A highly regio- and chemoselective synthesis of vicinal bromohydrins by ring opening of terminal epoxides with dibromoborane-dimethyl sulfide

Article abstract of DOI:10.1016/j.jorganchem.2006.11.032

Dibromoborane-dimethyl sulfide (BHBr₂-SMe₂) displays high degrees of chemo- and regioselectivity during the brominative cleavage of the epoxy group into vicinal bromohydrins in the presence of alkene, alkyne, allene, ether, acetal and acetonide, besides its hydroborating ability. Several reducible functional groups, such as chloride, aldehyde, ketone, azide, ester, nitrile and tert-amino ester, have been successfully accommodated during the epoxide opening process.

Full text of DOI:10.1016/j.jorganchem.2006.11.032

Journal of Organometallic Chemistry 692 (2007) 1608–1613
www.elsevier.com/locate/jorganchem
Note
A highly regio- and chemoselective synthesis of vicinal bromohydrins
by ring opening of terminal epoxides with
q
dibromoborane–dimethyl sulfide
*
Chandra D. Roy , Herbert C. Brown
Department of Chemistry, Herbert C. Brown Center for Borane Research, Purdue University, West Lafayette, IN 47907-2084, USA
Received 23 October 2006; received in revised form 19 November 2006; accepted 19 November 2006
Available online 1 December 2006
Abstract
2 2
Dibromoborane–dimethyl sulfide (BHBr –SMe ) displays high degrees of chemo- and regioselectivity during the brominative cleavage
of the epoxy group into vicinal bromohydrins in the presence of alkene, alkyne, allene, ether, acetal and acetonide, besides its hydrob-
orating ability. Several reducible functional groups, such as chloride, aldehyde, ketone, azide, ester, nitrile and tert-amino ester, have
been successfully accommodated during the epoxide opening process.
ꢀ
2006 Elsevier B.V. All rights reserved.
Keywords: Epoxides; Bromohydrin; Dibromoborane–dimethyl sulfide; Regioselectivity; Chemoselectivity
1
. Introduction
a number of structurally modified monofunctional B-halo-
boranes, such as, Me BBr [4a,4b], Ph BBr [4c] and
2
2
Vicinal halohydrins serve as valuable synthetic interme-
(Me N) BBr [4d] of diminished reactivity, have been syn-
2 2
diates [1] which have found wide applications in the synthe-
sis of halogenated marine products (laurenyne and
isodactylyne) and other biologically useful substances
thesized and tested for the regio- and chemoselective ring
opening of epoxides.
We have developed several new boron-based reagents,
(
thienamycin and immunosuppressant ISP-1) [2]. The most
such as, Ipc BX (B-halodiisopinocampheylboranes) [5a,5b],
2
common and practical method for the synthesis of b-halo-
hydrins is the halogenative cleavage of epoxides. Although
numerous methods and reagents have been developed to
effect such transformations, they are not always fully satis-
factory, especially with structurally complex organic mole-
cules bearing sensitive functional groups [3]. Due to their
high reactivity and Lewis acidity of B-haloboranes (BX3),
Ter BX (B-haloditerpenylboranes) [5c], (MeO) BX [5d,5e]
2
2
that have proven to be highly effective in the regio-,
chemo-, and enantioselective halogenative ring opening of
epoxides. Encouraged by the report on the chemoselective
cleavage of epoxide using BH Cl–SMe by Bovicelli et al.
2
2
[6], we exploited the synthetic utility of commercially avail-
able reagents, BH Br–SMe and BHBr –SMe , as highly
2
2
2
2
regioselective reagents for the conversion of epoxides into
vicinal bromohydrins [7]. Since both bromine and hydro-
gen atoms in these reagents are transferable, it is of great
interest to explore the chemoselectivity of these reagents
in the ring opening of epoxides. Recently, we systematically
investigated the regio- and chemoselective cleavage of ter-
minal epoxides using BH Br–SMe [8]. As expected, 1,2-
q
This paper is dedicated to the memory of my mentor, the late Professor
Herbert C. Brown (1912–2004). The work described herein was performed
at Purdue University during my stay as a post-doctoral research associate
(
1995–2001).
*
Corresponding author. Present address: EMD Biosciences, Inc., 10394
2
2
Pacific Center Court, San Diego, CA 92121, USA. Tel.: +1 858 450 5618;
fax: +1 858 453 3552.
epoxyoct-7-ene underwent 30–35% hydroboration at
E-mail address: chandra61804@yahoo.com (C.D. Roy).
0 ꢁC. Also, the partial reduction of aromatic aldehydes
0
022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.11.032

C.D. Roy, H.C. Brown / Journal of Organometallic Chemistry 692 (2007) 1608–1613
1609
and ketones was observed. Later, these problems were
O)2BH
Br
Br
BHBr2-SMe2
CH Cl , RT
O
overcome by conducting the reactions at ꢀ25 ꢁC, especially
for alkenes and ketones. Considering the reactivity of
BH Br–SMe towards alkenes, aldehydes and ketones, it
2
O) BH
C10H21
C10H21
+ C10H21
2
2
1
Major
Minor
2
2
was of considerable interest to explore another commer-
cially available reagent, which might regio- and chemose-
lectively cleave the epoxy moiety into bromohydrins in
the presence of alkenes, ketones and other reactive func-
tionalities, preferably at ambient temperature. Besides
being an excellent hydroborating agent [9a], BHBr –SMe
H2O
OH
Br
Br
OH
C10H21
+
C10H21
Major
2
Minor
3
2
2
has also been utilized in (a) deoxygenation of sulfoxides
9b] and (b) syntheses of 3-O-carboranylcarbenes and metal
[
Scheme 1. Regioselective cleavage of 1,2-epoxydodecane with BHBr
2
–
SMe in CH Cl
2
2
2
.
isocyanoborohydrides [9c]. Accordingly, we undertook a
systematic study of the chemoselective ring opening of
epoxides in the presence of a variety of reactive functional
groups utilizing BHBr –SMe . In this note, we wish to
is transferred at C-2 carbon (benzylic position) by follow-
ing an apparent S 1-type mechanism. The cleavage of
2
2
N
report the regio- and chemoselective synthesis of vicinal
bromohydrins from terminal epoxides utilizing the com-
mercially available (Aldrich) reagent, BHBr –SMe .
C–O bond in 2-methyltetrahydrofuran was observed to
be comparatively slow, but yielded primary bromide as a
major product (total yield: 90%; regioselectivity: 71/29).
2
2
2
. Results and discussion
2.2. Chemoselective ring opening of 1,2-epoxyoct-2-ene 10
2
.1. Regioselective ring opening of terminal epoxides
First, we reexamined the chemoselective ring opening of
1
,2-epoxyoct-7-ene 10, which cleanly underwent bromina-
Dibromoborane–dimethyl sulfide very readily cleaved
tive cleavage (87–90% yield, regioisomeric ratios (11 &
2) = 83/17, major primary bromide) at room temperature,
three representative terminal epoxides (entries 1–3) in
5 min at room temperature (Chart 1, Table 1). Dibrom-
oborane–dimethyl sulfide (BHBr –SMe ) cleaved
,2-epoxydodecane 1 (entry 1) to the corresponding regio-
isomeric bromohydrins (2 and 3) in excellent chemical yield
90%) with regioselectivity (primary bromide 2/secondary
bromide 3 = 9/1) in CH Cl in 0.25 h at room temperature
1
1
without hydroborating the terminal alkene (Scheme 2). In
the case of BH Br–SMe , the partial hydroboration of
the terminal double bond was observed at both 0 ꢁC and
RT. Therefore, BHBr –SMe should be preferred over
BH Br– SMe while conducting such a reaction on com-
plex unsaturated target molecules.
2
2
2
2
1
2
2
(
2
2
2
2
(
Scheme 1). Except for styrene oxide, the transfer of
bromine was observed at the less hindered carbon (C-1),
2.3. Chemoselective ring opening of 1,2-epoxydodecane 1
0
by S 2 -type mechanism, in the cases of terminal sub-
N
strates. In the case of styrene oxide 7 (entry 3), bromine
After establishing the reaction conditions, we investi-
gated the chemoselective cleavage of the 1,2-epoxydode-
cane 1 in the presence of few representative alkenes and
alkynes at room temperature. This reagent preferentially
reacts with the epoxy group in the presence of alkenes
OH
Br
O
Br
OH
R
R
R
(entries 4–6), alkyne (entry 8) and allene (entry 7) (Scheme
1
, R = C10H21
, R = PhCH2
, R = Ph
2, R = C10H21
5, R = PhCH2
8, R = Ph
3, R = C10H21
6, R = PhCH2
9, R = Ph
3
, Table 2). It was interesting to observe the chemoselective
4
cleavage of ethereal C–O bond of the epoxy group in the
presence of allyl-, aryl- and benzyl ethers (entries 4, 5 and
18), at room temperature.
7
Chart 1. Representative epoxides and product bromohydrins.
Table 1
Brominative cleavage of terminal epoxides with BHBr
2
–SMe
2
2 2
in CH Cl solvent
a
b,c
Isolated yield (%)
Entry
O
Reaction conditions
OH
Br
R
Br
OH
R
R
1
2
3
a
C
PhCH
Ph
10
H
21
RT/0.25 h
RT/0.25 h
RT/0.25 h
90
89
07
10
11
93
90
95
83
2
1
.10 equiv. of reagent used.
b
c
Isolated yields.
Combined yield.

1610
C.D. Roy, H.C. Brown / Journal of Organometallic Chemistry 692 (2007) 1608–1613
OH Br
Br
OH
+
17%
12
8
3%
11
BHBr -SMe
2
2
8
7%
0
oC - RT, 0.25 h
BHBr -SMe2
O
BH2Br-SMe2
Cleavage of Epoxide
No Hydroboration
2
Cleavage of Epoxide
Partial Hydroboration
0oC - RT, 16 h
0oC or RT, 1 h
1
0
BH Br-SMe
2
2
9
0%
o
-35 C, 16 h
OH
Br
Br
OH
+
8
9%
11%
12
1
1
Scheme 2. Chemoselective cleavage of 1,2-epoxyoct-7-ene with BH
2
2 2 2 2 2
Br–SMe and BHBr –SMe in CH Cl .
O
OH
Br
pressed at ꢀ25 ꢁC (Scheme 5). Again, considerable
amounts of reduction of acetophenone and 4-cyanoace-
tophenone were observed at 0 ꢁC with BH Br–SMe . No
C10H21
Br
OH
C10H21
Major
C10H21
1
. BHBr -SMe2
2
2
2
Minor
+
+
reduction of ketones, acetophenone and 4-acetylbenzonit-
rile (entries 14 and 15), were observed even at room tem-
perature (with BHBr –SMe ). Other reducible functional
2
. H O
2
Chx
H
Chx
C
CH2
C CH2
2
2
H
groups, such as, chloro, ester and nitrile (entries 12 and
16–18) were found to be unreactive even at room tempera-
ture during the epoxide opening process. The scope and
generality of this chemoselective transformation is illus-
trated with various reactive functional groups and the
results are summarized in Table 2.
Scheme 3. Chemoselective cleavage of 1,2-epoxydodecane with BHBr
2
–
SMe in the presence of an allene, propa-1,2-dienylcyclohexane in CH Cl .
2
2
2
Acetals, ketals, and orthoesters are very useful synthetic
intermediates, but they are very labile, especially in the
presence of Lewis acids. Consequently, we examined the
cleavage of 1,2-epoxydodecane in the presence of 1,2:3,5-
di-O-isopropylidene-D-xylofuranose and glucopyranoside
In summary, BHBr –SMe chemoselectively cleaves the
2
2
epoxy moiety in the presence of many other reactive alk-
enes, alkynes, and carbon–oxygen bonds, such as alkyl-,
allyl-, aryl-, benzyl ethers, pyranylacetal, and ketal. This
reagent has accommodated 1,2:3,5-di-O-isopropylidene-D-
xylofuranose during the epoxide cleavage, which is very
useful in the synthesis of carbohydrates and other marine
natural products. Several reducible functional groups, such
as aldehyde, ketone, nitrile, azide, chloro, and esters,
remain unaffected during the reaction. This reagent has
many advantages over currently available methodologies
because of its simple reaction conditions, high regio- and
chemoselectivity, and also commercial availability, which
should make it synthetically more useful and valuable.
(
entries 10 and 11). No cleavage of xylofuranose or gluco-
pyranoside was observed at ꢀ25 ꢁC. These structures are
the integral parts of sugars and related molecules that are
highly sensitive to such Lewis acids. No reduction of the
azido group (entry 9) was observed during the epoxide
opening reaction, under the present experimental condi-
tions. Dichloroborane–dimethyl sulfide, BHCl –SMe [10]
is known to reduce organyl azides to the corresponding
amines (Scheme 4). Bromohydrins were obtained in excel-
lent yields with high regioselectivity and the recovery of
most of the added ‘‘reactive’’ compounds was essentially
quantitative.
2
2
Knowing the reducing ability of BHBr –SMe , the epox-
3. Experimental
2
2
ide opening reactions were carried out with BHBr –SMe
2
2
in the presence of an equivalent amount of other com-
pounds bearing reducible functionalities, such as, chloride,
aldehyde, ketone, ester, and nitrile. In the cases of aromatic
aldehydes (entries 12 and 13), considerable amounts of
reduction products were observed at 0 ꢁC, which were sup-
3.1. General
Manipulations and reactions with air-sensitive
compounds were carried out under nitrogen atmosphere.
1
13
11
H,
C, and
B NMR spectra were recorded on

C.D. Roy, H.C. Brown / Journal of Organometallic Chemistry 692 (2007) 1608–1613
1611
Table 2
Chemoselective cleavage of 1,2-epoxydodecane with BHBr
2
2
–SMe in the presence of various reactive compounds
a
b
b
Entry
4
Reactive compound
Reaction conditions
Bromohydrins yield (%)
Recovered reactive compound (%)
O
RT/0.25 h
98
99
Ph
5
6
OBn
RT/0.25 h
RT/0.25 h
98
99
90
O
O
95
95
S
7
Chx
RT/0.25 h
85
C
C CH2
H
8
9
RT/0.25 h
95
95
95
95
OAc
N3
0 ꢁC/0.5 h
1
1
0
1
O
ꢀ25 ꢁC/3 h
ꢀ25 ꢁC/3 h
85
80
95
95
O
O
O
O
OAc
OAc
O
AcO
OAc
OAc
1
1
1
1
1
1
2
3
4
5
6
7
ꢀ25 ꢁC/3 h
ꢀ25 ꢁC/3 h
RT/0.25 h
RT/0.25 h
RT/0.25 h
RT/0.25 h
95
95
95
95
95
85
98
98
99
99
98
85
Cl
CHO
CHO
NC
COCH3
NC
COCH3
CH2CN
Me
N
CO2Et
Me
1
8
RT/0.25 h
98
99
EtO
.0 equiv. of reagent used.
CO2Me
a
1
b
1
Yields of the product bromohydrins and the recovered reactive compounds were determined by H NMR using biphenyl as an internal standard.
Varian-Gemini 300 MHz multinuclear NMR spectrometer.
The B NMR chemical shifts are in d relative to BF3–
and subsequent acetylation of trans-2-azidocyclohexan-1-ol.
Regioselectivity of the reaction was determined by integrat-
ing and comparing the selected signals (either –CHBr and –
CH Br protons or –CHOH and CH OH protons) of the
1
1
OEt . All the starting materials (epoxides and other reac-
2
tive compounds used for chemoselectivity study) were
purchased from Aldrich Chemical Co. Glucosepentaace-
tate was gifted by Dr. P. Mathivanan, Purdue University.
trans-1-Acetoxy-2-azidocyclohexane was prepared by the
cleavage of meso-cyclohexene oxide with sodium azide
2
2
1
regioisomers by H NMR spectroscopy. The error in deter-
mining the regio- and chemoselectivity (using biphenyl as
1
an internal standard) using integration method by
NMR spectroscopy should be within ± 5%.
H

1612
C.D. Roy, H.C. Brown / Journal of Organometallic Chemistry 692 (2007) 1608–1613
1
3
O
OH
Br
1H, –CH OH), 2.09 (s, 1H, –CH OH);
C NMR
2
2
C10H21
Br
OH
(75 MHz, CDCl ) d: 138.2, 128.9, 128.8, 127.9, 67.5, 56.9
3
C10H21
Major
AcO
C10H21
(the minor isomer 2-bromo-1-phenylethanol 8 shows
1
. BHBr -SMe2
2
Minor
+
+
characteristic peaks at d 4.90 (m, PhCH(OH)–) and 3.60
2
. H O
2
AcO
N3
N3
(dd, –CH Br)).
2
3
.2.4. 1-Bromooct-7-en-2-ol 11
1
H NMR (300 MHz, CDCl ) d: 6.60 (m, 1H, CH @
Scheme 4. Chemoselective cleavage of 1,2-epoxydodecane with BHBr
SMe in the presence of trans-1-acetoxy-2-azidocyclohexane in CH Cl
2
–
3
2
CH–), 5.00 (m, 2H, CH @CH–), 3.80 (m, 1H, –CHOH–),
2
2
2
.
2
3
.55 (dd, 1H, –CH Br), 3.40 (dd, 1H, –CH Br), 2.20 (m,
2 2
1
3
3H, –CH –, –CHOH), 1.70–1.20 (m, 6H, –CH –);
C
2
2
O
OH
Br
NMR (75 MHz, CDCl ) d: 138.6, 114.5, 71.0, 40.6, 34.9,
33.5, 28.7, 25.0.
3
C10H21
+
Br
OH
C10H21
C10H21
Minor
1
. BHBr -SMe
2 2
Major
+
2
. H2O
3
.2.5. 2-Bromooct-7-en-1-ol 12
1
NC
CHO
NC
CHO
H NMR (300 MHz, CDCl ) d: 5.80 (m, 1H, CH @
3
2
CH–), 5.00 (m, 2H, CH @CH–), 4.15 (m, 1H, –CHBr–),
2
Scheme 5. Chemoselective cleavage of 1,2-epoxydodecane with BHBr
SMe in the presence of 4-cyanobenzaldehyde in CH Cl
2
–
3
.80 (m, 2H, –CH OH), 2.10–1.40 (m, 9H, –CH – and
2
2
2
2
2
.
13
CHOH); C NMR (75 MHz, CDCl ) d: 138.5, 114.7,
3
67.2, 59.9, 34.7, 33.4, 28.2, 26.9.
3.2. A representative procedure for the regioselective
cleavage of 1,2-epoxydodecane 1
3.3. General procedure for the chemoselective cleavage of
,2-epoxydodecane in the presence of propa-1,2-
dienylcyclohexane
1
BHBr –SMe (1.1 ml, 1.1 mmol, 1.0 M in CH Cl ) was
2
2
2
2
added slowly to a stirred methylene chloride solution
5 ml) of 1,2-epoxydodecane 1 (2.0 mmol) at room temper-
(
BHBr –SMe (1 ml, 1.0 mmol, 1.0 M in CH Cl ) was
2
2
2
2
ature under nitrogen atmosphere. After 0.25 h, the interme-
diate dialkoxyborane species was treated with water (5 ml)
and the resulting bromohydrins were extracted with
CH Cl (3 · 25 ml), dried over anhydrous MgSO , and
added slowly to a stirred methylene chloride solution
(5 ml) of 1,2-epoxydodecane 1 (1.0 mmol) and propa-
1,2-dienylcyclohexane (1.0 mmol) at room temperature
under nitrogen atmosphere. After 0.25 h, the intermediate
dialkoxyborane species was treated with water (5 ml) and
the resulting bromohydrins were extracted with CH Cl
2
2
4
concentrated. The % chemical transformation of the regio-
isomeric bromohydrins (2 and 3) was determined by com-
paring the integrations of selected proton signals using
2
2
(3 · 25 ml), dried over anhydrous MgSO4, and
concentrated. The chemical conversion of the regioiso-
meric bromohydrins and the % recovery of the added
allene, were calculated by comparing the integrations of
1
H NMR spectroscopy after adding biphenyl (0.25 mmol)
as an internal standard (Table 1). The major regioisomers
were also purified on silica gel column and the chemical
yields were determined. All the bromohydrins are well
characterized in the literature.
1
selected proton signals using H NMR spectroscopy after
adding biphenyl (0.25 mmol) as an internal standard
(Table 2).
3
.2.1. 1-Bromododecan-2-ol 2 [3h]
1
H NMR (300 MHz, CDCl ): d 3.70 (m, 1H, –CHOH),
3
Acknowledgements
3
.50 (dd, 1H, –CH Br), 3.35 (dd, 1H, –CH Br), 2.10 (d, 1H,
2
2
–
CHOH), 1.60–1.10 (m, 18H, –CH –), 0.88 (t, 3H, –CH )
2
3
Financial supports from the Herbert C. Brown Center
for Borane Research and the Purdue Borane Research
Fund are gratefully acknowledged.
(
the minor isomer 2-bromododecan-1-ol 3 shows distinct
characteristic peak at d 4.15 (m, –CHBr)).
3
.2.2. 1-Bromo-3-phenylpropan-2-ol 5 [3a]
1
References
H NMR (300 MHz, CDCl ): d: 7.35–7.10 (m, 5H,
3
ArH), 3.95 (m, 1H, –CHOH), 3.19 (ddd, 2H, –CH Br),
2
[1] (a) M.V. Bhatt, S.U. Kulkarni, Synthesis (1983) 249, and references
2
.80 (d, 2H, PhCH –), 2.20 (d, 1H, –CHOH) (the minor
2
cited therein;
isomer 2-bromo-3-phenylpropan-1-ol 6 shows relevant
characteristic peak at d 4.10 (m, –CHBr)).
(b) P.A. Bartlett, in: J.D. Morrison (Ed.), Asymmetric Synthesis, vol.
3
(
, Academic Press, New York, 1984, p. 411;
c) C. Bonini, G. Righi, Synthesis (1994) 225, and references cited
therein;
d) J. Mann, Chem. Soc. Rev. 16 (1987) 381;
3
.2.3. 2-Bromo-2-phenylethanol 9 [3b]
1
(
H NMR (300 MHz, CDCl ): d 7.43–7.30 (m, 5H, ArH),
3
(e) R.C. Larock, Comprehensive Organic Transformations, Wiley-
VCH, New York, 1999, p. 1027.
5
.06 (dd, 1H, –CHBr–), 4.06 (dd, 1H, –CH OH), 3.96 (dd,
2

C.D. Roy, H.C. Brown / Journal of Organometallic Chemistry 692 (2007) 1608–1613
1613
[
[
2] (a) D.J. Faulkner, Nat. Prod. Rep. (1984) 251;
[5] (a) N.N. Joshi, M. Srebnik, H.C. Brown, J. Am. Chem. Soc. 110
(1988) 6246;
(
(
b) D.J. Faulkner, Nat. Prod. Rep. (1986) 1;
c) R.E. Erickson, in: P.J. Scheuer (Ed.), Marine Natural Products,
(b) M. Srebnik, N.N. Joshi, H.C. Brown, Israel J. Chem. 29 (1989) 229;
(c) C.D. Roy, H.C. Brown, Tetrahedron: Asymmetry 17 (2006)
1931;
(d) C.D. Roy, H.C. Brown, J. Chem. Res. (2006) 639, and
references cited therein;
vol. 5, Academic Press, New York, 1986, p. 131;
d) G.W. Gribble, Chem. Soc. Rev. 28 (1999) 335.
3] (a) D.R. Dalton, V.P. Dutta, J. Chem. Soc. B (1971) 85;
b) H. Kotsuki, T. Shimanouchi, R. Ohshima, S. Fujiwara, Tetrahe-
dron 54 (1998) 2709;
(
(
(e) C.D. Roy, Aust. J. Chem. 59 (2006) 657, and references cited
therein;
(
(
c) H. Sharghi, H. Naeimi, J. Chem. Res. (S) (1999) 310;
d) C.A.M. Afonso, N.M.L. Vieira, W.B. Motherwell, Synlett (2000)
(f) C.D. Roy, Aust. J. Chem. 59 (2006) 834.
[6] P. Bovicelli, E. Mincione, G. Ortaggi, Tetrahedron Lett. 32 (1991)
3719, and references cited therein.
[7] H.C. Brown, C.D. Roy, Mol. Online 2 (1998) 114, and references
cited therein.
382;
(
(
e) M. Soroka, W. Goldeman, Tetrahedron 61 (2005) 4233;
f) B.C. Ranu, S. Banerjee, J. Org. Chem. 70 (2005) 4517, and
references cited therein;
(
(
(
g) B. Das, M. Krishnaiah, K. Venkateswarlu, Tetrahedron Lett. 47
2006) 4457;
h) C. Betti, D. Landini, A. Maia, Synlett (2006) 1335, and references
[8] (a) C.D. Roy, H.C. Brown, Presented at the 217th ACS National
Meeting, Anaheim, CA, USA, March, 1999, Abstract No. ORGN-
127;
cited therein;
i) N. Iranpoor, H. Firouzabadi, R. Azadi, F. Ebrahimzadeh, Can. J.
Chem. 84 (2006) 69.
(b) C.D. Roy, H.C. Brown, Aust. J. Chem., in press.
[9] (a) H.C. Brown, N. Ravindran, S.U. Kulkarni, J. Org. Chem. 44
(1980) 384;
(
[
4] (a) Y. Guindon, C. Yoakim, H.E. Morton, Tetrahedron Lett. 24
(b) C.D. Roy, H.C. Brown, J. Chem. Res. (2006) 642;
(c) M. Zaidlewicz, H.C. Brown, in: L.A. Paquette (Ed.), Encyclopedia
of Reagents for Organic Synthesis, vol. 3, John Wiley & Sons, New
York, 1995, p. 1548.
(
(
1983) 2969;
b) Y. Guindon, M. Therien, Y. Girard, C. Yoakim, J. Org. Chem.
5
(
3
(
2 (1987) 1680;
c) Y. Guindon, C. Yoakim, H.E. Morton, J. Org. Chem. 49 (1984)
912;
d) T.W. Bell, J.A. Ciaccio, Tetrahedron Lett. 27 (1986) 827.
[10] (a) A.M. Salunkhe, H.C. Brown, Tetrahedron Lett. 36 (1995) 7987;
(b) A.M. Salunkhe, P.V. Ramachandran, H.C. Brown, Tetrahedron
58 (2002) 10059.