غير المشبعة a – b آلية تفاعلات إضافة مركبات النحاس العضوية للمركبات الكربونيلية

Abstract EN

Michael addition of organocuprate reagents toward a-b unsaturated carbonyl compounds are among the most reliable methods for regio-and stereoselective coupling of C-C bonds.

The steriochemical studies of reaction intermediates between lithium dialkylcuprate with enones provides evidence for a pathuay d(Cu)p* (enones) and copper(III) Cb adducts as important intermediates in cuprate -mediated conjugate addition of carbon.

a-b enones possessing a y heteroatom substituent exhibit more complex reactivity towards cuprates than do simple a-b enones.

The conjugate addition process generally takes place with the addition of carbon to C (b) in the anti sense relative to the heteroatom at C(y) in our view the preference for anti stereochemistry probably arises from a stereoelectronie effect in which the y - heteroatom removes electron density hepereconjugatively from the d(Cu)p* (enones) or the Cu(III) – Cb adduct with maximum stabilization occurring in the anti geometry from the evidence desecribed herein conclude that (1) the conjugat addition reaction of lithium dialkylcuprates with enones proceed via reversible d,p* complex and copper(III) Cb - adduct formation (in that order) and (2) an intial electron transfer step from cuprate to enone is not obligatory.

studies are in progress to determine whether electron transfer can be an obligatory first setp with certain Michael acceptors or cuprates, we believe that the use in situ of silyl eletrophiles is a powerful tool for the study of mechanisms of organometallic reactions.