Direct Catalytic Asymmetric and Regiodivergent N1-and C3-Allenylic Alkylation of Indoles

Herein we report a Pd-catalyzed asymmetric allenylic alkylation strategy for the direct functionalization of 1H-indoles by employing P-chiral BIBOP-type ligands. The regioselectivity (N1/C3) of this process can be switched efficiently. Using Cs2CO3 at elevated temperatures in MeCN, N1-alkylated indoles bearing axial chirality with a stereocenter non-adjacent (b) to the nitrogen are produced in good yields with high enantioselectivity and complete N1-regioselectivity regardless of the electronic properties and substitution patterns of diverse indoles. Using K2CO3 at room temperature in CH2Cl2, chiral C3-alkylated indoles can also be obtained. Notably, we introduce a new class of tri-substituted allenylic electrophiles that proceeded through different pathways from di-substituted allenylic electrophiles.

Automated summary

Here we present a Pd-catalyzed asymmetric allenylic alkylation strategy using P-chiral BIBOP-type ligands for the direct functionalization of 1H-indoles. The regioselectivity of this process can be efficiently switched between N1 and C3. N1-alkylated indoles with axial chirality and non-adjacent stereocenter (b) to the nitrogen were obtained in good yields with high enantioselectivity and complete N1-regioselectivity regardless of the electronic properties and substitution patterns of diverse indoles using Cs2CO3 at elevated temperatures in MeCN. Chiral C3-alkylated indoles can also be achieved using K2CO3 at room temperature in CH2Cl2. Notably, a new class of tri-substituted allenylic electrophiles was introduced, which proceeded through different pathways from di-substituted allenylic electrophiles.