Marie-Claude Roux-Schmitt

Factors controlling the regioselectivity of additions to α-enones—VI: Reactions of acetonitrile and phenylacetonitrile anions

Abstract Reaction of α-enones 1a-g with acetonitrile anion 5 , in THF at −80° gives, irreversibly, alcohols 7 or 11 , resulting from carbonyl carbon attack, whatever the associated cation is (K + or Li + ). The reaction is considered to be under charge control. In THF, lithiated phenylacetonitrile 6 gives the alcohols 8 and 12 under kinetic control with benzalacetone 1b , 2-cyclohexenone 1d and 3-methyl 2-cyclohexenone 1e . Lithium alcoholate formation is reversible and ketones 10b, 14a and 14b formation, resulting from carbon 4 attack, is thermodynamically controlled. The other α-enones studied lead, under the same reaction conditions, to ketones 10a, 10c, 14c and 14d only. In a THF-HMPA mixture, reagent 6 only gives the starting α-enone, ketones 10 and 14 . The lower lying the α-enone LUMO level, the faster the reaction, which indicates, in the present case, that the transition state for carbon carbon double bond attack occurs relatively early in the reaction path.

Stereochemistry of the aldol condensation of benzaldehydes with alpha-chloro esters : An example of the gauche effect of adjacent polar bonds

Abstract Under irreversible conditions, the stereochemical course of the aldol condensation of benzaldehydes with esters R 1 CHClCO 2 R (R 1 = H or Me) in the presence of NaH, NaOR or KOR depends only on the nature of R. Solvent and temperature have negligible effects. The reaction has been performed with eight ortho - or para -substituted benzaldehydes; only in the case of o -methoxybenzaldehyde has a different stereochemical result been obtained. Possible transition states for the Darzens reaction are discussed and it is shown that all of the data are consistent with a mechanism involving addition of a pyramidal carbanion to the aldehyde CO group via the rotameric forms predicted on the basis of the gauche effect

Additions of anionic nucleophiles to carbonyl compounds: Cation and e-lectrophile nature influence on ionic association vs carbonyl complexation control

Abstract the reaction of benzaldehyde mth LiCH2CN in THF is controlled by carbonyl complexation while uith KCH2CN the reaction is controlled by ionic association. In the reaction of m.Cl.C6H4CHCN−Li+ with substituted benzaldehydes carbonyl complexation prevails with p.CH3OC6H4CHO while ionic association dominates uith PhCHO and p.CNC6H4CHO.

1,6 Addition of carbanionic reagents to 10-methyl hexahydronaphthalenone

Abstract 1,6 addition of carbanionic reagents to bicyclic dienone 1 requires anionic activation : according to the acidity of the corresponding carbon acids, good yields in 7α -adducts can be obtained either in THF-HMPA with nBuLi or tBuOK as bases or under solid-liquid phase transfer catalysis.

Easy conjugate additions to Δ1(9)-octal-2-one and its 10-methyl derivative

Abstract Conjugate additions of lithiated arylacetonitriles to 2-octalones give good yields of cis -decalone products. The stereochemistry of the adducts is determined by 13C NMR spectroscopy.