyle. Preparation, dedoublement et reactivite☆

Abstract The stable dieneiron tricarbonyl complex of the unstable 2-formylbutadiene was prepared from isoprene by two different ways and resolved via chiral semioxamazone formation. The complex reacts easily with Grignard or other carbanionic reagents leading to the corresponding alcohols from which the stable diene alcohols can now be obtained by decomplexation. The reaction of the aldehyde complex proceeds nearly diastereospecifically with organolithium compounds and cuprates, these reagents showing an inversed diastereoselection. This contrasts with the behaviour of magnesium and titanium derivatives which lead only to mixtures of those diastereoisomers. Wittig and Horner-Emmons olefinations were also studied in order to examine the diastereoselectivity of the subsequent diazoalkane cycloaddition and the possibility for synthesis of Ips-type insect pheromones via hydroboration.

Synthese stereo et enantioselective par l'intermediare de complexes du fer de derives chrysanthemiques dieniques et d'aldehydes hemicaroniques cis et trans.

Abstract A stereo and enantioselective synthesis of cis and trans hemicaronic aldehydes, starting from the optically active sorbic aldehyde-irontricarbonyl comples, is described.

Une methode simple de liberation des ligands organiques de leurs complexes de fer carbonyle.

Resume Disengagement of organic ligands from their Ironcarbonyl Complexes is easely achieved by oxidation with aqueous hydrogen peroxide under basic conditions.

Cyclopropenes electrophiles—II : Synthese par photolyse de dimethyl-3,3 pyrazolenines

Abstract The photolysis of 3,3-dimethyl-3H-pyrazoles derived from 2-diazopropane and acetylenic esters and nitriles leads in good yields to electrophilic cyclopropenes Starting from acetylenic ketones, only the 4-keto-3H-pyrazoles give acylcyclopropenes, the photolysis of the 5-keto-derivatives leading mainly to vinylketenes.

Vinylcarbenes acycliques: reactions de cycloadditions intermoleculaires

Abstract The photolysis of 3,3-dimethyl-3H-pyrazoles in unsaturated solvents leads in good yields and often with high stereoselectivity, to vinylcarbene cycloadducts. This direct synthesis of vinylcyclopropanes, vinylcyclopropenes and divinylcyclopropanes shows that acyclic vinyl carbenes are not necessarily intramolecularly stabilized. They can actually be trapped by olefins, acetylenes or dienes, depending on the carbene substituents. Cyano vinyl carbenes are the most efficient intermolecular cycloaddenda examined so far, but carbalkoxy and even ketovinylcarbenes can undergo cyclopropanation reactions with dienes, with little competition from the Wolff rearrangement in the last case.

Cyclopropènes électrophiles—I : Cycloadditions du diazo-2 propane sur les esters, cétones et nitriles acétyléniques; synthèse de diméthyl-3,3 pyrazolénines

Abstract 2-Diazopropane adds rapidly to acetylenic esters, ketones and nitriles leading to stable dimethyl-3H-pyrazoles, potential precursors of electrophilic cyclopropenes.

The bicyclo [2.1.0] Pentane way to the diquinane alcohol part of natural triquinanes. A high yield access starting from trimethylsilyloxycyclopentene.

Abstract Trimethylsilyloxycyclopentene reacts exclusively with ethyl propiolate in the presence of ZrCl4 to give a [2+2] adduct (alcohol 6, 90 %). After protection, the stereoselective cyclopropanation via 1,3-dipolar addition of 2-diazopropane followed by sensitized photocleavage, leads with good yields to the bicyclo [2.1.0] pentane derivative 11. By deprotection and solvolytic cleavage with dilute mineral acid, the diquinane alcohol 5 is obtained quantitatively and stereospecifically.

Additions 1,3-dipolaires du diazo-2-propane sur le diacetylene et evolution photochimique des 3H-pyrazoles formes.

Abstract Diacetylene reacts with 2-diazopropane to give the acetylenic 3H-pyrazole I and the bis 3H-pyrazole II. By photolysis both azo-heterocycles lead to rearranged acetylenic compounds. The observed products are best explained by the intervention of unsaturated carbenes which do not cyclize into cyclopropenes.

Total stereospecific synthesis of cis-chrysanthemic methyl ester : the cyclopropenic way.☆

By cycloaddition of 2-diazopropane to isobutenylpropiolic methyl ester one obtains two isomeric gem-dimethyl 3H-pyrazoles. Both isomers give by photolysis the same cyclopropene which can be selectively hydrogenated to cis-chrysanthemic methyl ester.

(2-Stannylated butadiene) tricarbonyl iron complexes: Practical reagents for the synthesis of 2-acyldienes

Abstract A new route to the stable (2-acylbutadiene) tricarbonyl iron complexes is described, based on the palladium catalyzed coupling between acid chlorides and 2-stannylated butadiene complexes.