Kupferkatalysierte Si‐B‐Bindungsaktivierung in der verzweigtselektiven allylischen Substitution linearer Allylchloride

Abstract

Von Alpha bis Gamma: Chlorid ist allen gängigen Abgangsgruppen bei der γ‐selektiven allylischen Substitution linearer Vorstufen überlegen. Der Einstieg in den Katalysezyklus ist eine neuartige, kupferkatalysierte Si‐B‐Bindungsaktivierung (siehe Schema; γ/α≥98:2, 7 Beispiele; Si=SiMe2Ph, B=Bpin mit pin=Pinakolato).

Copper‐Catalyzed 1,2‐Addition of Nucleophilic Silicon to Aldehydes: Mechanistic Insight and Catalytic Systems

“…The nucleophilic attack of the CuÀSi on the electrophile, that is, the formal insertion of the electrophilic moiety into the Cu À Si bond, is supposed to be crucially involved in catalytic silylation reactions. [1][2][3][5][6][7][8] To study this essential step in detail, we employed the complex [(iPrNHC)Cu À SiMe 2 Ph] (3; iPrNHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) in stoichiometric reactions with an aldehyde. This complex is readily generated by the reaction of the alcoholato complex [(iPrNHC)CuÀOtBu] (1) and Me 2 PhSiÀBpin [27] (2) (pin = pinacolato).…”

“…Keywords: aldehydes · copper · nucleophilic addition · silicon · transmetalation · X-ray diffraction [ pounds [1][2][3][5][6][7][8] might therefore be useful in a catalytic onestep access to a-silyl alcohols from aldehydes. We report here two independent protocols for the catalytic 1,2-addition of a silicon nucleophile to aromatic and aliphatic aldehydes by employing either a well-defined NHCÀCuOtBu complex or the CuCN-NaOMe combination without added ligand.…”

Unprecedented Copper(I) Bifluoride Complexes: Synthesis, Characterization and Reactivity

“…Once more an activating agent was required. [32] Bifluoride complexes, once again were shown to be active in both reactions, generating good yields, and did not require an activating agent (Table 3, entries 1 and 2). Unfortunately, the chiral complexes studied here did not lead to a high enantioselectivity (Table 3, entry 3).…”

Copper(I)‐Catalyzed Allylic Substitution of Silyl Nucleophiles through SiSi Bond Activation

“…Oestreich and co‐workers recently reported a copper(I)‐catalyzed silylation using silylborane as well as silylzinc reagents 5c,9f. However, there have been no reports on the use of disilanes as the silyl group source in copper(I)‐catalyzed allylsilane synthesis.…”