Copper(I) Thiolate Catalysts in Asymmetric Conjugate Addition Reactions

Abstract

[structure: see text] Full conversion and enantioselectivities up to 83% have been obtained in the conjugate addition reactions of diethyl zinc to Michael acceptors catalyzed by well-defined (chiral) copper(I) aminoarenethiolates. Interesting differences between organozinc or Grignard reagents have been found: for cyclic enones R(2)Zn reagents afford better results, whereas earlier work showed that RMgX reagents react more selectively with acyclic enones.

Copper‐catalyzed asymmetric 1,4‐conjugate addition of dialkylzinc to enones

“…The most explored chiral ligands types were phosphorus‐based ligands including phosphites,3 diphosphites,4 phosphoramidites,5 P,O‐6 and P,N‐ligands 7. Other classes of ligands explored, without a phosphorus atom, included chiral sulfonamides,8 diaminocarbenes,9 oxazolines,10 S,O‐,11 N,N‐12 and N,S‐13 ligands. On the other hand, binaphthol‐based ligands are some of the most widely studied in 1,4‐conjugate addition.…”

A recyclable nanosize aminoarenethiolato copper(I) catalyst for C–C coupling reactions

“…The catalytic performance of metallodendrimer 9 (entries 6-10) is similar to those of unsupported copper(I) complexes 1a and 1b (entries 2 and 5) or even exceeds these (compare entries 3 and 4 with entries 7 and 8) ( Table 1). The influence of para-substitution had already been studied with catalyst 1b (entry 5) [14].…”

“…thermally stable and have considerable stability towards oxidation by air. Furthermore, mechanistic studies established that the covalent thiolato-copper bond is maintained throughout the catalytic cycle in processes involving the use of RLi [13], RMgX [6] and R 2 Zn reagents [14]. A recent example, shown in Fig.…”

Cu‐ and Ni‐Catalyzed Conjugated Additions of Organozincs and Organoaluminums to α,β‐Unsaturated Carbonyl Compounds

“…In this case, the conjugated addition of Et 2 Zn to cyclohexenone proceeded with a moderate enantioselectivity (64% ee) with L50a, whilst following the addition of Et 3 Al the best result was obtained with L50b (48% ee). Among other ligands used for enantioselective conjugated addition may be included binaphthols with a thioether moiety L51 [132], monothiolbinaphthol S-derivatives L52 [133], oxazolines L53 [134], and aminoarenethiolates L54 [135] ( Figure 2.16). The conjugated addition of Et 2 Zn to cyclohexenone in the presence of L51a proceeded with 85% ee in MTBE, whereas for chalcone a 96% ee was obtained with L51b.…”