Synthesis of N-Bn-3-substituted-2,3-dihydropyrazino[1,2-a]indol-4(1H)-ones 10 from 1 and N-Bn-α-amino acid methyl ester 9^a.

Entryb	R1	R2	1	R3	R4	9	t (h)	10 (%)
1	H	H	1a	CH2Ph	Me	9a	24	84 10a
2	H	H	1a	CH(CH3)2	Et	9b	48	71 10b
3	H	H	1a	CH(CH3)(C2H5)	Me	9c	16	67 10c
4	Cl	H	1d	CH(CH3)(C2H5)	Me	9c	17	54 10d
5	OMe	H	1c	CH2Ph	Me	9a	16	68 10e

^aUnless otherwise stated, reactions were carried out on a 0.290 mmol scale at 120 °C using 1.5 equiv. of 9, 2 equiv. of K₂CO₃ in 3.0 mL of MeCN.

^bYields are given for isolated products.