Methylpentanediolborane: Easy access to new air- and chromatography-stable, highly functionalized vinylboronates

Article abstract of DOI:10.1021/jo070504g

(Chemical Equation Presented) Methylpentanediolborane (MPBH) 1 can be prepared easily by reaction of hexyleneglycol with BH₃/ DMS or B ₂H₆ generated from NaBH₄ and I₂. MPBH hydroborates stereo- and re

Full text of DOI:10.1021/jo070504g

Methylpentanediolborane: Easy Access to New Air- and
Chromatography-Stable, Highly Functionalized Vinylboronates
Nageswaran PraveenGanesh, Sylvain d’Hondt, and Pierre Yves Chavant*
De´partement de Chimie Mole´culaire, CNRS, UniVersite´ Joseph Fourier,
BP-53, 38041 Grenoble Cedex 9, France
Pierre-YVes.ChaVant@ujf-grenoble.fr
ReceiVed March 16, 2007
Methylpentanediolborane (MPBH) 1 can be prepared easily by reaction of hexyleneglycol with BH3/
DMS or B2H6 generated from NaBH4 and I2. MPBH hydroborates stereo- and regioselectively highly
functionalized alkynes, including propargyl bromide and propionaldehyde acetal. MPBH compares
favorably with pinacolborane in terms of reactivity. The obtained vinylboronic esters are air- and
chromatography-stable.
Introduction
pinacolborane (PinBH).6 Several catalysts7,8 have considerably
improved the efficiency and scope of this hydroboration.
Nevertheless, analogous methods in the dioxaborinanes series
received little attention.7b,9 Although the preparation of 4,4,6-
trimethyl-1,3,2-dioxaborinane 1 from cheap hexyleneglycol (2-
methyl-2,4-pentanediol) 210 and the ability of 1 to hydroborate
alkynes to produce stable vinylboronic esters have been known
since 1966, this reagent was scarcely used.11
In the course of our study on the boron-to-zinc transmetalation
of vinylboronic esters,1 we found that the air-, water-, and
chromatography-stable pinacol esters2 could be used, but in
rather harsh conditions that limited the scope. Preliminary
experiments3 with less hindered cyclic esters, for example with
2-(hexen-1-yl)-5,5-dimethyl-[1,3,2]dioxaborinane, were encour-
aging, but we had to prepare these reagents by esterification of
the vinylboronic acid with the diol at the end of a multistep
process.4 Thus, we sought other vinylboronic esters that would
be less hindered than pinacol esters, but that could also be
prepared, purified, and stored very easily.
We describe here easy and efficient preparations of 4,4,6-
trimethyl-1,3,2-dioxaborinane 1 (methylpentanediolborane,
MPBH; Scheme 1). We show that hydroboration with 1
catalyzed by Schwartz’s reagent8 allows a straightforward and
A straightforward access to vinylboronic esters is the direct
hydroboration of alkynes, well known for catecholborane5 or
(6) Tucker, C. E.; Davidson, J.; Knochel, P. J. Org. Chem. 1992, 57,
3482.
(1) Pandya, S. U.; Pinet, S.; Chavant, P. Y.; Valle´e, Y. Eur. J. Org.
Chem. 2003, 3621.
(2) Vaultier, M.; Alcaraz, G. In Science of Synthesis; Kaufmann, D., Ed.;
Thieme Chemistry: Stuttgart, 2004; Vol. 6, p 721.
(3) DeCandia, C.; Chavant, P. Y. (D.C.M., Universite´ J. Fourier Grenoble,
unpublished results, 2003).
(4) (a) Hoffmann, R. W.; Dresely, S. Synthesis 1988, 103. See also: (b)
Rasset-Deloge, C.; Vaultier, M. Bull. Soc. Chim. Fr. 1994, 131, 919. (c)
Kamabuchi, A.; Moriya, T.; Miyaura, N.; Suzuki, A. Synth. Commun. 1993,
23, 2851. (d) Gravel, M.; Toure, B. B.; Hall, D. G. Org. Prep. Proced. Int.
2004, 36, 573. (e) Lombardo, M.; Morganti, S.; Tozzi, M.; Trombini, C.
Eur. J. Org. Chem. 2002, 2823.
(7) (a) Shirakawa, K.; Arase, A.; Hoshi, M. Synthesis 2004, 1814 and
references therein. (b) Vogels, C. M.; Westcott, S. A. Curr. Org. Chem.
2005, 9, 687. (c) Murata, M.; Kawakita, K.; Asana, T.; Watanabe, S.;
Masuda, Y. Bull. Chem. Soc. Jpn. 2002, 75, 825. (d) Suseela, Y.; Prasad,
A. S. B.; Periasamy, M. J. Chem. Soc., Chem. Commun. 1990, 446. (e)
Murata, M.; Oyama, T.; Watanabe, S.; Masuda, Y. Synthesis 2000, 778.
(f) Ohmura, T.; Yamamoto, Y.; Miyaura, N. J. Am. Chem. Soc. 2000, 122,
4990. (g) Pereira, S.; Srebnik, M. Tetrahedron Lett. 1996, 37, 3283.
(8) (a) Pereira, S.; Srebnik, M. Organometallics 1995, 14, 3127. (b)
Wang, Y. D.; Kimball, G.; Prashad, A. S.; Wang, Y. Tetrahedron Lett.
2005, 46, 8777.
(9) Crudden, C. M.; Edwards, D. Eur. J. Org. Chem. 2003, 4695.
(10) Woods, W. G.; Strong, P. L. J. Am. Chem. Soc. 1966, 88, 4667.
(5) Lane, C. F.; Kabalka, G. W. Tetrahedron 1976, 32, 981.
10.1021/jo070504g CCC: $37.00 © 2007 American Chemical Society
Published on Web 05/11/2007
4510
J. Org. Chem. 2007, 72, 4510-4514

Air- and Chromatography-Stable Vinylboronates
TABLE 1. Hydroboration of Alkynes with MPBH
SCHEME 1. Preparations of MPBH
product
R1 )
isolated yield
3
4
5
6
7
Ph
n-Bu
93a(79d)
90a
stereoselective preparation of various highly functionalized E
vinylboronic esters under mild conditions.
cyclohexen-1-yl
(CH2)3Cl
TMS
CH2OMe
CH2OAc
CH2OCOPh
CH2OtBu
CH2Cl
66a
66a
61a
Results
8
9
70b(49a)
68b(43a)
0c
Preparation of MPBH 1 and Hydroboration of 1-Alkynes.
Our first preparation of MPBH 1 was directly inspired by the
work of Tucker et al.6 Reaction of neat borane/dimethylsulfide
complex with 2-methyl-2,4-pentanediol 2 in dry dichlo-
romethane at 0 °C led very efficiently to the formation of MPBH
1. 11B and 1H NMR indicated that the sole impurity was excess
BH3/DMS.12 Commercial solutions of BH3 in THF led to impure
samples.13
10
11
12
13
14
15
82a
68b
CH2Br
CH(OEt)2
COOtBu
73a
80a
19a,c
a Obtained using MPBH in toluene. b Obtained using MPBH in DCM.
c Remainder: starting material. d DCM, 40 °C, 4 h.
We also investigated a procedure inspired by the work of
Suseela and Periasamy,14 who showed that B2H6 can be
conveniently generated from I2 and NaBH4 in ether solvents.
Thus, we used a dropwise addition of a solution of I2 in diglyme
into a solution of NaBH4 in the same solvent to generate a
stream of B2H6 (and H2). The gas was diluted with a stream of
N2 and bubbled in a separate flask through a solution of
hexyleneglycol 2 in toluene or dichloromethane at 0 °C. A fast,
slightly exothermic reaction took place.15 To obtain complete
conversion of diol 2, it was sufficient to generate 1.5 mol equiv
of B2H6 (from 1.5 equiv of I2 and 3 equiv of NaBH4). MPBH
these solutions of impure dioxaborinane led to complex
mixtures. One explanation is that concurrent hydroboration and
disproportionation led to a mixture of boronic and borinic
species.
Hydroboration of 1-Alkynes with 1. We next used these
toluene or dichloromethane (DCM) solutions of MPBH 1 for
the hydroboration of various 1-alkynes, with a special interest
for alkynes carrying heteroatoms on position 3. We chose the
commercially available, easy-to-handle Schwartz’s reagent8a as
the catalyst, and the reactions were run in toluene or DCM at
room temperature overnight. In these conditions, both prepara-
tions of MPBH led to the same results; DMS was not interfering.
No reaction took place in the absence of catalyst. After
completion, a simple filtration of the crude material on basic
alumina yielded the vinylboronic ester in pure form.
As illustrated in Table 1, the MPBH/Cp2ZrClH system
hydroborated readily, in moderate to excellent yields and
excellent purity, diversely functionalized alkynes, including
propargyl chloride,4d,e bromide,17 or protected propionaldehyde.4b,c
Propargyl alcohol could be used, when protected as an acetate
or tert-butyl ether (products 9 and 11). Surprisingly, the
corresponding benzoate (10) could not be hydroborated, despite
repeated attempts. Toluene solutions of 1 are more easily stored
than DCM solutions, but toluene removal can be problematic
with volatile vinylboronic esters (8 and 9). The electron-poor
t-butyl propiolate reacted very sluggishly at 20 °C (product 15).
Comparison with Pinacolborane. The goal of the present
work was to provide a convenient access to vinylboronic esters
that would not be pinacol esters, and this is obviously the main
difference between MPBH and PinBH. Nevertheless, it could
be interesting to compare the intrinsic reactivity of MPBH and
PinBH in the Zr-catalyzed hydroboration.
1 was obtained in excellent purity, as confirmed by 1H and 11
B
NMR of the solution.
The standardized toluene or dichloromethane solutions of
MPBH 1 could be kept for several months at 4 °C without any
change in their NMR spectra.
Noticeably, the same protocol could be applied to the
preparation of DMS-free solutions of pinacolborane in toluene,
also in high purity. The uptake of borane by the pinacol solution
was slower, and a larger excess of diborane was required (6
equiv of NaBH4 involved instead of 3).16
Both preparations failed to produce pure samples of 5,5-
dimethyl-1,3,2-dioxaborinane from 2,2-dimethyl-1,3-propanediol.
In all attempts, fast disproportionation of the borinane led to
contamination by a trialkoxyborane species (11B NMR: 17
ppm). Worse, subsequent attempts to hydroborate alkynes with
(11) (a) Ma¨nnig, D.; No¨th, H. Angew. Chem., Int. Ed. 1985, 24, 87. (b)
Kono, H.; Ito, K.; Nagai, Y. Chem. Lett. 1975, 1095. (c) Fish, R. H. J.
Org. Chem. 1973, 38, 158. (d) Fish, R. H. J. Am. Chem. Soc. 1968, 90,
4435. Interesting applications of the parent 2-vinyl-4,4,6-trimethyl-1,3,2-
dioxaborinane: (e) Lightfoot, A. P.; Twiddle, S. J. R.; Whiting, A. Org.
Biomol. Chem. 2005, 3, 3167. (f) Lightfoot, A. P.; Twiddle, S. J. R.; Whiting,
A. Synlett 2005, 529. (g) Lightfoot, A. P.; Maw, G.; Thirsk, C.; Twiddle,
S. J. R.; Whiting, A. Tetrahedron Lett. 2003, 44, 7645.
(12) 25.2 ppm (sharp, d, J ) 170 Hz).
(13) Potyen, M.; Josyula, K. V. B.; Schuck, M.; Lu, S.; Gao, P.; Hewitt,
C. Org. Process Res. DeV. 2007, 11, 210.
(14) Suseela, Y.; Periasamy, M. J. Organomet. Chem. 1993, 450, 47.
(15) We observed that only H2 is evolving at the beginning of the
addition, since the first step is the formation of NaB2H7: Brown, H. C.;
Tierney, P. A. J. Am. Chem. Soc. 1958, 80, 1552.
For this study, we used solutions of MPBH and PinBH in
DCM, prepared by the NaBH4/I2 procedure. We chose to
perform competition experiments (Scheme 2): a mixture of 1
equiv each of both boranes (MPBH 1 and PinBH) was reacted
with the 1-alkyne (1-hexyne or phenylacetylene or propargyl
bromide) in the presence of 10% Cp2ZrClH, at 20 °C. We
(16) This difference showed that the uptake diborane by the pinacol is
not quantitative. We checked by experiments involving sequential bubblers
that it is the same with hexyleneglycol. Thus, the excess of diborane is
actually swept through the solution by the H2/N2 mixture and must be
carefully trapped.
(17) Gaddoni, L.; Lombardo, M.; Trombini, C. Tetrahedron Lett. 1998,
39, 7571.
J. Org. Chem, Vol. 72, No. 12, 2007 4511

Ganesh et al.
SCHEME 2. Competition Experiments
1.18 g) in dry dichloromethane or toluene (2.36 mL) was stirred
and cooled to 0 °C. A solution of BH3/DMS (11 mmol, 10 M in
methyl sulfide, Aldrich) was added over 20-30 min to control the
brisk evolution of gas. The reaction was stirred for 1 h at 0 °C and
was then warmed to 25 °C and stirred for an additional 1 h until
there was no further evolution of gas. The resulting solution was
checked by 11B and 1H NMR; conversion of the diol was
quantitative. This solution was used as such for hydroboration.
Preparation of MPBH 1 from NaBH4 and I2. Caution:
Diborane is a toxic and pyrophoric gas! H2 eVolution! Preparation
should be carried out under an efficient fume hood! In a 100-mL
double-necked round-bottomed flask fitted with a pressure-equal-
izing dropping funnel, an efficient magnetic stirring, and a N2 inlet,
NaBH4 (1.14 g, 30 mmol) was suspended in 6 mL of bis(2-meth-
oxyethyl) ether (diglyme). This flask was connected through a
double-ended needle to a second 25-mL cylindrical flask containing
a solution of 2-methyl-2,4-pentanediol (1.18 g, 10 mmol) in 11.8
mL of dry dichloromethane or toluene, placed in an ice bath. The
second flask was vented through a second double-ended needle
bubbling into ethanol (to trap excess diborane). The dropping funnel
was loaded with a solution of I2 (15 mmol, 3.84 g) in diglyme (18
mL). The I2 solution was added dropwise over 1 h; the temperature
rose gently to 40 °C. The evolved gases15 were bubbled through
the solution of diol 2 in the second flask. All along the process, a
small stream of N2 (2-5 bubbles per second) was applied through
the whole apparatus to ensure complete transfer of the diborane.
At the end of the addition of I2, the temperature of the second flask
was brought to 20 °C, and the stream of N2 was continued for 1 h;
this step allowed the elimination of any excess diborane in the
solution of MPBH 1. The solution was transferred to a volumetric
monitored by GC (internal standard) the formation of the
corresponding vinylboronate 3 (respectively 4 or 13) and its
pinacol-derived isomer 3′ (respectively 4′ or 13′). This protocol
ruled out any experimental bias that could evolve from
contaminants in boranes or reagents (that could either poison
the catalyst or act as catalysts18).
We found that the curves of formation of all boronates were
linear, up to about 40% conversion of 1. Rates ratios were
estimated from the slopes of the trend lines in this region. In
the case of the reactive 1-hexyne (3 equiv), 3 formed 5 times
faster than 3′. With phenylacetylene (1 equiv), 4 formed 10 times
faster than 4′. In a separate experiment, we repeated Pereira
and Srebnik’s8a preparation of 4′ with our DMS-free solution
of PinBH and obtained 4′ in 61% isolated yield (lit.8a 75%;
corresponding yield in 4 from MPBH 93%; see Table 1).
The largest difference appeared with propargyl bromide.
MPBH led to 13 in 73% isolated yield (5% cat.; Table 1). In
the same conditions, no reaction took place between propargyl
bromide and DMS-free PinBH (10% cat.).19 We performed a
competition experiment (2 equiv of propargyl bromide) and
observed evolution of 13 and traces of 13′; 13 was formed 14
times faster. After 20 h at 20 °C, the final GC yield was 67%
for 13 and 5% for 13′. In both phenylacetylene and propargyl
bromide competition experiments, the reaction did not proceed
further; 11B NMR showed that both borinanes had disappeared.
Thus, we have shown that MPBH 1, very easily prepared
from hexyleneglycol and BH3/DMS or NaBH4/I2, is an excellent
reagent for the preparation of an unexploited11 series of air-
and chromatography-stable vinylboronic esters. A great variety
of functional groups is tolerated, allowing an easy preparation
of highly functionalized, valuable synthetic intermediates. We
are currently investigating the hydroboration of alkenes with
MPBH in the presence of Wilkinson’s catalyst.7g For example,
styrene provided exclusively the 2-borylated isomer 4,4,6-
trimethyl-2-phenethyl-[1,3,2]dioxaborinane 16 (DCM, 1% RhCl-
(PPh3)3, 0 °C, 16 h, quant.). An application of these vinylboronic
esters to the vinylation of nitrones will be reported shortly.
1
flask and diluted to 20 mL. 11B and H NMR indicated that the
conversion of the diol was quantitative. Thus, the solution was
considered 0.50 M in MPBH 1. The solution could be kept at 4 °C
for several months without change. Storage at room temperature
was deleterious.
General Experimental Procedure for the Hydroboration of
Alkynes by MPBH 1. A 5-mL round-bottom flask equipped with
a side arm and magnetic stirring was charged with HZrCp2Cl (0.05
mmol, 13 mg) and dry dichloromethane or toluene (1 mL) under a
N2 atmosphere and cooled to 0 °C. Alkyne (1.0 mmol) was then
added dropwise, the mixture then was stirred for 2 min, and MPBH
1 (1.1 mmol) was introduced dropwise via a syringe. Stirring was
continued for 16 h at 20 °C, at which point GC analysis of a reaction
aliquot showed completion of reaction. Isolation of the product was
achieved by removing volatile matter under reduced pressure
followed by flash column chromatography (3% ether in hexane)
to provide the desired product as a clear oil.
All products were found to be >95% purity by gas chromatog-
raphy (FID).
The above procedure was also applied for the hydroboration of
styrene by changing the catalyst to (PPh3)3RhCl (0.01 mmol, 9 mg).
Spectroscopic Data. In the 75.5 MHz 13C NMR spectra, C atoms
that are directly bonded to boron, marked (br), were approximately
250 Hz wide and can easily remain undetected.
Experimental Section
All reactions were performed under nitrogen using usual Schlenk
techniques, in oven-dried glassware, with magnetic stirring. Solu-
tions of BH3 in THF (1 M) and BH3/DMS (10 M) were purchased
from Aldrich. DCM and 2-methyl-2,4-pentanediol were distilled
from CaH2. Toluene was distilled from sodium.
Preparation of MPBH 1 from BH3/DMS. Caution: Stench!
H2 eVolution! A solution of 2-methyl-2,4-pentanediol (10 mmol,
1
1: MPBH (4,4,6-Trimethyl-1,3,2-dioxaborinane): H NMR
(300 MHz, CDCl3) δ ppm 4.16 (dqd, J ) 11.8, 6.2, 3.0 Hz, 1H),
1.76 (ddd, J ) 13.9, 3.0, 1.7 Hz, 1H), 1.50 (dd, J ) 13.9, 11.8 Hz,
1H), 1.27 (s, 3H), 1.26 (s, 3H), 1.23 (d, J ) 6.21 Hz, 3H). 13C
NMR (75.5 MHz, CDCl3) δ ppm 70.8, 64.6, 46.1, 31.0, 28.1, 22.9.
11B NMR (96 MHz, CDCl3) δ ppm 25.2 (d, J ) 170 Hz). IR (neat,
cm-1): 2551, 2498.
(18) Pereira and Srebnik pointed out (ref 8a) that some hydroboration
could take place without Cp2ZrClH, depending on the preparation of PinBH.
Hydroboration of 1-alkynes with PinBH is catalyzed by dicyclohexylborane
(ref 7a); thus, the possibility of catalysis by products containing B-H bonds
should be considered. Reference 7f showed that ether and amine ligands
affect positively the Cp2ZrClH catalysis.
(19) Hydroboration of propargyl bromide by Cy2BH: Lombardo, M.;
Morganti, S.; Trombini, C. J. Org. Chem. 2000, 65, 8767. Hydroboration
of propargyl chloride with PinBH catalyzed by Cy2BH was reported in ref
7a.
3: 4,4,6-Trimethyl-2-styryl-[1,3,2]dioxaborinane: 1H NMR
(300 MHz, CDCl3) δ ppm 7.5-7.4 (m, 2H), 7.35-7.2 (m, 4H),
6.11 (d, J ) 18.2 Hz, 1H), 4.26 (dqd, J ) 11.7, 6.2, 3.0 Hz, 1H),
1.80 (dd, J ) 13.8, 3.0 Hz, 1H), 1.53 (dd, J ) 13.8, 11.7 Hz, 1H),
1.33 (s, 3H), 1.32 (s, 3H), 1.30 (d, J ) 6.2 Hz, 3H). 13C NMR
(75.5 MHz, CDCl3) δ ppm 146.4, 137.9, 128.3, 128.2, 126.8, 121
(br), 70.7, 64.7, 45.9, 31.2, 28.1, 23.1. 11B NMR (96 MHz, CDCl3)
δ 25.8 ppm. IR (cm-1): 3023, 2974, 1624, 1577, 1213, 1162, 993,
4512 J. Org. Chem., Vol. 72, No. 12, 2007

Air- and Chromatography-Stable Vinylboronates
750. LRMS (EI) m/z (%) 230(100) [M+], 130(71), 215(69), 229-
(25), 231(17), 232(3). HRMS EI m/z calcd for C14H19BO2
m/z (%) 227(100) [M + H+], 244(52). HRMS (DCI NH3) m/z calcd
+
+
for C11H23BNO4 244.1715; found 244.1708.
230.1473; found 230.1478.
11: 2-(3-tert-Butoxypropenyl)-4,4,6-trimethyl-[1,3,2]diox-
aborinane: 1H NMR (300 MHz, CDCl3) δ ppm 6.48 (dt, J ) 17.8,
4.9 Hz, 1H), 5.52 (dt, J ) 17.8, 1.2 Hz, 1H), 4.12 (dqd, J ) 12.1,
6.2, 2.9 Hz, 1H), 3.88 (dd, J ) 4.9, 1.2 Hz, 2H), 1.69 (dd, J )
13.9, 2.9 Hz, 1H), 1.39 (dd, J ) 13.9,12.1 Hz, 1H), 1.20 (s, 6H),
1.17 (d, J ) 6.2 Hz, 3H), 1.12 (s, 9H). 13C NMR (75.5 MHz,
CDCl3) δ ppm 147.3, 123.4 (br), 72.8, 70.4, 64.4, 63.9, 45.9, 31.1,
27.9, 27.4 (×3), 23.0. 11B NMR (96 MHz, CDCl3) δ 25.4 ppm. IR
(cm-1): 1644, 1391, 997, 768, 620. LRMS (DCI NH3/isobutane)
m/z (%) 258(100) [M + NH4+], 202(39), 256(11), 257(21), 259-
(6). HRMS (ESI) calcd for C13H25O3BNa+ 263.17890(100),
262.18253(25), 264.18226(14); found 263.17891(100), 262.18258-
(25), 264.18213(14).
4: 2-Hex-1-enyl-4,4,6-trimethyl-[1,3,2]dioxaborinane: 1H NMR
(300 MHz, CDCl3) δ ppm 6.52 (dt, J ) 17.7, 6.4 Hz, 1H), 5.34
(dt, J ) 17.7, 1.6 Hz, 1H), 4.20 (dqd, J ) 11.8, 6.2, 2.9 Hz, 1H),
2.12 (m, 2H), 1.77 (dd, J ) 13.9, 2.9 Hz, 1H), 1.49 (dd, J ) 13.9,
11.8 Hz, 1H), 1.43-1.30 (m, 4H), 1.29 (s, 6H), 1.26 (d, J )
6.2 Hz, 3H), 0.88 (t, J ) 7.1 Hz, 3H). 13C NMR (75.5 MHz, CDCl3)
δ ppm 150.9, 123.7 (br), 70.3, 64.4, 45.9, 35.0, 31.2, 30.5, 28.0,
23.1, 22.2, 13.8. 11B NMR (96 MHz, CDCl3) δ 25.6 ppm. IR
(cm-1): 2973, 1639, 1388, 1164, 998, 768. LRMS (DCI NH3/
isobutane) m/z (%) 228(100) [M + NH4+]. HRMS (DCI NH3) m/z
+
calcd for C12H27BNO2 228.2129; found 228.2135.
5: 2-Cyclohexen-1-enyl-4,4,6-trimethyl-[1,3,2]dioxaborinane:
1H NMR (300 MHz, CDCl3) δ ppm 6.91 (d, J ) 17.6 Hz, 1H),
5.88 (br t, J ) 3.2 Hz, 1H), 5.34 (d, J ) 17.6 Hz, 1H), 4.20 (dqd,
J ) 11.8, 6.2, 3.0 Hz, 1H), 2.18-2.04 (m, 2H), 1.76 (dd, J ) 13.9,
3.0 Hz, 1H), 1.68-1.53 (m, 4H), 1.47 (dd, J ) 13.9, 11.8 Hz, 1H),
1.30-1.27 (m, 8H), 1.25 (d, J ) 6.2 Hz, 3H). 13C NMR (75.5 MHz,
CDCl3) δ ppm 150.1, 137.1 (br), 132.4, 117.4, 70.4, 64.5, 45.9,
31.1, 28.0, 25.9, 23.9, 23.1, 22.4, 22.3. 11B NMR (96 MHz, CDCl3)
δ 26.0 ppm. IR (cm-1): 3018, 2974, 2929, 1634, 1607, 1300, 1162,
997, 795, 771. LRMS (DCI NH3/isobutane) m/z (%) 235(100) [M
+ H+], 247(40), 248(23), 250(34), 251(4). HRMS (DCI NH3) m/z
calcd for C14H24BO2 235.1864; found 235.1861.
12: 2-(3-Chloropropenyl)-4,4,6-trimethyl-[1,3,2]dioxabori-
1
nane: H NMR (200 MHz, CDCl3) δ ppm 6.52 (dt, J ) 17.4,
6.3 Hz, 1H), 5.62 (dt, J ) 17.4, 1.4 Hz, 1H), 4.22 (dqd, J ) 11.5,
6.2, 3.0 Hz, 1H), 4.07 (dd, J ) 6.3, 1.4 Hz, 2H), 1.80 (dd, J )
13.9, 3.0 Hz, 1H), 1.49 (dd, J ) 13.9, 11.5 Hz, 1H), 1.29 (s, 6H),
1.26 (d, J ) 6.2 Hz, 3H). 13C NMR (75.5 MHz, CDCl3) δ ppm
143.3, 128.1 (br), 70.8, 64.7, 46.2, 45.8, 31.0, 27.9, 22.9. 11B NMR
(96 MHz, CDCl3) δ 25.3 ppm. IR (cm-1): 2974, 1641, 1421, 1162,
993, 767. We could not obtain any coherent mass spectrum for
this compound.
13: 2-(3-Bromopropenyl)-4,4,6-trimethyl-[1,3,2]dioxabori-
1
6: 2-(5-Chloropent-1-enyl)-4,4,6-trimethyl-[1,3,2]dioxabori-
nane: H NMR (300 MHz, CDCl3) δ ppm 6.50 (td, J ) 17.3,
1
nane: H NMR (200 MHz, CDCl3) δ ppm 6.42 (dt, J ) 17.7,
7.2 Hz, 1H), 5.51 (td, J ) 17.3, 1.1 Hz, 1H), 4.13 (dqd, J ) 11.8,
6.2, 3.0 Hz, 1H), 3.88 (dd, J ) 7.16, 1.1 Hz, 2H), 1.71 (dd, J )
13.9, 3.0 Hz, 1H), 1.41 (dd, J ) 13.9, 11.8 Hz, 1H), 1.21 (s, 6H),
1.18 (d, J ) 6.2 Hz, 3H). 13C NMR (75.5 MHz, CDCl3) δ ppm
143.5, 128.6 (br), 70.9, 64.7, 45.8, 34.1, 31.1, 28.0, 23.0. 11B NMR
(96 MHz, CDCl3) δ 25.2 ppm. IR (cm-1): 2973, 2933, 1634, 1425,
1230, 1196, 1162, 993, 771. We could not obtain any coherent
mass spectrum for this compound.
6.4 Hz, 1H), 5.33 (dt, J ) 17.7, 1.5 Hz, 1H), 4.16 (dqd, J ) 11.7,
6.2, 3.0 Hz, 1H), 3.48 (t, J ) 6.7 Hz, 2H), 2.29-2.13 (tt, J ) 8.1,
6.7 Hz, 2H), 1.85 (q, J ) 8.1 Hz, 1H), 1.73 (dd, J ) 13.9, 3.0 Hz,
1H), 1.44 (dd, J ) 13.9, 11.7 Hz, 1H), 1.24 (s, 6H), 1.21 (d, J )
6.2 Hz, 3H). 13C NMR (75.5 MHz, CDCl3) δ ppm 148.3, 125.2
(br), 70.5, 64.5, 45.9, 44.3, 32.3, 31.2(×2), 28.0, 23.0. 11B NMR
(96 MHz, CDCl3) δ 25.5 ppm. IR (cm-1): 2970, 2933, 1641, 1392,
1164, 995, 771. LRMS (DCI NH3/isobutane) m/z (%) 248(100) [M
+ NH4+], 234(11), 236(7). HRMS (DCI NH3) m/z calcd for C11H24-
BClNO2 248.1583; found 248.1586.
14: 2-(3,3-Diethoxypropenyl)-4,4,6-trimethyl-[1,3,2]diox-
aborinane: 1H NMR (300 MHz, CDCl3) δ ppm 6.34 (dd, J ) 18.0,
5.0 Hz, 1H), 5.60 (dd, J ) 18.0, 1.2 Hz, 1H), 4.78 (dd, J ) 5.0,
1.2 Hz, 1H), 4.13 (dqd, J ) 11.7, 6.2, 3.0 Hz, 1H), 3.57 (m, 2H),
3.44 (dq, J ) 9.5, 7.1 Hz, 2H), 1.71 (dd, J ) 13.8, 3.0 Hz, 1H),
1.40 (dd, J ) 13.8, 11.7 Hz, 1H), 1.21 (s, 6H), 1.18 (d, J )
6.2 Hz, 3H), 1.13 (t, J ) 7.1 Hz, 6H). 13C NMR (75.5 MHz, CDCl3)
δ ppm 145.2, 126.9 (br), 102.4, 70.7, 64.6, 61.0(×2), 45.9, 31.1,
28.0, 23.0, 15.1(×2). 11B NMR (96 MHz, CDCl3) δ 25.5 ppm. IR
(cm-1): 2971, 2933, 1648, 1421, 1054, 1000, 896, 767. We could
not obtain any coherent mass spectrum for this compound.
15: 3-(4,4,6-Trimethyl-[1,3,2]dioxaborinan-2-yl)-acrylic Acid
tert-Butyl Ester: 1H NMR (300 MHz, CDCl3) δ ppm 6.61 (d, J )
18.0 Hz, 1H), 6.46 (d, J ) 18.0 Hz, 1H), 4.24 (dqd, J ) 12.3, 6.2,
3.0 Hz, 1H), 1.82 (dd, J ) 14.0, 3.0 Hz, 1H), 1.47 (s, 9H), 1.46
(m, 1H), 1.30 (s, 6H), 1.27 (d, J ) 6.19 Hz, 3H). 13C NMR
(75.5 MHz, CDCl3) δ ppm 165.5, 138 (br), 137.8, 79.8, 71.0, 64.9,
45.7, 30.9, 27.9(×3), 22.8. 11B NMR (96 MHz, CDCl3) δ 25.4 ppm.
IR (cm-1): 3046, 2971, 2933, 1714, 1623, 1432, 1150, 1003, 765.
LRMS (DCI NH3/isobutane) m/z (%) 272(57) [M + NH4+], 215-
(31), 216(100), 217(24), 271(35), 273(7). HRMS (ESI) calcd for
C26H46O8B2Na+ 531.32710(100), 530.33073(50), 532.33054(29);
found 531.32705(100), 530.33071(41), 532.32991(42).
7: 4,4,6-Trimethyl-2-(2-trimethylsilanylvinyl)-[1,3,2]diox-
aborinane: 1H NMR (300 MHz, CDCl3) δ ppm 7.01 (d, J )
21.6 Hz, 1H), 6.18 (d, J ) 21.6 Hz, 1H), 4.24 (dqd, J ) 11.7, 6.2,
3.0 Hz, 1H), 1.79 (dd, J ) 13.8, 3.0 Hz, 1H), 1.51 (dd, J ) 13.8,
11.7 Hz, 1H), 1.32 (s, 3H), 1.31 (s, 3H), 1.29 (d, J ) 6.2 Hz, 3H),
0.07 (s, 9H). 13C NMR (75.5 MHz, CDCl3) δ ppm: 153.3, 142
(br), 70.7, 64.7, 45.9, 31.1, 28.0, 26.8, 23.1, -1.6. 11B NMR
(96 MHz, CDCl3) δ 24.6 ppm. IR (cm-1): 2970, 1592, 1418, 1389,
1018, 862, 1166, 837, 744. LRMS (DCI NH3/isobutane) m/z (%)
228(100) [M + NH4+], 209(9), 243(36), 245(12). HRMS (DCI
NH3) m/z calcd for C11H27BNO2Si 244.1899; found 244.1909.
8: 2-(3-Methoxypropenyl)-4,4,6-trimethyl-[1,3,2]dioxabori-
nane: 1H NMR (200 MHz, CDCl3) δ ppm 6.46 (dt, J ) 17.9, 5.1,
1H), 5.52 (dt, J ) 17.9, 1.3 Hz, 1H), 4.16 (dqd, J ) 11.6, 6.3,
3.0 Hz, 1H), 3.91 (dd, J ) 5.1, 1.3 Hz, 2H), 3.28 (s, 3H), 1.73 (dd,
J ) 13.8, 3.0 Hz, 1H), 1.43 (dd, J ) 13.8, 11.6 Hz, 1H), 1.24 (s,
6H), 1.20 (d, J ) 6.3 Hz, 3H). 13C NMR (75.5 MHz, CDCl3) δ
ppm 145.5, 126 (br), 74.4, 70.6, 64.6, 58.0, 45.9, 31.1, 28.0, 23.0.
11B NMR (96 MHz, CDCl3) δ 25.5 ppm. IR (cm-1): 2974, 1644,
1392, 1120, 1001, 768, 620. LRMS (DCI NH3/isobutane) m/z (%)
216(100) [M + NH4+], 184(26), 199(20), 215(36), 217(14). HRMS
(DCI NH3) m/z calcd for C10H23BNO3+ 216.1766; found 216.1708.
9: 2-(3-Acetoxypropenyl)-4,4,6-trimethyl-[1,3,2]dioxabori-
16: 4,4,6-Trimethyl-2-phenethyl-[1,3,2]dioxaborinane: 1H
NMR (300 MHz, CDCl3) δ ppm 7.27-7.08 (m, 5H), 4.13 (dqd, J
) 11.7, 6.2, 3.0 Hz, 1H), 1.71 (dd, J ) 13.9, 3.0 Hz, 1H), 2.72-
2.65 (m, 2H), 1.39 (dd, J ) 13.9, 11.7 Hz, 1H), 1.24 (s, 3H), 1.23
(s, 3H), 1.21 (d, J ) 6.2 Hz, 3H), 1.02 (m, 2H). 13C NMR
(75.5 MHz, CDCl3) δ ppm 145.1, 128.0, 127.9, 125.1, 70.4, 64.4,
45.9, 31.1, 30.2, 28.0, 23.1, 17 (br). 11B NMR (96 MHz, CDCl3) δ
29.7 ppm. IR (cm-1): 3024, 2974, 2933, 1389, 1182, 793, 771,
751. LRMS (DCI NH3/isobutane) m/z (%) 250(100) [M + NH4+].
1
nane: H NMR (200 MHz, CDCl3) δ ppm 6.44 (td, J ) 17.8,
4.9 Hz, 1H), 5.52 (td, J ) 17.8, 1.7 Hz, 1H), 4.55 (dd, J ) 4.9, 1.7
Hz, 2H), 4.15 (dqd, J ) 11.6, 6.2, 3.1 Hz, 1H), 2.01 (s, 3H), 1.73
(dd, J ) 13.9, 3.1 Hz, 1H), 1.42 (dd, J ) 13.9, 11.6 Hz, 1H), 1.22
(s, 6H), 1.19 (d, J ) 6.2 Hz, 3H). 13C NMR (75.5 MHz, CDCl3) δ
ppm 170.4, 142.3, 125 (br), 70.7, 65.6, 64.6, 45.8, 31.0, 27.9, 22.9,
20.7. 11B NMR (96 MHz, CDCl3) δ 25.6 ppm. IR (cm-1): 3015,
2975, 2935, 1744, 1163, 993, 768. LRMS (DCI NH3/isobutane)
+
HRMS (DCI NH3) m/z calcd for C14H25BNO2 250.1973; found
250.1966.
J. Org. Chem, Vol. 72, No. 12, 2007 4513

Ganesh et al.
Acknowledgment. This article is dedicated to P. Knochel
and C. Tucker. We gratefully thank Pr. G. Cahiez (CNRS) for
fruitful discussion and Universite´ J. Fourier (DCM-SERCO,
ICMG FR-2607) and CNRS (UMR-5250) for financial support.
N.P.G. thanks UJF (DCM) for a grant.
coupling: Murata, M.; Oda, T.; Watanabe, S.; Masuda, Y.
Synthesis 2007, 351.
Supporting Information Available: Detailed experimental
procedures and copies of NMR spectra of all new compounds. This
material is available free of charge via the Internet at http://pubs.
acs.org.
Note added in proof. During the edition of this article, the
authors became aware of the recent paper by Murata et al., which
reported the use of MPBH 1 in borylation reaction and Suzuki
JO070504G
4514 J. Org. Chem., Vol. 72, No. 12, 2007