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C. Metallinos et al. / Tetrahedron 62 (2006) 11145–11157
(m, 4H), 1.93–1.86 (m, 1H), 1.81 (quintet, 2H, J¼6.0 Hz),
1.58–1.30 (m, 7H), 0.92 (t, 3H, J¼7.2 Hz); 13C NMR
(75.5 MHz, acetone-d6): d 133.5, 133.1, 120.0, 119.7,
119.0, 118.8, 52.8, 43.1, 37.2, 29.2, 28.7, 27.9, 27.4, 23.6,
23.3, 14.4; EIMS [m/z (%)]: 244 (M+, 55), 187 (100);
HRMS (EI) calcd for C16H24N2: 244.1939, found: 244.1935.
2H), 4.43–4.40 (m, 2H), 4.25 (br, 2H), 2.91–2.75 (m, 4H),
2.61 (dt, 2H, J¼15.9, 5.2 Hz), 1.97–1.88 (m, 2H); 13C
NMR (75.5 MHz, acetone-d6): d 146.3, 132.8, 129.0,
127.7, 127.4, 119.6, 118.9, 57.0, 31.4, 26.9; EIMS [m/z
(%)]: 340 (M+, 54); HRMS (EI) calcd for C24H24N2:
340.1939, found: 340.1942; Anal. Calcd for C24H24N2: C,
84.67; H, 7.11. Found: C, 84.35; H, 7.10.
4.1.8. rac-2-Isopropyl-1,2,3,4,7,8,9,10-octahydro-1,10-
phenanthroline (19d). According to the typical procedure,
a solution of 11d (105 mg, 0.47 mmol) in glacial acetic acid
(7 mL) and MeOH (3 mL) was treated with NaBH3CN
(105 mg, 1.67 mmol), and the reaction mixture was heated
to reflux. Three subsequent additions of NaBH3CN
(105 mg each) were made every 2 h for over 6 h total. Stan-
dard workup and column chromatography (silica gel,
88:10:2 hexanes/EtOAc/Et3N, Rf¼0.22) gave diamine 19d
(76 mg, 70%) as a pale yellow oil; IR (KBr, neat): nmax
3339, 3037, 2954, 2927, 2870, 2841, 1583, 1485, 1437,
4.1.11. meso/rac-2,9-Dimethyl-1,2,3,4,7,8,9,10-octahy-
dro-1,10-phenanthroline (19g). According to the typical
procedure, a solution of neocuproine 12b (217 mg,
1.00 mmol) in glacial acetic acid (3.5 mL) and MeOH
(1.5 mL) was treated with NaBH3CN (217 mg, 3.45 mmol),
and the reaction mixture was heated to reflux. Three subse-
quent additions of NaBH3CN (217 mg each) were made
every 2 h for over 6 h total. Standard workup and column
chromatography (silica gel, 92:8 PhMe/Et3N, Rf¼0.22)
gave 19g (158 mg, 73%), a colorless solid, as a 1:1 mixture
of meso and rac stereoisomers; mp 63–65 ꢁC; IR (KBr): nmax
3324, 3036, 2959, 2918, 2839, 1582, 1480, 1446, 1334,
1
1347, 1256 cmꢀ1; H NMR (300 MHz, acetone-d6): d 6.26
(d, 1H, J¼7.8 Hz), 6.23 (d, 1H, J¼8.1 Hz), 3.81 (br, 1H),
3.48 (br, 1H), 3.31–3.18 (m, 2H), 2.98–2.92 (m, 1H),
2.72–2.62 (m, 4H), 1.90–1.69 (m, 4H), 1.55–1.50 (m, 1H),
1.00 (d, 3H, J¼6.9 Hz), 0.98 (d, 3H, J¼6.9 Hz); 13C NMR
(75.5 MHz, acetone-d6): d 133.8, 133.1, 120.1, 119.8,
119.0, 118.8, 58.5, 43.1, 33.3, 27.9, 27.6, 25.5, 23.3, 19.0,
18.6; EIMS [m/z (%)]: 230 (M+, 28), 187 (100); HRMS
(EI) calcd for C15H22N2: 230.1783, found: 230.1795.
1
1255 cmꢀ1; H NMR (300 MHz, acetone-d6): d 6.23 (s,
2H), 3.64 (br, 1H), 3.55 (br, 1H), 3.31–3.23 (m, 2H), 2.78–
2.54 (m, 4H), 1.87–1.82 (m, 2H), 1.48–1.38 (m, 2H), 1.18
(d, 3H, J¼6.3 Hz), 1.17 (d, 3H, J¼6.3 Hz); 13C NMR
(75.5 MHz, acetone-d6): d 133.1, 133.0, 119.4, 119.3,
118.8, 118.7, 48.4, 48.3, 31.2, 27.5, 27.5, 22.9, 22.7; FABMS
[m/z (%)]: 216 (M+, 100); HRMS (FAB) calcd for C14H20N2:
216.1626, found: 216.1619.
4.1.9. rac-2-tert-Butyl-1,2,3,4,7,8,9,10-octahydro-1,10-
phenanthroline (19e). According to the typical procedure,
a solution of 11e (171 mg, 0.75 mmol) in glacial acetic
acid (8 mL) and MeOH (2 mL) was treated with NaBH3CN
(177 mg, 2.82 mmol), and the reaction mixture was heated
to reflux. Three subsequent additions of NaBH3CN (177 mg
each) were made every 2 h for over 6 h total. Standard
workup and column chromatography (silica gel, 90:10 hex-
anes/EtOAc, Rf¼0.32) gave diamine 19e (42 mg, 23%) as a
colorless solid; mp 71–72 ꢁC; IR (KBr): nmax 3346, 3300,
2955, 2933, 2851, 1614, 1582, 1475, 1429, 1335 cmꢀ1; 1H
NMR (300 MHz, acetone-d6): d 6.27 (d, 1H, J¼7.2 Hz),
6.24 (d, 1H, J¼7.8 Hz), 3.82 (br, 1H), 3.44 (br, 1H), 3.28–
3.21 (m, 2H), 2.86 (dt, 1H, J¼10.8, 2.4 Hz), 2.79–2.56 (m,
4H), 1.99–1.93 (m, 1H), 1.83–1.74 (m, 2H), 1.53–1.41 (m,
1H), 0.99 (s, 9H); 13C NMR (75.5 MHz, acetone-d6):
d 134.3, 133.2, 120.3, 120.0, 119.0, 118.7, 62.2, 43.1,
34.1, 28.3, 27.9, 26.3, 24.2, 23.3; EIMS [m/z (%)]: 244
(M+, 18), 187 (100); HRMS (EI) calcd for C16H24N2:
244.1939, found: 244.1942.
4.1.12. meso/rac-2,9-Di-n-butyl-1,2,3,4,7,8,9,10-octahy-
dro-1,10-phenanthroline (19h). According to the typical
procedure, a solution of 12c (236 mg, 0.81 mmol) in glacial
acetic acid (7 mL) and MeOH (3 mL) was treated with
NaBH3CN (236 mg, 3.76 mmol), and the reaction mixture
was heated to reflux. Three subsequent additions of
NaBH3CN (236 mg each) were made every 2 h for over
6 h total. Standard workup and column chromatography
(silica gel, 94:5:1 hexanes/EtOAc/Et3N, Rf¼0.14) gave 19h
(156 mg, 65%), a colorless oil, as a 1:1 mixture of meso and
rac stereoisomers; IR (KBr, neat): nmax 3339, 3038, 2953,
2926, 2869, 2855, 1584, 1482, 1438, 1347, 1258 cmꢀ1; 1H
NMR (600 MHz, acetone-d6): d 6.26 (s, 1H), 6.25 (s, 1H),
3.57 (br, 1H), 3.48 (br, 1H), 3.16–3.11 (m, 2H), 2.79–2.67
(m, 2H), 2.63–2.59 (m, 2H), 1.92–1.89 (m, 2H), 1.57–1.34
(m, 12H), 0.92 (t, 6H, J¼6.9 Hz); 13C NMR (75.5 MHz, ace-
tone-d6): d 133.2, 133.2, 120.0, 119.9, 119.0, 118.8, 52.9,
52.8, 37.2, 37.1, 29.1, 29.0, 28.9, 28.7, 23.6, 23.6, 14.4;
EIMS [m/z (%)]: 300 (M+, 72), 243 (89), 239 (100);
HRMS (EI) calcd for C20H32N2: 300.2565, found: 300.2561.
4.1.10. meso/rac-2,9-Diphenyl-1,2,3,4,7,8,9,10-octahy-
dro-1,10-phenanthroline (19f). According to the typical
procedure, a solution of 12a (250 mg, 0.75 mmol) in glacial
acetic acid (8 mL) and MeOH (2 mL) was treated with
NaBH3CN (250 mg, 3.98 mmol), and the reaction mixture
was heated to reflux. Three subsequent additions of
NaBH3CN (250 mg each) were made every 2 h for over
6 h total. Standard workup and column chromatography (sil-
ica gel, 96:4 hexanes/EtOAc, Rf¼0.38) gave diamine 19f
(161 mg, 63%), a pale yellow solid, as a mixture of stereo-
isomers; mp 107–110 ꢁC; IR (KBr): nmax 3339, 3030,
2944, 2919, 2835, 1580, 1473, 1420, 1335, 1252 cmꢀ1; 1H
NMR (300 MHz, acetone-d6): d 7.39 (d, 4H, J¼7.0 Hz),
7.30 (t, 4H, J¼7.0 Hz), 7.22 (d, 2H, J¼7.2 Hz), 6.35 (s,
4.1.13. meso/rac-2,9-Diisopropyl-1,2,3,4,7,8,9,10-octa-
hydro-1,10-phenanthroline (19i). According to the typical
procedure, a solution of 12d (233 mg, 0.88 mmol) in glacial
acetic acid (8 mL) and MeOH (2 mL) was treated with
NaBH3CN (233 mg, 3.71 mmol), and the reaction mixture
was heated to reflux. Three subsequent additions of
NaBH3CN (233 mg each) were made every 2 h for over
6 h total. Standard workup and column chromatography
(silica gel, 94:5:1 hexanes/EtOAc/Et3N, Rf¼0.22) gave a
diamine 19i (149 mg, 62%), a colorless solid, as an unequal
mixture of meso and rac stereoisomers; mp 49–50 ꢁC; IR
(KBr): nmax 3352, 3041, 2959, 2915, 2873, 2836, 1586,
;
1483, 1432, 1336, 1261 cmꢀ1 1H NMR (300 MHz,