Katalytische enantioselektive konjugierte 1,6‐Addition von Grignard‐Reagentien an lineare Dienoate

Regiodivergent 1,4 versus 1,6 Asymmetric Copper‐Catalyzed Conjugate Addition

“…reported the asymmetric synthesis of benzylic tertiary and quaternary stereogenic centers in good yields and selectivities by using a 1,6‐conjugate addition of dialkylzinc reagents to Meldrum's acid acceptors in the presence of L1 6. Also, Feringa's group demonstrated that ferrocene‐based diphosphine ligands, such as ( R )‐1‐[( S )‐2‐diphenylphosphino)ferrocenyl]ethyldicyclohexylphosphine (( R , S )‐josiphos), led to 1,6‐conjugate addition to linear dienoates using Grignard reagents 7. They obtained high enantioselectivities (up to 97 % ee ) and regioselectivities.…”

“…To examine the scope of the 1,6 ACA, we next studied the addition of Grignard reagents to 1 . Using chiral ligands L1 – L3 , as well as binap10 or josiphos,7 only led to the 1,6 adduct (after reconjugation) in low enantioselectivity. However, when N‐heterocyclic carbene (NHC) ligand L4 11 was employed, the 1,4 adduct was obtained as the slightly major regioisomer!…”

Enantioselective 1,6‐Conjugate Addition of Dialkylzinc Reagents to Acyclic Dienones Catalyzed by Cu‐DiPPAM Complex—Extension to Asymmetric Sequential 1,6/1,4‐Conjugate Addition

“…When the regioselectivity cannot be controlled by the substitution pattern at the β‐ and δ‐carbon atoms, a 1,6‐process was frequently observed 5d. f, 6 However, Alexakis showed that the regioisomeric outcome of the Cu/Josiphos‐catalyzed addition of Me 3 Al to nitrodienes can be directed through the choice of both the substituent at the δ‐position and the conditions 8. Furthermore, Zhang reported recently a highly 1,4‐selective and enantioselective addition of Grignard reagents to linear dienones bearing two aromatic substituents, catalyzed by a Cu/ferrocene‐based phosphinooxazoline L1 (Figure 1).…”

Copper‐Catalyzed Asymmetric Allylic Alkylation of Halocrotonates: Efficient Synthesis of Versatile Chiral Multifunctional Building Blocks

“…Azobis(isobutyronitrile) was purchased from Janssen Chimica. BnOH, H 2 O 2 and K 3 Fe(CN) 6 were purchased from Merck. DMAP, hydrazine hydrate, TBDPSCl and methanesulfonamide were purchased from ACROS.…”

“…Recent examples of chemo-, regio-and enantioselective reactions of this type are the hetero-AAA [4c] [Scheme 1, Eq. (a)] and the asymmetric 1,6-addition [6] [Scheme 1, Eq. (b)].…”