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G. K. Friestad et al. / Tetrahedron 63 (2007) 3964–3972
temperature for 16 h. Concentration and flash chromato-
graphy (7:1 to 3:1 Hex/EtOAc) afforded 12a (1.941 g,
85%) as a colorless oil; IR (film) 2927, 2855, 1603, 1494,
were dried and concentrated. The crude aldehyde was dis-
solved in toluene (20 mL) and dibenzylhydrazine (2.50 g,
10.9 mmol) was added. After 16 h at room temperature,
concentration and flash chromatography (10:1 to 1:1 Hex/
EtOAc) afforded 12b (2.93 g, 100%) as a colorless oil;
[a]2D4 ꢁ6.94 (c 0.605, CHCl3); IR (film) 2927, 2897, 2852,
1
1453, 1253, 1097, 940 cmꢁ1; H NMR (300 MHz, CDCl3)
d (ppm) 7.45–7.12 (m, 10H), 6.65 (t, J¼5.4 Hz, 1H), 4.34
(s, 4H), 3.75 (t, J¼6.5 Hz, 2H), 2.45 (q, J¼6.5 Hz, 2H),
0.92 (s, 9H), 0.06 (s, 6H); 13C NMR (75 MHz, CDCl3)
d (ppm) 138.0, 135.4, 128.3, 127.7, 126.9, 61.6, 58.2, 36.4,
25.9, 18.2, ꢁ5.4; MS (EI) m/z (relative intensity) 382 (M+,
7%), 325 (66%), 237 (36%), 233 (40%), 131 (70%), 91
(100%). Anal. Calcd for C23H34N2OSi: C, 72.20; H, 8.96;
N, 7.32. Found: C, 72.42; H, 9.03; N, 7.34.
1605, 1255 cmꢁ1 1H NMR (300 MHz, CDCl3) d 7.45–
;
7.04 (m, 10H), 6.59 (dd, J¼5.65, 5.65 Hz, 1H), 4.29 (unre-
solved ABq, 4H), 3.90 (apparent sextet, J¼6.0 Hz, 1H),
2.36–2.26 (m, 2H), 1.06 (d, J¼6.1 Hz, 3H), 0.84 (s, 9H),
0.01 (s, 3H), ꢁ0.03 (s, 3H); MS (EI) m/z (relative intensity)
397 ([M+H]+, 100%), 301 (13%), 265 (12%). Anal. Calcd
for C24H36N2OSi: C, 72.67; H, 9.15; N, 7.06; Si, 7.08. Found:
C, 72.89; H, 9.18; N, 7.13.
4.2.6. 3-(2,2-Dibenzylhydrazono)propan-1-ol (13). To
a solution of hydrazone 12a (313 mg, 0.818 mmol) in THF
(10 mL) was added tetrabutylammonium fluoride (1 M
solution in THF, 0.90 mL, 0.90 mmol) and the mixture was
stirred at room temperature for 1 h. Concentration and flash
chromatography (5:1 to 1:1 Hex/EtOAc) afforded 13
(195 mg, 89%) as a yellow oil; IR (film) 3371 (br), 2921,
1597, 1491, 1450, 1070 cmꢁ1; 1H NMR (300 MHz, CDCl3)
d (ppm) 7.40–7.18 (m, 10H), 6.66 (t, J¼3.90 Hz, 1H), 4.29 (s,
4H), 3.78 (t, J¼5.4 Hz, 2H), 3.00 (s, 1H), 2.34 (td, J¼5.4,
4.0 Hz, 1H); 13C NMR (75 MHz, CDCl3) d (ppm) 137.7,
136.1, 128.5, 127.8, 127.1, 60.4, 58.4, 34.5; MS (EI) m/z (rel-
ative intensity) 268 (M+, 30%), 210 (30%), 177 (10%), 159
(35%), 131 (45%), 92 (80%), 91 (100%), 65 (40%). Anal.
Calcd for C17H20N2O: C, 76.09; H, 7.51; N, 10.44. Found:
C, 76.41; H, 7.39; N, 10.11.
4.2.9. 2-(3-((1-Bromovinyl)dimethylsilyloxy)propyl-
idene)-1,1-diphenylhydrazine (17a). To a solution of
hydroxyhydrazine 16a24 (474 mg, 2.09 mmol) in benzene
(21 mL) at 0 ꢂC were added triethylamine (0.38 mL,
2.7 mmol) and N,N-dimethylaminopyridine (26 mg,
0.21 mmol) followed by the addition of 2b (7.0 M in benz-
ene, 0.40 mL, 2.7 mmol). The reaction mixture was stirred
for 4 h, concentrated, diluted with EtOAc, and washed with
brine. The organic phase was dried and filtered through a
plug of silica gel affording 17a (794 mg, 98%) as a colorless
oil; IR (film) 3064, 2960, 2591, 2494, 1300, 1254,
1
1090 cmꢁ1; H NMR (300 MHz, CDCl3) d 7.47–7.38 (m,
4H), 7.21–7.08 (m, 6H), 6.60 (t, J¼5.2 Hz, 1H), 6.35
(ABq, J¼1.8 Hz, Dn¼16.5 Hz, 2H), 3.90 (t, J¼6.7 Hz,
2H), 2.61 (td, J¼6.7, 5.3 Hz, 2H), 0.32 (s, 6H); 13C NMR
(75 MHz, CDCl3) d 144.2, 136.4, 135.3, 131.0, 130.0,
124.0, 122.3, 61.5, 35.8, ꢁ2.9; MS (EI) m/z (relative inten-
sity) 404 (M+, 81Br, 20%), 402 (M+, 79Br, 20%), 195
(25%), 169 (35%), 168 (100%), 167 (68%). Anal. Calcd
for C19H23BrN2OSi: C, 56.57; H, 5.75; Br, 19.81; N, 6.94.
Found: C, 56.84; H, 5.84; Br, 19.54; N, 7.04.
4.2.7. 1,1-Dibenzyl-2-(3-((1-bromovinyl)dimethylsilyl-
oxy)propylidene)hydrazine (14). To a solution of hydroxy-
hydrazine 13 (406 mg, 1.51 mmol) in THF (15 mL) at 0 ꢂC
were added triethylamine (0.30 mL, 2.0 mmol) and DMAP
(20 mg, 0.151 mmol) followed by addition of (1-bromo-
vinyl)chlorodimethylsilane (2b, 7.0 M in benzene, 0.40 mL,
2.8 mmol). The reaction mixture was stirred for 4 h, concen-
trated, diluted with EtOAc, and extracted with brine. The or-
ganic phase was dried and filtered through a plug of silica gel
affording 14 (640 mg, 98%) as a colorless oil; IR (film) 2958,
2917, 1589, 1491, 1454, 1254, 1090, 833, 796, 731,
4.2.10. 3-(2,2-Diphenylhydrazinyl)pent-4-en-1-ol (18a).
A solution of hydrazone 17a (165 mg, 0.41 mmol) in
benzene (20 mL) was deoxygenated (nitrogen was bubbled
through the solution via a syringe needle for 20 min). To
this was added a solution of AIBN (33 mg, 0.20 mmol)
and tributyltin hydride (0.16 mL, 0.57 mmol) in benzene
(1.6 mL). The solution was heated at reflux for 16 h. A solu-
tion of TBAF (1 M in THF, 0.9 mL, 0.90 mmol) was added
and reflux was continued for 4 h. Filtration through silica
gel, concentration, and flash chromatography (5:1 to 1:2
petroleum ether/EtOAc) afforded 18a (86 mg, 78%) as a col-
orless oil; IR (film) 3362 (br), 3060, 2917, 2852, 1588, 1491,
1
698 cmꢁ1; H NMR (300 MHz, CDCl3) d ppm 8.02–7.75
(m, 10H), 7.19 (t, J¼5.3 Hz, 1H), 6.92 (ABq, J¼1.8 Hz, Dn¼
18.4 Hz, 2H), 4.91 (s, 4H), 4.37 (t, J¼6.6 Hz, 2H), 3.06 (dt,
J¼11.94, 6.6 Hz, 1H), 0.87 (s, 6H); 13C NMR (75 MHz,
CDCl3) d (ppm) 138.0, 135.4, 134.5, 130.9, 128.4, 127.8,
127.0, 61.8, 58.1, 36.0, ꢁ2.9; MS (EI) m/z (relative intensity)
432 (M+, 81Br, 8%), 430 (M+, 79Br, 8%), 237 (24%), 139
(46%), 131 (86%), 91 (100%). Anal. Calcd for
C21H27BrN2OSi: C, 58.46; H, 6.31; N, 6.49. Found: C,
58.56; H, 6.50; N, 6.24.
1
1270 cmꢁ1; H NMR (500 MHz, CDCl3) d 7.30–7.26 (m,
4H), 7.15–7.13 (m, 4H), 7.01–6.98 (m, 2H), 6.92 (m, 1H),
5.86 (ddd, J¼17.0, 10.4, 8.2 Hz, 1H), 5.15–5.10 (m, 2H),
3.78 (ddd, J¼11.7, 5.9, 5.9 Hz, 1H), 3.66 (ddd, J¼11.0,
7.4, 5.4 Hz, 1H), 3.62–3.58 (m, 1H), 1.90 (dddd, J¼18.1,
7.3, 5.4, 5.4 Hz, 1H), 1.79 (ddd, J¼12.4, 6.9, 6.6, 5.9 Hz,
1H), 1.27 (s, 1H); 13C NMR (125 MHz, CDCl3) d 147.9,
138.9, 129.1, 122.3, 120.5, 117.6, 60.4, 59.4, 35.8; MS
(CI) m/z (relative intensity) 269 ([M+H]+, 10%), 184
(40%), 168 (100%). Anal. Calcd for C17H20N2O: C, 76.09;
H, 7.51; N, 10.44. Found: C, 75.99; H, 7.53; N, 10.25.
4.2.8. (S)-1,1-Dibenzyl-2-(3-(tert-butyldimethylsilyloxy)-
butylidene) hydrazine (12b). To a solution of methyl
(S)-3-(tert-butyldimethylsilyloxy)butanoate30
(1.707 g,
7.34 mmol) in hexane (8.8 mL) was added diisobutyl-
aluminum hydride (1 M in hexane, 8.8 mL, 8.8 mmol) over
30 min at –78 ꢂC. After 1 h, the reaction was quenched
with saturated aqueous Na/K tartrate solution (35 mL),
then diluted with diethyl ether (25 mL) and CH2Cl2
(25 mL), and stirred vigorously for 30 min. The organic
phase was separated and the aqueous phase was washed
with diethyl ether (3ꢃ25 mL). The combined organic layers
Alternative procedure, catalytic Bu3SnH: to a solution of
hydrazone 17a (86 mg, 0.21 mmol) in benzene (2 mL) were