Abstract
The highly enantioselective asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates with anthrones is presented. The reaction is simply catalyzed by cinchona alkaloid derivatives affording the final alkylated products in good yields and excellent enantioselectivities.
Highlights
Asymmetric allylic substitution has been one of the most important tools in organic chemistry since its discovery by Tsuji and Trost in the early 70 s1,2
Initial experiments were performed for the quinine-catalyzed reactions of anthrone with MBH carbonate 2a
We screened the best conditions for the reaction
Summary
Initial experiments were performed for the quinine-catalyzed reactions of anthrone with MBH carbonate 2a. The reaction tolerates several substituents on the aromatic ring, for example 4-methyl derivative afforded the final addition product 4d in excellent yield and very good enantioselectivity (90% yield; 92% ee). We tested the reaction with a heteroaromatic derivative, which afforded the final compound 4k with excellent yield and enantioselectivity. The reaction with enones tolerates a wide range of substituents such as halides (4r, 4s), electron-withdrawing (4q, 4t) or electron-donating groups (4p) rendering, in all the examples, the final compounds in good yields (76–92% yield) and enantioselectivities 79–92% ee). The reaction shows a good group tolerance including halogens (5b,5r), cyano derivatives (5m) and ketones (5r and 5u) giving the final reduced products as almost diastereopure and with moderate to good yields (52–90%). The X-ray crystal structure unambiguously shows that the diastereomer obtained from the hydrogenation of 4r has an (S, S) absolute configuration
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