With the optimized reaction conditions in hand, the substrate scope of (E)-2,2-dimethyl-6-alkyl-4H-1,3-dioxin-4-ones was studied (Fig. 2). Linear alkyls, including ethyl (3b), npropyl (3c), and nheptyl (3d), were well tolerated and the corresponding products were isolated in good yields with high enantioselectivity. β-Branched alkyl (ibutyl) (3e) was also accepted at the δ-position. The substrates bearing a α-branched alkyl with bigger steric hindrance (3f and 3g), afforded the allylated products in moderate yields and slightly decreased enantioselectivity. Then, substrates with an alkyl containing a functional group, such as benzyl (3a), terminal alkene (3h), internal alkyne (3i), alkyl chloride (3j), ester (3k), TBS-ether (3l), and N-Boc (3n) were examined. To our joy, the products were obtained in moderate to high yields and high enantioselectivity. Notably, alkyl chloride and ester group were not touched by the nucleophilic allylcopper-NHC species, demonstrating that allylcopper-NHC species was less nucleophilic than allylcopper-bisphosphine species. Unfortunately, the substrate containing a free alcohol (3m) was not tolerated. A substrate with a preexisting chiral center (3o) was also studied. The allylated product was generated in 72% yield with 91% de, indicating that the asymmetric induction was mainly controlled by the copper(I) catalyst. It should be noted that in some cases, the reaction temperature was increased to get good yields.
Hosomi Sakurai Reaction Pdf Free
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