Table 2. Synthesis of 2-Substituted Racemic and Diastereomeric 4-Piperidones.

entry	R	8 (%)a	2 + 2′ (%)b	ratiod of 2:2′
1	Me	a (42)c	a (37)c	1.1:1.0
2	n-Pr	b (36)c	b (27)c	1.4:1.0
3	Ph	c (79)	c (63)	2.6:1.0
4	4-ClC6H4	d (84)	d (68)	2.8:1.0
5	4-OMeC6H4	e (84)	e (57)	3.7:1.0

^aReaction conditions: 7a–e, benzylamine, NaHCO₃, CH₃CN/H₂O (3:1), 16 °C (40 min) → 95 °C, 1.5 h.

^bReaction conditions: 7a–e, S-α-phenylethylamine, NaHCO₃, CH₃CN/H₂O (3:1), 16 °C (40 min) → 95 °C, 1.5 h.

^cCrude ketone used as starting material.

^dThe ratio was derived from the isolated product yields (for entries 1, 4, and 5) or determined by analysis of the ¹H NMR spectra (for entries 2 and 3).