Organocyanocopper-trifluoroborane mediated 1,3-chirality transfer reaction of .gamma.-(mesyloxy)-.alpha.-alkyl .alpha.,.beta.-enoates for the construction of chiral quaternary carbon centers with high optical purity

Stereospecific and Stereodivergent Construction of Tertiary and Quaternary Carbon Centers through Switchable Directed/Nondirected Allylic Substitution

“…The absolute configuration of the substitution products was determined upon transformation of (−)‐ 7 b to the known ester (−)‐ 9 ( [Eq. (3)]; DDQ=2,3‐dichloro‐5,6‐dicyano‐ p ‐benzoquinone) 7b …”

“…Here the problem of a thermodynamically unfavorable enoate deconjugation combines with that of chemoselectivity caused by the additional ethyl ester functionality (allylic substitution vs. conjugate addition) 3. 7a, b Interestingly, the directed allylic substitution occurred with complete chemo‐, regio‐, and stereoselectivity and with excellent chirality transfer to give the substitution products (−)‐ 7 g – i (Table 2, entries 7–9).…”

A Novel Method To Generate Chiral Quaternary Carbon Centers of High Enantiomeric Purity Using a Highly Stereoselective Addition of Vinylalanes to a Chiral Aldehyde

“…(17) Quaternary centers of high optical purity are notoriously difficult to construct. [5] However, trisubstituted carbonates such as 2 (R 2 Me) did not react with cuprate reagents because of the high energy required to attain one of the two reactive conformations A or C (Scheme 2, top). [2±4] The prospect of making quaternary carbon centers using the approach described above (Scheme 1, R 2 Me) was appealing because the cuprate addition step should be selective regardless of the substitution on the allylic moiety.…”

Analyses of Anionic Cu(I) Complexes via Electrospray Mass Spectrometry

“…Such mixtures of salts are oftentimes designated “CuX· n LiX” ( e.g., CuCN·2LiCl), a shorthand accounting of stoichiometry which imparts little information about composition or structure ( vide infra ). Similar descriptors have been used for cuprates ( e.g., “RCu(CN)Li·LiX”) and have recently served as a focal point of controversy surrounding the existence of “higher order” (HO) cyanocuprates . We now describe our preliminary results on the use of electrospray ionization mass spectrometry (ESIMS) to characterize commonly used cuprate precursor Cu(I) salts infused as THF solutions.…”