J. Robertson et al. / Tetrahedron 64 (2008) 11896–11907
11903
8.3, 2.2, H-6), 7.32 (1H, d, J 2.2, H-4), 7.44 (2H, d, J 8.7, two of p-Anis),
7.74 (1H, d, J 8.3, H-7); dC (125 MHz, CDCl3) 41.5, 55.2, 56.1, 108.1,
112.3, 113.7, 119.7, 123.9, 125.0, 127.5, 131.0, 134.6, 141.5, 159.5, 164.5,
167.8, 167.9; m/z (ESIþ) 346 (MNaþ, 100%); HRMS (ESIþ) found
346.1050, C19H17NNaO4 (MNaþ) requires 346.1050.
(1H, d, J 2.5, H(Ar)-3), 6.92 (1H, dd, J 8.6, 2.5, H(Ar)-5), 6.97 (2H, d, J
8.8) and 7.86 (2H, d, J 8.8, p-Anis), 7.94 (1H, d, J 8.6, H(Ar)-6), 9.71
(1H, s, NH); dC (125 MHz, CDCl3) 9.6, 13.6, 22.4, 27.3, 28.7, 55.5 (ꢂ2),
110.3, 112.7, 114.0, 115.2, 124.9, 125.8, 129.7, 133.3, 144.6, 152.8,
162.2, 163.3, 164.3, 165.7; m/z (ESIþ) 673 (M120SnNH4$CH3CN,
100%), 384 (20); HRMS (ESIþ) found 616.2447, C31H46NO1420Sn
(MHþ) requires 616.2450.
6.3.10. 6-Methoxy-2-(4-methoxybenzoyl)-4-methylene-3,4-
dihydroisoquinoline-1(2H)-one (21c)
Pale yellow oil; Rf 0.39 (petrol/ethyl acetate, 1:1); nmax (thin
film)/cmꢁ1 2963 w, 2841 w, 1674 s, 1604 s, 1511 m, 1461 w, 1241 m,
1168 m, 1030 w, 912 w, 844 w, 731 w; dH (500 MHz, CDCl3) 3.84 (3H,
s, OMe), 3.92 (3H, s, OMe), 4.62 (2H, s, NCH2), 5.45 (1H, s) and 5.73
(1H, s, ]CH2), 6.88 (2H, d, J 8.8, two of p-Anis), 6.97 (1H, dd, J 8.7,
2.5, H-7), 7.09 (1H, d, J 2.5, H-5), 7.62 (2H, d, J 8.8, two of p-Anis),
8.09 (1H, d, J 8.7, H-8); dC (125 MHz, CDCl3) 50.8, 55.3, 55.6, 107.8,
113.4,113.5,115.4,120.0, 128.1,130.9,132.1, 136.8, 139.3, 162.6, 163.9,
165.1, 173.4; m/z (ESIþ) 382 (MNH4$CH3CNþ, 100%); HRMS (ESIþ)
found 346.1049, C19H17NNaO4 (MNaþ) requires 346.1050.
6.3.15. N-Formyl-N-{2-[4-(trifluoromethyl)phenyl]prop-2-enyl}-4-
(trifluoromethyl)benzamide (24d)
Pale yellow oil; Rf 0.26 (petrol/ethyl acetate, 3:1); nmax (thin
film)/cmꢁ1 2919 w, 1729 w, 1674 s, 1514 w, 1410 s, 1169 w, 1128 m,
1067 m, 850 w; dH (500 MHz, CDCl3) 4.93 (2H, s, NCH2), 5.35 (1H, s)
and 5.49 (1H, s, ]CH2), 7.42 (2H, d, J 8.1), 7.55 (2H, d, J 8.3), 7.62 (2H,
d, J 8.3) and 7.72 (2H, d, J 8.1, 2ꢂAr), 8.85 (1H, s, CHO); dC (125 MHz,
CDCl3) [some overlapping, weak 19F-coupled peaks in the region
120–130 ppm could not be deconvoluted] 43.6, 116.5, 125.5, 126.1,
127.1, 128.9, 134.0, 136.5, 141.9, 142.3, 162.9, 170.6; dF (377 MHz,
CDCl3) ꢁ63.2, ꢁ62.6; m/z (ESIþ) 424 (MNaþ, 100%); HRMS (ESIþ)
found 424.0739, C19H13F6NNaO2 (MNaþ) requires 424.0743.
6.3.11. N-(4-Methoxybenzoyl)-N-(prop-2-enyl)-4-
methoxybenzamide (22c)
Pale yellow oil; Rf 0.40 (petrol/ethyl acetate, 1:1); nmax (thin
film)/cmꢁ1 2937 w, 2840 w, 1685 m, 1648 m, 1604 s, 1511 m, 1461 w,
1420 w, 1334 m, 1241 s, 1168 m, 1029 w, 844 w, 761 w; dH (500 MHz,
CDCl3) 3.75 (6H, s, 2ꢂOMe), 4.58 (2H, d, J 5.8, NCH2), 5.21 (1H, d, J
10.3) and 5.32 (1H, d, J 17.2, ]CH2), 6.05 (1H, ddt, J 17.2, 10.3, 5.8,
CH]CH2), 6.70 (4H, d, J 8.8) and 7.50 (4H, d, J 8.8, 2ꢂp-Anis); dC
(125 MHz, CDCl3) 49.6, 55.3, 113.6, 118.1, 128.6, 131.0, 133.0, 162.5,
173.3; m/z (ESIþ) 384 (MNH4$CH3CNþ, 50%), 382 (100); HRMS
(ESIþ) found 348.1208, C19H19NNaO4 (MNaþ) requires 348.1206.
6.4. General procedure for radical reaction of 30a–e
To a stirred solution of the benzamide derivative (0.9 mmol) and
AIBN (12 mg, 73
mmol) in degassed benzene (20 mL) at reflux was
added a solution of tributyltin hydride (290
mL, 1.08 mmol) and
AIBN (36 mg, 0.22 mmol) in benzene (10 mL) over 1 h. The reaction
mixture was heated at reflux for a further 2 h, then cooled, con-
centrated in vacuo and the residue eluted with ethyl acetate
through a stationary phase of KF (10%) impregnated silica (10 g) to
remove tin residues. The products were then isolated by flash
chromatography (petrol/ethyl acetate, 10:1).
6.3.12. 1-(4-Methoxybenzoyl)-4-(4-methoxyphenyl)
pyrrolidin-2-one (23c)43
Colourless oil; Rf 0.19 (petrol/ethyl acetate, 1:1); nmax (thin film)/
cmꢁ1 1672 s, 1605 s, 1514 m, 1255 s; dH (500 MHz, CDCl3) 2.77 (1H,
dd, J 17.4, 9.3) and 2.99 (1H, dd, J 17.4, 8.3, COCH2), 3.62–3.68 (1H, m,
CHAr), 3.83 (3H, s, OMe), 3.87 (3H, s, OMe) overlaying 3.87–3.95
(1H, m) and 4.28 (1H, dd, J 11.4, 7.6, NCH2), 6.93 (4H, d, J 8.6), 7.25
(2H, d, J 8.6) and 7.69 (2H, d, J 8.6, 2ꢂp-Anis); dC (125 MHz, CDCl3)
35.9, 40.9, 54.4, 55.3, 55.4, 113.2, 114.4, 126.1, 127.7, 131.8, 132.3,
158.9, 163.0, 169.8, 173.5; m/z (GC–MS, CIþ) 326 (MHþ, 10%), 192
(100), 152 (40), 148 (60), 135 (20); HRMS (GC–MS, CIþ) found
326.1403, C19H20NO4 (MHþ) requires 326.1392.
6.4.1. tert-Butyl biphenyl-2-yl-N-formylcarbamate 32a
Starting with benzamide 31a (400 mg, 0.94 mmol), formamide
32a was obtained as a colourless oil (156 mg, 56%); nmax (thin film)/
cmꢁ1 1738 s, 1713 s, 1504 m, 1370 s, 1290 s, 1153 m, 772 w; dH
(400 MHz, CDCl3) 1.27 (9H, s, C(CH3)3), 7.19 (1H, d J 7.5) and 7.22–
7.48 (8H, m, 2ꢂAr), 9.28 (1H, s, CHO); dC (100 MHz, CDCl3) 27.5, 84.1,
127.6,128.3,128.4,129.0,129.1129.2,130.6,132.2,138.6,140.7,151.8,
163.5; HRMS (ESIþ) found 198.0919, C13H12NO [(MꢁBoc)Hþ]
requires 198.0919. Also obtained was 5-tert-butyloxycarbonylphenan-
thridin-6(5H)-one (33a) (61 mg, 22%) as a white solid; mp 139–
140 ꢀC; nmax (KBr)/cmꢁ1 1767 s, 1668 s, 1609 m, 1456 m, 1371 s, 1247
m, 1150 m; dH (400 MHz, CDCl3) 1.75 (9H, s, C(CH3)3), 7.13 (1H, d, J
7.5), 7.31 (1H, dd, J 7.5, 7.0), 7.49 (1H, dd, J 7.5, 7.0), 7.59 (1H, dd, J 7.5,
7.0), 7.79 (1H, t, J 7.0), 8.20–8.25 (2H, m) and 8.49 (1H, d, J 7.5, Ar); dC
(100 MHz, CDCl3) 27.6, 86.5, 114.5, 118.4, 122.0, 123.4, 125.1, 127.6,
128.3, 129.1, 130.6, 132.3, 134.5, 151.2, 159.9, 163.5; HRMS (ESIþ)
found 196.0763, C13H10NO [M(ꢁBoc)Hþ] requires 196.0762.
6.3.13. 6-Methoxy-2-(4-methoxybenzoyl)-4-[(tributylstannyl)
methyl]-3,4-dihydroisoquinoline-1(2H)-one (26c)
Colourless oil; Rf 0.67 (petrol/ethyl acetate, 1:1); nmax (thin film)/
cmꢁ1 2957 m, 2962 m, 1679 s, 1605 s, 1512 w, 1493 w, 1377 w, 1238
s, 1167 m, 1032 m, 841 w, 802 w; dH (500 MHz, CDCl3) 0.81–0.88
(15H, m), 1.21–1.32 (8H, m) and 1.37–1.46 (6H, m, CH2SnBu3), 3.25–
3.32 (1H, m, CHAr), 3.85 (3H, s, OMe), 3.90 (3H, s, OMe), 3.95 (1H,
dd, J 12.7, 4.5) and 4.03 (1H, dd, J 12.7, 3.3, NCH2), 6.77 (1H, d, J 2.3,
H-5), 6.86 (1H, dd, J 8.7, 2.3, H-7), 6.91 (2H, d, J 8.8) and 7.68 (2H, d, J
8.8, p-Anis), 8.05 (1H, d, J 8.7, H-8); dC (125 MHz, CDCl3) 9.5, 13.6,
14.6, 27.3, 29.1, 37.0, 51.4, 55.4, 55.5, 111.5, 112.6, 113.4, 119.7, 128.5,
130.8, 132.3, 149.5, 162.5, 163.9, 165.3, 173.9; m/z (ESIþ)
673 (M120SnNH4$CH3CN, 100%); HRMS (ESIþ) found 616.2437,
C31H46NO1420Sn (MHþ) requires 616.2450.
6.4.2. tert-Butyl N-formyl-(40-methoxybiphenyl-2-yl)
carbamate 32b
Starting with benzamide 31b (500 mg, 1.10 mmol), formamide
32b (162 mg, 45%) was obtained as a pale yellow oil; nmax (thin
film)/cmꢁ1 1736 s, 1714 s, 1479 m, 1293 s, 1154 m, 1029 m; dH
(400 MHz, CDCl3) 1.28 (9H, s, C(CH3)3), 3.80 (3H, s, CH3O), 6.90 (2H,
d, J 7.0), 7.13 (1H, d, J 6.5), 7.18 (2H, d, J 7.0) and 7.35–7.45 (3H, m,
2ꢂAr), 9.27 (1H, s, CHO); dC (100 MHz, CDCl3) 27.6, 55.3, 84.1, 113.8,
128.0, 129.0, 129.1, 129.6, 130.7, 131.0, 132.3, 140.4, 151.9, 159.2,
163.5; HRMS (ESIþ) found 228.1023, C14H14NO2 [(MꢁBoc)Hþ] re-
quires 228.1025. Also obtained was 5-tert-butyloxycarbonyl-9-
methoxyphenanthridin-6(5H)-one (33b) (93 mg, 25%) as a white
solid; mp 132–135 ꢀC; nmax (KBr)/cmꢁ1 1774 s, 1695 s, 1570 m, 1465
m, 1273 m, 1040 m; dH (400 MHz, CDCl3) 1.72 (9H, s, C(CH3)3), 3.98
(3H, s, CH3O), 7.11 (2H, d, J 8.8), 7.27 (1H, t, J 7.5), 7.43 (1H, dd, J 8.0,
6.3.14. N-(4-Methoxybenzoyl)-N-4-methoxy-2-[3-
(tributylstannyl)prop-1-en-2-yl]benzamide (27c)
Colourless oil; Rf 0.24 (petrol/ethyl acetate, 1:1); nmax (thin film)/
cmꢁ1 2957 m, 2926 m, 1731 m, 1677 w, 1604 s, 1474 m, 1228 s, 1174
w, 1030 w; dH (500 MHz, CDCl3) 0.69–0.74 (6H, m), 0.80–0.85 (9H,
m), 1.15–1.32 (12H, m, SnBu3), 2.10 (2H, s, CH2SnBu3), 3.87 (3H, s,
OMe), 3.88 (3H, s, OMe), 5.04 (1H, s) and 5.10 (1H, s, ]CH2), 6.72