Addition reactions of bis(pinacolato)diborane(4) to carbonyl enones and synthesis of (pinacolato)2BCH2B and (pinacolato)2BCH2CH2B by insertion and coupling

Article abstract of DOI:10.1021/om010282r

The title compound adds to αβ-unsaturated carbonyls to give the products of 1,4-addition after hydrolysis of the intermediate boron enolates, in 68-86% isolated yield (four examples). In addition, we discovered that diazomethane reacts with bis(pinacolato

Full text of DOI:10.1021/om010282r

3962
Organometallics 2001, 20, 3962-3965
Notes
Ad d ition Rea ction s of Bis(p in a cola to)d ibor a n e(4) to
Ca r bon yl En on es a n d Syn th esis of (p in a cola to)2BCH2B
a n d (p in a cola to)2BCH2CH2B by In ser tion a n d Cou p lin g
Hijazi Abu Ali,† Israel Goldberg,‡ and Morris Srebnik*,†
Department of Medicinal Chemistry and Natural Products, School of Pharmacy, Hebrew
University in J erusalem, J erusalem, Israel, and School of Chemistry, Tel-Aviv University,
Ramat-Aviv 69987, Tel-Aviv, Israel
Received April 6, 2001
Summary: The title compound adds to R,â-unsaturated
carbonyls to give the products of 1,4-addition after
hydrolysis of the intermediate boron enolates, in 68-
86% isolated yield (four examples). In addition, we
discovered that diazomethane reacts with bis(pinacola-
to)diborane to insert methylene to give (pinacolato)2BCH2B
in 83% yield. An alternative synthesis involved coupling
of (pinacolato)BCH2I with various metals.
2-ones,13 and various other substrates.14 Mechanistic
and theoretical studies of diboration have also been
reported.15 The latter reaction reported by Marder and
Norman et al. is particularly interesting, in that it opens
the way for addition of diborane(4) compounds to other
R,â-unsaturated systems. Three-membered16 and five-
membered17 aminodiborane(4) derivatives undergo in-
sertion reactions with CO and isonitrile to give inter-
Boronic acids have a variety of important uses and
applications. They are highly valued synthetic inter-
mediates1 and also possess significant biological activ-
ity.2 Hydroboration,3 haloboration,4 reactions with or-
ganometallics,5 and homologation6 are important proto-
cols for their preparation. A more recent and very
convenient method for the preparation of boronic acids
involves diborane(4) derivatives.7 In particular, tet-
raalkoxydiborane(4) compounds have been shown to add
to alkenes,8 alkynes,9 1,3-butadienes,10 allylic acetates,11
methylenecyclopropanes,12 substituted 4-arylbut-3-en-
(9) (a) Ishiyama, T.; Matsuda, N.; Murata, M.; Ozawa, F.; Suzuki,
A.; Miyaura, N. Organometallics 1996, 15, 713. (b) Hiyama, T.;
Yamamoto, M.; Miyaura, N. Chem. Lett. 1996, 1117. (c) Lesley, G.;
Nguyen, P.; Taylor, N. J .; Marder, T. B.; Scott, A. J .; Clegg, W.;
Norman, N. C. Organometallics 1996, 15, 5137. (d) Ishiyama, T.;
Matsuda, N.; Miyaura, N.; Suzuki, A. J . Am. Chem. Soc. 1993, 115,
11018. (e) Iverson, C. N.; Smith, M. R., III. Organometallics 1996, 15,
5155. (f) Anderson, K. M.; Lesley, M. J . G.; Norman, N. C.; Orpen, A.
G.; Starbuck, J . New J . Chem. 1999, 23, 1053. (g) Suginome, M.;
Matsuda, T.; Ito, Y. Organometallics 1998, 17, 5233. Boryl alkynes:
(h) Bluhm, M.; Maderna, A.; Pritzkow, H.; Bethke, S.; Gleiter, R.;
Siebert, W. Eur. J . Inorg. Chem. 1999, 1693.
(10) (a) Ishiyama, T.; Yamamoto, M.; Miyaura, N. Chem. Commun.
1996, 2073. (b) Clegg, W.; J ohann, T. R. F.; Marder, T. B.; Norman,
N. C.; Orpen, A. G.; Peakman, T. M.; Quayle, M. J .; Rice, C. R.; Scott,
A. J . J . Chem. Soc., Dalton Trans. 1998, 1431.
(11) Ishiyama, T.; Momota, S.; Miyaura, N. Synlett 1999, 11, 1790.
(12) (a) Ishiyama, T.; Ahiko, T.-A.; Miyaura, N. Tetrahedron Lett.
1996, 37, 6889. (b) Ishiyama, T.; Momota, S.; Miyaura, N. Synlett 1999,
11, 1790.
† Hebrew University in J erusalem.
‡ Tel-Aviv University.
(1) Pelter, A.; Smith, K.; Brown, H. C. Borane Reagents. In Best
Synthetic Methods; Katritzky, A. R., Meth-Cohn, M., Rees, C. W., Eds.;
Academic Press: London, 1988.
(2) (a) For a review of biologically active boron analogues, see:
Morin, C. Tetrahedron 1994, 50, 12521. (b) For the use of boranes in
boron neutron capture therapy, see: Soloway, A. H.; Tjarks, W.;
barnum, B. A.; Rong, F.-G.; Barth, R. F.; Codogni. I. M.; Wilson, J . G.
Chem. Rev. 1998, 98. 1515.
(3) Brown, H. C.; Ramachandran, P. V. In Sixty Years of Hydride
Reductions; ACS Symposium Series 641; American Chemical Society:
Washington, DC, 1996; p 1.
(4) Suzuki, A.; Dhillon, R. S. In Synthetic Organic Chemistry;
Springer-Verlag: Berlin, 1986; p 23.
(13) Lawson, Y. G.; Lesley, M. J . G.; Marder, T. B.; Norman, N. C.;
Rice, C. R. Chem. Commun. 1997, 2051.
(14) Aryl halides: (a): Ishiyama, T.; Itoh, Y.; Kitano, T.; Miyaura,
N. Tetrahedron Lett. 1997, 38, 3447. Imines: (b) Mann, G.; J ohn, K.
D.; Baker, R. T. Org. Lett. 2000, 2, 2105. (c) Cameron, T. M.; Baker,
R. T.; Wescott, S. A. Chem. Commun. 1998, 2395. Hydrazines: (d)
Hommer, H.; No¨th, H.; Sachdev, H.; Schmidt, M.; Schwenk, H.; Chem.
Ber. 1995, 128, 1187. Carbenoids: (e) Hata, T.; Kitagawa, H.; Masai,
H.; Kurahashi, T.; Shimuzu, M.; Hiyama, T. Angew. Chem., Int. Ed.
2001, 40, 790.
(15) Mechanism: (a) Clark, G. R.; Irvine, G. J .; Roper, W. R.; Wright,
L. J . Organometallics 1997, 16, 5499. (b) Dai, C.; Stringer, G.; Marder,
T. B.; Scott, A. J .; Clegg, W.; Norman, N. C. Inorg. Chem. 1997, 36,
272. (c) Marder, T. B.; Norman, N. C.; Rice, C. R.; Robins, E. G. Chem.
Commun. 1997, 53. (d) Irvine, G. J .; Lesley, M. J . G.; Marder, T. B.;
Norman, N. C.; Rice, C. R.; Robins, E. G.; Roper, W. R.; Whittell, G.
R.; Wright, L. J . Chem. Rev. 1998, 98, 2685. (e) Clegg, W.; Lawlor, F.
J .; Marder, T. B.; Nguyen, P.; Norman, N. C.; Orpen, A. G.; Quayle,
M. J .; Rice, C. R.; Scott, A. J .; Souza, F. E. S.; Stringer, G.; Whittell,
G. R. J . Chem. Soc., Dalton Trans. 1998, 301. Theoretical studies on
alkenes and alkynes: (f) Cui, Q.; Musaev, D. G.; Morokuma, K.
Organometallics 1997, 16, 1355. (g) Chadha, R.; Ray. N. K. J . Phys.
Chem. 1982, 86, 3293. (h) Ahmed, L.; Castillo, J .; Saulys, D. A.;
Morrison, J . A. Inorg. Chem. 1992, 31, 706. (i) Chadha, R.; Ray, N. K.
Theor. Chim. Acta 1982, 60, 573. (j) Cui, Q.; Musaev, D. G.; Morokuma,
K. Organometallics 1998, 17, 1383. (k) Cui, Q.; Musaev, D. G.;
Morokuma, K. Organometallics 1998, 17, 742.
(5) For numerous examples, see: Mikhailov, B. M.; Bubnov, Yu. N.
Organoboron Compounds in Organic Synthesis; Harwood Academic:
Chur, Switzerland, 1984.
(6) Matteson, D. S. Stereodirected Synthesis with Organoboranes;
Springer: Berlin, 1995.
(7) (a) Lesley, G.; Marder, T. B.; Norman, N. C.; Rice, C. R. Main
Group Chem. News 1997, 5, 4. (b) Marder, T. B.; Norman, N. C. Top.
Catal. 1998, 5, 63. (c) Ishiyama, T.; Miyaura, N. J . Organomet. Chem.
2000, 611, 392.
(8) (a) Marder, T. B.; Norman, N. C.; Rice, C. R. Tetrehedron Lett.
1998, 155. (b) Iverson, C. N.; Smith, M. R., III. Organometallics 1997,
16, 2757. (c) Ishiyama, T.; Yamamoto, M.; Miyaura, N. Chem. Commun.
1997, 689. (d) Takahashi, K.; Ishiyama, T.; Miyaura, N. Chem. Lett.
2000, 982. (e) Han, L. B.; Tanaka, M. Chem. Commun. 1999, 395. (f)
Dai, C. Y.; Robins, E. G.; Scott, A. J .; Clegg, W.; Yufit, D. S.; Howard,
J . A. K.; Marder, T. B. Chem. Commun. 1998, 1983. (g) Baker, R. T.;
Nguyen, P.; Marder, T. B.; Wescott, S. A. Angew. Chem., Int. Ed. Engl.
1995, 34, 1336.
(16) Paetzold, P.; Redenz-Stormanns, B.; Boese, R. Angew, Chem.
Int. Ed. Engl. 1990, 29, 900.
10.1021/om010282r CCC: $20.00 © 2001 American Chemical Society
Publication on Web 08/03/2001

Notes
Organometallics, Vol. 20, No. 18, 2001 3963
Sch em e 1. 1,4-Ad d ition of
Bis(p in a cola to)d ibor a n e to r,â-Un sa tu r a ted
Ca r bon yls
mediates that rearrange to interesting compounds. In
the following we report our findings on addition of bis-
(pinacolato)diborane(4) to cyclic enones, trans-cinnama-
ldehyde, and methyl trans-cinnamate and CH2N2 in-
sertion into the boron-boron bond.
Resu lts a n d Discu ssion
P r ep a r a tion of Bis(p in a cola to)d ibor a n e(4). Bis-
(pinacolato)diborane(4) is usually prepared from bis-
(dimethylamino)haloborane.18 We had difficulty in ob-
taining dimethylamine or its derivatives from commercial
sources and sought an alternative amine.19 Various
(R2N)2BX, i.e., with R ) Et, i-Pr, etc. and X ) Cl, Br,
failed to give B-B compounds in the dehalogenation
step. However, dipyrrolidinoamine behaved like di-
methylamine in that bis(pyrrolidino)bromoborane was
debrominated by sodium to give tetrakis(pyrrolidino)-
diborane(4).20 The precursor, tris(pyrrolidino)borane, is
readily prepared from BBr3 in pentane at -40 °C and 6
equiv of pyrrolidine (eq 1). After the bromide salt was
filtered, distillation afforded tris(pyrrolidino)borane in
81% yield: mp 40 °C, bp 105 °C/1.5 mmHg.
Ad d ition Rea ction s of Bis(p in a cola to)d ibor a n e-
(4). On the basis of the reported 1,4-addition of cat-
echolborane to R,â-unsaturated carbonyl compounds,21
Marder and Norman et al. showed that bis(pinacolato)-
diborane(4) adds to 4-arylbut-3-en-2-ones to give hy-
drolysis sensitive boron enolates that readily rearrange
to â-boryl ketones.13 Here we report that bis(pinacolato)-
diborane(4) also adds to 4-isopropylcyclohexenone, cy-
cloheptenone, trans-cinnamaldehyde, and methyl trans-
cinnamate in a 1,4-manner to give â-boryl carbonyl
compounds (3a -d ) after hydrolysis (Scheme 1).
compared to the starting material. The trans relative
stereochemistry of 3a was determined by J -resolved
homonuclear coupling.
In ser t ion of CH 2N2 a n d P r ep a r a t ion of (p in a -
cola to)2BCH2B a n d (p in a cola to)2BCH2CH2B. BCB
compounds are usually prepared by double hydrobora-
tion of terminal alkynes with dialkylboranes.22 They are
interesting precursors to gem-bimetallics such as BCLi23
and BCMgX.24 We report here that the parent com-
pound, (pinacolato)2BCH2B, can be prepared in high
yield by reaction with diazomethane (eq 2). This reaction
has not been described before.
The intermediate enol borates, 2, are moisture-
sensitive and were not isolated. Compounds 3a -d are
stable, and their structures were determined by 1H, 13C,
and 11B NMR, GCMS, and elemental analyses. The
methylene protons in compounds 3a ,c,d are diaste-
reotopic and gave two signals in the 1H NMR. The
assignments were confirmed by 2D C-H HETCOR and
3
APT experiments. The J H-H coupling constants (for
3c,d ) are consistent with the assignments. In the 1H
and 13C NMR spectra of compounds 3c,d the diaste-
reotopic methyl groups in pinacol gave different signals.
This was not observed in compounds 3a ,b. However, the
diastereotopic isopropyl methyl groups in 3a showed
different signals. This may partially be due to hindered
rotation of the isopropyl group next to the bulky
dioxaborolane group. The peaks of the isopropyl methyl
groups are located at 0.82 and 0.97 ppm, showing shifts
of 0.1 ppm upfield and 0.4 ppm downfield, respectively,
The reaction of diazomethane with bis(pinacolato)-
diborane(4) gave good results. Insertions into (R2N)2B-
B(NR2)2, where R ) Me, Et, Pr, were not successful. Two
mechanisms for the insertion are possible: (1) addition/
1,2-migration to and from boron as in the Hooz reac-
(17) Teichmann, J .; Stock, H.; Pritzkow, H.; Siebert, W. Eur. J .
Inorg. Chem. 1998, 459.
(18) Brotherton, R. J .; McCloskey, A. L.; Boone, J . L.; Manasevit,
H. M. J . Am. Chem. Soc. 1960, 82, 6245.
(19) A special import license is required in Israel to order dimethy-
lamine and its derivatives from Aldrich.
(20) (a) No¨th, H.; Z. Naturforsch. 1984, 39b, 1463. (b) Abu Ali, H.;
Goldberg, I. ; Srebnik, M. Inorg. Chem., submitted for publication. (c)
Abu Ali, H.; Goldberg, I. ; Srebnik, M. Acta Crystallogr., in press.
(21) (a) Evans, D. A.; Fu, G. C. J . Org. Chem. 1990, 55, 5678. (b)
Mastumoto, Y.; Hayashi, T. Synlett 1991, 349.
(22) (a) With tetraethyldiborane(4): Ko¨ster, R.; Binger, P. Angew.
Chem. 1962, 74, 652. (b) With 9-BBN: Brown, H. C.; Rhodes, S. P. J .
Am. Chem. Soc. 1969, 91, 4306. (c) With tetracyclohexyldiborane:
Zweifel, G.; Arzoumanian, H. J . Am. Chem. Soc. 1967, 89, 291.
(23) (a) Zweifel, G.; Fischer, R. P.; Horng, A. Synthesis 1973, 37. (b)
Ashe, A. J ., III; Shu, P. J . Am. Chem. Soc. 1971, 93, 1804. (c) Cainelli,
G.; Dal Bello, G.; Zubiani, G. Tetrahedron Lett. 1966, 4315. (d)
Mukaiyama, T.; Murakami, M.; Oriyami, T.; Yamaguchi, M. Chem.
Lett. 1981, 1193.
(24) Reddy, C. K.; Periasamy, M. Tetrahedron Lett. 1993, 49, 8877.

3964 Organometallics, Vol. 20, No. 18, 2001
Notes
1H and 13C NMR spectra were recorded in CDCl3 solution
with a Varian Unity spectrometer (300 or 75 MHz) using Me4-
Si as an internal standard. 11B NMR spectra were recorded
Ta ble 1. Cou p lin g of ICH2BX2 w ith Differ en t
Meta lsa
entry
metal/excess, %
solvent
BCCB:BCBb
% yieldc
with
a Bruker MSL-400 spectrometer (128 MHz) using
1
2
3
4
5
6
Na/15
Na/35
Na/15
Na/15
K/15
benzene
benzene
toluene
THF
benzene
ether
34:66
96:4
84:16
68:32
67:33
50:50
94
94
90
85
88
85
BF3‚OEt2 as an external standard. GCMS analyses were
performed on an HP GCMS instrument (Model GCD PLUS),
with an EI detector and 30 m methyl silicone column.
Dibor on Rea gen t. Bis(pinacolato)diborane(4) was pre-
pared from tetrakis(pyrrolidino)diborane(4) by Wurtz coupling
of bis(pyrrolidino)bromoborane and then obtained by solvolysis
of tetrakis(pyrrolidino)diborane(4) with 2 equiv of pinacol in
benzene solution at room temperature.20
Mg/60
a
b
X2 ) pinacolato. Conditions: overnight reflux. Determined
by GCMS. c Isolated yield for both BCCB and BCB before purifica-
tion by column chromatography.
Gen er a l P r oced u r e for Hyd r obor a tion of Va r iou s
Un sa tu r a ted Ca r bon yl Com p ou n d s. A dry nitrogen-flushed
50 mL flask equipped with a magnetic stirring bar and a reflux
condenser attached to a mercury bubbler through a septum
inlet was charged with Pt(PPh3)4 (56 mg, 0.045 mmol) and bis-
(pinacolato)diborane(4) (381 mg, 1.5 mmol). The carbonyl
compound (1.4 mmol) dissolved in 20 mL of toluene was then
added. After the mixture was stirred overnight at 110 °C, the
toluene was removed under vacuum. The mixture was washed
with a small amount of cold water and extracted with pentane.
The extracts were dried over anhydrous magnesium sulfate.
The pentane was removed under vacuum, and the product was
purified by silica gel column chromatography, with 10% ether/
petroleum ether as eluent.
tion25 or (2) oxidative addition of B-B to a Pt(0)
complex, insertion of CH2 into the Pt-B bond, migra-
tion, and reductive elimination.11 No insertion was
observed without Pt(0); therefore, the latter mechanism
is probably operating. However, reaction of ethyl diaz-
oacetate with bis(pinacolato)diborane(4) with or without
a transition metal did not give any products.
We developed an alternative synthesis of diboryl-
methane and 1,2-diborylethane from (pinacolato)BCH2I26
by coupling with metals (eq 3). The quantity and the
3a : 80% (0.3 g) yield. 1H NMR (CDCl3): δ 0.82 (d, 3H, CH3,
3
3J H-H ) 6.6 Hz), 0.97 (d, 3H, CH3, J H-H ) 6.6 Hz), 1.23 (s,
12H, CH3), 1.46 (m, 1H, CHB), 1.53 (m, 1H, CH2), 1.78 (m,
1H, CH), 1.81 (m, 1H, CH), 1.98 (m, 1H, CH2), 2.3 (m, 2H,
CH2(CdO)), 2.37 (m, 2H, CH2(CdO)). 13C{1H} NMR (CDCl3):
δ 16.67 (CH3), 21.75 (CH3), 24.65 (CH3), 27.20 (CH2), 30.75
(CH), 41.72 (CH2), 41.70 (CH2), 42.64 (CH), 83.37 (CCH3),
212.54 (CdO) (CHB cannot be detected). 11B NMR (CDCl3): δ
33.46. Anal. Calcd for C15H27O3B: C, 67.73; H, 10.35. Found:
C, 67.35; H, 10.56. MS (EI): m/z (%) 266 (M+, 5.74), 251 (2.06),
209 (12.87), 165 (29.64), 141 (9.35), 123 (47.74), 83 (100), 69
(25.47), 41 (78.36), 28 (19.75).
3b: 86% (0.29 g) yield. 1H NMR (CDCl3): δ 1.21 (s, 12H,
CH3), 1.44 (m, 2H, CH2), 1.59 (m, 2H, CHB), 1.84 (m, 2H, CH2),
1.92 (m, 2H, CH2), 2.50 (m, 4H, CH2). 13C{1H} NMR (CDCl3):
δ 23.85 (CH2), 30.60 (CH2), 31.39 (CH2), 43.29 (CH2), 44.37
(CH2), 82.98 (CCH3), 215.06 (CdO), 20.11 (CHB, broad). 11B
NMR (CDCl3): δ 33.78. Anal. Calcd for C13H23O3B: C, 65.60;
H, 9.76. Found: C, 65.38; H, 9.72. MS (EI): m/z (%) 238 (M+,
6.47), 223 (3.60), 210 (1.28), 180 (100), 165 (14.85), 152 (33.29),
129 (23.47), 110 (25.60), 95 (34.39), 83 (57.08), 69 (31.28), 55
(62.41), 41 (73.63), 28 (8.31).
metal determine the ratio of BCB/BCCB (Table 1). The
best results for BCCB were obtained by using a 35%
excess of Na, whereas for BCB a 15% excess of Na was
superior. Both (pinacolato)2BCH2B and (pinacolato)2-
BCH2CH2B could be hydrolyzed to the free bis boronic
acids by refluxing for 3 h in aqueous HCl (eq 3). Both
BCCB and the BCB esters and acids are stable to
moisture and heat. The esters are extremely soluble in
hydrocarbon and polar solvents, but the acids are
soluble only in water and DMSO. The methylene
protons in the BCCB ester (0.85 ppm) are shifted upfield
relative to the protons in the BCB compound (1.25 ppm).
Both the BCB and BCCB esters showed M+-Me in their
MS spectra. A prominent M+ - 141 peak at m/e 141
was observed for the BCCB ester. However, a prominent
M+ - 184 peak at m/e 84 was observed for the BCB
ester.
3c: 74% (0.27 g) yield. 1H NMR (CDCl3): δ 1.66 (s, 6H, CH3),
3
2
1.24 (s, 6H, CH3), 2.81 (m, 2H, CH2, J H-H ) 5.15, J H-H
)
11.21, 3J H-H ) 18.4 Hz), 3.04 (dd, 1H, CH, 3J H-H ) 5.15, 3J H-H
) 18.4 Hz), 7.25 (m, 5H, Ph), 9.80 (s, 1H, CdO(H)). 13C{1H}
NMR (CDCl3): δ 24.46 (CH3), 24.53 (CH3), 47.54 (CH2), 83.64
(CCH3), 125.72 (para CH), 128.42 (ortho or meta CH), 128.57
(ortho or meta CH), 141.18 (ipso), 201.86 (CdO) (CHB cannot
be detected). 11B NMR (CDCl3): δ 32.88. Anal. Calcd for
C
15H21O3B: C, 69.29; H, 8.16. Found: C, 69.83; H, 7.98. MS
(EI): m/z (%) M+ 260, 245 (M+ - 15, 1.43), 202 (4.96), 177
(6.25), 160 (12.75), 145 (30.89), 132, (56.48), 117 (100), 105
(27.11), 77 (31.50), 84 (49.64) 59 (29.06), 43 (91.38).
Exp er im en ta l Section
Gen er a l Com m en ts. All reactions were carried out under
a
nitrogen atmosphere using vacuum line and glovebox
3d : 68% (0.28 g) yield. 1H NMR (CDCl3): δ 1.17 (s, 6H,
techniques. Solvents were purified by distillation from ap-
propriate drying agents under a nitrogen atmosphere. Starting
materials were purchased from commercial suppliers and used
without further purification.
3
2
CH3), 1.22 (s, 6H, CH3), 2.67 (dd, 1H, CH2, J H-H ) 5.2, J H-H
2
3
) 11.4 Hz), 2.74 (dd, 1H, CH2, J H-H ) 11.4, J H-H ) 18.35
Hz), 2.89 (dd, 1H, CH, 3J H-H ) 5.2, 3J H-H ) 18.35 Hz), 3.65 (s,
3H, OCH3), 7.25 (m, 5H, Ph). 13C{1H} NMR (CDCl3): δ 24.45
(CH3), 24.56 (CH3), 37.10 (OCH3), 51.57 (CH2), 83.56 (CCH3),
125.67 (para CH), 128.16 (ortho or meta CH), 128.38 (ortho or
meta CH), 141.27 (ipso), 173.82 (CdO) (CHB cannot be
detected). 11B NMR (CDCl3): δ 32.98. Anal. Calcd for
(25) (a) Hooz, J .; Morrison, G. F. Can. J . Chem. 1970, 48, 868. (b)
Hooz, J .; Gunn, D. M. Tetraheedron Lett. 1969, 3455. (c) Hooz, J .; Linke,
S. J . Am. Chem. Soc. 1968, 90, 5936. (d) Hooz, J .; Gunn, D. M.; Kono,
H. Can. J . Chem. 1971, 49, 2371. (e) Hooz, J .; Gunn, D. M. J . Chem.
Soc., Chem. Commun. 1969, 139.
(26) Matteson, D. S.; Majumdar, D. J . Organomet. Chem. 1979, 170,
259.
C
16H23O4B: C, 66.26; H, 8.01. Found: C, 66.63; H, 7.95. MS
(EI): m/z (%) 290 (M+, 16.40), 259 (4.59), 232 (13.97), 201

Notes
Organometallics, Vol. 20, No. 18, 2001 3965
(1.44), 190 (20.94), 159 (3.70), 146 (21.98), 131 (54.35), 105
(28.44), 104 (100), 83 (54.65), 77 (11.91), 59 (23.15), 43 (26.51).
P r ep a r a tion of (p in a cola to)2BCH2B by Dia zom eth a n e
In ser tion . A dry nitrogen-flushed 50 mL flask equipped with
a magnetic stirring bar was charged with Pt(PPh3)4 (74.7 mg,
0.06 mmol) and bis(pinacolato)diborane(4) (508 mg, 2 mmol);
20 mL of diethyl ether was then added to the mixture.
Diazomethane27 (0.0168 mg/mL in ether, 5 mL, 0.084 mg) was
slowly added to the mixture at 0 °C. After an additional 2 h
the solution was warmed to room temperature and stirred
overnight. The solvent was removed under vacuum, and the
residue was extracted with pentane, which was then removed
under vacuum, and the product was purified by silica gel
column chromatography with 10% ether/petroleum ether as
eluent to give the product as a colorless oil in 83% (0.44 g)
yield. 1H NMR (CDCl3): δ 1.23 (s, 24H, CH3), 1.25 (s, 2H, CH2).
13C{1H} NMR (CDCl3): δ 25.11 (CH3), 83.25 (CCH3), (CHB
cannot be detected). 11B NMR (CDCl3): δ 34.12. Anal. Calcd
for C13H26O4B2: C, 58.26; H, 9.7. Found: C, 58.63; H, 9.65. MS
(EI): m/z (%) 268 (M+, 1.01), 253 (40.65), 238 (2.59), 210 (1.99),
195 (1.29), 168 (9.97), 153 (8.27), 126 (11.45), 127 (8.45), 113
(3.89), 84 (100), 69 (16.17), 55 (10.92), 41 (16.39).
Gen er a l P r oced u r e for t h e Cou p lin g R ea ct ion of
(p in a cola to)BCH2I. A solution of (pinacolato)boratamethyl-
ene iodide, (pinacolato)BCH2I26 (5.36 g, 0.02 mol), in 10 mL of
the indicated solvent was added slowly to a mixture of the
metal (0.02 mol + excess) and 15 mL of solvent and heated at
reflux overnight. The resulting solid was filtered, and the
solvent was then removed under vacuum. See Table 1 for
detailed reaction conditions. The two products were purified
by silica gel column chromatography with 10% ether/petroleum
ether as eluent to give pure colorless oily compounds.
(p in a cola to)2BCH2CH2B. 1H NMR (CDCl3): δ 0.85 (s, 4H,
CH2), 1.24 (s, 24H, CH3). 13C{1H} NMR (CDCl3): δ 4.45 (s,
broad, CH2B), 24.72 (CH3), 82.70 (CCH3). 11B NMR (CDCl3):
δ 32.98. Anal. Calcd for C14H28O4B2: C, 59.62; H, 10.00.
Found: C, 59.91; H,10.07. MS (EI): m/z (%) 282 (M+), 267 (M+
- 15, 1.40), 253 (0.03), 224 (17.06), 209 (0.06), 185 (1.69), 167
(5.74), 141 (100), 101 (10.09), 84 (31.38), 69 (8.5), 55 (10.33),
41 (12.53).
(HO)2BCH2CH2B(OH)2. Four milliliters of 6 M HCl was
added with stirring to (pinacolato)2BCH2CH2B (0.7 g, 2.6
mmol) dissolved in 5 mL of water. The mixture was heated at
reflux for 3 h. The water was then removed under vacuum
and the residue washed twice with ether and dried under
vacuum to give the product as a pure solid in 90% (0.28 g)
yield, mp 262 °C. Anal. Calcd for C2H8O4B2: C, 20.41; H, 6.85.
Found: C, 20.19; H, 6.76. 1H NMR (DMSO): δ 0.55 (s, 4H,
CH2), 7.28 (s, broad, 4H, OH). 13C{1H} NMR (DMSO-d6): δ
9.13 (s, broad, CH2B). 11B NMR (DMSO-d6): δ 33.78.
(HO)2BCH2B(OH)2. Three milliliters of 6 M HCl was added
with stirring to (pinacolato)2BCH2B (0.35 g, 1.31 mmol)
dissolved in 5 mL of water. The mixture was heated at reflux
for 3 h. The water was then removed under vacuum and the
residue washed twice with ether and dried under vacuum to
give the product as a pure solid in 93% (0.12 g) yield; mp 245
°C. Anal. Calcd for CH6O4B2: C, 11.58; H, 5.85. Found: C,
1
11.42; H, 5.91. H NMR (DMSO): δ 1.18 (s, 2H, CH2), 7.31 (s,
broad, 4H, OH). 13C{1H} NMR (DMSO-d6): δ 10.21 (s, broad,
CH2B). 11B NMR (DMSO-d6): δ 34.93.
Ack n ow led gm en t. We thank the Israeli Academy
of Sciences and the Grass Center for Drug Design at
the School of Pharmacy for support of this work.
(27) de Boer, T. J .; Backer, H. J . Recl. Trav. Chim. Pays-Bas 1954,
73, 229.
OM010282R