Hemiaminals are common in natural products as well as bioactive compounds. Hemiaminals
with an indole moiety are particularly attractive due to the significant bioactivity
of indoles. Herein, we reported an efficient organocatalyzed indole N-1 nucleophilic
addition of α-oxoaldehydes to deliver various indole hemiaminals in good yields (up
to 92%) and excellent regioselectivities with DABCO or triethylamine as the catalyst.
The method is characterized by mild reaction conditions, widely available reagents,
and general substrate scope, and it is also applicable to late-stage transformations
without affecting the hemiaminal group. In addition, we carried out this reaction
in an enantioselective fashion in good yields and high ee values with two general
substrates.
Key words
organocatalysis - indole - hemiaminals - nucleophilic addition
