Willy Dumont

Efficicient, high yield, oxidation of thiols and selenols to disulphides and diselenides

Abstract Thiols and selenols are smoothly oxidised in high yield to disulphides and diselenides by sodium perborate at room temperature.

Synthesis of selenoacetals

Abstract This paper reports our results concerning the syntheses of various bis(alkylseleno)alkanes and some of their arylseleno analogues by different methods. The scope and limitation of each of them are presented.

Stereoselective synthesis of methyl (1R) trans- and (1R) cis-hemicaronaldehydes from natural tartaric acid : application to the synthesis of s-bioallethrin and deltamethrin insecticides

Abstract Very efficient enantioselective syntheses of (1R)- trans -and cis -hemicaronaldehydes precursors of (1R)-trans chrysanthemic acid and its (1R)-cis dibromovinyl analogue starting from natural tartaric acid or D-mannitol are described. They are based on the reaction between isopropylidenetriphenylphosphorane or isopropylidenediphenylsulfurane and chiral γ-alkoxy-α,β-unsaturated esters. The general problem of the diastereoselective addition to such esters is discussed.

CHEMOSELECTIVE REDUCTION OF ORGANOSELENOCYANATES TO DISELENIDES AND SELENOLATES

Abstract Selenocyanates produce selenolates or diselenides on reaction with metal hydrides (NaH, LiHBEt 3 , LiBH 4 , NaBH 4 ). The former transformation is performed with 2 molar equivalents of sodium hydride or lithium triethyl borohydride or 1.25 molar equivalent of metal borohydrides. The second one is performed with lower amount of reducing agent (1 molar equivalent of sodium hydride or lithium triethyl borohydride or 0.25 equivalent of metal borohydrides). Intermediate formation of a selenol or a selenolate which reacts on the unreacted selenocyanate is suspected in the later transformation.

From tartaric acid to the most biologically active insecticides: Straightforward enantioselective synthesis of deltamethrin

Abstract Isopropylidenediphenylsulfurane reacts with γ-alkoxy αβ—unsaturated esters and produces γ—alkoxy cyclopropane carboxylates. This reaction is almost completely stereospecific and takes place with very high asymmetric induction. It has been successfully applied for the enantioselective synthesis, from natural tartaric acid, of deltamethrin the most active insecticide commercially available.

Synthesis of α-selenoalkyllithium compounds

Abstract α-Phenylselenoalkyllithiums and α-methylselenoalkyllithiums have been prepared from the corresponding selenoacetals and alkyllithiums. Several features of this reaction are disclosed. For example, the reaction is more readily achieved on phenylselenoacetals than on methylseleno analogues. Those derived from hindered carbonyl compounds are less readily cleaved.s-BuLi/THF proved superior to n-BuLi in THF, itself better than n-BuLi in ether.

Regioselective 1–4 addition of acyl and equivalents to α-enones

Abstract 2-lithio-1,3-dithianes, bis(phenylthio)alkyllithiums and bis(methylseleno)alkyllithiums add 1–4 to α-enones if HMPT is present in the medium prior to the addition of enones. Most of the reactions occur under kinetic control.

Cleavage of the CSe bond of cyclic selenoacetals derived from 4-t-butyl cyclohexanone with butyllithiums and tin and silyl hydrides

Abstract Selenoacetals derived from 1,3-propanediselenol and 1,2-ethanediselenol are much less prone to be cleaved by butyllithiums than their open chain analogues. The stereochemistry of the products resulting from these reactions as well as from the cleavage of the CSe bond under radical conditions is disclosed.

Chemoselective Reduction of Organoselenocyanates to Diselenides

Abstract Selenocyanates possess an extremely high propensity to produce diselenides on reaction with selenols or selenolates. This is effectively observed when one molar equivalent of metal hydride or lithium triethyl borohydride or one fourth molar equivalent of metal borohydrides are reacted with organic selenocyanates.

Synthesis and reactivity of α-lithio α-trimethylsilyl cyclopropanes and related derivatives

Abstract α-lithio α-trimethylsilyl cyclopropanes have been prepared by two different routes. They have been tested as precursors of alkylidene cyclopropanes, cyclopropylidienes and α-silyl α-vinyl cyclopropanes.