Table 2.

Cross-functionalization experiments to examine the competitive reactivity of α-haloglycine esters 4a–c.^[a–d]

Entry	Time (h)		0	0.25	0.5	1	1.5	2.5	3.5	6	8	10
1 Condition A Uncat.	α-haloglycine % consumption	4a	0	12	15	18	12	30	32	33	30	36
		4b	0	37	40	57	53	47	40[d]	47	50	43
		4c	0	8	14	14	24	32	43	54	59	76
	% Yield (7)		0	9	11	12	14	19	20	28	29	37
2 Condition B TA (10 mol%)	α-haloglycine % consumption	4a	0	18	15	18	15	15	21	21	15	27
		4b	0	33	50	43	50	47	53	67	40	37[d]
		4c	0	27	49	49	57	59	70	70	73	86
	% Yield (7)		0	20	23	25	29	32	36	40	43	45

^[a]Reactions performed on 0.5 mmol scale, conditions A: 4a–4c (1.0 eq.), conditions B: 4a–4c (1.0 eq.) with thiourea T_A (10 mol-%).

^[b]The conversions were determined using ¹H NMR with mesitylene as internal standard, from reaction aliquots in CHCl₃ transferred in NMR tubes and adjusted to a mixture of CHCl₃/CD₃CN (2:1) at low temperature.

^[c]Average measurements are reported from triplicate experiments.

^[d]A bromide-chloride exchange is likely occurring through an external ion-return between the two glycinyl iminium ion-pairs 6b:6c (X = Br, Cl).