Jean-Pierre Pete

Highly Efficient and Stereoselective Radical Addition of Tertiary Amines to Electron‐Deficient Alkenes − Application to the Enantioselective Synthesis of Necine Bases

A convenient and highly efficient method for the regio- and stereoselective addition of tertiary amines to electron-deficient alkenes has been elaborated. It is based on a radical chain reaction of α-aminyl radicals with alkenes, induced by a photoelectron transfer process between tertiary amines 2a−j and excited electron donor substituted phenyl ketones. The influence of the nature of the amino substituents and of the alkene on the reaction have been examined. In the presence of (5R)-5-menthyloxy-2-(5H)-furanone (1) as electron-deficient alkene, the addition of N-alkylpyrrolidines 2a−e occurred with a complete facial selectivity and up to 94% isolated yields. This method has been applied to a fast, efficient and enantioselective synthesis of necine bases.

Highly enantioselective protonation of photodienols an unusual substituent effect on the induced chirality

Abstract Enantiosalectivities up to 91% have been reached during the photodeconjugation of α, β -unsaturated esters or lactones using catalytic amounts of new chiral cyclic inductors derived from (+) camphor. Modification of the substitution on the nitrogen of the inductor can reverse the configuration of the new chiral center.

Highly efficient photochemical addition of tertiary amines to electron deficient alkenes. Diastereoselective addition to (5R)-5-menthyloxy-2[5H]-furanone

Tertiary amines derived from pyrrolidines can be added very efficiently (isolated yields up to 94%) to (5R)-5-mentyloxy-2[5H]-furanone. The addition, which follows a radical chain mechanism initiated by a photoinitiated electron transfer (PET) from the tertiary amine to the excited aromatic ketone, occurs with a complete facial selectivity on the furanone ring. The method can be generalized to the addition of tertiary amines and N-protected secondary amines to electron deficient alkenes.

Photoreductive cyclization: Application to the total synthesis of (±) Hirsutene

Abstract The photochemical reduction of a δ,e-unsaturated ketone is used as a key step in the synthesis of (±) hirsutene. (±) Hirsutene is synthetized in nine steps from cyclopentenone. The crucial step is a photoreductive cyclization of a δ,e-unsaturated ketone.

Photoreactivity of α-tetrasubstituted arylketones: Production and asymmetric tautomerization of arylenols

Abstract In the presence of catalytic amounts of optically active aminoalcohols, the irradiation of α-disubstituted indanones, tetralones and propiophenones bearing at least one hydrogen in the γ-position led to Norrish type II cleavage compounds which were obtained with enantiomeric excesses reaching 89%. The influence of the reaction conditions (temperature, wavelength of the UV light and nature of the alcohol) has been analyzed.

Hydroxyacids as efficient chiral spacers for asymmetric intramolecular [2+2] photocycloadditions☆

Abstract An indirect and efficient enantioselective [2+2] photocycloaddition between 3-carboxycyclohex-2-enone and allyl alcohol, involving a three step sequence, is described. When the reagents are linked by covalent bonds to a chiral spacer such as L-lactic or (R)-3-hydroxybutyric acids, the corresponding photocycloadducts are isolated in high yields. with very high regio and diastereostereoselectivies. The reaction affords polyfunctional cyclobutanes as pure enantiomers.

Synthèse totale du (±) hirsutène

Abstract The photochemical reduction of δ,ϵ-unsaturated ketones allows a short synthesis of (±) hirsutene.

The isoinversion principle for the asymmetric tautomerization of photodienols.

Abstract From the study of the tautomerization of prochiral dienols photogenerated in an organic solvent between −76 and +30°C in the presence of optically active aminoalcohols and in using the methodology developed by Scharfs group, the isoinversion temperature of the asymmetric process has been estimated to be −55°C.

New Access to Spiranic β-Lactams

Abstract N-benzyl α,β-unsaturated γ-oxoamides undergo under irradiation intramolecular hydrogen abstraction and consecutive cyclisation leading to spiranic β-lactams; Extension of the reaction to one spiranic oxapenam is also reported.

Diacetone D-glucose: Efficient chiral building block for asymmetric photodeconjugation

Abstract Irradiation of α-substituted, α,β-unsaturated esters of1,2;5,6-di-O-isopropylidene-ga-D-glucofuranose leads to the formation of β,γ-isomers with high d.e. (up to 98%) whatever the substitution of the chain. A very strong dependence of the nature of the protonating agent upon the selectivity and the configuration of the new chiral center is observed.