Organocycloborates
FULL PAPER
perature and a white precipitate started to form. The mixture was stirred
overnight, diluted with THF (50 mL), and filtered hot to give a clear so-
lution. A small amount of this solution was dried in vacuo and analysed
by NMR spectroscopy.
to yield 21a; 1H NMR: d=1.19–1.72 ppm (m, br); 13C NMR: d=15.71,
28.00, 28.45, 29.95 (br), 36.80 ppm (br); 11B NMR: d=82.2 ppm.
21b: The previously obtained Grignard reagent 21a was redissolved in
Et2O and a solution of 1,4-dioxane (2.3 mL, 27.0 mmol) in Et2O (10 mL)
was added dropwise. The mixture was stirred overnight and the white
precipitate of MgBr2·dioxane was separated from the solution by centri-
fugation. The resulting clear solution was dried in vacuo to give 21b as
NMR data for 14a: 1H NMR: d=0.40–1.60 (m); 13C NMR: d=13.41,
22.50, 23.90 (br), 31.12 (br), 31.25, 32.11, 32.72, 33.50; 11B NMR: d=85.0.
The solution of 14a in THF was refluxed at 668C for three days. The re-
sulting clear solution was concentrated to a small volume in vacuo and
cooled to 08C to give colourless crystals of 19 in 76% yield. 1H NMR:
d=0.10 (br), 0.70–1.00 (br, m), 1.20–1.50 (br, m), 1.76 ppm (br);
13C NMR: d=12.19, 12.65, 14.40, 21.67, 31.17, 39.52 ppm (br); 11B NMR:
d=ꢀ 20.5 ppm; MS (ESI): m/z (%): 209 (100) [C14H30B].
6: A solution of the crude borane 11 in Et2O (20 mL) was added drop-
wise to a suspension of Mg turnings in Et2O (15 mL) at ambient tempera-
ture. When the reaction was complete, the system was allowed to reach
ambient temperature and a white precipitate started to form. The mix-
ture was stirred overnight, diluted with THF (50 mL), and filtered hot to
give a clear solution. 1,4-Dioxane (2.3 mL, 27.0 mmol) in Et2O (10 mL)
was added dropwise and the resulting solution was stirred overnight. The
white precipitate of MgBr2·dioxane was separated from the solution by
centrifugation, and the clear solution was concentrated to a small volume
in vacuo and cooled to 08C to give colourless crystals of 6 in 86% yield.
1H NMR: d=ꢀ0.17 (br), 0.08 (br), 0.72–1.57 ppm (m, br); 13C NMR: d=
30.10, 31.68, 32.66, 32.74 ppm; 11B NMR: d=ꢀ12.5 ppm; MS (ESI): m/z
(%): 233 (100) [C16H30B].
1
an off- white oil in 85% yield. H NMR: d=1.18–1.72 (m, br, 26H), 1.96
(m, 2H; R2BCH2CH2CH2Br), 3.42 ppm (t, 3JH,H =6.79 Hz, 2H;
R2BCH2CH2CH2Br); 13C NMR: d=19.39, 27.95, 28.42, 29.92, 36.74 ppm
(br); 11B NMR: d=82.5 ppm; elemental analysis calcd (%) for
C30H56B2Mg (462.7): C 77.87, H 12.20; found: C 77.82, H 11.98.
Crystal data for 15: [C20H40O5BrMg](C12H22B)·C4H8O, Mr =713.95, tri-
clinic, (no. 2), a=10.6422(5), b=13.8529(5), c=13.9367(6) , a=
71.397(4), b=89.688(4), g=87.648(4)8, V=1945.57(14) 3, Z=2, 1calcd
=
1.219 gcmꢀ3, m(MoKa)=1.113 mmꢀ1, T=173 K, colourless prisms, Oxford
Diffraction Xcalibur 3 diffractometer; 11919 independent measured re-
flections, F2 refinement, R1 =0.075, wR2 =0.126, 11384 independent ob-
served absorption-corrected reflections [jFo j>4s(jFoj), 2qmax =648], 441
parameters. CCDC-273774 contains the supplementary crystallographic
data for this compound. These data can be obtained free of charge from
data_request/cif.
Crystal data for 16: [C20H40O5BrMg](C14H26B)·C4H8O, Mr =742.00, mon-
oclinic, P21/n (no. 14), a=10.7897(9), b=25.8464(19), c=14.5063(10) ,
b=93.220(6)8, V=4039.1(5) 3, Z=4, 1calcd =1.220 gcmꢀ3
, m(MoKa)=
1.074 mmꢀ1, T=173 K, colourless blocks, Oxford Diffraction Xcalibur 3
diffractometer; 5234 independent measured reflections, F2 refinement,
R1 =0.184, wR2 =0.448, 5166 independent observed absorption-corrected
reflections [jFo j>4s(jFoj), 2qmax =458], 429 parameters. CCDC-273775
contains the supplementary crystallographic data for this compound.
These data can be obtained free of charge from The Cambridge Crystal-
20: A solution of 9-BBN (dimer) (6.7 g, 27.3 mmol) in THF (50 mL) was
added dropwise to
a colourless solution of allyl bromide (4.8 mL,
55.5 mmol) in CH2Cl2 (10 mL) at ꢀ308C. When the addition was com-
plete, the solution was allowed to reach ambient temperature and stirred
overnight. The resulting colourless solution was dried in vacuo to give 20
as a pale yellow oil in 94% yield, which was used without further purifi-
cation for the synthesis of 20a. 1H NMR: d=1.15 (t, 3JH,H =8.17 Hz, 2H;
R2BCH2CH2CH2Br), 1.34 (m, 4H; [(CH2)2(CH2)4(CH)2]B(CH2)3Br)),
1.71–1.80 (m, br, 10H; [(CH2)2(CH2)4(CH)2]B(CH2)3Br)), 1.96 (m, 2H;
R2BCH2CH2CH2Br),
3.40 ppm
(t,
3JH,H =7.05 Hz,
2H;
R2BCH2CH2CH2Br); 13C NMR: d=24.56, 29.59 (br), 30.10, 33.67,
38.04 ppm; 11B NMR: d=86.6 ppm.
Acknowledgements
20a: The previously obtained 20 was redissolved in Et2O (50 mL) was
added dropwise to Mg turnings in Et2O at ambient temperature. The
system was allowed to reach ambient temperature and stirred overnight.
The resulting grey solution was filtered and dried in vacuo to give 20a as
a white powder. 1H NMR: d=1.22–1.85 ppm (m, br); 13C NMR: d=
20.43, 24.29, 31.30 (br), 33.86 ppm; 11B NMR: d=78.2 ppm.
We thank EPSRC for financial support.
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20b: The previously obtained Grignard reagent 20a was redissolved in
Et2O and a solution of 1,4-dioxane (0.57 g, 6.47 mmol) was added drop-
wise. Immediately, a white precipitate of MgBr2·dioxane formed. After
the addition was complete the system was allowed to stir for 2 h. The
white precipitate was filtered and washed twice with Et2O (210 mL).
The mother liquor was dried in vacuo and 20b was isolated as a white
solid in 85% yield. 1H NMR: d=1.21–1.91 ppm (m, br); 13C NMR: d=
20.42, 24.31, 31.10 (br), 33.86 ppm; 11B NMR: d=77.8 ppm; elemental
analysis calcd (%) for C22H40B2Mg (350.5): C 75.39, H 11.50; found: C
75.61, H 11.36.
21: According to the procedure described for 20 a solution of cyclohex-
ene (6 mL, 59.2 mmol) in THF (20 mL) was treated with a 1.0m solution
of BH3·THF (30 mL, 30.0 mmol), and subsequently treated with a solu-
tion of allyl bromide (2.6 mL, 30.0 mmol) in THF (20 mL) to give 21 as a
colourless oil in 87% yield, which was used without further purification
for the synthesis of 20a. 1H NMR: d=1.16–1.73 (m, br, 24H), 1.96 (m,
2H;
R2BCH2CH2CH2Br),
3.42 ppm
(t,
3JH,H =6.79 Hz,
2H;
R2BCH2CH2CH2Br); 13C NMR: d=27.90, 28.06, 28.42, 29.16, 36.60 (br),
37.58 ppm; 11B NMR: d=81.4 ppm.
21a: The previously obtained 21 was dissolved in Et2O (20 mL) and
added dropwise to a suspension of Mg turnings in Et2O at ambient tem-
perature. The system was allowed to reach ambient temperature and stir-
red overnight. The resulting grey solution was filtered and dried in vacuo
Chem. Eur. J. 2006, 12, 600 – 606
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