Chelation-Aided Generation of Ketone α,β-Dianions and Their Use as Copper Ate Complexes. Unprecedented Enolate Intervention in the Conjugate Addition to Enones

Thermochemical Considerations of Metal Enolates

“…For example, no 5-methyl-2-furanol (41) is detected in the rearrangement of γ -methylene-γ -butyrolactone (42) to α-angelicalactone (43) 228 . Understanding the contribution to aromaticity of Re in the 2-rhenafurans (39,40) and the exocyclic and endocyclic methylene groups in 42 and 43 would be most instructive. acidities of the diverse sites for deprotonation is welcomed.…”

Nickel-catalyzed acylstannylation and alkynylstannylation of 1,2-dienes

“…Thus, both stereoisomers 28 and 30 were prepared selectively starting with 3j simply by changing the order of operation. Stereoselective isomerization of 3j to 29 might be attributed to an intramolecular interaction between the oxygen and tin atoms in 29 [12,22]. Cross-coupling reaction of 3j with benzoyl chloride proceeded similarly to give enedione 31. aDimethylation of 3j gave 3o, which also cross-coupled with 26 to afford 32.…”

Mechanisms of Copper‐mediated Addition and Substitution Reactions

“…Four-centered addition of RCu to an enone was widely discussed in the 1960s (Scheme 10.3a) [51][52][53], while discussions on six-centered transition states have continued until recent times (Scheme 10.3b) [54]. These mechanisms do not, however, explain the formation of E=Z mixtures of enolate stereoisomers [20,55] and must now be considered obsolete.…”

“…The difference is that the product of conjugate addition (PD) remains as a lithium enolate complexed with RCu I (Scheme 10.5), while the initial product of carbocupration (INT2, Scheme 10.7) undergoes further reaction (Li/Cu transmetalation) and generates a new organocuprate compound. (Note however that this difference could become more subtle since the product of conjugate addition (PD) might behave more like an a-cuprio(I) ketone complexed with a lithium cation [52] than a lithium enolate complexed with copper(I)). In neither reaction was any evidence of radical intermediates (i.e., SET) found by theoretical calculations [79].…”