124
P.D. Woodgate et al. / Journal of Organometallic Chemistry 629 (2001) 114–130
1
3
(
(
0.493 g, 3.31 mmol) and 4-N,N-dimethylaminopyridine
20 mg, 0.16 mmol). The mixture was refluxed under
7.22–7.26 (m, H(12), H(14)). C-NMR: l 21.0 (C(6));
22.7 (C(20)); 23.6 (C(2)); 29.6 (C(7)); 36.2 (C(3)); 38.2
(C(1)); 39.2(5) (C(10)); 47.5 (C(5)); 106.7(5) (C(18));
119.1 (C(13)); 127.4 (C(12)); 128.7 (C(11)); 131.8
(C(14)); 137.7 (C(9)); 146.3 (C(4)); 150.0 (C(8)). MS;
nitrogen for 2.5 h, then cooled and filtered through
Celite. Removal of the solvent followed by flash chro-
matography (hexanes–ether, 8:2) gave 13-bromo-4a-(2%-
pyridylthio)-18-norpodocarpa-8,11,13-triene (17) (1.090
+
+
m/z: 292 (25, M ), 290 (25, M ), 277 (28, 292−Me ),
275 (28, 290−Me ), 196 (M−Me −Br ).
+
g, 90.5%) as a colourless oil. Found: 403.0800 [M ].
8
24
1
+
Calc. for C H BrNS: 403.0792. Found: 401.0810 [M
2
1
79
−1
3.11. Methyl pentacarbonyl[(methoxy)(13-(podocarpa-
,11,13-trien-19-oate))carbene]chromium (18)
]
. Calc. for C H BrNS: 401.0813. IR (wmax, cm ):
21 24
8
1
1
574 (s, CꢁC), 1557 (s, CꢁC), 1480, 1449, 1413, 1120,
1
092, 759, 724. H-NMR: l 1.20 (s, H(20)); 1.35 (ddd,
−
1
Butyllithium (0.84 ml, 2.5 mol l ) was added to a
solution of methyl 13-bromo-podocarpa-8,11,13-trien-
9-oate (11) (0.741 g, 2.11 mmol) in THF (15 ml) at
J=13.1, 13.1, 4.0 Hz, H(1ax)); 1.45 (s, H(19)); 1.59–
1
1
2
5
.90 (m, H(2ax), H(2eq), H(6ax)); 1.97 (dd, J=12.3,
.8 Hz, H(5)); 2.08 (dtd, J=13.2, 3.2, 1.4 Hz, H(3eq));
.19 (dd, J=13.2, 4.1 Hz, H(1eq)); 2.23 (ddd, J=13.2,
.1 Hz, H(3ax)); 2.55 (ddt, J=13.2, 7.2, 1.8 Hz,
1
−
−
78°C under nitrogen. The solution was stirred at
78°C for 2 min then added to a slurry of Cr(CO)6
(
0.487 g, 2.21 mmol) in ether (15 ml) at 0°C. After 45
H(6eq)); 2.79 (ddd, J=16.6, 11.2, 7.0 Hz, H(7ax)); 2.88
bdd, J=16.6, 5.9 Hz, H(7eq)); 7.06 (d, J=8.5 Hz,
min, methyl triflate (0.35 ml, 3.09 mmol) was added
and the solution was stirred for 2 h at r.t. The mixture
was diluted with ether (and the extracts were washed
with water and dried. Radial chromatography (hex-
anes–ether, 9:1) gave methyl pentacarbonyl[-
(methoxy)(13 - (podocarpa - 8,11,13 - trien - 19 - oate))-
carbene]chromium (18) (0.221 g, 21%) as a red oil.
Attempts to obtain an analytically pure sample of 18
using preparative TLC were unsuccessful, small
amounts of methyl podocarpa-8,11,13-trien-19-oate be-
(
H(11)); 7.09 (ddd, J=7.5, 4.9, 1.1 Hz, H(4%)); 7.16 (d,
J=2.1 Hz, H(14)); 7.19 (dd, J=8.4, 2.2 Hz, H(12));
7
.39 (dd, J=7.7, 0.9 Hz, H(6%)); 7.52 (td, J=7.7, 1.9
Hz, H(5%)); 8.50 (ddd, J=4.8, 1.9, 1.0 Hz, H(3%)).
1
3
C-NMR: l 19.8(2) (C(2)); 19.8(7) (C(6)); 21.6 (C(20));
2
5.4 (C(19)); 29.7 (C(7)); 37.8 (C(3)); 39.3 (C(10)); 40.3
C(1)); 47.3 (C(5)); 57.6 (C(4)); 119.0 (C(13)); 121.7
C(4%)); 126.3 (C(12)); 128.6 (C(11)); 129.7 (C(6%)); 131.7
(
(
(
1
(
C(14)); 136.1 (C(5%)); 137.8(5) (C(9)); 148.4 (C(8));
+
ing present. Found: 506.1061 [M ]. Calc. for
+
49.8 (C(3%)); 157.0 (C(1%). MS; m/z: 403 (1, M ), 401
−
1
C H CrO : 506.1033. IR (wmax, cm ): 2059 (s, CꢀO),
+
1, M ), 370, (1, 403-SH ), 368 (1, 401−SH ), 322 (1,
25 26
8
1
983 (sh, CꢀO), 1932 (br, CꢀO). u , nm: 419, 234.
max
M−Br ), 277 (7, 403−Me −C H NS), 275 (7, 401−
Me −C H NS), 221 (9), 211 (20), 209 (20), 112 (100,
C H NS ).
5
5
1
H-NMR: l 1.03 (s, H(20)); 1.10 (ddd, J=13.6, 13.6,
5
+
5
4
1
.3 Hz, H(3ax)); 1.29 (s, H(18)); 1.39 (ddd, J=13.4,
3.4, 3.6 Hz, H(1ax)); 1.55 (d, J=10.7 Hz, H(5)); 1.65
5
6
(
dp, J=14.0, 3.3 Hz, H(2eq)); 1.91–2.06 (m, H(2ax),
H(6ax)); 2.15–2.31 (m, H(1eq), H(3eq), H(6eq)); 2.81
ddd, J= 16.9, 12.2, 6.2 Hz, H(7ax)); 2.95 (bdd, J=
6.9, 5.1 Hz, H(7eq)); 3.66 (s, 19-OMe); 4.76 (s,
OMe ); 7.11 (bs, H(14)); 7.26–7.31 (m, H(11),
3.10. 13-Bromo-19-norpodocarpa-8,11,13-tetraene (15)
(
1
A suspension of m-chloroperoxybenzoic acid (85%
w/w, 0.542 g, 2.68 mmol) in CH Cl (15 ml) was added
2
2
carbene
13
slowly to a cooled (−78°C) and stirred solution of 13
bromo-4a-(2%-pyridylthio)-18-norpodocarpa-8,11,13-
triene (17) (1.076 g, 2.68 mmol) in CH Cl (10 ml)
H(12)). C-NMR: l 19.8(5) (C(2)); 20.8 (C(6)); 22.8
C(20)); 28.5 (C(18)); 30.1 (C(7)); 37.5 (C(3)); 38.8
(C(10)); 39.1 (C(1)); 44.0 (C(4)); 51.3 (19-OMe); 52.4
-
(
2
2
under an atmosphere of nitrogen. After 1 h the suspen-
sion was allowed to come to r.t. and added dropwise to
dry benzene (100 ml) at reflux. After 1 h the solution
was cooled to r.t. Flash chromatography (hexanes–
ether, 9:1) gave 13-bromo-19-norpodocarpa-8,11,13-te-
traene (15) (0.679 g, 87%) as a colourless oil. Found:
(
(
(
C(5)); 67.1(5) (OMecarbene); 122.7 (C(12)); 125.1
C(11)); 125.4 (C(14)); 135.2 (C(13)); 150.7 (C(8)); 151.9
C(9)); 177.7 (C(19)); 216.5 (CꢀO ); 224.1 (CꢀOtrans);
cis
+
3
48.2 (C
). MS; m/z: 506 (2, M ), 478 (5, M−
carbene
CO), 450 (3, M−2CO), 422 (6, M−3CO), 394 (18,
M−4CO), 366 (100, M−5CO).
+
81
2
2
92.0647 [M ]. Calc. for C H Br: 292.0650. Found:
1
6
19
79
+
90.0659 [M ]. Calc. for C H Br: 290.0670. IR (wmax,
1
6
19
3.12. Pentacarbonyl[(methoxy)(13-(19-norpodo-
carpa-4(18),8,11,13-tetraene))carbene]chromium (20)
−
1
1
cm ): 1648 (s, CꢁC), 1480, 1440, 1090. H-NMR: l
0
.98 (s, H(20)); 1.53 (ddd, J=13.0, 13.0, 4.6 Hz,
−
1
H(1ax)); 1.65–1.87 (m, H(2eq), H(2ax), H(6ax),
H(6eq)); 2.05 (ddd, J=13.1, 13.1, 4.5 Hz, H(3ax)); 2.18
Butyllithium (0.93 ml, 2.5 mol l , 2.33 mmol) was
added to a solution of 13-bromo-19-norpodocarpa-
4(18),8,11,13-tetraene (15) (0.679 g, 2.33 mmol) in THF
(10 ml) cooled to −78°C. The solution was stirred at
−78°C for 2 min then added via cannula to a slurry of
(
dd, J=12.0, 1.1 Hz, H(5)); 2.23 (bd, J=12.8 Hz,
H(1eq)); 2.38 (ddd, J=13.1, 4.3, 2.2 Hz, H(3eq)); 2.88
4 lines, H(7ax), H(7eq)); 4.60 (d, J=1.5 Hz, H(18));
.86 (d, J=1.5 Hz, H(18)); 7.16 (d, J=9.4 Hz, H(11));
(
4
Cr(CO) (0.541 g, 2.46 mmol) in ether (15 ml) at 0°C.
6