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Guo et al. Chem Synth 2023;3:34 https://dx.doi.org/10.20517/cs.2023.04 Page 5 of 11

Figure 3. Scope of Reactions.

Bromoenals bearing naphthalene or heteroaromatic rings (2-furyl and 2-thienyl) did not influence the
efficiency, affording the corresponding d -methylated products 3j-l with good to excellent outcomes (90%-
3
97% yields, 11:1-> 20:1 dr values and > 99% values for all the cases). Subsequently, the generation of
trideuteromethyl oxindolyl 1,3-diketones 2 was evaluated. For trideuteromethyl oxindolyl 1,3-diketones,
several substituents at the 4-, 5-, 6-, and 7-positons on the oxindole ring were also compatible with the
reaction to generate the d -methylated products 3m-3q in excellent yields (94%-97%) with good to excellent
3
diastereoselectivities (10:1-> 20:1 dr values) and excellent enantioselectivities (> 99% ee values). Substrates
with N-benzyl and N-allyl groups reacted efficiently to form d -methylated products 3r and 3s in 94% and
3
87% yields with 17:1 dr, > 20:1 dr values and > 99%, 96% ee values, respectively. Unfortunately, β-alkyl-
substituted enals failed to deliver the product in our reaction.

After successfully documenting the synthesis of trideuteromethyl molecules with three stereogenic centers
under NHC organocatalysis, to further evaluate the scope and limitations of this strategy, other alkyl groups
were introduced into the prochiral substrates [Figure 4]. The CD group can be replaced with a methyl
3
group, with the corresponding product 4a formed in 96% yield with 13:1 dr and > 99% ee. Compound 1