Optimization of conditions for the catalytic formyl-selective deuteration reaction^a.

Entry	Deviation from standard conditions	Deuterationb (%)
1	None	94
2	7b instead of 7a	63
3	7c instead of 7a	71
4	7d instead of 7a	78
5	NMP instead of DCM	13
6	MeCN instead of DCM	38
7	CHCl3 instead of DCM	62
8	2 mol% of TBADT	77
9	20 mol% of 7a	80
10	No TBADT	<5
11	No 7a	<5
12	No light	<5

^aReaction conditions, unless otherwise noted: 1a (0.3 mmol), TBADT (0.012 mmol), 7a (0.12 mmol), and 1 : 1 (v/v) DCM/D₂O (3.0 mL) under an Ar atmosphere.

^bDeuterium incorporation was determined by integration of the residual formyl proton in the ¹H NMR spectrum. DCM = dichloromethane and NMP = N-methyl-2-pyrrolidinone.