Table 1.

Optimization of reaction conditions^a

Entry	Base	Temp. (°C)	Yieldb (%)
1c,d	2-Chloropyridine	−10	36
2d	2-Chloropyridine	−10	56
3	2-Chloropyridine	−10	61
4	2-Fluoropyridine	−10	45
5	Pentafluoropyridine	−10	38
6	2-Methoxypyridine	−10	0
7	Pyridine	−10	21
8	None	−10	34
9	2-Chloropyridine	−41	84
10	2-Chloropyridine	−78	70
11e	2-Chloropyridine	−41	64
12f	2-Chloropyridine	−41	85

^aConditions: 1 (1.0 mmol), benzylamine (1.1 mmol), benzaldehyde(1.1 mmol), 4 Å mol sieves (1.0 g), CH₂Cl₂ (10.0 mL), rt, 18 h; then base (1.2 mmol), Tf₂O (1.1 mmol), temperature; then rt, 24 h.

^bIsolated yield.

^c4 Å mol sieves were not added.

^dN-Benzylidenebenzylamine (1.1 mmol) was used instead of benzylamine and benzaldehyde.

^eReflux during final step.

^f48 h for final step.