Jean Rodriguez

Metal-free Michael addition initiated multicomponent oxidative cyclodehydration route to polysubstituted pyridines from 1,3-dicarbonyls

A simple metal-free, step-economic and selective access to pyridines from readily available substrates is reported, involving a flexible 4 A molecular sieves promoted Michael addition initiated domino three-component reaction between a 1,3-dicarbonyl, a Michael acceptor and a synthetic equivalent of ammonia.

The MARDi Cascade: A Michael‐Initiated Domino‐Multicomponent Approach for the Stereoselective Synthesis of Seven‐Membered Rings

The MARDi cascade is a recently invented three-component Michael-initiated condensation involving 1,3-dicarbonyl derivatives. It allows regio- and stereocontrolled access to a variety of functionalised and substituted seven-membered rings. The substitution array can be diastereoselectively modulated by appropriate choice of the reaction partners, and the reaction allows the control of up to five newly created stereocentres and a complete chiral induction in the case of an optically active ketone precursor. The high level of diastereoselectivity observed has been attributed to total thermodynamic control of the reaction. The attractiveness of the present domino three-component approach to seven-membered rings resides in the diversity of carbo- and heterocyclic structures that can be accessed with total regiocontrol and high stereocontrol by starting from simple substrates, under user and environmentally friendly conditions, as now required in modern organic chemistry.

Isomerisation de diènes-1,5 fonctionnalisés par le fer pentacarbonyle

Abstract A series of various, functionnalized 4-vinylcyclohexene derivatives, substituted with electron-withdrawing or -donating groups on the exocyclic double bond, have been isomerized by pentacarbonyliron, under thermodynamic control with heating, into a mixture of conjugated cyclohexadiene tricarbonyliron complexes, of which the 2-substituted derivative is the predominant. When ferrous chloride is used as the co-catalyst, the isomerisation proceeds under kinetic control to give the 1-substituted cyclohexadienetricarbonyliron complex as the major derivative. Reaction mechanisms, have been proposed for these isomerisation processes, which provide a new selective route to such derivatives. The formation of η4-1,4-cyclohexadienetricarbonyl complexes as intermediates has been excluded, and it is shown that the thermal isomerisation proceeds via η2-complexes that are formed by successive 1,3-hydrogen shifts.

Mécanisme de la formation de complexes η4-cyclohexadiène fer tricarbonyle substitués par isomérisation de dérivés vinyl-4 cyclohexéniques

Abstract Using 4-vinylcyclohexenes with electron-donating or -withdrawing substituents on the exocyclic double bond, we could show that the thermal isomerisation process leading to η 4 -cyclohexadiene tricarbonyliron complexes involves η 2 -intermediates formed by successive 1,3-hydrogen shifts. The formation of the η 4 -1,4-cyclohexadienetricarbonyliron complex can be excluded.