Table 2.

DIBAL reductions of quinolin-2-ones 23a–e using the optimised method to synthesise 22.^a

Quinolin-2-one	R1	R2	23 (%)	24 (%)	25 (%)
23a	Ph	H	0	100	0
23b	Ph	Me	0	38	62
23c	H	H	12	88	0
23d	H	Et	0b	63b	21b
23e	H	Bn	0c	35c	Tracec

^aDIBAL (1.0 M in toluene, 1.2 equivalents or 2.0 equivalents for 23a and 23c) added to a refluxing solution of quinolin-2-one 23a–e (0.5–3.0 mmol) in toluene stirred rapidly at reflux until TLC analysis indicated completion. Then quenched with 20% aq w/v NaOH, extracted with EtOAc, washed with H₂O and brine, dried (MgSO₄) and evaporated. Yields of 23a–e, 24a–e and 25a–e were estimated from ¹H NMR analysis of the crude mixture (see Supporting Information File 1). ^bA ring-opened ethylaniline (9%) and another byproduct were also present (7%). ^cA ring-opened benzylaniline was also present (61%).