Hydroboration and haloboration of propyne and 1-butyne

Article abstract of DOI:10.1515/znb-2002-0306

Hydroboration of propyne and 1-butyne with HBCl₂ obtained from BCl₃ and Me₃SiH in equimolar amounts leads to 1,1-bis(dichloroboryl)alkanes 1. When BCl₃ is used in excess, no 1,1-bis(dichloroboryl)alkanes 1 but E

Full text of DOI:10.1515/znb-2002-0306

Hydroboration and Haloboration of Propyne and 1-Butyne
Michael J. Bayer, Hans Pritzkow, and Walter Siebert
Anorganisch-Chemisches Institut der Universita¨t Heidelberg,
Im Neuenheimer Feld 270, D-69120 Heidelberg
Reprint requests to Prof. W. Siebert. Fax: + 49 (0)6221-545609.
E-mail: ci5@ix.urz.uni-heidelberg.de
Dedicated to Prof. Donald S. Matteson
Z. Naturforsch. 57 b, 295–300 (2002); received December 20, 2001
Hydroboration, Haloboration, Boron
Hydroboration of propyne and 1-butyne with HBCl2 obtained from BCl3 and Me3SiH in
equimolar amounts leads to 1,1-bis(dichloroboryl)alkanes 1. When BCl3 is used in excess,
no 1,1-bis(dichloroboryl)alkanes 1 but E-1-dichloroborylalkene 2 besides E-1-dichloroboryl-2-
chloro-alk-1-ene 3 are formed. Other by-products are tris(2-chloro-alk-1-ene-1-yl)borane4 and
bis(2-chloro-alk-1-ene-1-yl)chloroborane 5. The reaction of 3 with catechol and the formation
of pyridine adducts of 4 and 5 lead to crystalline products. The composition of the products
was determined by NMR spectroscopy, MS spectrometry and X-ray structure analyses of 6a,
6b, 7a and 8b.
Introduction
culties in determiningthe configuration of the hex-
enylboranes [9].
In 1976 the first double hydroboration of ter-
minal alkynes with HBCl2 was reported by H. C.
Brown and N. Ravindran usingHBCl 2 OEt2/BCl3
[1] as hydroboration reagent [2]. Because hydro-
boration reactions with Me3SiH/BCl3 are more con-
venient [3], acetylene [4], 3,3-dimethyl-1-butyne
[5, 6], phenylacetylene [7], and mesitylacetylene [7]
have been hydroborated accordingto this method.
Zhao et al. [8] observed that 1-octyne and 1-hex-
yne undergo both monohydroboration and chloro-
boration when the alkyne was reacted with HBCl2
SMe2 in a 1.4 : 1 ratio at –20 C in the pres-
ence of BCl3. At 0 C double hydroboration took
place preferentially [8]. The bromoboration of 1-
hexyne, investigated by Blackborow [9], shows that
Z- or E-bromo-hex-1-ene-1-yldibromoborane (I),
Z,E- and Z,Z-bis(2-bromo-hex-1-ene-1-yl)bromo-
borane (II) and Z,Z,Z-tris(2-bromo-hex-1-ene-1-
yl)borane (III) can be prepared by addition of a
stoichiometric amount of 1-hexyne to tribromo-
borane. The Z-I, Z,Z-II and Z,Z,Z-III isomers, re-
spectively, are formed preferentially. In the case of
chloroboration no definite results regarding the pre-
ferred configurations of chlorohexenyldichlorobo-
rane, bis(chlorohexenyl)chloroborane and tris(chlo-
rohexenyl)borane were reported because of diffi-
We report here on the hydroboration of propyne
and 1-butyne with BCl3 and Me3SiH in equimo-
lar amounts, which leads to the expected 1,1-bis-
(dichloroboryl)alkanes 1, whereas the reaction of
propyne with BCl3 and Me3SiH in the molar ratio
1.25 : 1 forms a product mixture of monohydrobo-
rated and haloborated compounds. Furthermore the
chloroboration products of propyne and 1-butyne
were investigated. This included substitution reac-
tions of the organo-chloroborane products to obtain
crystalline derivatives, suitable for X-ray structure
analyses.
Results and Discussion
Synthesis and reactivity of organo-chloroboranes
Hydroboration of propyne and 1-butyne with
equimolar amounts of Me3SiH and BCl3 at –78 C
in pentane leads to the products 1a and 1b, respec-
tively, in good yields. The NMR spectra of 1a are in
1
agreement with the reported data [6]. The H, 11B
and 13C NMR spectra of 1b exhibit the expected
c
¨
¨
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M. J. Bayer et al. · Hydroboration and Haloboration of Propyne and 1-Butyne
Table 1. Crystal data and structure refinement for 6a, 7a, 6b, and 8b.
6a
7a
6b8b
Empirical formula
Formula weight
Crystal system
Space group
C9H8BClO2
194.42
monoclinic
P21/n
11.075(7)
5.449(2)
15.337(10)
90
C14H17BCl3N
316.46
orthorhombic
P212121
9.2888(4)
9.9593(5)
17.5772(8)
90
C10H10BClO2
208.44
monoclinic
P21/n
5.3239(3)
16.5545(9)
11.3143(6)
90
C13H17BCl3N
304.44
triclinic
¯
P1
˚
Unit cell dims: a [A]
8.2252(4)
9.4989(5)
10.6474(5)
105.541(1)
99.737(1)
96.955(1)
777.7(1)
2
˚
b [A]
c [A]
˚
[ ]
[ ]
[ ]
100.21(5)
90
90
94.070(1)
90
90
3
˚
Volume [A ]
910.8(9)
4
1626.1(1)
4
994.7(1)
4
Z
Calcd. density [g/cm3]
1.418
1.293
1.392
1.300
1
Absorp. coeff. [mm
F(000)
]
0.38
0.55
0.350
0.571
400
656
432
316
Crystal size [mm]
Temperature [K]
0.08 0.12 0.42
173
0.28 0.30 0.38
173
0.45 0.30 0.29
190
0.48 0.37 0.30
190
[ ]
28.35
28.27
32.24
32.40
max
Unique reflections
Observed refls [I > 2 (I)]
Parameters
Final R1 [I > 2 (I)]
Final wR2
Largest diff. peak/hole [e/A ]
(8422)
(6709)
151
0.0562
0.1802
+0.44/–0.34
3865
3303
5146
3551
2836
4432
240
170
231
0.0286
0.0711
+0.28/–0.13
0.0352
0.1039
+0.40/–0.22
0.0369
0.1058
3
˚
+1.06/–0.60
signals (for details see experimental section). An EI
mass spectrum of 1b shows the molecular ion peak
[M+] at m/z = 218.
chloroborane (5a) which also should be formed
as intermediate duringthe chloroboration of three
Both hydroboration 2 and chloroboration prod- molecules of propyne. Heatingof compound 3 leads
ucts 3 and 4 are obtained in the reaction of propyne to the symmetrical product 4 with elimination of
and 1-butyne, respectively, with BCl3 and Me3SiH BCl3.
in the molar ratio 1.25 : 1. The isolation of the com-
In order to have evidence for the exact configura-
pounds 2 and 3 is difficult because of similar boil- tion the products 3, 4 and 5b were reacted with cate-
ingpoints. Compounds 3 and 4 are also formed chol or pyridine to obtain crystalline derivatives ap-
in absence of Me3SiH in excellent yields. Depend- propriate for X-ray structure analyses. Compounds
ingon how longpropyne or 1-butyne, respectively,
3a, b gave the substitution products 6a, b, while 4
is bubbled through the reaction solution, the prod- and 5b yielded the donor-acceptor compounds 7a,
uct ratio of monoalkenylated to trisalkenylated bo- 7b and 8b.
rane varies. In the case of 1-butyne, the appear-
ance of E,E-bis(2-chloro-but-1-ene-1yl)chlorobor- monoalkenylated 6a and 6b, the bisalkenylated 8b
ane (5b) is observed. It is surprisingthat no indi- and the trisalkenylated compound 7a have E con-
The crystal structure analyses reveal that the
cation is found for the existence of bis(propenyl)- figuration. Most probably the kinetically preferred
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M. J. Bayer et al. · Hydroboration and Haloboration of Propyne and 1-Butyne
297
Fig. 1. Structure of 6a in the crystal; selected bond lengths
˚
[A] and angles [ ]: B1-C1 1.532(2), C1-C2 1.320(2), C2-
Cl1 1.760(2), C2-C3 1.483(3), B1-O1 1.392(2), B1-O2
1.396(2), C1-B1-O1 121.8(1), C1-B1-O2 127.7(2), O1-
B1-O2 110.6(1).
Fig. 3. Structure of 7a in the crystal; selected bond lengths
˚
[A] and angles[ ]: B1-C1 1.627(2), B1-C4 1.627(2),
B1-C7 1.623(2), B1-N1 1.646(2), C1-C2 1.319(2), C4-
C5 1.324(2), C7-C8 1.324(2), C2-Cl1 1.785(2), C5-Cl2
1.777(1), C8-Cl3 1.782(2), C1-B1-N1 103.8(1), C4-B1-
N1 108.6(1), C7-B1-N1 108.1(1), C1-B1-C4 110.9(1),
C1-B1-C7 116.5(1), C4-B1-C7 108.6(1).
Fig. 2. Structure of 6b in the crystal; selected bond lengths
˚
[A] and angles [ ]: B1-C7 1.534(2), C7-C8 1.317(2), C8-
Cl1 1.757(1), B1-O1 1.395(1), B1-O2 1.395(1), C7-B1-
O1 127.1(1), C7-B1-O2 121.8(1), O1-B1-O2 111.1(1).
Z-isomers are formed first at low temperature. Un-
der distillation conditions the activation energy nec-
essary for isomerisation is supplied, so that finally
the thermodynamically most stable E-configurated
products are formed. The olefinic protons of 3b,
4b, 5b, 6b, 7b and 8b would be expected to show
a triplet pattern, however, the fine structures were
not well resolved and therefore the resonances were
treated as “singlets”.
Fig. 4. Structure of 8b in the crystal; selected bond lengths
˚
[A] and angles[ ]: B1-C1 1.603(2), B1-C5 1.606(2),
B1-Cl1 1.923(1), B1-N1 1.617(2), C1-C2 1.331(2), C5-
C6 1.331(2), C2-Cl2 1.771(1), C6-Cl3 1.778(1), C1-B1-
C5 116.1(1), C1-B1-N1 111.8(1), C5-B1-N1 107.7(1),
C1-B1-Cl1 107.2(1), C5-B1-Cl1 110.7(1), N1-B1-Cl1
102.5(1).
Crystal structures of 6a, 6b, 7a and 8b
To elucidate the structures, X-ray diffraction
studies were carried out (crystal data and structure
refinement parameters for 6a, 6b, 7a and 8b are
presented in Table 1). The colorless crystals of 6a,
grown at –30 C from a solution in dichloromethane,
belongto the monoclinic system, space group P2 /n.
The molecular structure is shown in Fig. 1. The co-
ordination of the boron atom is trigonal planar.
monoclinic space group P21/n. The molecular struc-
ture is shown in Fig. 2. For all distances and bonding
angles no significant differences in comparison to
the structural data of 6a are observed.
1
Crystals of 7a and 8b were grown from toluene
A single crystal of 6b was grown from a solution at –30 C. 7a crystallizes in the orthorhombic space
in dichloromethane at 20 C. 6b crystallizes in the group P212121, while 8b belongs to the triclinic
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298
M. J. Bayer et al. · Hydroboration and Haloboration of Propyne and 1-Butyne
¯
space group P1. The molecular structures are shown the residue is distilled to yield 38.4 gof 2a (55.1%), 12.3 g
of 3a (13.7%) and 5.4 gof 4a (4.0%). 2a: B. p. 40 C /
200 mbar. – H NMR (200.13 MHz, CDCl3): = 1.98
in Figs 3 and 4. The coordination of the boron atoms
is distorted tetrahedral. The B-N distances (1.646
and 1.617 A) are in agreement with those found in
1
3
4
˚
(dd, J = 6.6 Hz, J = 1.5 Hz, 3 H, CHCH3), 6.08 (dq,
3J = 17.2 Hz, 4J = 1.5 Hz, 1 H, BCH), 7.10 - 7.29 (m, 1
other pyridine adducts [10, 11].
H, CHCH3). – 13
C
1H NMR (50.32 MHz, CDCl3):
=
22.0 (CHCH3), 132 (br., BCH), 160.8 (CHCH3). – 11B
NMR (64.21 MHz, CDCl3): = 52.5. – MS (EI, 70 eV):
m/z (%) = 122 (23) [M+], 86 (100) [C3H4BCl+].
Experimental Section
All experiments were performed under argon using
the Schlenk technique. Solvents were dried, distilled and
3a: B. p. 65 C / 200 mbar. – 1H NMR (200.13 MHz,
saturated with nitrogen. Glassware was dried with a heat- CDCl3): = 2.60 (d, 4J = 0.8 Hz, 3 H, CClCH3), 6.22 (q,
gun under high vacuum. – 1H, 13C and 11B NMR: Bruker
DRX 200 spectrometer, Et2O BF3 was used as the exter- CDCl3):
4J = 0.8 Hz, 1 H, BCH). – 13C 1H NMR (50.32 MHz,
= 26.4 (CClCH3), 128 (br., BCH), 162.9
nal standard for 11B NMR. As internal references for 1H (CClCH3). – 11B NMR (64.21 MHz, CDCl3): = 50.5. –
and 13C NMR spectra the signals of the deuterated sol-
MS (EI, 70 eV): m/z (%) = 156 (15) [M+], 120 (54) [M+
+
vents were used and calculated for TMS. The mass spectra - HCl], 81 (100) [BCl2 ]. – HR-MS (EI): m/z = 155.9504
were measured on a ZAB-2F VH Micromass CTD spec- (M+), calcd. 12C3 H411B135Cl3: 155.9472 ( = 3.3 mmu).
1
trometer (EI and HR-EI techniques) and on a Jeol MS
station JMS 700 (EI, and HR-EI techniques). – Melting CDCl3): = 2.32 (d, 4J = 0.6 Hz, 9 H, CClCH3), 6.3 (br.,
points (uncorrected) were measured with a Bu¨chi appa- 3 H, BCH). – 13C 1H NMR (50.32 MHz, CDCl3):
4a: B. p. 120 C / 200 mbar. – 1H NMR (200.13 MHz,
=
ratus usingcapillaries which were filled under argon or
26.4 (CClCH3), 134 (br., BCH), 152.3 (CClCH3).- 11B
nitrogen and sealed.
NMR (64.21 MHz, CDCl3): = 54.7. – MS (EI, 70 eV):
m/z (%) = 236 (1) [M+], 196 (18) [M+ - C3H4], 161 (33)
+
[M+ - C3H4Cl], 41 (100) [C3H5 ]. – HR-MS (EI): m/z =
1,1-Bis(dichloroboryl)butane (1b)
1
236.0071 (M+), calcd. 12C9 H1211B135Cl3: 236.0045 (
=
Dried 1-butyne is bubbled at –78 C through a solution
of 76 g(0.65 mol) of BCl 3 in 250 ml of pentane. At the
same time a solution of 48.3 g(0.65 mol) of trimethylsi-
lane in 50 ml of pentane is added slowly via a dropping
funnel so that almost all 1-butyne passingthrough the so-
2.6 mmu).
Alternative synthesis of 3a and 4a
Dried propyne is bubbled at –78 C through a solution
lution is absorbed. Then the reaction mixture is allowed of 47.3 g(0.4 mol) of BCl 3 in 250 ml of pentane for 1 h.
to warm to 20 C. After removal of the pentane at 50 mbar Then the reaction mixture is allowed to warm to 20 C.
the residue is distilled to yield 61.1 gof 1b (85.8%). – An 11B NMR spectrum of the crude product shows that
B. p. 85 C/200 mbar. – 1H NMR (200.13 MHz, CDCl3): only 3a is formed. Then pentane is removed in a vacuum
3
= 0.91 (t, J = 7.2 Hz, 3 H, CH2CH3), 1.32 (m, 2 and the residue is purified by distillation to give 42.7 g of
H, CH2CH3), 1.94 (m, 2 H, B2CHCH2), 2.62 (m, 1 H, 3a (67.6%) and 5.7 gof 4a (6.0%).
B2CHCH2). – 13
C
1H NMR (50.32 MHz, CDCl3):
=
14.3 (CH2CH3), 24.9 (CH2CH3), 32.9 (B2CHCH2), 49
E-1-Dichloro-2-chloro-but-1-ene (3b), E,E-bis(2-chloro-
but-1-ene-1-yl)chloro-borane (5b) and E,E,E-tris(2-
chloro-but-1-ene-1-yl)borane (4b)
(br., B2CHCH2). – 11B NMR (64.21 MHz, CDCl3):
=
60.3. – MS (EI, 70 eV): m/z (%) = 218 (1) [M+], 183 (3)
+
[M+ - Cl], 102 (100) [M+ - Cl - BCl2], 81 (89) [BCl2 ],
+
+
Dried 1-butyne is bubbled at –78 C through a solution
of 47.3 g(0.4 mol) of BCl 3 in 250 ml of pentane for 3 h.
Then the reaction mixture is allowed to warm to 20 C.
After removal of pentane at 50 mbar the residue is distilled
to yield 54.8 gof 3b (79.1%, B. p. 88 C / 160 mbar) and
4.3 gof 5b (4.7%, B. p. 52 C / 0.05 mbar). A third fraction
43 (66) [C3H7 ], 29 (67) [C2H5 ].
E-1-Dichloroboryl-prop-1-ene (2a), E-1-dichloroboryl-
2-chloro-prop-1-ene (3a) and E,E,E-tris(2-chloro-prop-
1-ene-1-yl)borane (4a)
Dried propyne is bubbled at –78 C through a solution is obtained at 90 - 100 C / 0.05 mbar consistingof 3.17 g
of 67 g(0.55 mol) of BCl 3 in 150 ml of pentane. At the of 5b (3.5%) and 2.22 gof 4b (2.0%). The separation of
same time a solution of 29.0 g(0.39 mol) of trimethylsi-
lane in 50 ml of pentane is added slowly via a dropping NMR). 3b: B. p. 88 C/160 mbar. – H NMR (200.13
4b from 5b was not possible (yield determined by 11B
1
3
funnel so that almost all propyne passingthrough the so-
MHz, CDCl3): = 1.23 (t, J = 7.4 Hz, 3 H, CH2CH3),
lution is absorbed. Then the reaction mixture is allowed 2.93 (q, 3J = 7.4 Hz, 2 H, CH2CH3), 6.24 (s, 1 H, BCH). –
to warm to 20 C. After removal of the pentane at 50 mbar 13C 1H NMR (50.32 MHz, CDCl3): = 13.0 (CH2CH3),
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M. J. Bayer et al. · Hydroboration and Haloboration of Propyne and 1-Butyne
299
32.0 (CH2CH3), 127 (br., BCH), 169.1 (CClCH2). – 11
B
(q, 3J = 7.4 Hz, 2 H, CH2CH3), 5.86 (s, 1 H, BCH), 7.00
NMR (64.21 MHz, CDCl3): = 50.4. – MS (EI, 70 eV): - 7.25 (m, 4 H, C6H4). – 13C 1H NMR (50.32 MHz,
m/z (%) = 170 (6) [M+], 155 (1) [M+ - CH3], 134 (7) [M+ CDCl3): = 13.2 (CH2CH3), 32.3 (CH2CH3), 112.5,
- HCl], 98 (16) [M+ - 2HCl], 81 (76) [BCl2 ], 54 (100) 122.8, 147.8 (C6H4), 159 (br., BCH), 162.2 (CClCH2).
+
+
[C4H6 ], 36 (90) [HCl+]. – HR-MS (EI): m/z = 169.9636
–
11B NMR (64.21 MHz, CDCl3): = 29.9. – MS (EI,
1
(M+), calcd. 12C4 H611B135Cl3: 169.9628 ( = 0.8 mmu). 70 eV): m/z (%) = 208 (13) [M+], 173 (2) [M+ - Cl],
1
5b: B. p. 52 C/0.05 mbar. – H NMR (200.13 MHz, 154 (100) [M+ - C4H6], 144 (7) [M+ - Cl - C2H5], 119 (2)
3
CDCl3): = 1.21 (t, J = 7.4 Hz, 6 H, CH2CH3), 2.79 [C6H4O2B+]. – HR-MS (EI): m/z= 208.0465 (M+), calcd.
(q, J = 7.4 Hz, 4 H, CH2CH3), 6.22 (s, 2 H, BCH). -
C
1H1011B135Cl116O2: 208.0468 ( = 0.3 mmu).
10
3
12
13C 1H NMR (50.32 MHz, CDCl3): = 13.1 (CH2CH3),
32.4 (CH2CH3), 130 (br., BCH), 163.3 (CClCH2). – 11
B
E,E,E-Tris(2-chloro-prop-1-ene-1-yl)borane-pyridine
NMR (64.21 MHz, CDCl3): = 53.7. - MS (EI, 70 eV):
m/z (%) = 224 (14) [M+], 189 (24) [M+ - Cl], 134 (100)
[M+ - H - C4H6Cl], 98 (97) [M+ - H - HCl - C4H6Cl],
adduct (7a)
The solution of 0.51 g(2.1 mmol) of 4a in 20 ml of
pentane is cooled to –10 C and 0.17 g(2.1 mmol) of
pyridine is added dropwise. After the solution is allowed
to warm to 20 C, pentane is removed in a vacuum to
yield 0.64 gof colorless 7a (94.1%). – M. p. 78 C. – 1H
NMR (200.13 MHz, CDCl3): = 1.95 (d, 4J = 0.8 Hz, 9
H, CClCH3), 5.84 (q, 4J = 0.8 Hz, 3 H, BCH), 7.66 (m,
2 H, py-H), 8.07 (m, 1 H, py-H), 8.66 (m, 2 H, py-H). –
13C 1H NMR (50.32 MHz, CDCl3): = 24.4 (CClCH3),
138 (br., BCH), 145.7 (CClCH3), 126.1, 135.0, 140.9 (py-
C). – 11B NMR (64.21 MHz, CDCl3): = –3.3.
+
54 (91) [C4H6 ]. – HR-MS (EI): m/z = 224.0837 (M+),
1
calcd. 12C8 H1211B135Cl3: 224.0878 ( = 4.1 mmu).
4b:1H NMR(200.13 MHz, CDCl3): =1.15(t, 3J=7.4
Hz, 9 H, CH2CH3), 2.59 (q, 3J = 7.4 Hz, 6 H, CH2CH3),
6.25 (s, 3 H, BCH). - 13C 1H NMR (50.32 MHz,
CDCl3): = 13.1 (CH2CH3), 32.6 (CH2CH3), 134 (br.,
BCH), 157.7 (CClCH2). - 11B NMR (64.21 MHz, CDCl3):
= 52.7. - MS (EI, 70 eV): m/z (%) = 277 (8) [M+ - H],
243 (27) [M+ - Cl], 215 (16) [M+ + H - Cl - C2H5],
189 (60) [M+ - C4H6Cl], 161 (40) [M+ + H - C4H6Cl -
+
C2H5], 99 (63) [C4H5ClB+] 55 (100) [C4H7 ]. - HR-MS
(EI): m/z = 278.0600 (M+), calcd.
C
1H1811B135Cl3:
12
12
E,E-Bis(2-chloro-but-1-ene-1-yl)chloroborane-pyridine
adduct (8b)
278.0633 ( = 3.3 mmu).
The solution of 1.03 g(4.6 mmol) of 5b in 30 ml of
pentane is cooled to –10 C and 0.36 g(4.6 mmol) of
pyridine is added dropwise. After the solution is allowed
to warm to 20 C, pentane is removed in a vacuum to
yield 1.27 gof colorless 8b (91.2%). – M. p. 72 C. – 1H
NMR (200.13 MHz, CDCl3): = 1.03 (t, 3J = 7.3 Hz, 6
H, CH2CH3), 2.39 (q, 3J = 7.3 Hz, 4 H, CH2CH3), 5.87
(s, 2 H, BCH), 7.71 (m, 2 H, py-H), 8.13 (m, 1 H, py-
H), 8.90 (m, 2 H, py-H). – 13C 1H NMR (50.32 MHz,
CDCl3): = 12.3 (CH2CH3), 30.9 (CH2CH3), 135 (br.,
E-1-[1,3,2-Benzodioxaborol-2-yl]-2-chloro-prop-1-ene
(6a)
Catechol (110 mg, 1 mmol) is dissolved in 20 ml
of CH2Cl2 and 160 mg(1 mmol) of 3a is added drop-
wise at –60 C. After the solution is allowed to warm to
20 C, CH2Cl2 is removed in a vacuum to give 169 mg
of colorless 6a (85.4%). – M. p. 48 C. – 1H NMR
4
(200.13 MHz, CDCl3): = 2.52 (d, J = 0.7 Hz, 3 H,
4
CClCH3), 5.86 (q, J = 0.7 Hz, 1 H, BCH), 7.18-7.20
BCH), 144.7 (CClCH2), 126.0, 135.0, 142.0 (py-C). – 11
B
(m, 4 H, C6H4). - 13C 1H NMR (50.32 MHz, CDCl3):
= 26.5 (CClCH3), 112.6, 123.1, 148.1 (C6H4), 153 (br.,
BCH), 156.0 (CClCH3). - 11B NMR (64.21 MHz, CDCl3):
= 30.0. - MS (EI, 70 eV):m/z (%) = 194 (28) [M+], 154
(100) [M+ - C3H4]. - HR-MS (EI): m/z = 194.0304 (M+),
NMR (64.21 MHz, CDCl3): = 2.5.
E,E,E-Tris(2-chloro-but-1-ene-1-yl)borane-pyridine
adduct (7b)
1
calcd. 12C9 H811B135Cl116O2: 194.0306 ( = 0.2 mmu).
The solution of 1.00 gof the mixture of 4b and 5b,
containing0.51 g(1.83 mmol) of 4b, in 30 ml of pentane
is cooled to –10 C and 0.31 g(3.9 mmol) of pyridine is
added dropwise. After the solution is allowed to warm to
E-1-[1,3,2-Benzodioxaborol-2-yl]-2-chloro-but-1-ene
(6b)
Catechol (1.10 g, 10 mmol) is dissolved in 80 ml of 20 C, pentane is removed in a vacuum to yield 1.23 gof
CH2Cl2 and 1.71 g(10 mmol) of 3b is added dropwise at the product mixture of 7b and 8b which contains 0.51 g
-60 C. After the solution is allowed to warm to 20 C, (77.7%) of colorless 7b. 7b: 1H NMR (200.13 MHz,
3
CH2Cl2 is removed in a vacuum to yield 1.90 gof color-
CDCl3): = 0.93 (t, J =7.3 Hz, 9 H, CH2CH3), 2.17
less 6b (91.3%). – M. p. 28 C – 1H NMR (200.13 MHz, (q, 3J = 7.3 Hz, 6 H, CH2CH3), 5.89 (s, 3 H, BCH), 7.58
CDCl3): = 1.24 (t, J = 7.4 Hz, 3 H, CH2CH3), 2.89 (m, 2 H, py-H), 8.04 (m, 1 H, py-H), 8.68 (m, 2 H, py-H). –
3
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300
M. J. Bayer et al. · Hydroboration and Haloboration of Propyne and 1-Butyne
13C 1H NMR (50.32 MHz, CDCl3): = 12.1 (CH2CH3), were refined with anisotropic displacement parameters.
31.0 (CH2CH3), 141 (br., BCH), 144.7 (CClCH2), 126.0, Hydrogen atoms were located in difference Fourier syn-
141.5, 145.6 (py-C). – 11B NMR (64.21 MHz, CDCl3): theses and refined with isotropic displacement parameters
= –4.2.
(with exception for those of the disordered ethyl group
in 6b, which were inserted in calculated positions and
refined usinga ridingmodel). Crystallographic data (ex-
cludingstructure factors) for the structures reported in
this paper have been deposited with the Cambridge Crys-
tallographic Data Centre as supplementary publication
Crystal structure determinations of 6a, 6b, 7a, 8b
A summary of the crystal data and details of the struc-
ture determinations is given in Table 1. Data were col-
lected on a Bruker AXS area detector Smart 1000 (Mo- nos. CCDC-176330 (6a), -176331 (6b), -176332 (7a), -
˚
K -radiation, = 0.71073 A, -scans) at low tempera- 176333 (8b).
Copies of the data can be obtained free of charge on
ture. Data were corrected for Lp- and absorption effects
(semi-empirical, SADABS [12]). The structures were application to CCDC, 12 Union Road, Cambridge CB2
solved by direct methods and refined by full-matrix least- 1EZ, UK [Fax: (internat.) +44-1223/336-033;E-mail: de-
squares methods based on F2 (SHELXTL) [13]. The crys-
posit@ccdc.cam.ac.uk].
tals of 6a were twinned. A data set of non-overlapped and
exactly overlapped reflections of both components was
Acknowledgements
prepared usingthe program GEMINI [14]. The structure
was refined usingthe TWIN option in SHELXL97 [15].
The ethyl group in 6b is disordered. Non-hydrogen atoms
Our thanks go to Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie for supporting
our work.
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