The hydroboration of propargyl bromide. Simple one-pot three-component routes to (Z)-1-bromoalk-1-en-4-ols and to anti-homoallylic alcohols

Article abstract of DOI:10.1021/jo005633a

The hydroboration of propargyl bromide with dialkylboranes takes place regioselectively to give 3-bromoprop-1-en-1-yl dialkylboranes 13 which, upon quaternization with bromide ion, undergo a series of transformations into a number of allylic boron species. By a suitable choice of the experimental conditions it is possible to trap the reaction intermediates with aldehydes and to steer the process toward either the synthesis of (Z)-1-bromoalk-1-en-4-ols 6 or anti-homoallylic alcohols 8. Two one-pot three-component processes were developed based on a sequence of four reactions; preparation of dialkylborane and hydroboration of propargyl bromide are the first steps. Then, quaternization with TEBABr may be carried out either in the presence of the aldehyde when (Z)-1-bromoalk-1-en-4-ols 6 are requested, or in the absence of the aldehyde in order to allow the formation of γ-substituted allyl borane 18 which, successively, adds to the aldehyde affording antihomoallylic alcohols 8.

Full text of DOI:10.1021/jo005633a

J . Org. Chem. 2000, 65, 8767-8773
8767
Th e Hyd r obor a tion of P r op a r gyl Br om id e. Sim p le On e-P ot
Th r ee-Com p on en t Rou tes to (Z)-1-Br om oa lk -1-en -4-ols a n d to
a n ti-Hom oa llylic Alcoh ols
Marco Lombardo,* Stefano Morganti, and Claudio Trombini*
Dipartimento di Chimica “G.Ciamician”, Universita` di Bologna, via Selmi 2, I-40126 Bologna, Italy
trombini@ciam.unibo.it
Received September 4, 2000
The hydroboration of propargyl bromide with dialkylboranes takes place regioselectively to give
3-bromoprop-1-en-1-yl dialkylboranes 13 which, upon quaternization with bromide ion, undergo a
series of transformations into a number of allylic boron species. By a suitable choice of the
experimental conditions it is possible to trap the reaction intermediates with aldehydes and to
steer the process toward either the synthesis of (Z)-1-bromoalk-1-en-4-ols 6 or anti-homoallylic
alcohols 8. Two one-pot three-component processes were developed based on a sequence of four
reactions; preparation of dialkylborane and hydroboration of propargyl bromide are the first steps.
Then, quaternization with TEBABr may be carried out either in the presence of the aldehyde when
(Z)-1-bromoalk-1-en-4-ols 6 are requested, or in the absence of the aldehyde in order to allow the
formation of γ-substituted allyl borane 18 which, successively, adds to the aldehyde affording anti-
homoallylic alcohols 8.
In tr od u ction
developed by our laboratory and based on the 1,4-
hydroboration of R,â-unsaturated acyclic enones followed
by addition of the intermediate (Z)-boron enolate to an
aldehyde.6
Here we wish to present one-pot synthetic protocols to
homoallylic alcohols based on the hydroboration of pro-
pargyl bromide as the first step.
The recourse to one-pot sequential transformations is
generally highly desirable in organic synthesis because
of the economic and environmental benefits associated
to the reduction of the overall number of synthetic steps,
such as reduction of cost, time, and waste production.1
Sequential transformations include the following: (i)
domino reactions, also described as cascade or tandem
reactions, where a spontaneous sequence of elementary
steps occurs, and (ii) consecutive reactions, where a one-
pot sequence of transformations is promoted by the
sequential addition of reagents, catalysts, etc. Boron
chemistry sounds particularly suitable for developing
synthetic protocols based on one-pot sequential trans-
formations. Selected examples extracted from the litera-
ture include the following: (i) Matteson sequential
homologations of boronates with chloromethyllithium,2
(ii) sequential Diels-Alder/aldehyde allylation reactions
starting from 1,3-dien-1-yl boronates,3 (iii) homologation/
aldehyde homoallenylation reactions starting from alle-
nyl boronates,4 (iv) aldol addition/aldehyde allylation
reactions starting from enol borates,5 (v) and a regio and
stereocontrolled protocol for the synthesis of syn-aldols
The regioselective hydroboration of propargyl chloride
by means of dialkylboranes was studied in the early
1970s by Zweifel.7 He reported that quaternization of the
3-chloroprop-1-en-1-yl boranes 1 with methyllithium
brought about the collapse of the intermediate “ate”
species 2 to give R-substituted allylboranes 3 (Scheme
1). The latter compound underwent rapid fluxional
conversion into the thermodynamically more stable γ-sub-
stituted allyl borane 4. Finally, deuteriolysis of 4 afforded
monosubstituted alkenes 5.
Recently, we found that the hydroboration product of
propargyl bromide by means of dialkylboranes may be
converted into R or γ-substituted allyl boranes by a
catalytic amount of a quaternary ammonium bromide.8
A deeper insight into the catalytic cycles involved in these
reactions, allows us to present now new protocols for the
selective synthesis of a variety of substituted homoallylic
alcohols of general structure 6-8 (Figure 1).
* To whom correspondence should be addressed. Phone: +39 051
2099513. Fax: +39 051 2099456.
(1) (a) Tietze, L. F.; Beifuss, U. Angew. Chem., Int. Ed. Engl. 1993,
32, 131-164. (b) Tietze, L. F. Chem. Rev. 1996, 96, 115-136. (c)
Denmark, S. E.; Thorarensen, A. Chem. Rev. 1996, 96, 137-166. (d)
Winkler, J . D. Chem. Rev. 1996, 96, 167-176. (e) Ryu, I.; Sonoda, N.;
Curran, D. P. Chem. Rev. 1996, 96, 177-194. (f) Parsons, P. J .; Penkett,
C. S.; Shell, A. J . Chem. Rev. 1996, 96, 195-206. (g) Wang, K. K. Chem.
Rev. 1996, 96, 207-222. (h) Padwa, A.; Weingarten, M. D. Chem. Rev.
1996, 96, 223-270. (i) Harvey, D. F.; Sigano, D. M. Chem. Rev. 1996,
96, 271-288.
Resu lts a n d Discu ssion
At the outset of this work, it was verified that 3-bro-
moprop-1-en-1-yl dicyclohexylborane (9), prepared from
a freshly distilled solution of propargyl bromide, could
(2) Matteson, D. S.; Singh, R. P.; Schafman, B.; Yang, J .-J . J . Org.
Chem. 1998, 63, 4466. See also: Matteson, D. S. CHEMTECH 1999,
6 and references therein.
(5) Hoffmann, R. W.; Froech, S. Tetrahedron Lett. 1985, 26, 1643-
1646.
(6) Boldrini, G. P.; Bortolotti, M.; Mancini, F.; Tagliavini, E.;
Trombini, C.; Umani-Ronchi, A. J . Org. Chem. 1991, 56, 5820-5826.
(7) Zweifel, G.; Horng, A. Synthesis 1973, 672-674.
(8) Gaddoni, L.; Lombardo, M.; Trombini, C. Tetrahedron Lett. 1998,
39, 7571-7574.
(3) Renard, P.-I.; Lallemand, J .-Y. Tetrahedron: Asymmetry 1996,
7, 2523-2524.
(4) Soundararajan, R.; Li, G.; Brown, H. C. J . Org. Chem. 1996, 61,
100-104.
10.1021/jo005633a CCC: $19.00 © 2000 American Chemical Society
Published on Web 11/10/2000

8768 J . Org. Chem., Vol. 65, No. 25, 2000
Lombardo et al.
Sch em e 1
F igu r e 1. Structures of homoallylic alcohols 6-8.
be stored for a few days under argon at 0 °C without
appreciable decomposition, while extensive decomposition
occurred within 5-10 h when a yellowish commercial
toluene solution of propargyl bromide was used. To shed
light into this different behavior, we hydroborated a
yellowish old commercial toluene solution of propargyl
bromide with dicyclohexylborane and, after 15 h at 20
°C, we quenched two aliquots of the reaction mixture with
alkaline hydrogen peroxide and benzaldehyde, respec-
tively. Products 8a and 11, reported in Scheme 2,
unambiguously revealed that a reaction cascade had to
take place, converging into a (E)-1-cyclohexylprop-1-en-
3-yl borane species 10.
Sch em e 2a
The E geometry of 10 was deduced on the basis of the
E geometry of the oxidation product 11 and of the anti
relative stereochemistry of 8a , confirmed upon transfor-
mation into the 4,5-trans-disubstituted 1,3-dioxane 12.
In our opinion, a catalytic amount of free bromide ion
(X ) Br in Scheme 2) was present in the aged sample of
propargyl bromide as the result of substrate decomposi-
tion, and it was responsible for a reaction cascade
involving quaternization of 9 and converging to the
γ-substituted allyl borane 10.
When the same reactions where reproduced using
freshly distilled propargyl bromide, we did not detect any
trace of 8a or 11.
Delighted by the disclosure of a straightforward route
to substituted allylic boranes,9 we carried out further
experiments using the system dicyclohexyl borane and
freshly distilled propargyl bromide, and studied the effect
exerted by a source of bromide ions such as triethylben-
zylammonium bromide (TEBABr).
The most significant results are collected in Table 1.
The presence of a catalytic amount (10% mol) of
TEBABr speeded up the formation of allylic boranes in
1 h and, depending on the solvent and on the order of
addition of TEBABr and benzaldehyde, homoallylic al-
cohols 6a , 7a , or 8a could be selectively obtained. More
in detail, 6a was produced in major extent when quat-
ernization with TEBABr was carried out in THF in the
presence of benzaldehyde (henceforth we refer to this
addition order as protocol A) (entry 1); 7a and 8a were
the prominent products when an equilibration time (teq)
was adopted between the quaternization with TEBABr
and the addition of the aldehyde (protocol B), in nonco-
ordinating solvents (entries 5 and 6) or in THF (entries
2-4), respectively.
a
Key: (i) 15 h at 20 °C; (ii) 30% H2O2/3 M NaOH; (iii) PhCHO;
(iv) O3; (v) BH3‚THF; (vi) 2,2-dimethoxypropane, H+.
Entries 2-4, in particular, reveal that 6a was gradu-
ally replaced by 8a as the major product when either teq
or the equilibration temperature (Teq) were increased.
The results obtained are consistent with the general
reaction scheme depicted in Figure 2. Bromide ion adds
to 13 to give the “ate” ion 14, which collapses via
anionotropic 1,2-shift of a boron ligand to the migration
terminus represented by the 3-bromoprop-1-en-1-yl group.
Bromide displays a migratory aptitude higher than
cyclohexyl and, consequently, the R-bromoallylborane 15
is the major product (path A), when R ) c-C6H11 and at
short reaction time. After a longer equilibration time,
R-substituted and γ-substituted allyl boranes 17 and 18
become the dominant products. Disappearance of 15 after
teq ) 1 h indicates that two different reaction channels
are possible, converging into the R-substituted allyl
borane 17: a direct route due to the alkyl group migra-
tion in 14 (path B), and a second involving bromide
quaternization of 15 to give the new borate complex 16,
followed by alkyl migration. Once the R-alkyl substituted
allyl borane 17 is formed, conversion into the more
thermodynamically stable γ-alkyl substituted allyl bo-
rane 18 takes place with a rate constant depending on
temperature,9a solvent and on the R group (vide infra).
Unravelling the overall reactions cascade shown in
Figure 2, gave us the fundamental background for
(9) (a) Roush, W. R. In Comprehensive Organic Synthesis; Trost B.
M., Fleming I., Eds.; Pergamon Press: Oxford, 1991; Vol. 2, pp 1-53.
(b) Hoffmann, R. W. Angew. Chem., Int. Ed. Engl. 1987, 26, 489-594.

Synthesis of Homoallylic Alcohols via Boranes
J . Org. Chem., Vol. 65, No. 25, 2000 8769
Ta ble 1. Qu en ch in g Exp er im en ts of 9 w ith Ben za ld eh yd e (3 h a t 0 °C) a fter Equ ilibr a tion w ith TEBABr (10% Mol)a
entry
solvent
protocolb
teq (h)
Teq (°C)
6a c (E/ Z) (%)
7a c (E/ Z) (%)
8a c (anti/syn) (%)
1
2
3
4
5
6
7
THF
THF
THF
THF
A
B
B
B
B
B
B
65 (15:85)
32 (15:85)
14 (15:85)
nd
<3
ndd
1
2
1
1
1
1
0
0
20
20
20
20
nd
33 (>98:2)
54 (>98:2)
68 (>98:2)
<3
nd
nd
nC5H12
nC5H12/CH2Cl2 9:1
nC5H12/THF 3:1
5
37 (90:10)
55 (90:10)
4
11 (18/82)
9 (16/84)
3
28 (>98:2)
a
b
Freshly distilled propargyl bromide was used for the preparation of 9. Protocol A: to a THF solution of 9 are added, in turn, the
aldehyde and TEBABr. Protocol B: to a THF solution of 9 TEBABr is added, and after equilibration (teq, Teq) the aldehyde is added. For
further details see the Experimental Section. c Isolated yields. Not detected.
d
F igu r e 2. Overall mechanistic scheme for the bromide-catalyzed reaction cascade of 13.
Ta ble 2. Syn th esis of (Z)-1-Br om oa lk -1-en -4-ols 6 by
Ad op tin g P r otocol A, in THF a t 0 °C a n d Usin g
Dicycloh exylbor a n e
developing two selective one-pot protocols for the syn-
thesis of homoallylic alcohols 6 and 8 in THF, respec-
tively.
entry
RCHO
PhCHO
PhCHdCHCHO
(CH3)2CHCHO
CH3(CH2)5CHO
cC6H11CHO
yielda (%) E/Z
other products (%)
Thus, synthesis of 6 can be achieved if dicyclohexylbo-
rane is used and if protocol A is adopted, allowing the
intermediate R-bromoallylborane 15 to be trapped by the
aldehyde before it undergoes further quaternization to
1610 and final conversion to 17. In all of our experiments
we never detected products due to fluxional equilibration
of 15; these results seems to be not in agreement with
observations by Oehlschlager et al. who studied the
behavior of the chloro analogous of 15.11 It is known that
metalation of allyl chloride with hindered lithium di-
alkylamides12 affords configurationally stable R-chloro-
allyllithium which may be trapped by R2BOR′ to give
R-chloroallyl boronates (R ) alkoxy)13 or R-chloroallyl
boranes (R ) alkyl),12 respectively. The latter derivatives,
prepared in diethyl ether at -95 °C in the presence of
BF3, according to the Oehlschlager procedure, proved to
undergo rapid haptotropic rearrangement, as a conse-
quence of the presence of the Lewis acid. In our proce-
1
2
3
4
5
6a (56)
6b (65)
6c (46)
6d (55)
6e (63)
15:85
18:82
16:84
12:88
14:86
7a (<3)
7b (5), 8b (10)
7c (2), 8c (2)
7d + 8d (7)
7e + 8e (11)
a
Isolated yields.
dure, additional Lewis acids are absent and 15 displays
constitutional stability.
Table 2 collects a few examples of syntheses of (Z)-1-
bromoalk-1-en-4-ols 6.
Our stereochemical results are in agreement with
observations by Hoffmann on the addition of allylbor-
onates carrying a halogen atom or other electronegative
substituents in the R position to aldehydes which leads
to (Z)-homoallylic alcohols.14 The usefulness of 6 is
enhanced by possibility to apply on it palladium-catalyzed
cross coupling reactions leading to (Z)-configurated γ-alkyl
substituted homoallylic alcohols.
(10) For a phenylselenium equivalent of 16, see: Yamamoto, Y.;
Saito, Y.; Maruyama, K. J . Org. Chem. 1983, 48, 5408-5409.
(11) (a) J ayaraman, S.; Hu, S.; Oehlschlager, A. C. Tetrahedron Lett.
1995, 36, 4765-4768. (b) Hu, S.; J ayaraman, S.; Oehlschlager, A. C.
J . Org. Chem. 1996, 61, 7513-7520. (c) Hu, S.; J ayaraman, S.;
Oehlschlager, A. C. J . Org. Chem. 1998, 63, 8843-8849. (d) Hu, S.;
J ayaraman, S.; Oehlschlager, A. C. J . Org. Chem. 1999, 64, 3719-
3721.
The second synthetic procedure we developed leads to
anti-homoallylic alcohols 8.
The synthesis of anti-8 requires complete disappear-
ance of 15 and complete conversion of 17 into 18.15 This
is simply achieved by adopting protocol B and using THF
as solvent. Results collected in Table 3 show that THF
favors the complete conversion of 17 into 18 if a teq ) 1
(12) MacDonald, T. L.; Narayanan, B. A.; O’Dell, D. E. J . Org. Chem.
1981, 46, 1504-1506.
(13) (a) Brown, H. C.; Rangaishenvi, M. V. Tetrahedron Lett. 1990,
31, 7113-7114. (b) Brown, H. C.; Rangaishenvi, M. V. Tetrahedron
Lett. 1990, 31, 7115-7118. The same R-chloroallyl boronates may be
prepared by anionotropic shift in borate species carrying a vinylic and
a chloromethyl substituent: (c) Matteson, D. S.; Ray, R.; Rocks, R. R.;
Tsay, D. J . Organometallics 1983, 2, 1536. (d) Hoffmann, R. W.;
Landmann, B. Angew. Chem., Int. Ed. Engl. 1984, 23, 437.
(14) (a) Hoffmann, R. W.; Landmann, B. Chem. Ber. 1986, 119,
2013-2024. (b) Hoffmann, R. W.; Landmann, B. Chem. Ber. 1986, 119,
1039-1053. (c) Hoffmann, R. W.; Landmann, B. Tetrahedron Lett.
1983, 3209-3212.

8770 J . Org. Chem., Vol. 65, No. 25, 2000
Lombardo et al.
other products (%)
Ta ble 3. Syn th esis of a n ti-8 Ad op tin g P r otocol B (THF , teq ) 1 h , Teq ) 0 °C f 20 °C)
run
R in R2BH
R′CHO
yielda (%)
anti/syn
1
2
3
4
5
6
7
8
9
cyclohexyl
cyclohexyl
cyclohexyl
cyclohexyl
cyclohexyl
cyclohexyl
cyclopentyl
cyclopentyl
n-octyle
PhCHO
(CH3)2CHCHO
CH3(CH2)5CHO
CH2dC(CH3)CHO
O-TBDMS-L-lactaldehyde
2,3-O-isopropylidene-D-glyceraldehyde
PhCHO
(CH3)2CHCHO
PhCHO
PhCHO
8a (68)
8c (72)
8d (82)
8f (84)
8g (80)
8h (40)
8i (45)
8j (60)
8k (40)
8l (13)
8l (38)
>98:2
>98:2
>98:2
>98:2
c
ndb
nd
nd
nd
nd
nd
nd
nd
nd
d
>98:2
>98:2
>98:2
>98:2
>98:2
10
11
siamyl
7l (50%)
7l (28%)
siamylf
PhCHO
a
b
d
Isolated yields. Not detected. c No facial selectivity was observed. Facial diastereoselectivity (de) was 70%. e Thexyl octylborane
f
was formally used. See Experimental. teq ) 15 h.
h at 20 °C is adopted when cyclohexyl, cyclopentyl, or a
primary alkyl migrating group are used (entries 1-9).
Besides solvent and temperature, the haptotropic
rearrangement in substituted allylic boranes also de-
pends on the nature of the alkyl substituent on the allyl
fragment. In fact, a very slow rearrangement at room
temperature in THF was observed in the case of the
siamyl subsituent, as demonstrated by the results of
entries 10 and 11, where the 8l/7l ratio increased from
0.3 to 1.3 when teq was increased from 1 to 15 h.
Chemical yields reported in Tables 1-3 deserve a
comment: they refer to pure isolated products and
generally lie in the 40-80% range. By a synthetic point
of view they can be considered acceptable values since
they correspond to the overall yield of a one-pot multistep
sequence which requires 7 h for its completion, starting
from the preparation of the dialkylborane up to the final
workup of the condensation reaction.
A main limit of the scope of the proposed synthetic
protocols is represented by the limited number of dialkyl-
boranes which may be directly produced by hydroboration
of two equivalents of an alkene.16 Indirect routes to
dialkylboranes, such as hydroboration of two equivalents
of an alkene with chloroborane or bromoborane followed
by reduction with aluminum hydrides17 are less practical
and leave acidic species into the reaction mixture which
may affect the haptotropic rearrangement. Since both the
hydroboration of terminal alkynes and that of terminal
alkenes are very fast, we developed the following solution
for the preparation of 13 carrying an octyl group on
boron. We envisaged in thexylborane a good regioselective
hydroborating agent and treated it with an equimolar
solution of 1-octene and propargyl bromide at -20 °C,
then leaving the temperature to raise to 20 °C. Final yield
of 8k (40%, Table 3, entry 9) is acceptable, considering
that nine elementary steps are involved in this one-pot
sequence.
namely a solvent change from THF to less polar media.
Under these conditions the equilibration time was re-
quired to allow the conversion of 13 into 17 in acceptable
amount, but the fluxional transformation of 17 into the
thermodynamically more stable γ-substituted isomer 18
appeared to be much slower than the addition to the
aldehyde, thus favoring 7 as major product. A general
and practical synthetic protocol leading to 7 is under
development and will be published in due course.
Con clu sion s
A mechanistic study of the reaction of 3-bromoprop-1-
en-1-yl dialkyl boranes 13 with bromide ion is presented.
A reaction cascade made of anionotropic migrations,
quaternization reactions and haptotropic rearrangements
takes place affording three types of allylic boranes,
namely R-bromoallylborane 15, R-alkylallylborane 17 and
γ-alkylallylborane 18. By a careful choice of the experi-
mental parameters, conditions can be found in which
each single borane prevails. Interesting observations
were done on the borotropic shift converting 17 into 18.
It does strongly depend on the solvent polarity, reaction
rate being very high in THF and quite lower in pentane;
at the best of our knowledge a careful study of the
kinetics of borotropic rearrangements in crotyl boranes
and boronates in different solvents is still lacking and
could be highly desirable. Furthermore, steric bulk of the
alkyl substituent of the allylic moiety in substituted allyl
boranes does considerably affect the haptotropic rear-
rangement.
The overall mechanistic picture allowed us to develop
two one-pot three-component protocols leading to (Z)-1-
bromo-alk-1-en-4-ols 6 or to anti-homoallylic alcohols 8.
In particular, we wish to emphasize that very few studies
are available in the literature relative to the preparation
of anti-8 using substituted allyl organometallic reagents
with R * Me,18 in comparison with the terrific amount
of papers which dealt in the last two decades with the
synthesis of their crotyl analogues.9,19
Coming back to entries 5 and 6 of Table 1, homoallylic
alcohols 7 are also, in principle, accessible via protocol
B by a simple change of the experimental conditions,
Exp er im en ta l Section
(15) The 1,3-borotropic shift in allylic boranes has been widely
studied by dynamic NMR experiments and in terms of stereochemical
outcome of the process. See, for example: (a) Kramer, G. W.; Brown,
H. C. J . Organomet. Chem. 1977, 132, 9-27. (b) Brown, H. C.; J adhav,
P. K.; Bhat, K. S. J . Am. Chem. Soc. 1985, 107, 2564-2565. (c) Bubnov,
Y. N.; Gurskii, M. F.; Gridnev, I. D.; Ignatenko, A. V.; Ustynyuk, Y.
A.; Mstislavsky, V. I. J . Organomet. Chem. 1992, 424, 127-132. (d)
Hoffmann, R. W.; Polachowski, A. Chem. Eur. J . 1998, 4, 1724-1730.
(16) Pelter, A.; Smith, K. In Comprehensive Organic Chemistry;
Neville J ones, D., Ed., Pergamon Press: Oxford, 1979; Vol. 3, pp 695-
790.
Gen er a l Meth od s. 1H and 13C NMR spectra were recorded
at 300 or 200 MHz and 75 or 50 MHz, respectively, in CDCl3
using tetramethylsilane (TMS) as internal standard. Chemical
shifts are reported in ppm (δ) downfield from TMS. GC-MS
(18) (a) Fu¨rstner, A. Chem. Rev. 1999, 99, 991-1045. (b) Salmon,
A.; Carboni, B. J . Organomet. Chem. 1998, 567, 31-38. (c) Takeda,
T.; Miura, I.; Horikawa, Y.; Fujiwara, T. Tetrahedron Lett. 1995, 36,
1495-1498.
(17) Brown, H. C.; Basavaiah, D.; Kulkarni, S. J . Organomet. Chem.
1982, 225, 63-69.
(19) Bloch, R. Chem. Rev. 1998, 98, 1407-1438.

Synthesis of Homoallylic Alcohols via Boranes
J . Org. Chem., Vol. 65, No. 25, 2000 8771
analyses (70 eV) were performed with a quadrupole instru-
ment. Solvents were dried using standard methods: THF was
distilled from lithium aluminum hydride (LAH) and pentane
from sodium benzophenone immediately prior to use. All
reactions were carried out in oven-dried glassware under an
atmosphere of dry argon. All reagents were commercially
available (Fluka, Aldrich) and were used without further
purification, unless otherwise stated.
Ma t er ia ls. Propargyl bromide was distilled immediately
prior the use. Triethylbenzylammonium bromide (TEBABr)
was dried and stored under argon in a vacuum desiccator in
the presence of P2O5. A 2M solution of BH3‚SMe2 in THF
(Fluka) was handled using Schlenk techniques. Stocks of
dicyclohexyl borane have been also prepared, stored under
argon at -10 °C, and used for about two weeks.
tocol B (Ta ble 3, En tr y 1). A 2 M solution of BH3‚SMe2 in
THF (0.5 mL, 1 mmol) was added at 0 °C to a solution of
cyclohexene (0.2 mL, 2 mmol) in THF (2 mL), and the reaction
mixture was vigorously stirred at 0 °C for 1 h. Propargyl
bromide (0.1 mL, 1 mmol) was added, and the mixture was
stirred for an additional 1 h, until the white precipitate of
dicyclohexyl borane dissolved. TEBABr (0.013 g) was added,
and the reaction mixture was equilibrated with stirring for 1
h while the temperature was allowed to raise to 20 °C.
Benzaldehyde (0.1 mL, 1 mmol) was added, and the mixture
was stirred at 20 °C for 3 h. The reaction was quenched at 0
°C by the consecutive addition of 3 N NaOH and 30% H2O2
followed by stirring for 30 min. The aqueous layer was
extracted with ether (3 × 5 mL), and the combined organic
phase was dried (Na2SO4) and concentrated under reduced
pressure. Purification of the residue by flash-chromatography
(SiO2, cyclohexane/ether 95:5) afforded 0.16 g (0.68 mmol, 68%)
(E)-3-Cycloh exylp r op -2-en -1-ol (11). A 2M solution of
BH3‚SMe2 in THF (2 mL, 4 mmol) was added at 0 °C to a
solution of cyclohexene (0.8 mL, 8 mmol) in THF (8 mL), and
the reaction mixture was vigorously stirred at 0 °C for 2 h.
Aged propargyl bromide (0.4 mL, 4 mmol) was added, and the
mixture was stirred for 15 h at 20 °C. Oxidative quenching
(H2O2/NaOH), followed by extraction with ether and purifica-
tion by flash-chromatography (SiO2, cyclohexane) afforded 0.47
g (3.36 mmol, 84%) of 11. 1H NMR (300 MHz): δ 1.06-1.43
(m, 5H), 1.63-1.75 (m, 5H), 1.90-2.05 (m, 1H), 4.09 (d, J )
5.4 Hz, 2H), 5.58 (dd, J ) 5.4/15.6 Hz, 1H), 5.66 (dd, J ) 5.4,
15.6 Hz, 1H). 13C NMR (75 MHz): δ 25.9, 26.1, 32.7, 40.2, 63.6,
126.3, 138.8. MS (EI): m/z 122 ([M+ - 18], 30), 109 (34), 99
1
of anti-8a . Signals due to syn-8a in the crude H NMR spectra
were close to the detection limit or absent.
1
a n ti-1-P h en yl-2-cycloh exylbu t-3-en -1-ol (8a ). H NMR
(300 MHz): δ 0.95-1.32 (m, 6H), 1.58-1.82 (m, 5H), 2.14 (br
dt, J ∼ 3.9/9.0 Hz, 1H), 4.70 (d, J ) 8.1 Hz, 1H), 5.10 (dd, J )
2.1/17.1 Hz, 1H), 5.26 (dd, J ) 2.1/10.1 Hz, 1H), 5.83 (dt, J )
10.1/17.1 Hz, 1H), 7.27-7.40 (m, 5H). 13C NMR (75 MHz): δ
26.3, 26.4, 26.5, 28.6, 37.8, 58.6, 73.8, 119.3, 126.7, 127.4, 128.1,
136.6, 143.0. MS (EI): m/z 124 (33), 107 (100), 82 (13), 81 (11),
79 (32), 77 (16), 67 (7). Anal. Calcd for C16H22O (230.35): C,
83.43; H, 9.63. Found: C, 83.35; H, 9.68.
(70), 81 (100), 67 (98), 55 (54). Anal. Calcd for C9H16
(140.23): C, 77.09; H, 11.50. Found: C, 77.14; H, 11.45.
O
Gen er a l P r oced u r e for th e Syn th esis of (Z)-1-Br o-
m oa lk -1-en -4-ols (6). P r otocol A (Ta ble 2, En tr y 1). A 2
M solution of BH3‚SMe2 in THF (0.5 mL, 1 mmol) was added
at 0 °C to a solution of cyclohexene (0.2 mL, 2 mmol) in THF
(2 mL), and the reaction mixture was vigorously stirred at 0
°C for 1 h. Propargyl bromide (0.1 mL, 1 mmol) was added,
and the mixture was stirred for an additional hour, until the
white precipitate of dicyclohexyl borane dissolved. Benzalde-
hyde (0.1 mL, 1 mmol) was added followed by TEBABr (0.013
g), and the temperature was allowed to raise to 20 °C under
stirring for 3 h. The reaction was quenched at 0 °C by
consecutive addition of 3 N NaOH and 30% H2O2 followed by
stirring for 30 min. The aqueous layer was extracted with ether
(3 × 5 mL), and the combined organic layers were dried (Na2-
SO4) and concentrated under reduced pressure to afford a 15:
85 mixture of (E)- and (Z)-diastereoisomers. The diastereo-
t r a n s-2,2-Dim e t h yl-4-p h e n yl-5-cycloh e xyl-1,3-d iox-
a n e (12). A solution of 8a (0.23 g, 1 mmol) in CH2Cl2 (20 mL)
was ozonized for 30 min at -78 °C. The reaction mixture was
quenched at -78 °C with BH3‚SMe2 (∼10M, 0.4 mL, 4 mmol)
and allowed to reach 20 °C. The reaction mixture was
quenched with 3N HCl and extracted with CH2Cl2 (3 × 5 mL).
The combined organic layers were dried (Na2SO4), concen-
trated at reduced pressure and the residue was purified by
flash-chromatography (SiO2, cyclohexane:acetate 80:20) to
afford 0.182 g (0.78 mmol, 78%) of 1-phenyl-2-cyclohexylpro-
pan-1,3-diol. 1H NMR (300 MHz): δ 0.80-1.90 (m, 11H), 1.96-
2.15 (m, 2H), 3.74-3.82 (m, 2H), 5.03 (d, J ) 9.3 Hz, 1H),
7.20-7.45 (m, 5H). 13C NMR (75 MHz): δ 26.5, 26.6, 26.9, 29.4,
31.6, 35.9, 51.7, 61.9, 76.6, 126.0, 127.2, 128.2, 144.0. Anal.
Calcd for C15H22O2 (234.34): C, 76.88; H, 9.46. Found: C,
76.95; H, 9.43.
1
meric ratio was determined by GC-MS and H NMR analyses
of the crude reaction mixture. Purification of the residue by
careful flash-chromatography (SiO2, cyclohexane/ether 95:5)
afforded 0.05 g of analytically pure (Z)-6a (0.22 mmol, 22%)
and 0.08 g (0.80 mmol, 34%) of a 25:75 mixture of (E)- and
(Z)-6a . Spectral data of the major pure diastereoisomer are
reported, while only 13C NMR and GC-MS spectra are reported
for (E)-6a . 1H NMR coupling constants allowed us to assign
the stereochemistry of major (Z)-6a , re-enforced by 13C NMR
chemical shifts of both (E)- and (Z)-6a , on the basis of
comparison with literature data.14a,20
To a solution of the diol (0.165 g, 0.7 mmol) in CH2Cl2 (2
mL) were added 2,2-dimethoxypropane (0.18 mL, 1.4 mmol)
and a catalytic amount of Amberlyst 15H, and the reaction
mixture was stirred at 20 °C for 1 h. The solution was filtered
(Celite) and evaporated to dryness. Purification of the residue
by flash chromatography (SiO2, cyclohexane/acetate 90:10)
afforded 0.178 g (0.65 mmol, 83%) of title compound 12 as a
1
white solid. Mp: 77-78 °C. H NMR (300 MHz): δ 0.75-1.98
(m, 8H), 1.46 (s, 3H), 1.55 (s, 3H), 1.55-1.80 (m, 3H), 1.81-
1.86 (m, 1H), 3.84-4.05 (m, 2H), 4.82 (d, J ) 10.7 Hz, 1H),
7.20-7.42 (m, 5H). 13C NMR (75 MHz): δ 26.5, 26.7, 26.8, 28.0,
29.7, 31.4, 36.5, 46.0, 61.3, 75.0, 98.5, 127.5, 127.9, 128.3, 140.6.
MS (EI): m/z 259 ([M+ - 15], 2), 117 (25), 110 (100), 107 (46),
95 (14), 91 (11), 81(50), 67 (16), 55 (7). Anal. Calcd for C18H26O2
(274.40): C, 78.79; H, 9.55. Found: C, 78.82; H, 9.49.
(Z)-1-P h en yl-4-b r om obu t -3-en -1-ol (6a ). 1H NMR (300
MHz): δ 2.66 (dd, J ) 6.3/14.5 Hz, 1H), 2.75 (dd, J ) 7.8/14.5
Hz, 1H), 4.85 (br t, J ∼ 6.6 Hz, 1H), 6.19 (q, J ) 6.9 Hz, 1H),
6.29 (d, J ) 6.9 Hz, 1H), 7.28-7.42 (m, 5H). 13C NMR (75
MHz): δ 39.2, 72.9, 109.9, 125.7, 127.7, 128.4, 130.7, 143.4.
MS (EI): m/z 128 (2), 108 (8), 107 (100), 105 (8), 79 (85), 77
(53), 51 (19). Anal. Calcd for C10H11BrO (227.10): C, 52.89; H,
4.88. Found: C, 52.81; H, 4.84.
(Ta ble 3, En tr y 5): 2-ter t-Bu tyld im eth ylsilyloxy-4-
cycloh exylh ex-5-en -3-ol (8g). By applying protocol B to
O-tbutyldimethylsilyl-L-lactaldehyde, the title product was
obtained in overall 83% yield as a 50/50 mixture of (2S,3S,4R)-
8g and (2S,3R,4S)-8g; the diastereomeric ratio was determined
by 1H NMR analysis of the crude reaction mixture. Assignment
of stereochemical relationships was made by converting ho-
moallylic alcohols into their corresponding 1,3-dioxolane-2-ones
(Scheme 3). 13C NMR chemical shifts of carbons directly
connected to the cyclic framework allowed us to assign the
relative cis/trans stereochemistry. In the case of cis substitu-
(E)-1-P h en yl-4-br om obu t-3-en -1-ol (6a ). 13C NMR (75
MHz): δ ) 42.3, 73.0, 107.1, 125.6, 127.7, 128.3, 133.7, 143.2.
MS (EI): m/z 128 (2), 108 (8), 107 (100), 105 (8), 79 (80), 77
(55), 51 (20).
Gen er a l P r oced u r e for th e Syn th esis of a n ti-Hom oa l-
lylic Alcoh ols 8 Sta r tin g fr om P r op a r gyl Br om id e. P r o-
(20) Silverstein, R. M.; Bassler, G. C.; Morril, C. T. Spectrometric
Identification of Organic Compounds, 5th ed.; Wiley: New York, 1991;
pp 237-239.

8772 J . Org. Chem., Vol. 65, No. 25, 2000
Lombardo et al.
10.3 Hz, 1H), 5.78 (dt, J ) 10.3/17.3 Hz, 1H). 13C NMR (75
MHz): δ 19.1, 26.4, 26.5, 30.8, 31.1, 37.3, 52.5, 69.2, 74.8,
117.7, 136.9. Anal. Calcd for C12H22O2 (198.31): C, 72.68; H,
11.18. Found: C, 72.73; H, 11.23.
Sch em e 3
(2S,3R,4S)-4-Cycloh exylh ex-5-en e-2,3-d iol 19. Applying
the same procedure reported above to (2S,3R,4S)-8g, (2S,3R,4S)-
19 was obtained in 94% overall yield. [R]20 ) +6.7 (c ) 1.1,
D
1
CHCl3). H NMR (300 MHz): δ 0.80-1.48 (m, 6H), 1.22 (d, J
) 6.4 Hz, 3H), 1.52-1.79 (m, 6H), 1.84 (d, J ) 7.8 Hz, 1H),
1.99 (dt, J ) 6.0/9.9 Hz, 1H), 3.68 (dt, J ) 4.9/6.0 Hz, 1H),
3.83 (ddq, J ) 4.9/6.4/7.8 Hz, 1H), 5.12 (dd, J ) 2.1/17.1 Hz,
1H), 5.23 (dd, J ) 2.1/9.9 Hz, 1H), 5.80 (dt, J ) 9.9/17.1 Hz,
1H); 13C NMR (75 MHz): δ ) 17.8, 25.6, 26.5 (2C), 29.4, 31.7,
37.6, 52.4, 68.9, 73.8, 118.5, 137.3. Anal. Calcd for C12H22O2
(198.31): C, 72.68; H, 11.18. Found: C, 72.75; H, 11.14.
[4S-[4r(S*),5â]-4-(1-Cycloh exyl-2-p r op en yl)-5-m eth yl-
1,3-d ioxola n -2-on e 20. Bis(trichloromethyl) carbonate (0.058
g, 0.19 mmol) and triethylamine (0.055 mL, 0.39 mmol) were
added to a solution of (2S,3S,4R)-19 (0.035 g, 0.18 mmol) in
CH2Cl2 (1 mL). After 1 h, the reaction was quenched with
water, and the aqueous layer was extracted with CH2Cl2 (3 ×
5 mL). The combined organic layers were dried (Na2SO4) and
evaporated under reduced pressure. The residue was purified
by flash chromatography (SiO2, cyclohexane/ethyl acetate 90:
10) affording 0.038 g (0.17 mmol, 94%) of trans cyclic carbonate
1
20. [R]20 ) -19.0 (c ) 1.64, CHCl3). H NMR (300 MHz): δ
D
tion, a marked γ-gauche effect results in a upfield shift of both
resonance lines of 3-5 ppm with respect to the trans iso-
mer.20,21
0.81-1.47 (m, 6H), 1.44 (d, J ) 6.4 Hz, 3H), 1.45-1.89 (m,
6H), 4.42 (dd, J ) 2.6/7.0 Hz, 1H), 4.51 (br quintet, J ) 7.0
Hz, 1H), 5.11 (dd, J ) 1.8/17.1 Hz, 1H), 5.30 (dd, J ) 1.8/10.3
Hz, 1H), 5.68 (dt, J ) 10.3/17.1 Hz, 1H). 13C NMR (75 MHz):
δ 19.1, 26.1 (2C), 26.2, 30.7, 30.8, 38.5, 52.7, 76.4, 83.0, 120.5,
133.4, 154.6. MS (EI): m/z 142 (66), 123 (13), 98 (62), 83 (36),
81 (99), 80 (78), 79 (75), 69 (17), 67 (57), 55 (100). Anal. Calcd
for C13H20O3 (224.30): C, 69.61; H, 8.99. Found: C, 69.55; H,
9.05.
(2S,3S,4R)-8g. Y ) 42%. Rf ) 0.37 (cyclohexane/ethyl
1
acetate 95:5). [R]20 ) +8.6 (c ) 1.50, CHCl3). H NMR (300
D
MHz): δ 0.09 (s, 6H), 0.90 (s, 9H), 0.72-1.01 (m, 2H), 1.08 (d,
J ) 6.1 Hz, 3H), 1.12-1.34 (m, 4H), 1.41-1.81 (m, 5H), 1.82-
1.95 (m, 1H), 3.46 (dd, J ) 3.2/7.5 Hz, 1H), 3.70 (dq, J ) 6.4/
7.5 Hz, 1H), 4.90 (dd, J ) 2.4/17.3 Hz, 1H), 5.09 (dd, J ) 2.4/
10.2 Hz, 1H), 5.78 (dt, J ) 10.2/17.3 Hz, 1H). 13C NMR (75
MHz): δ -4.8, -4.0, 18.0, 19.4, 25.8, 26.5, 26.7, 31.1, 31.2,
[4R-[4r(S*),5â]-4-(1-Cycloh exyl-2-p r op en yl)-5-m eth yl-
1,3-d ioxola n -2-on e 20. Applying the same procedure reported
above to (2S,3R,4S)-19, cis cyclic carbonate 20 was obtained
37.9, 51.8, 70.8, 75.0, 116.7, 137.3. MS (EI): m/z 255 ([M+
-
57], 1), 189 (4), 173 (15), 163 (10), 159 (34), 131 (34), 119 (100),
103 (13), 95 (8), 82 (36), 75 (62), 73 (50), 67 (10), 55(15). Anal.
Calcd for C18H36O2Si (312.57): C, 69.17; H, 11.61. Found: C,
69.23; H, 11.68.
in 90% overall yield. [R]20 ) +8.0 (c ) 2.80, CHCl3). 1H NMR
D
(300 MHz): δ ) 0.84-1.40 (m, 6H), 1.43 (d, J ) 6.5 Hz, 3H),
1.51-1.81 (m, 5H), 2.17-2.24 (m, 1H), 4.76 (dd, J ) 6.0/6.7
Hz, 1H), 4.85 (br quintet, J ) 6.7 Hz, 1H), 5.14 (dd, J ) 1.7/
17.2 Hz, 1H), 5.27 (dd, J ) 1.7/10.4 Hz, 1H), 5.74 (dt, J ) 10.4/
17.2 Hz, 1H). 13C NMR (75 MHz): δ ) 14.3, 26.2, 26.3, 26.4,
29.0, 31.3, 39.6, 49.0, 76.6, 79.9, 119.7, 133.7, 154.6. MS (EI):
m/z 142 (80), 123 (19), 99 (10), 98 (51), 83 (36), 81 (100), 80
(60), 79 (55), 69 (13), 67 (40), 55 (53). Anal. Calcd for C13H20O3
(224.30): C, 69.61; H, 8.99. Found: C, 69.53; H, 8.94.
(Ta ble 3, En tr y 6): 2,2-Dim eth yl-r-(1-cycloh exyl-2-
p r op en yl)-1,3-d ioxola n e-4-m eth a n ol (8h ). By applying pro-
tocol B to D-glyceraldehyde acetonide, the title product was
obtained in overall 40% yield as a 85/15 mixture of [4R-[4R*-
[R*(R*)]]]-8h and [4R-[4R*[S*(S*)]]]-8h ; the diastereomeric
ratio was determined by 1H NMR on the crude reaction
mixture. We assigned the anti-anti stereorelationship to the
most abundant isomer on the basis of the well-known intrinsic
diastereofacial preference of glyceraldehyde acetonide observed
in the addition of allyl organometallic species,22 allylic bor-
onates,23 and borolanes.24
(2S,3R,4S)-8g. Y ) 41%. Rf ) 0.18 (cyclohexane/ethyl
acetate 95:5). [R]20 ) +6.7 (c ) 1.0, CHCl3). 1H NMR (300
D
MHz): δ 0.08 (s, 3H), 0.09 (s, 3H), 0.90 (s, 9H), 0.92-1.44 (m,
6H), 1.13 (d, J ) 6.2 Hz, 3H), 1.51-1.80 (m, 5H), 2.01 (br dt,
J ∼ 6.1/9.6 Hz, 1H), 3.63 (dd, J ) 4.5/6.6 Hz, 1H), 3.86 (dq, J
) 4.5/6.2 Hz, 1H), 5.04 (dd, J ) 2.2/17.2 Hz, 1H), 5.17 (dd, J
) 2.2/10.3 Hz, 1H), 5.76 (dt, J ) 10.3/17.2 Hz, 1H). 13C NMR
(75 MHz): δ -4.8, -4.2, 17.4, 18.1, 25.8, 26.6, 29.2, 31.7, 38.2,
51.3, 69.6, 74.7, 117.4, 137.1. MS (EI): m/z 255 ([M+- 57], 1),
189 (2), 173 (8), 163 (8), 159 (57), 131 (28), 119 (100), 115 (13),
103 (19), 95 (7), 81 (51), 75 (60), 73 (60), 67 (15), 55(16). Anal.
Calcd for C18H36O2Si (312.57): C, 69.17; H, 11.61. Found: C,
69.14; H, 11.65.
(2S,3S,4R)-4-Cycloh exylh ex-5-en e-2,3-d iol 19. A 1 M
solution of tetrabutylammonium fluoride in THF (0.76 mL,
0.76 mmol) was added to a solution of (2S,3S,4R)-8g (0.2 g,
0.64 mmol) in THF (2 mL), and the reaction mixture was
stirred at 20 °C for 4 h. The reaction was quenched with water,
and the aqueous layer was extracted twice with ether. The
combined organic layers were dried (Na2SO4) and evaporated
at reduced pressure. The residue was purified by flash chro-
matography (SiO2, cyclohexane/ethyl acetate 70:30) to afford
[4R-[4R*[S*(S*)]]]-8h . Y ) 6%. Rf ) 0.30 (cyclohexane/
ethyl acetate 90:10). [R]20 ) +1.0 (c ) 0.9, CHCl3). H NMR
1
D
(300 MHz): δ 0.72-1.42 (m, 6H), 1.36 (s, 3H), 1.43 (s, 3H),
1.45-1.78 (m, 5H), 1.78-1.92 (m, 1H), 3.59 (dd, J ) 6.7/8.0
Hz, 1H), 3.72 (dd, J ) 2.6/7.9 Hz, 1H), 3.99 (dd, J ) 6.4/8.0
Hz, 1H), 4.08 (dt, J ) 6.7/7.9 Hz, 1H), 4.91 (dd, J ) 2.2/17.2
Hz, 1H), 5.13 (dd, J ) 2.2/10.3 Hz, 1H), 5.81 (dt, J ) 10.3/17.2
0.116 g (0.56 mmol, 92%) of (2S,3S,4R)-19. [R]20 ) -11.7 (c
D
) 1.1, CHCl3). 1H NMR (300 MHz): δ 0.79-1.08 (m, 2H), 1.18
(d, J ) 6.3 Hz, 3H), 1.18-1.38 (m, 3H), 1.55-1.80 (m, 6H),
1.80-1.90 (m, 1H), 2.05 (d, J ) 5.1 Hz, 1H), 2.13 (d, J ) 4.1
Hz, 1H), 3.51 (dt, J ) 4.1/6.3 Hz, 1H), 3.73 (dquintet, J ) 5.1/
6.3 Hz, 1H), 5.02 (dd, J ) 2.2/17.3 Hz, 1H), 5.18 (dd, J ) 2.2/
(22) J urczak, J .; Pikul, S.; Bauer, T. Tetrahedron 1986, 42, 447-
488 and references therein.
(23) (a) Hoffman, R. W.; Eichler, G.; Endesfelder, A. Liebigs Ann.
1983, 2000-2007. (b) Roush, W. R.; Adam, M. A.; Walts, A. E.; Harris,
D. J . J . Am. Chem. Soc. 1986, 108, 3422-3434. (c) Roush, W. R.;
Grover, P. T. J . Org. Chem. 1995, 60, 3806-3813 and ref. therein.
(24) Garcia, J .; Kim, B. M.; Masamune, S. J . Org. Chem. 1987, 52,
4831-4832.
(21) (a) Iida, T.; Itaya, T. Tetrahedron 1993, 49, 10511-10530. (b)
Kleinpeter, E.; Borsdorf, R. 13C NMR Spectroskopie der Organischen
Chemie; Akademie-Verlag: Berlin, 1981. For similar effects in acyclic
compounds, see also: Kleinpeter, E.; Meusinger, R.; Duschek, C.;
Borsdorf, R. Magn. Reson. Chem. 1987, 25, 990-995.

Synthesis of Homoallylic Alcohols via Boranes
J . Org. Chem., Vol. 65, No. 25, 2000 8773
Hz, 1H). 13C NMR (75 MHz): δ 25.5, 26.4, 26.6, 26.9, 31.08,
31.14, 37.4, 52.9, 65.8, 72.3, 78.3, 109.4, 117.3, 136.9. MS
(EI): m/z 239 ([M+ - 15], 6), 153(4), 131 (100), 124 (6), 101
(51), 95 (7), 83 (16), 81 (13), 59 (35), 55 (17). Anal. Calcd for
°C for 1 h. Benzaldehyde (0.2 mL, 2 mmol) was added, and
the reaction mixture was stirred at 20 °C for 3 h. Oxidative
workup (H2O2/NaOH) followed by extraction with ether (3 ×
5 mL) and purification by flash chromatography (SiO2, cyclo-
hexane/ethyl acetate 95:5) afforded 0.21 g (0.8 mmol, 40%) of
the title compound. 1H NMR (300 MHz): δ 0.87 (t, J ) 6.6
Hz, 3H), 1.02-1.35 (m, 14H), 2.30 (br quintet, J ∼ 7.5 Hz, 1H),
4.39 (d, J ) 7.8 Hz, 1H), 5.20 (ddd, J ) 0.6/2.1/17.1 Hz, 1H),
5.27 (dd, J ) 2.1/10.2 Hz, 1H), 5.67 (ddd, J ) 9.0/10.2/17.1
Hz, 1H), 7.22-7.41 (m, 5H). 13C NMR (50 MHz): δ 14.1, 22.6,
27.1, 29.2, 29.4 (2C), 30.3, 31.8, 52.5, 76.5, 118.3, 126.8, 127.3,
128.0, 139.2, 142.4. MS (EI): m/z 154 (2), 129 (2), 115 (1), 107
C
15H26O3 (254.37): C, 70.83; H, 10.30. Found: C, 70.92; H,
10.35.
[4R-[4R*[R*(R*)]]]-8h . Y ) 34%. Rf ) 0.15 (cyclohexane/
ethyl acetate 90:10). [R]20 ) +3.0 (c ) 1.40, CHCl3). 1H NMR
D
(300 MHz): δ ) 0.82-1.29 (m, 5H), 1.36 (s, 3H), 1.42 (s, 3H),
1.32-1.53 (m, 1H), 1.58-1.82 (m, 5H), 1.95 (ddd, J ) 3.5/7.5/
10.3 Hz, 1H), 3.90-4.07 (m, 4H), 5.08 (dd, J ) 2.2/17.1 Hz,
1H), 5.18 (dd, J ) 2.2/10.3 Hz, 1H), 5.74 (dt, J ) 10.3/17.1 Hz,
1H). 13C NMR (75 MHz): δ ) 25.3, 26.37, 26.40, 26.5, 26.7,
30.7, 31.1, 37.8, 52.2, 65.6, 71.0, 77.8, 108.3, 118.2, 136.5. MS
(EI): m/z 239 ([M+ - 15], 12), 153 (9), 131 (46), 124 (15), 101
(100), 95 (12), 83 (25), 81 (24), 59 (43), 55 (22). Anal. Calcd for
(100), 91 (3), 79 (33), 77 (17), 55 (5). Anal. Calcd for C18H28
(260.42): C, 83.02; H, 10.84. Found: C, 83.09; H, 10.80.
O
Ack n ow led gm en t. This work was supported by
MURST-Rome (National Project “Stereoselezione in
Sintesi Organica. Metodologie e Applicazioni”) and
University of Bologna (funds for selected topics).
C
15H26O3 (254.37): C, 70.83; H, 10.30. Found: C, 70.77; H,
10.26.
(Ta ble 3, En tr y 9): a n ti-1-P h en yl-2-eth en yld eca n -1-ol
(8k ). To a stirred THF solution (3 mL) of 2,3-dimethyl-2-butene
(0.24 mL, 2 mmol) was added BH3‚SMe2 (2 M solution in THF,
1 mL, 2 mmol) at -20 °C. After 2 h at -20 °C, a solution of
propargyl bromide (0.2 mL, 2 mmol) and 1-octene (0.32 mL, 2
mmol) in THF (1 mL) was added, and the solution was allowed
to reach 20 °C in 2 h under stirring. TEBABr (0.055 g) was
added, and the heterogeneous mixture was equilibrated at 20
Su p p or tin g In for m a tion Ava ila ble: Spectral and ana-
lytical data for compounds 6b-e, 7l, 8c,d ,f,i,j,l. This material
is available free of charge via the Internet at http://pubs.acs.org.
J O005633A