Jean F. Normant

Boron fluoride promoted opening of epoxides by organocopper and cuprate reagents

In the presence of BF3 the reaction rate of organocopper and cuprate reagents with poorly reactive epoxides is dramatically enhanced. Lithium organocuprates are the best choice among the various organocopper and cuprate reagents tested. Even the dimesityl cyanocuprate is able to react with cyclohexene oxide in excellent yield. No products of cationic rearrangements are observed. The reaction with various epoxides shows a complete stereochemical (pure anti opening) and regiochemical control (attack on the less hindered side of the epoxide).

Enantioselective Carbometalation of Cinnamyl Derivatives: New Access to Chiral Disubstituted Cyclopropanes— Configurational Stability of Benzylic Organozinc Halides

Enantioselectiveadditionofan alkyllithiumcompound acrossa doublebond is achieved by the complexation of various primary or secondary organolithium compounds with (−)-sparteine [Eq. (a)]. This synthetic route is effective, simple, and may be useful for the synthesis of chiral disubstituted cyclopropanes.

Diastereoselective syn or anti opening of propargylic epoxides. Synthesis of α-allenic alcohols

Abstract Propargylic epoxides easily react with Grignard reagents and catalytic amounts of copper(I) salt to afford α-allenic alcohols. The reaction is highly diastereoselective and its stereochemical outcome ( syn or anti isomer) can be fully controlled. The syn diastereomer, probably arising through an addition-elimination mechanism, is better obtained with RMgCl and copper(I) bromide, whereas the anti diastereomer, is better obtained with RMgBr and a complexed copper(I) salt. With RLi and a catalytic amount of copper salt, phenethynyl cyclohexene oxide reacts through reductive lithition, affording, stereoselectivety, an allenyl lithium reagent.

Asymmetric cleavage of chiral acetals by R2CuLi,BF3 reagents

The title reagents cleave diastereoselectively the acetals derived from various aldehydes and chiral 2–3 butane diol (or higher homologs). This reaction affords an asymetric synthesis of secondary alcohols from an aldehyde and a trivial organolithium reagent.

Reactivity of RCu,BF3 and R2CuLi,BF3 towards the ether linkage. Epoxides, acetals and orthoformates

The association of BF3 to organocopper and cuprate reagents increases dramatically their reactivity towards epoxides. The same reagents cleave acetals to afford the product of substitution of one alkoxy group, whereas orthoformates lead to acetals under conditions where no further attack occurs.

Resolution and determination of enantiomeric excesses of chiral aldehydes via chiral imidazolidines

Enantiomeric purity of chiral aldehydes was determined by NMR analysis of derived imidazolidines. The diastereomeric imidazolidines were easily separted by silica gel column and converted into enantiomerically pure aldehyde by acid hydrolysis.

Vinyl-copper derivatives XIII: Synthesis of conjugated dienes of very high stereoisomeric purity

Conjugated dienes are obtained by coupling of alkenyl cuprates and alkenyl halides in the presence of ZnBr2 and a catalytic amount of PdoL4.

General methodology for the synthesis of conjugated dienic insect sex pheromones

A general methodology for the synthesis of various types of dienic insect sex pheromones (Z-E, E-Z, Z-Z) is based on the carbocupration of acetylene by functionalised or non-functionalised lithium dialkyl cuprates, followed by the coupling of the resulting Z dialkenyl cuprates with functionalised or non-functionalised E or Z alkenyl iodides under Pd° catalysis. The following compounds were efficiently synthesized with a high degree of stereoisomeric purity: (E-Z)7, 9-dodecadien,-l-yl acetate 1 (Lobesia botrana), (E-Z)10, 12-hexadecadien,-l-ol 2 (Bombyx mori), (Z-E)9, 11-tetradecadien,-l-yl acetate 3 Spodoptera littoralis), (Z-E)5, 7-dodecadien-l-ol 4 (Malascoma disstria), (Z-Z)11, 13-Hexadecadien-l-al 5 (Amyelois transitella), (Z)9,ll-dodecadien-l-yl acetate 6 (Diparopsis castanea) and (Z-Z)9,11-tridecadien-l-yl acetate 22 (a known “pseudo-pheromone”).

Vinylcopper derivatives. XI. Reactivity of Z-alkenylcuprates towards various electrophiles. Application to the synthesis of some natural products

Abstract Z -Alkenylcuprates 1 and 2 , prepared in situ by addition of acetylene to alkylcuprates, react with a variety of electrophiles (epoxides, carbon dioxide, aldehydes) and give conjugate addition products with α,β-unsaturated aldehydes, ketones and esters, and with activated cyclopropanes. They also add across the triple bond of some alkynes. The synthesis of natural products ( 7,9,22 ) is described.

Diastereoselective conjugate addition with acetals, oxazolidines and imidazolidines as chiral auxiliaries

Organocopper reagents undergo highly diastereoselective conjugate addition on cinnamates bearing a chiral oxazolidine or imidazolidine ring.