6792
A. Bredihhin, U. Ma¨eorg / Tetrahedron 64 (2008) 6788–6793
Method b (1 equiv n-BuLi). An oven-dried flask was charged
CDCl3, TMS):
d
¼7.16–7.24 (m, 2H, Ph), 6.91–6.96 (m, 2H, Ph), 6.69–
with 3c (184 mg, 1 mmol), evacuated, backfilled with argon and
then THF (5 mL) was added. Reaction mixture was cooled down to
ꢁ78 ꢀC, then 1.6 M n-BuLi (0.65 mL, 1 mmol) solution in hexane
was added dropwise and the resulting mixture was stirred for
15 min. The mixture was allowed to warm up to ꢁ60 ꢀC for 15 min
and allyl bromide (0.09 mL, 1 mmol) was added. Reaction mixture
was allowed to warm up to room temperature. Reaction was
complete in 2 h as judged from TLC. Then H2O (0.1 mL) was added
and volatiles were evaporated. To the resulting mixture CHCl3
(10 mL) and MgSO4 were added. Then mixture was filtered and
volatiles were removed. Residue was purified by column chroma-
tography on silica (EtOAc/hexane 1:8). Colourless oil of 204 mg was
obtained, which gave exactly the same results of analysis as 5b.
Yield was 91%.
6.76 (m, 1H, Ph), 5.72–5.91 (m, 1H, CH]CH2), 5.16–5.25 (m, 2H,
CH]CH2), 3.96–3.99 (m, 2H, NCH2–CH]CH2), 3.40 (s, 1H, NH), 2.54
(s, 3H, NCH3). 13C NMR (50 MHz, CDCl3, TMS):
d
¼150.1, 133.6, 129.0,
118.3, 117.6, 113.8, 53.2, 34.9. FTIR
2941, 2874, 1595, 1498, 1333, 1230, 917, 737, 691.
n
(cmꢁ1): 3337, 3064, 3028, 2982,
4.3.7. N0-Benzyl-N0-ethyl-N-methylacetohydrazide (7a)
Compound 6a (281 mg, 1.71 mmol) was dissolved in CH2Cl2
(5 mL), then pyridine (0.14 mL, 1.71 mmol) and Ac2O (0.16 mL,
1.71 mmol) were added. After 2 h the reaction was complete. Then
CH2Cl2 (20 mL) and 1 M KOH (10 mL) were added. The fractions
were separated and the aqueous fraction was additionally extracted
with CH2Cl2 (2ꢂ10 mL). The organic fractions were combined to-
gether and dried with MgSO4. Then the volatiles were removed. The
residue was purified by column chromatography (EtOAc/hexane
1:1) yielding the title compound 7a (236 mg, 67%) as a colourless oil.
4.3.3. Di-tert-butyl 1-benzylhydrazine-1,2-dicarboxylate (5c)11
Method a. Compound 5c was prepared as described for 5a
starting with 3d. Crude product was purified by column chroma-
tography on silica (EtOAc/hexane 1:4). The title compound 5c
(230 mg, 71%) was obtained as colourless crystals, mp 103–105 ꢀC.
Rf (EtOAc/hexane 1:1) 0.33. 1H NMR (200 MHz, CDCl3, TMS):
d¼7.23
(s, 5H, Ph), 3.76 (s, 2H, CH2Ph), 2.89 (s, 3H, NCH3), 2.66–2.78 (m, 2H,
CH2CH3), 1.97 (s, 3H, COCH3), 0.98 (t, J¼7.2 Hz, 3H, CH2CH3). 13C
NMR (50 MHz, CDCl3, TMS):
d
¼174.2, 136.7, 129.3, 128.5, 127.7, 59.2,
Rf (EtOAc/hexane 1:4) 0.38. 1H NMR (200 MHz, CDCl3, TMS):
d
¼7.29
47.2, 22.9, 20.8, 12.2. FTIR
2838, 1651, 1441, 1384, 753, 701. HRMS (ESI): m/z calcd for
12H19N2O (MHþ): 207.1492; found: 207.1492.
n
(cmꢁ1): 3079, 3074, 3023, 2977, 2936,
(s, 5H, Ph), 6.33 (s, 1H, BocNH), 4.63 (s, 2H, CH2Ph), 1.48 (s, 9H,
C(CH3)3), 1.43 (s, 9H, C(CH3)3). 13C NMR (50 MHz, CDCl3, TMS):
C
d
¼155.4, 155.1, 137.4, 128.6, 127.6, 81.5, 81.2, 53.9, 28.4, 28.3. FTIR
n
(cmꢁ1): 3326, 3090, 3069, 3038, 2977, 2936, 2879, 1708, 1364,
4.3.8. N0-Allyl-N-methyl-N0-phenylacetohydrazide (7b)
1395, 1251, 1159, 747, 696.
Compound 6b (162 mg, 1 mmol) was dissolved in CH2Cl2 (5 mL),
then pyridine (0.9 mL, 1.1 mmol) and Ac2O (0.10 mL, 1 mmol) were
added. After 2 h the volatiles were evaporated. The residue was
purified by column chromatography (EtOAc/hexane 1:1) yielding
the title compound 7b (200 mg, 98%) as a colourless oil. Rf (EtOAc/
4.3.4. Di-tert-butyl 1-allylhydrazine-1,2-dicarboxylate (5d)11
Method b. Compound 5d was prepared as described for 5b
starting with 3d. Crude product was purified by column chroma-
tography on silica (EtOAc/hexane 1:4). The title compound 5d
(218 mg, 80%) was obtained as colourless crystals, mp 74–75 ꢀC. Rf
hexane 1:1) 0.51. 1H NMR (200 MHz, CDCl3, TMS):
d
¼7.25–7.33 (m,
2H, Ph), 6.71–6.95 (m, 3H, Ph), 5.87–6.06 (m, 1H, CH]CH2), 5.25–
5.40 (m, 2H, CH]CH2), 3.86–4.22 (m, 2H, NCH2–CH]CH2), 2.96 (s,
3H, NCH3), 2.14 (s, 3H, COCH3). 13C NMR (50 MHz, CDCl3, TMS):
(EtOAc/hexane 1:4) 0.44. 1H NMR (200 MHz, CDCl3, TMS):
d
¼6.51/
6.26 (s, 1H, BocNH), 5.75–5.95 (m, 1H, CH]CH2), 5.13–5.21 (m, 2H,
CH]CH2), 4.04–4.07 (m, 2H, NCH2–CH]CH2),1.47 (s,18H, C(CH3)3).
d
¼174.8, 146.5, 132.7, 129.7, 120.6, 119.1, 113.6, 54.2, 29.9, 20.4. FTIR
13C NMR (50 MHz, CDCl3, TMS):
d
¼155.2, 133.3, 117.5, 81.3, 81.1,
n
(cmꢁ1): 3069, 3013, 2977, 2930, 2838, 1662, 1600, 1492, 1374,
53.0, 28.3. FTIR
n
(cmꢁ1): 3311, 3079, 2972, 2930, 1698, 1390, 1354,
1235, 747. HRMS (ESI): m/z calcd for C12H17N2O (MHþ): 205.1335;
1251, 1148, 927, 850, 753.
found: 205.1334.
4.3.5. 1-Benzyl-1-ethyl-2-methylhydrazine (6a)
4.3.9. Ethyl 2-allyl-1-methyl-2-phenylhydrazinecarboxylate (7c)
Compound 6b (162 mg, 1 mmol) was dissolved in CH2Cl2 (5 mL),
then pyridine (0.9 mL, 1.1 mmol) and ClCOOEt (0.10 mL, 1 mmol)
were added. After 2 h the volatiles were evaporated. The residue
was purified by column chromatography (EtOAc/hexane 1:4)
yielding the title compound 7c (228 mg, 97%) as a colourless oil. Rf
Compound 4a (0.604 g, 2.28 mmol) was dissolved in TFA/CH2Cl2
1:2 mixture (10 mL). After 1 h, when reaction was complete, vola-
tiles were removed. Then residue was dissolved in CH2Cl2 (20 mL)
and 1 M KOH (10 mL) was added to the obtained solution. The
fractions were separated and aqueous fraction was additionally
extracted with CH2Cl2 (3ꢂ10 mL). The organic fractions were
combined together and dried with MgSO4. Then volatiles were
removed yielding the title compound 6a (350 mg, 93%) as a colour-
less oil. Rf (EtOAc/hexane 1:4) 0.50. 1H NMR (200 MHz, CDCl3, TMS):
(EtOAc/hexane 1:4) 0.46. 1H NMR (200 MHz, CDCl3, TMS):
d
¼7.18–
7.26 (m, 2H, Ph), 6.63–6.84 (m, 3H, Ph), 5.87–6.03 (m,1H, CH]CH2),
5.17–5.36 (m, 2H, CH]CH2), 4.00–4.15 (m, 4H, OCH2CH3, NCH2–
CH]CH2), 3.10 (s, 3H, NCH3), 1.12/1.26 (t, J¼6.9/7.1 Hz, 3H,
d
¼7.26–7.33 (m, 5H, Ph), 3.75 (s, 2H, CH2Ph), 2.73 (s, 1H, NH), 2.59
(q, J¼7.2 Hz, 2H, CH2CH3), 2.52 (s, 3H, NCH3), 1.10 (t, J¼7.2 Hz, 3H,
CH2CH3). 13C NMR (50 MHz, CDCl3, TMS):
¼138.5, 129.2, 128.2,
127.0, 60.1, 49.3, 35.6, 12.1. FTIR
(cmꢁ1): 3208, 3069, 3023, 2966,
OCH2CH3). 13C NMR (50 MHz, CDCl3, TMS):
129.3, 119.3, 117.7, 112.7, 61.9, 54.6, 35.4. FTIR
d
n
¼156.9, 147.6, 134.1,
(cmꢁ1): 3064, 2982,
d
2936, 2900, 1708, 1600, 1503, 1338, 1174, 747. HRMS (ESI): m/z calcd
n
for C13H19N2O2 (MHþ): 235.1441; found: 235.1440.
2936, 2869, 2828, 1682, 1446, 1354, 1138, 732, 686. HRMS (ESI): m/z
calcd for C10H17N2 (MHþ): 165.1386; found: 165.1383.
4.3.10. N0-Allyl-2,2,2-trifluoro-N-methyl-N0-phenylaceto-
hydrazide (7d)
4.3.6. 1-Allyl-2-methyl-1-phenylhydrazine (6b)18
Compound 6b (162 mg, 1 mmol) was dissolved in CH2Cl2 (5 mL),
then pyridine (0.9 mL, 1.1 mmol) and TFAA (0.15 mL, 1 mmol) were
added. After 2 h the volatiles were evaporated. The residue was
purified by column chromatography (EtOAc/hexane 1:4) yielding
the title compound 7d (240 mg, 93%) as a colourless oil. Rf (EtOAc/
Compound 4b (1.71 g, 6.5 mmol) was dissolved inTFA/CH2Cl2 1:2
mixture (30 mL). After 1 h, when reaction was complete, volatiles
were removed. Then CH2Cl2 (30 mL) and 1 M KOH (30 mL) were
added to the residue. Fractions were separated and aqueous fraction
was additionally extracted with CH2Cl2 (3ꢂ15 mL). The organic
fractions were combined together and dried with MgSO4. Then
volatiles were removed yielding the title compound 6b (1.023 g, 97%)
as a colourless oil. Rf (EtOAc/hexane 1:4) 0.50. 1H NMR (200 MHz,
hexane 1:4) 0.46. 1H NMR (200 MHz, CDCl3, TMS):
d
¼7.25–7.33
(m, 2H, Ph), 6.94–7.01 (m, 1H, Ph), 6.79–6.83 (m, 2H, Ph), 5.91–6.11
(m, 1H, CH]CH2), 5.25–5.40 (m, 2H, CH]CH2), 3.92–4.24 (m, 2H,
NCH2–CH]CH2), 3.01 (s, 3H, NCH3). 13C NMR (50 MHz, CDCl3, TMS):