Molybdenum-Catalyzed Stannylations
(4-Nitr op h en ylisocya n o)m olybd en u m P en ta ca r bon yl
6. A solution of Mo(CO)6 (570 mg, 2.15 mmol) in 10 mL of
absolute THF was refluxed in an oven-dried apparatus for 24
h under Ar. After the heating bath was removed, isonitrile 5
(254 mg, 1.71 mmol) in 3 mL of absolute THF was added to
the yellow solution, and the solution was refluxed for further
3 h. The solution darkened via red to black. The solvent was
evaporated in vacuo, and the crude product was purified by
flash chromatography on silica (DCM/hexanes 1/1). Complex
6 was isolated as a red solid (440 mg, 1.15 mmol, 67%). 1H
NMR (300 MHz, CDCl3): δ 7.52 (d, J ) 9.0 Hz, 2H), 8.31 (d,
J ) 8.9 Hz, 2H). 13C NMR (75 MHz, CDCl3): δ 125.3, 127.3,
132.7, 147.0, 173.8, 203.3, 205.8. 95Mo NMR (20 MHz, tolu-
ene): δ -1836. IR (KBr, cm-1): ν 2138, 2062, 1939 (s, C-O
vs), 1956 (m, C-N vs), 1637, 1593 (w, CdC vs), 1593, 1490 (s,
N-O vs), 850 (w, C-NO2 vs). Raman (cm-1): ν 2139, 2058,
1995, 1937 (s, C-O vs), 1591, 1466 (s, N-O vs). HRMS (FAB+)
-53.1. Anal. Calcd for C29H60O2Sn2 (678.17): C, 51.36; H, 8.92.
Found: C, 51.34; H, 8.80.
2-Br om oben zyl-2-tr ibu tylsta n n yla llyl Eth er 14. Ether
14 was obtained according to the general procedure for
hydrostannations from 2-bromobenzylpropargyl ether 13 (98
mg, 0.43 mmol) and Bu3SnH (0.35 mL, 1.32 mmol) using
catalyst 3 (5 mg, 0.012 mmol) after flash chromatography
(hexanes/NEt3 99/1) as a colorless liquid (71 mg, 0.14 mmol,
1
32%). H NMR (300 MHz, CDCl3): δ 0.80-1.07 (m, 15H, 1H),
1.21-1.34 (m, 6H), 1.41 - 1.59 (m, 6H), 4.23 (m, J H,Sn ) 33.8
Hz, 2H), 4.53 (s, 2H), 5.29 (m, J H,Sn ) 61.4 Hz, 1H), 5.91 (m,
J H,Sn ) 129.5 Hz, 1H), 7.11 (m, 1H), 7.29 (m, 1H), 7.51 (m,
2H). 13C NMR (75 MHz, CDCl3): δ 9.4, 13.4, 27.1, 28.9, 71.1,
77.7, 122.2, 124.7, 127.0, 128.4, 128.6, 132.1, 137.8, 152.4. 119
-
Sn NMR (112 MHz, CDCl3): δ -46.3. HRMS (FAB+) m/e:
C
C
C
18H28O81Br120Sn [M - Bu]+ calcd 461.0325; found 461.0346.
18H28O81Br118Sn [M - Bu]+ calcd 459.0319; found 459.0348.
18H28O81Br116Sn [M - n-Bu]+ calcd 457.0320, found 457.0360.
m/e:
C
12H4N2O798Mo [M]+ calcd 385.9073; found 385.9060.
C
12H4N2O796Mo [M]+ calcd 385.9065; found 383.9035. C18H8-
2,3-Bis(tr ibu tylsta n n yl)a llyl-(2-br om oben zyl)eth er 15.
N4O895Mo [M]+ calcd 382.9077, found 382.9048. Anal. Calcd
for C12H4N2O7Mo (384.11): C, 37.52; H, 1.05; N, 7.29. Found:
C, 37.34; H, 1.18; N, 7.46.
According to the general procedure for distannations, 15 was
obtained from 2-bromobenzylpropargyl ether 13 (81 mg, 0.36
mmol), Bu3SnH (0.4 mL, 1.5 mmol), and catalyst 4 (3 mg, 6
µmol) in 2 mL of toluene after flash chromatography (hexanes/
ethyl acetate/NEt3 98/1/1) as a colorless liquid (32 mg, 0.039
mmol, 11%). 1H NMR (300 MHz, CDCl3): δ 0.79-0.97 (m,
30H), 1.31 (m, 12H), 1.49 (m, 12H), 4.22 (d, J ) 1.1 Hz, 2H),
4.52 (s, 2H), 6.94 (s, J H,Sn ) 173.8 Hz, 72.4 Hz, 1H), 7.12 (dt,
J ) 7.7 Hz, 1.5 Hz, 1H), 7.30 (dt, J ) 7.5 Hz, 1.2 Hz, 1H), 7.51
(dd, J ) 7.9 Hz, 1.2 Hz, 2H). 13C NMR (75 MHz, CDCl3): δ
10.5, 10.8, 13.6, 27.4, 27.5, 29.3, 70.8, 83.1, 122.2, 127.6, 128.1,
128.2, 132.2, 138.0, 144.0, 164.2. 119Sn NMR (112 MHz,
CDCl3): δ -65.2, -55.0. Anal. Calcd for C34H63BrOSn2
(805.16): C, 50.72; H, 7.89. Found: C, 50.87; H, 7.69.
Gen er a l P r oced u r e for Hyd r osta n n a tion s. In an oven-
dried Schlenk tube were dissolved 1 equiv of alkyne and 2 mol
% of catalyst 3 in absolute THF under Ar together with 1 mol
% of hydroquinone. The solution was heated to 55 °C before 2
equiv of Bu3SnH was added. After 4 h at this temperature 1
equiv of Bu3SnH was added, and the mixture was stirred for
2 h at this temperature. After cooling to room temperature,
the solvent was evaporated in vacuo, and the crude product
was purified by flash chromatography on silica using a hexane/
ethyl acetate mixture containing 1% NEt3.
Gen er a l P r oced u r e for Dista n n a tion s. In an oven-dried
Schlenk tube were dissolved 1 equiv of the alkyne, 0.5-2.5
mol % of catalyst 4 or 6, and a point of a spatula of
hydroquinone in dry toluene and heated for 15 min at 60 °C.
After addition of 3.5-4 equiv of tributyl tinhydride heating
was continued for 12 h at 60 °C. After removal of the solvent
the crude product was chromatographed over silica gel. First
hexabutyldistannane and tributyl tinhydride were eluated
with pure hexane, and then the product could be isolated using
a hexane/ethyl acetate mixture containing 1% NEt3.
2-Iod oben zyl-2-tr ibu tylsta n n yla llyl Eth er 17. Ether 17
was obtained according to the general procedure for hy-
drostannations from 2-iodobenzylpropargyl ether 16 (253 mg,
0.93 mmol) and Bu3SnH (0.75 mL, 2.83 mmol) using catalyst
3 (10 mg, 0.023 mmol) after flash chromatography (hexanes/
1
NEt3 99/1) as a colorless liquid (183 mg, 0.32 mmol, 35%). H
NMR (300 MHz, CDCl3): δ 0.79-0.93 (m, 15 H, 1-H), 1.20-
1.33 (m, 6H), 1.41-1.54 (m, 6H), 4.22 (s, J H,Sn ) 34.2 Hz, 2H),
4.44 (s, 2H), 5.30 (d, J ) 2.4 Hz, J H,Sn ) 66.2 Hz, 1H), 5.92 (d,
J ) 2.4 Hz, J H,Sn ) 130.8 Hz, 1H), 6.96 (m, 1H), 7.32 (m, 1H),
7.44 (d, J ) 7.7 Hz, 1H), 7.78 (d, J ) 7.9 Hz, 1H). 13C NMR
(75 MHz, CDCl3): 9.6, 13.7, 27.4, 29.1, 75.9, 79.3, 125.0, 128.1,
128.4, 128.9, 139.0, 140.9, 156.3, 152.6. 119Sn NMR (112 MHz,
CDCl3): δ -46.1. Anal. Calcd for C22H37IOSn (563.12): C,
46.92; H, 6.62. Found: C, 47.21; H, 6.75.
2,3-Bis(tr ibu tylstan n yl)allyl-(2-iodoben zyl)eth er 18. Ac-
cording to the general procedure for distannations, 18 was
obtained from 2-iodobenzylpropargyl ether 16 (331 mg, 1.22
mmol), Bu3SnH (1.0 mL, 3.8 mmol), and catalyst 6 (11 mg,
0.029 mmol) in 3 mL of toluene after flash chromatography
(hexanes/ethyl acetate/NEt3 98/1/1) as a colorless liquid (683
mg, 0.80 mmol, 66%). 1H NMR (300 MHz, CDCl3): δ 0.82-
0.97 (m, 30H), 1.31 (m, 12H), 1.49 (m, 12H), 4.27 (d, J ) 1.7
Hz, 2H), 4.60 (s, 2H), 6.94 (s, J H,Sn ) 173.8 Hz, J H,Sn ) 67.8
Hz, 1H), 6.98 (dt, J ) 9.6 Hz, 1.5 Hz, 1H), 7.34 (dd, J ) 7.3
Hz, 3.0 Hz, 1H), 7.45 (dt, J ) 7.7 Hz, 0.9 Hz, 1H), 7.80 (dd, J
) 7.9 Hz, J ) 3.3 Hz, 2H). 13C NMR (75 MHz, CDCl3): δ 10.5,
10.8, 13.7, 27.4, 27.5, 29.2, 29.3, 75.4, 83.0, 97.2, 128.0, 128.4,
128.8, 138.9, 140.9, 144.1, 164.2. Anal. Calcd for C34H63IOSn2
(852.16): C, 47.92; H, 7.45. Found: C, 47.99; H, 7.44.
2-Tr ibu tylsta n n yl-2-p r op en yl Aceta te 10. Acetate 10
was prepared according to the general procedure for hy-
drostannations from propargyl acetate (620 mg, 6.30 mmol)
with catalyst 3 (51 mg, 0.12 mmol) and Bu3SnH (5.0 mL, 18.9
mmol) in 20 mL of THF. Flash chromatography (hexanes/ethyl
acetate/NEt3 95/4/1) gave rise to 10 as a colorless liquid (2.22
g, 5.72 mmol, 91%) and a mixture of regioisomers (R/â 96/4).
1H NMR (300 MHz, CDCl3): δ 0.80-1.05 (m, 15H), 1.32 (m,
6H), 1.47 (m, 6H), 2.06 (s, 3H), 4.71 (t, J ) 2.0 Hz, 2H), 5.30
(dt, J ) 1.9 Hz, 1.7 Hz, J H,Sn ) 59.3 Hz, 1H), 5.85 (dt, J ) 1.8
Hz, 1.7 Hz, J H,Sn ) 121.1 Hz, 1H). 13C NMR (75 MHz, CDCl3):
δ 9.3, 13.6, 20.8, 27.1, 29.0, 71.2, 125.2, 148.7, 170.2. 119Sn
NMR (112 MHz, CDCl3): δ -42.2. Selected signals of the minor
isomer 11: 1H NMR (300 MHz, CDCl3): δ 6.02 (dt, J ) 19.0
Hz, 5.3 Hz, 1H), 6.26 (d, J ) 19.0 Hz, 1H). 13C NMR (75 MHz,
CDCl3): δ 73.7, 131.8, 145.5. 119Sn NMR (112 MHz, CDCl3): δ
-48.1. Anal. Calcd for C17H34O2Sn (389.14): C, 52.48; H, 8.74.
Found: C, 52.23; H, 8.78.
2,3-Bis(tr ibu tylsta n n yl)a llyl Aceta te 12. According to the
general procedure for distannations, 12 was obtained from
propargyl acetate (100 mg, 1.02 mmol), Bu3SnH (1.0 mL, 3.8
mmol), and catalyst 4 (3 mg, 6 µmol) in 3 mL of toluene after
flash chromatography (hexanes/ethyl acetate/NEt3 95/4/1) as
a colorless liquid (601 mg, 0.89 mmol, 87%). 1H NMR (300
MHz, CDCl3): δ 0.81-0.98 (m, 30H), 1.32 (m, 12H), 1.48 (m,
12H), 2.07 (s, 3H), 4.65 (d, J ) 1.5 Hz, 2H), 6.80 (t, J ) 1.4
Hz, J H,Sn ) 173.5 Hz, J H,Sn ) 71.2 Hz, 1H). 13C NMR (75 MHz,
CDCl3): δ 10.5, 10.8, 13.6, 21.0, 27.4, 27.5, 29.1, 29.2, 79.0,
145.2, 160.5, 170.4. 119Sn NMR (112 MHz, CDCl3): δ -64.8,
4-Meth ylen isoch r om a n 19.11a,b Pd(PPh3)4 (75 mg, 0.052
mmol) was dissolved in a oven-dried Schlenk tube in 2.5 mL
of absolute toluene under Ar. A solution of 17 (270 mg, 0.52
mmol) in 1 mL of toluene was added, and the mixture was
heated to 75 °C for 48 h. Saturated KF solution was added,
and the mixture was stirred vigorously for 12 h. Precipitated
Bu3SnF was filtered off, and the solvent was evaporated in
vacuo. The residue was dissolved in ethyl acetate and filtered
again. The crude product was purified by flash chromatogra-
J . Org. Chem, Vol. 69, No. 2, 2004 473