V. Sai Sudhir, R. B. Nasir Baig, S. Chandrasekaran
FULL PAPER
5-(1-Phenylethyl)-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyrazin-6-
one: (3b): Rf = 0.30 (hexanes/EtOAc, 4:6). Yield: 254 mg (96%).
Methyl (2S)-3-Methyl-2-(6-oxo-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-
a]pyrazin-5-yl)butanoate (6c): Rf = 0.50 (hexanes/EtOAc, 4:6).
Colorless viscous oil. IR (neat): ν = 2980, 1656, 1472, 1346, 990,
Yield: 240 mg (95%). Colorless gummy liquid. IR (neat): ν = 2966,
˜
˜
701 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.48 (s, 1 H), 7.37– 1740, 1691, 1555, 1210, 992, 767 cm–1 1H NMR (300 MHz,
.
7.31 (m, 5 H), 6.21 (q, J = 6.9 Hz, 1 H), 5.12 (s, 1 H), 5.11 (s, 1
H), 4.51 (d, J = 16.2 Hz, 1 H), 4.14 (d, J = 16.2 Hz, 1 H), 1.64 (d,
J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 161.6,
137.9, 129.1, 128.7, 128.1, 127.5, 127.3, 50.8, 48.7, 36.3, 14.9 ppm.
HRMS: calcd. for C13H14N4O [M + Na]+ 265.1065; found
265.1066.
CDCl3): δ = 7.65 (s, 1 H), 5.16 (s, 2 H), 5.03 (d, J = 10.8 Hz, 1 H),
4.97 (d, J = 16.2 Hz, 1 H), 4.66 (d, J = 16.2 Hz, 1 H), 3.75 (s, 3
H), 2.39–2.27 (m, 1 H), 1.07 (d, J = 6.6 Hz, 3 H), 0.91 (d, J =
6.3 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 170.6, 162.9,
129.3, 127.7, 61.2, 52.3, 48.9, 38.3, 27.2, 19.5, 18.9 ppm. [α]2D2
=
–17.8 (c = 1.0, CHCl3). HRMS: calcd. for C11H16N4O3 [M + H]+
253.1300; found 253.1301.
5-Phenethyl-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyrazin-6-one
(3c): Rf = 0.40 (hexanes/EtOAc, 4:6). Yield: 252 mg (95%). White
Methyl (2S)-4-(Methylsulfanyl)-2-(6-oxo-4,5,6,7-tetrahydro-
[1,2,3]triazolo[1,5-a]pyrazin-5-yl)butanoate (6d): Rf = 0.30 (hexanes/
solid. M.p. 158 °C. IR (neat): ν = 2925, 1652, 1489, 1347, 1169,
˜
1
991, 836, 750, 701 cm–1. H NMR (300 MHz, CDCl3): δ = 7.52 (s,
EtOAc, 1:1). Yield: 288 mg (94 %). Colorless gummy liquid. IR
(neat): ν = 3474, 2921, 1740, 1665, 1475, 1430, 1199, 991 cm–1. H
1
˜
1 H), 7.33–7.20 (m, 5 H), 5.08 (s, 2 H), 4.43 (s, 2 H), 3.8 (t, J =
7.2 Hz, 2 H), 2.98 (t, J = 7.5 Hz, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 161.7, 137.9, 129.0, 128.9, 128.7, 127.2, 126.9, 49.4,
48.7, 43.1, 33.4 ppm. HRMS: calcd. for C13H14N4O [M + Na]+
265.1065; found 265.1059.
NMR (300 MHz, CDCl3): δ = 7.65 (s, 1 H), 5.18–5.14 (m, 3 H),
4.84 (d, J = 15.6 Hz, 1 H), 4.72 (d, J = 15.9 Hz, 1 H), 3.77 (s, 3 H),
2.60–2.40 (m, 3 H), 2.27–2.10 (m, 4 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 170.0, 162.9, 129.2, 127.4, 56.5, 52.6, 48.7, 40.2, 30.5,
27.3, 15.3 ppm. [α]2D3 = –2 (c = 1.0, CHCl3). HRMS: calcd. for
C11H16N4O3S [M + Na]+ 307.0841; found 307.0836.
5-[(1S)-1-(1-Naphthyl)ethyl]-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]-
pyrazin-6-one (3d): Rf = 0.30 (hexanes/EtOAc, 5:5). Yield: 311 mg
Methyl (2S)-4-Methyl-2-(6-oxo-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-
a]pyrazin-5-yl)pentanoate (6e): Rf = 0.40 (hexanes/EtOAc, 4:6).
(99%). White solid. M.p. 94 °C. IR (neat): ν = 3052, 2980, 1651,
˜
1
144, 1346, 784 cm–1. H NMR (300 MHz, CDCl3): δ = 7.96–7.85
Yield: 253 mg (95%). Colorless gummy liquid. IR (neat): ν = 3475,
˜
(m, 3 H), 7.66–7.46 (m, 4 H), 7.37 (s, 1 H), 6.79 (q, J = 6.9 Hz, 1
H), 5.19 (d, J = 17.7 Hz, 1 H), 5.09 (d, J = 18 Hz, 1 H), 4.39 (d, J
= 16.2 Hz, 1 H), 3.67 (d, J = 16.5 Hz, 1 H), 1.75 (d, J = 6.9 Hz, 3
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 161.1, 133.7, 133,
131.4, 129.4, 129.1, 128.8, 127.4, 127.1, 126.1, 125.2, 124.7, 122.7,
48.5, 48.2, 36.6, 15.3 ppm. [α]2D2 = –121.8 (c = 2.0, CHCl3). HRMS:
calcd. for C17H16N4O [M + Na]+ 315.1220; found 315.1230.
2957, 2875, 1740, 1667, 1471, 1349, 1185, 990 cm–1 1H NMR
.
(300 MHz, CDCl3): δ = 7.64 (s, 1 H), 5.42 (dd, J1 = 10.2 Hz, J2 =
5.7 Hz, 1 H), 5.15 (s, 2 H), 4.81 (d, J = 15.6 Hz, 1 H), 4.6 (d, J =
15.6 Hz, 1 H), 3.75 (s, 3 H), 1.94–1.77 (m, 2 H), 1.51–1.40 (m, 1
H), 0.96 (t, J = 6.9 Hz, 6 H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 171.1, 163, 129.3, 127.5, 54.1, 52.5, 48.8, 38.3, 36.6, 24.9, 23,
21.2 ppm. [α]2D2 = –9.2 (c = 1.0, CHCl3). HRMS: calcd. for
C12H18N4O3 [M + H]+ 267.1457; found 267.1456.
5-(2-Furylmethyl)-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyrazin-6-
one (3e): Rf = 0.40 (hexanes/EtOAc, 5:5). Yield: 229 mg (95%).
Methyl (2S)-2-(6-Oxo-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyr-
azin-5-yl)-2-phenylethanoate (6f): Rf = 0.30 (hexanes/EtOAc, 5:5).
Colorless oil. IR (neat): ν = 3511, 2986, 1665, 1485, 1424, 1347,
˜
1011, 751 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.91 (s, 1 H),
7.59 (s, 1 H), 6.40 (d, J = 3.3 Hz, 1 H), 6.36 (t, J = 2.1 Hz, 1 H),
5.1 (s, 2 H), 4.77 (s, 2 H), 4.72 (s, 2 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 161.4, 148.4, 142.8, 128.9, 127.2, 110.4, 109.8, 48.3,
42.5, 41.7 ppm. HRMS: calcd. for C10H10N4O2 [M + Na]+
241.0701; found 241.0706.
Yield: 284 mg (92%). Pale-yellow gummy liquid. IR (neat): ν =
˜
2926, 1740, 1647, 1441, 1347, 1201, 986, 698 cm–1 1H NMR
.
(300 MHz, CDCl3): δ = 7.45 (s, 1 H), 7.46–7.44 (m, 3 H), 7.30–
7.26 (m, 2 H), 6.53 (s, 1 H), 5.18 (s, 2 H), 4.84 (d, J = 15 Hz, 1 H),
4.12 (d, J = 15 Hz, 1 H), 3.82 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 169.9, 162.9, 131.8, 129.4, 129.3 (2 C), 129.2, 127.6,
59.9, 52.7, 48.7, 38.9 ppm. [α]2D3 = 9.5 (c = 1.0, CHCl3). HRMS:
calcd. for C14H14N4O3 [M + H]+ 309.0964; found 309.0964.
Methyl (2S)-2-(6-Oxo-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyr-
azin-5-yl)propanoate (6a): Rf = 0.30 (hexanes/EtOAc, 4:6). Yield:
216 mg (96%). Colorless gummy liquid. IR (neat): ν = 2953, 1742,
˜
Methyl (2S)-3-(1H-3-Indolyl)-2-(6-oxo-4,5,6,7-tetrahydro[1,2,3]tri-
azolo[1,5-a]pyrazin-5-yl)propanoate (6g): Rf = 0.30 (hexanes/EtOAc,
1
1692, 1666, 1556, 1350, 1201, 991, 735 cm–1. H NMR (300 MHz,
CDCl3): δ = 7.65 (s, 1 H), 5.31 (q, J = 7.5 Hz, 1 H), 5.15 (s, 2 H),
4.79 (d, J = 15.3 Hz, 1 H), 4.71 (d, J = 15.6 Hz, 1 H), 3.76 (s, 3
H), 1.57 (d, J = 7.2 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 170.9, 162.5, 129.3, 127.4, 52.6, 52.0, 48.7, 38.6, 14.1 ppm. [α]2D2
= –4 (c = 1.0, CHCl3). HRMS: calcd. for C9H12N4O3 [M + Na]+
225.0988; found 225.0981.
5:5). Yield: 351 mg (97%). Pale-yellow gummy liquid. IR (neat): ν
˜
= 3397, 2950, 1740, 1664, 1432, 1349, 1099, 833, 744 cm–1 1H
.
NMR (300 MHz, CDCl3): δ = 8.56 (s, 1 H), 7.55 (d, J = 7.8 Hz, 1
H), 7.37 (s, 1 H), 7.33–7.06 (m, 4 H), 6.95 (d, J = 2.1 Hz, 1 H),
5.31 (dd, J1 = 11.1 Hz, J2 = 5.1 Hz, 1 H), 5.04 (d, J = 17.7 Hz, 1
H), 4.92 (d, J = 18 Hz, 1 H), 4.52 (d, J = 15.6 Hz, 1 H), 4.43 (d, J
= 15.9 Hz, 1 H), 3.78 (s, 3 H), 3.57 (dd, J1 = 15.9 Hz, J2 = 5.1 Hz,
1 H), 3.42 (dd, J1 = 15.3 Hz, J2 = 10.8 Hz, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 170.4, 162.8, 136.3, 129.1, 127.6, 126.9,
122.5 (2 C), 119.8, 117.9, 111.7, 109.9, 58.1, 52.8, 48.8, 40.5,
24.2 ppm. [α]2D3 = –29.4 (c = 1.0, CHCl3). HRMS: calcd. for
C17H17N5O3 [M + Na]+ 362.1229; found 362.1223.
Methyl (2S)-2-(6-Oxo-4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyr-
azin-5-yl)-3-phenylpropanoate (6b): Rf = 0.30 (hexanes/EtOAc, 4:6).
Yield: 286 mg (95%). Colorless gummy liquid. IR (neat): ν = 2953,
˜
1741, 1666, 1474, 1435, 1200, 703 cm–1
CDCl3): δ = 7.51 (s, 1 H), 7.27–7.14 (m, 5 H), 5.28 (dd, J1
10.8 Hz, J2 = 5.7 Hz, 1 H), 5.05 (d, J = 18 Hz, 1 H), 4.91 (d, J =
.
1H NMR (300 MHz,
=
18 Hz, 1 H), 4.59 (d, J = 16 Hz, 1 H), 4.49 (d, J = 16 Hz, 1 H), Methyl (2S)-6-[(Benzyloxy)carbonyl]amino-2-(6-oxo-4,5,6,7-tetra-
3.76 (s, 3 H), 3.49 (dd, J1 = 14.7 Hz, J2 = 5.4 Hz, 1 H), 3.2 (dd, J1
= 14.7 Hz, J2 = 11.1 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 169.8, 162.5, 135.6, 128.9, 128.7, 128.5, 128.3, 127.2, 58.3, 52.6,
48.5, 40.3, 34.0 ppm. [α]2D3 = –5.8 (c = 1.0, CHCl3). HRMS: calcd.
for C15H16N4O3 [M + H]+ 301.1300; found 301.1302.
hydro[1,2,3]triazolo[1,5-a]pyrazin-5-yl)hexanoate (8a): Rf = 0.40
(hexanes/EtOAc, 4:6). Yield: 420 mg (96%). Colorless gummy li-
quid. IR (neat): ν = 3338, 2938, 2867, 1715, 1666, 1534, 1457, 1251,
˜
743, 699 cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.63 (s, 1 H),
7.34–7.32 (m, 5 H), 5.27 (dd, J1 = 10.5 Hz, J2 = 5.1 Hz, 1 H), 5.13
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Eur. J. Org. Chem. 2008, 2423–2429