Stereoselective migration of sterically hindered organoboranes in cyclic and acyclic systems. A stereoselective allylic C-H activation reaction

Article abstract of DOI:10.1016/j.tet.2003.09.043

The thermal migration of cyclic and acyclic organoboranes were studied. In most cases, a stereoselective 1,2-dyotropic migration was observed, allowing the stereocontrol of three contiguous chiral centers. Scope and limitations of this thermal migration are presented.

Full text of DOI:10.1016/j.tet.2003.09.043

Tetrahedron 59 (2003) 9187–9198
Stereoselective migration of sterically hindered organoboranes
in cyclic and acyclic systems. A stereoselective allylic
C–H activation reaction
*
Eike Hupe, Dmitri Denisenko and Paul Knochel
¨ ¨ ¨
Department Chemie, Ludwig-Maximilians-Universitat Munchen, Butenandtstrasse 5-13, D-81377 Munchen, Germany
Received 26 March 2003; revised 2 September 2003; accepted 15 September 2003
Abstract—The thermal migration of cyclic and acyclic organoboranes were studied. In most cases, a stereoselective 1,2-dyotropic migration
was observed, allowing the stereocontrol of three contiguous chiral centers. Scope and limitations of this thermal migration are presented.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
1,2-dimethylcyclopentene.3 We have examined a range of
tetrasubstituted cyclopentene derivatives of type 1 (see
Scheme 2 and Table 1).6
The diastereoselective synthesis of organic molecules is an
important research field and numerous important synthetic
contributions have been made in recent years.1 It was known
that organoboranes derived from disubstituted olefins by
hydroboration undergo a thermal isomerization at elevated
temperatures (100–1608C).2,3 We have shown that cyclic3,4
and acyclic5 tetrasubstituted olefins undergo a 1,2-thermal
migration under milder conditions. Furthermore, these
rearrangements occur with a good or excellent transfer of
the stereochemical information, allowing the control of up
to three stereogenic centers. Herein, we wish to report the
scope and the limitations of thermal rearrangements of
organoboranes according to the general Scheme 1.
Scheme 2.
Thus, the hydroboration of 1,2-diphenylcyclopentene (1a)
with BH3·THF (THF, 508C, 3 h) leads to a rearranged
organoborane, which after oxidation with NaOH (2 M in
H2O) and H2O2 (30% in H2O) furnishes 2,3-diphenyl-
cyclopentanol (2a) as a single diastereoisomer in 82% yield
(entry 1 of Table 1). We have always observed the migration
in the direction of the ring system and not in the direction of
the side-chain. This is due to the higher conformational
rigidity and better coplanarity of the adjacent C–H bond
with the C–B bond facilitating the dehydroboration step.
Scheme 1.
2. Results and discussion
The driving force for the rearrangement of organoboranes is
the release of steric strain. Organoboranes attached at a
tertiary carbon atom such as H2B-C(R1)(R2)(R3), obtained
by the hydroboration of tetrasubstituted alkenes, are
especially prone to undergo a thermal rearrangement
as first shown by Rickborn and Field in the case of
Similarly, 1,2-dialkylcyclopentenes (1b–1d) produce
after NaOH/H2O2-oxidation the cyclopentanols 2b–d in
51–71% yields with d.r.$98% (entries 2–4). 1,2-Dibenzyl-
cyclopentene (1e) reacts with an excellent yield leading
only to the expected cyclopentanol 2e (entry 5). By reacting
the intermediate organoborane with BCl3 (258C, 3 h)
Keywords: stereoselective synthesis; 1,2-migration; organoboranes; C–H-
activation; amination.
*
Corresponding author. Tel.: þ49-89-2180-77679; fax: þ49-89-2180-
77680; e-mail: paul.knochel@cup.uni-muenchen.de
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.09.043

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E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
Table 1. Products of type 2 and 3 obtained by thermal rearrangement of
organoboranes (3 h, 508C), resulting from the hydroboration of tetrasub-
stituted cyclopentene derivatives of type 1
methylcyclopentanol (2f) after oxidation in 70% yield
(d.r.$98%; entry 7).
Interestingly, by performing the reaction at 658C instead of
508C and with 96 h reaction time, a further migration of the
boron atom occurs producing 3-tert-butyl-4-methylcyclo-
pentanol (2g) in 64% yield as one diastereoisomer
(d.r.$98%) showing the importance of the temperature
control for performing these rearrangements (entry 8). The
relative stereochemistry of 2g confirms also the suprafacial
nature of the boron migration. Similarly, alkenylsilane 1g
affords after 24 h of heating at 508C the double migration
product 2h in 60% yield (entry 9). In the case of
unsymmetrical cyclopentenes like 1h and 1i, a mixture
of migration products in both directions was observed.
This low regioselectivity could not be improved despite
numerous experiments involving a change of the reaction
conditions or the substrate of type 1 were carried out (entries
10 and 11).
Entry
Olefin of type 1
Products of type 2 or 3
Yield (%)a
1
82
2
71
3
4
1c: R¼Pr
1d: R¼Bu
2c: R¼Pr
2d: R¼Bu
62
51
5
6
80
62
As reported earlier,4a bicyclic alkenes like 6 and 7 undergo
stereoselective migrations. The bicyclic olefin 6 reacts
similarly to the substituted cyclopentenes at 508C within 3 h
affording alcohol 8 in 82% yield after oxidative workup, and
amine 9 in 55% yield after amination (d.r.$98:2) (Scheme
3). The six-membered bicyclic system 7 reacts much slower
and requires 7 h reaction time at 708C. After oxidation with
NaOH/H2O2 and amination according to the procotol
described above, the expected products 10 and 11 are
obtained as one diastereoisomer (d.r.$98%) and in 72 and
57% yield (Scheme 3).
1e
7
8
9
70
1f
64b
60c
10
Scheme 3.
The hydroboration of exo-alkylidene cyclopentane deriva-
tives like 12 proceeds also smoothly (BH3·THF, 508C, 8 h)
leading only to the migration product in the cyclopentane
ring, affording the trans-products 13 and 14, respectively,
after oxidation and amination. The trans-stereochemistry is
11
a
Isolated yield of analytically pure compound.
The reaction mixture was stirred at 658C for 96 h.
The reaction mixture was stirred at 508C for 24 h.
b
c
followed by the addition of benzyl azide (258C, 1 h),7
benzylamine 3a is isolated in 62% yield (entry 6). Both
products (2e and 3a) are formed in high diasteroselectivity
(d.r.$98%). In the case of unsymmetrical disubstituted
cyclopentenes of type 1 (R1–R2), two intermediate
regioisomeric organoboranes 4 and 5 can be obtained. If
the difference of the steric hindrance between the two
substituents is large, the migration occurs preferentially on
the side of the least bulky substituent. Thus, 1-tert-butyl-2-
methylcyclopentene (1f) produces only 3-tert-butyl-2-
Scheme 4.

E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
9189
readily explained by a syn-migration8 of the intermediate
tertiary organoborane 15 leading to the trans-organoborane
16 (Scheme 4).5a
The regioselectivity of the migration inside the cyclopen-
tane ring is best explained by the favored arrangement of the
BH2 group and the syn-hydrogen atom Ha of 15, facilitating
the 1,2-migration step.
Stereoselective boron-migrations are also observed in open-
chain systems. The two isomeric stilbenes E- and Z-1,2-
dimethyl-1,2-diphenylethylenes (E- and Z-17) provide, after
hydroboration, thermal rearrangement at 708C (14 h reac-
tion time) and NaOH/H2O2-oxidation, the anti- and syn-
alcohols (anti-18 and syn-18), respectively, in 76 and 75%
yield. The observed stereoselectivity is readily explained by
assuming as usually a syn-dyotropic rearrangement9 via the
boranes 19, 20 and syn- and anti-21 (Scheme 5).
Scheme 6.
(BCl3, 258C, 4 h; then BnN3, 0–258C, overnight), leading to
the amine 26 in 57% yield as a mixture of two
diastereoisomers in a ratio of 92:8 as indicated by GC–
MS-analysis (see Section 4). The oxidation of 25 with
NaOH/H2O2 affords a 72:28 mixture of the secondary
alcohol 27 in 73% yield. A similar result was obtained
starting with 2-methyl-1,1-diphenylbut-1-ene (28), which
provides after amination of the intermediate organoborane
(29) the expected benzylic amine 30 in 70% yield
(d.r.¼92:8, Scheme 7).
Scheme 5.
The intermediate organoborane syn-21 was further con-
verted in a range of derivatives. By using the amination
procedure (BCl3 followed by BnN3),7 the benzylamine 22a
is obtained in 80% yield. The treatment of the organoborane
syn-21 with ethylene produces a diethylborane derivative,
which undergoes a boron–zinc exchange10 with Et2Zn
leading to an organozinc derivative, which after trans-
metalation with the THF soluble copper-salt, CuCN·2LiCl11
gives the copper intermediate 23. The reaction of 23 with
allyl bromide leads to the allylated product 22b in 72%
yield. The reaction with 2-bromo-1-phenylacetylene
furnishes the cross-coupling product 22c in 51% yield.12
The addition of benzoyl chloride to 23 leads to the aromatic
ketone 22d in 52% yield (Scheme 6).
Scheme 7.
The relative stereochemistry has been established by
performing an X-ray analysis of the 3,5-dinitrobenzoate
derived from the alcohol 27.5b,c This relative stereo-
chemistry is best explained by the thermal dehydroboration
of the primary intermediate of 24 (or 28) (e.g. 31). It will
proceed preferentially with the adjacent hydrogen Ha (and
not Hb), since this dehydroboration would result in the
formation of the least bulky alkene–borane complex (32)
having the bulky benzhydryl group (Ph2CH) and the
methyl substituent in a trans-arrangement (Scheme 8).
Tetrasubstituted double bonds bearing ethyl substituents
undergo also the boron migration at 50–658C. Although we
claimed to have complete control of the relative stereo-
chemistry of the newly chiral center generated from the
ethyl group,5 a closer look to the crude reaction mixtures
showed that the diastereoselectivity is less selective as
previously reported. Thus, heating 2-ethyl-1,1-diphenylbut-
1-ene (24) with BH3·THF (3 equiv.) for 4 h at 508C
produces the organoborane 25. Its conversion to the
corresponding benzylamine was performed as described
Scheme 8.

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E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
The rehydroboration of 32 will lead to organoborane 25.
The moderate diastereoselectivity of 27 obtained after
NaOH/H2O2 oxidation of 25 may be explained by
epimerization during the oxidation step, in contrast to the
amination reaction leading to products 26 and 30 with a
diastereoselectivity of 92:8 (Scheme 7).
Scheme 10.
This reaction proceeds also well with other various-
substituted stilbene derivatives. Thus, the E- and Z-stilbenes
E- and Z-33 undergo the thermal boron migration with
excellent diastereoselectivities leading to the anti- and syn-
organoboranes anti- and syn-34. After amination of 34
(BCl3, 258C, 4 h; then BnN3, 0–258C, overnight), the
corresponding benzylic amines (anti- and syn-35) were
obtained in 66 and 40% yield and with a diastereoselectivity
better than 90:10 between C(1) and C(2) (Scheme 9). The
relative stereochemistry of syn-34 was established by X-ray
analysis of the corresponding alcohol.5b,d
10). The diastereoselectivity between C(1) and C(2) was
95:5 and .99:1 between C(2) and C(3). The relative
stereochemistry, which was established by X-ray analysis of
the corresponding alcohol obtained by oxidative workup
(NaOH/H2O2),5b,e can be best explained by assuming as
previously (see Scheme 8) that the most stable alkene–
borane complex (41) is formed.
3. Conclusion
In summary, we have described that the migration of
organoboranes attached to a tertiary carbon atom proceeds
with good stereoselectivity in cyclic systems, the fastest
rearrangements occurring in cyclopentane rings. In unsym-
metrically substituted cyclopentenes, the migration was not
regioselective and complicated by multiple migration
products. Tetrasubstituted acyclic alkenes provide the
migration products under comparable reaction conditions.
The stereoselectivity of the migration is predictable but
strongly depends on the structure of the alkene and on the
reaction conditions. The diastereoselectivity was estab-
1
lished by H NMR and (or) GC–MS analysis, the relative
stereoselectivity was in several cases secured by X-ray
analysis. Attempts to use functionalized cyclic or acyclic
alkenes were complicated by various side-reactions and
found not to be synthetically useful under our reaction
conditions, limiting the scope of the reaction.
4. Experimental
4.1. General methods
Scheme 9.
Unless otherwise indicated, all reactions were carried out
under argon. Solvents were dried and freshly distilled.
Reactions were monitored by gas chromatography (GC and
GC–MS) or thin layer chromatography (TLC). The ratios
between diastereoisomers were determined by 1H NMR
spectroscopy and/or GC–MS analysis; GC–MS: column
HP-5MS (15 m£250 mm£0.25 mm); method A: 1 min at
1108C, ramp of 508C/min to 2508C, 10 min at 2508C,
method B: 1 min at 908C, ramp of 508C/min to 2508C, 8 min
at 2508C, method C: 1 min at 708C, ramp of 508C/min to
2508C, 8 min at 2508C.
Interestingly, the transmetalation of syn-34 to the corre-
sponding zinc–copper compound by reaction with i-Pr2Zn
(4 equiv., 258C, 3 h) followed by the addition of CuCN·
2LiCl (1 equiv., 2788C, 30 min) and subsequent allylation
occurred with good overall yield (61%) but led to a partial
epimerization of the intermediate organometallic reagent,
producing the allylated product syn-36 as a 60:40 mixture of
epimers at C(1) (Scheme 9). Also the NaOH/H2O2-
oxidation of anti-34 was not stereoselective furnishing the
alcohol anti-37 as a 75:25 mixture of epimers at C(1) in 82%
yield (Scheme 9). Remarkable regioselectivities have been
observed in the thermal migration of several tetrasubstituted
alkenes such as Z-38 and 39. Thus, the hydroboration of
Z-38 furnishes only the migration product in the direction
of the ethyl group. Furthermore, the migration was
stereoselective providing after the standard amination
sequence the benzylic amine 40 in 46% yield (Scheme
Starting materials. Preparation of starting materials not
known in the literature.
Disubstituted cyclopentenes 1b–d, 1g and 1h were prepared
from 1-bromo-2-alkyl(benzyl)cyclopentenes (general pro-
cedure II), prepared from 1,2-dibromocyclopentene13 (gen-
eral procedure I).

E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
9191
4.2. General procedure I. Preparation of 1-bromo-2-
alkyl(benzyl)-cyclopentenes
29.6, 29.3, 22.5, 21.7, 13.9; MS (EI): 204 (18), 202 (18,
Mþ), 123 (16), 81 (100), 67 (29); HRMS calcd for C9H15Br:
202.0357, found: 202.0337.
A solution of 1,2-dibromocyclopentene13 (3.39 g, 15 mmol)
in THF (30 mL) was cooled down to 2788C and treated
slowly with t-BuLi (20 mL, 30 mmol, 1.5 M in pentane).
The mixture was stirred at 2788C for 15 min before the
corresponding alkyl iodide (18 mmol) or benzyl bromide
(15 mmol) was added. After warming up to room tempera-
ture, the reaction mixture was quenched with water
(50 mL). The aqueous phase was extracted with pentane
(2£20 mL). The combined organic phases were washed
with water and brine and dried over MgSO4. After
evaporation of the solvent, the crude product was purified
by column chromatography (pentane) or by distillation to
give the desired 1-bromo-2-alkyl(benzyl)cyclopentene.
4.2.5. 1-Bromo-2-benzylcyclopentene. According to gen-
eral procedure I, 1,2-dibromocyclopentene13 was reacted
with t-BuLi and benzyl bromide (2.57 g, 15 mmol) to give
the corresponding cyclopentenyl bromide (3.13 g, 88%) as a
colourless oil. IR (film): 3085, 3062, 3027, 2953, 2849,
1
1494, 1453, 761, 700 cm21; H NMR (CDCl3, 300 MHz):
d¼7.32–7.26 (m, 2H), 7.23–7.18 (m, 3H), 3.50 (s, 2H),
2.71–2.64 (m, 2H), 2.24–2.18 (m, 2H), 1.95–1.85 (m, 2H);
13C NMR (CDCl3, 75 MHz): d¼139.8, 138.7, 128.6, 128.4,
126.2, 116.7, 39.9, 36.4, 33.6, 21.6; MS (EI): 238 (16), 236
(16, Mþ), 157 (100), 129 (63), 91 (47); HRMS calcd for
C12H13Br: 236.0201, found: 236.0182.
4.2.1. 1-Bromo-2-methylcyclopentene. According to gen-
eral procedure I, 1,2-dibromocyclopentene13 was reacted
with t-BuLi and methyl iodide (2.56 g, 18 mmol) to give the
corresponding cyclopentenyl bromide (1.50 g, 62%) as a
colourless oil, bp 61–638C/30 mbar. IR (film): 2916, 2855,
1711, 1443, 1025, 977 cm21; 1H NMR (CDCl3, 300 MHz):
d¼2.66–2.57 (m, 2H), 2.33–2.26 (m, 2H), 1.97–1.87 (m,
2H), 1.73–1.71 (m, 3H); 13C NMR (CDCl3, 75 MHz):
d¼137.1, 115.6, 39.9, 36.1, 21.7, 15.6; MS (EI): 162 (25),
160 (26, Mþ), 81 (100); HRMS calcd for C6H9Br: 159.9888,
found: 159.9855.
4.3. General procedure II. Preparation of 1,2-disubsti-
tuted cyclopentenes
1-Bromo-2-alkyl(benzyl)cyclopentene (10 mmol) was dis-
solved in THF (20 mL). The solution was cooled down to
2788C and treated slowly with t-BuLi (13.3 mL, 20 mmol,
1.5 M in pentane). The mixture was stirred at 2788C for
15 min before the corresponding alkyl iodide (12 mmol) or
TIPS-chloride (10 mmol, 1.93 g) was added. After warming
up to room temperature the reaction mixture was quenched
with water (30 mL). The aqueous phase was extracted with
pentane (2£20 mL). The combined organic phases were
washed with water and brine and dried over MgSO4. After
the solvents were removed under reduced pressure, the
crude product was purified by column chromatography
(pentane) and (or) by distillation to give the desired
1,2-disubstituted cyclopentene.
4.2.2. 1-Bromo-2-ethylcyclopentene. According to general
procedure I, 1,2-dibromocyclopentene13 was reacted with
t-BuLi and ethyl iodide (2.81 g, 18 mmol) to give the
corresponding cyclopentenyl bromide (1.89 g, 72%) as a
colourless oil. IR (film): 2967, 2936, 2876, 2853, 1709,
1
1460, 895 cm21; H NMR (CDCl3, 300 MHz): d¼2.65–
2.58 (m, 2H), 2.34–2.27 (m, 2H), 2.21–2.14 (m, 2H), 1.97–
1.87 (m, 2H), 0.99 (t, J¼7.5 Hz, 3H); 13C NMR (CDCl3,
75 MHz): d¼142.2, 114.5, 39.9, 33.2, 23.1, 21.7, 11.7; MS
(EI): 174 (24, Mþ), 95 (100); HRMS calcd for C7H11Br:
174.0044, found: 174.0028.
4.3.1. 1,2-Diethylcyclopentene (1b). According to general
procedure II, 1-bromo-2-ethylcyclopentene (1.75 g, 10 mmol)
was reacted with t-BuLi and ethyl iodide (1.87 g, 12 mmol).
Purification by column chromatography (pentane) gave the
corresponding alkene 1b (0.91 g, 73%) as a colourless oil.
1
IR (film): 2965, 2876, 2851, 1477, 1463, 1370 cm21; H
4.2.3. 1-Bromo-2-propylcyclopentene. According to gen-
eral procedure I, 1,2-dibromocyclopentene13 was reacted
with t-BuLi and n-propyl iodide (3.06 g, 18 mmol) to give
the corresponding cyclopentenyl bromide (1.25 g, 44%) as a
colourless oil. IR (film): 2959, 2933, 2870, 2847, 1710,
NMR (CDCl3, 300 MHz): d¼2.30 (t, J¼7.5 Hz, 4H), 2.06
(q, J¼7.7 Hz, 4H), 1.81–1.70 (m, 2H), 0.96 (t, J¼7.7 Hz,
6H); 13C NMR (CDCl3, 75 MHz): d¼136.1, 35.4, 21.6,
21.3, 13.2; MS (EI): 124 (26, Mþ), 95 (100); HRMS calcd
for C9H16: 124.1252, found: 124.1233.
1655, 1463, 1061 cm21 1H NMR (CDCl3, 300 MHz):
;
d¼2.66–2.57 (m, 2H), 2.32–2.26 (m, 2H), 2.16–2.11 (m,
2H), 1.96–1.86 (m, 2H), 1.50–1.38 (m, 2H), 0.91 (t,
J¼7.3 Hz, 3H); 13C NMR (CDCl3, 75 MHz): d¼141.0,
115.6, 39.9, 33.7, 31.8, 21.8, 20.4, 13.9; MS (EI): 190 (48),
188 (47, Mþ), 109 (100), 79 (62), 67 (48); HRMS calcd for
C8H13Br: 188.0201, found: 188.0204.
4.3.2. 1,2-Dipropylcyclopentene (1c). According to gen-
eral procedure II, 1-bromo-2-propylcyclopentene (1.13 g,
6 mmol) was reacted with t-BuLi (8 mL, 12 mmol) and
n-propyl iodide (1.22 g, 7.2 mmol). Purification by column
chromatography (pentane) gave the corresponding alkene
1c (0.64 g, 70%) as a colourless oil. IR (film): 2956, 2931,
1
2870, 2841, 1464 cm21; H NMR (CDCl3, 300 MHz): d¼
4.2.4. 1-Bromo-2-butylcyclopentene. According to general
procedure I, 1,2-dibromocyclopentene13 was reacted with
t-BuLi and n-butyl iodide (3.31 g, 18 mmol) to give the
corresponding cyclopentenyl bromide (2.41 g, 79%) as a
colourless oil. IR (film): 2958, 2931, 2858, 1710, 1656,
2.28 (t, J¼7.3 Hz, 4H), 2.02 (t, J¼7.7 Hz, 4H), 1.79–1.70
(m, 2H), 1.44–1.32 (m, 4H), 0.87 (t, J¼7.3 Hz, 6H); 13C
NMR (CDCl3, 75 MHz): d¼135.4, 35.8, 30.4, 21.8, 21.4,
14.1; MS (EI): 152 (75, Mþ), 123 (42), 109 (71), 81 (100),
67 (48); HRMS calcd for C11H20: 152.1565, found:
152.1551.
1
1466, 1067 cm21; H NMR (CDCl3, 300 MHz): d¼2.64–
2.58 (m, 2H), 2.31–2.26 (m, 2H), 2.18–2.13 (m, 2H), 1.96–
1.86 (m, 2H), 1.44–1.25 (m, 4H), 0.92 (t, J¼7.3 Hz, 3H);
13C NMR (CDCl3, 75 MHz): d¼141.1, 115.3, 39.9, 33.7,
4.3.3. 1,2-Dibutylcyclopentene (1d). According to general
procedure II, 1-bromo-2-butylcyclopentene (1.23 g, 11 mmol)

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E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
was reacted with t-BuLi (14.7 mL, 22 mmol) and n-butyl
iodide (2.43 g, 13.2 mmol). Purification by column chroma-
tography (pentane) gave the corresponding alkene 1d
(1.52 g, 77%) as a colourless oil. IR (film): 2956, 2929,
(100), 81 (64); HRMS calcd for C10H18: 138.1409, found:
138.1407.
4.3.6. 1-(Triisopropylsilyl)-2-methylcyclopentene (1g).
According to general procedure II, 1-bromo-2-methyl-
cyclopentene (1.61 g, 10 mmol) was reacted with t-BuLi
(13.3 mL, 20 mmol) and TIPS-chloride (1.92 g, 10 mmol).
Distillation gave the desired alkene 1g (1.31 g, 55%) as a
colourless oil, bp 71–728C/0.8 mbar. IR (film): 2944, 2890,
2872, 2858, 2841, 1466 cm21
;
1H NMR (CDCl3,
300 MHz): d¼2.27 (t, J¼7.3 Hz, 4H), 2.04 (t, J¼7.1 Hz,
4H), 1.79–1.68 (m, 2H), 1.45–1.21 (m, 8H), 0.89 (t, J¼
7.1 Hz, 6H); 13C NMR (CDCl3, 75 MHz): d¼135.4, 35.8,
30.5, 28.1, 22.7, 21.8, 14.0; MS (EI): 180 (21, Mþ), 123
(29), 95 (71), 81 (100), 67 (40); HRMS calcd for C13H24:
180.1878, found: 180.1888.
2865, 1607, 1464, 883, 674 cm21 1H NMR (CDCl3,
;
300 MHz): d¼2.47–2.40 (m, 2H), 2.38–2.31 (m, 2H),
1.82–1.80 (m, 3H), 1.80–1.70 (m, 2H), 1.28–1.16 (m, 3H),
1.06 (d, J¼7.1 Hz, 18H); 13C NMR (CDCl3, 75 MHz):
d¼151.6, 129.6, 41.5, 40.3, 24.2, 18.9, 18.3, 12.4; MS (EI):
238 (1, Mþ), 195 (100), 153 (100), 125 (42), 111 (32);
HRMS calcd for C15H30Si: 238.2117, found: 238.2107.
4.3.4. 1,2-Dibenzylcyclopentene (1e). A solution of
benzylzinc bromide, prepared from benzyl bromide
(5.13 g, 30 mmol) and zinc (2.42 g, 37 mmol) in THF
(20 mL),14 was transferred via cannula to a solution of
Pd(dba)2 (0.574 g, 1 mmol), PPh3 (0.524 g, 2 mmol) and
1,2-dibromocyclopentene13 (2.26 g, 10 mmol) in THF
(20 mL). The mixture was stirred at 608C for 36 h. After
the mixture was cooled to 08C, NH4Cl solution (30 mL, 2 M
in H2O) was added. The aqueous phase was extracted with
pentane (2£20 mL). The combined organic phases were
washed with water and brine and dried over MgSO4.
Solvents were removed under reduced pressure and the
crude product was purified by column chromatography
(pentane) to give the desired alkene 1e (1.76 g, 71%) as a
colourless oil. IR (film): 3084, 3062, 3026, 3002, 2922,
4.3.7. 1-Benzyl-2-ethylcyclopentene (1h). According to
general procedure II, 1-bromo-2-benzylcyclopentene (2.84 g,
12 mmol) was reacted with t-BuLi (16 mL, 24 mmol) and
ethyl iodide (2.25 g, 14.4 mmol). Purification by column
chromatography (pentane) gave the corresponding alkene
1h (2.19 g, 98%) as a colourless oil. IR (film): 3084, 3062,
1
3027, 2963, 2932, 2842, 1602, 1494, 1453, 698 cm21; H
NMR (CDCl3, 300 MHz): d¼7.34–7.29 (m, 2H), 7.24–
7.17 (m, 3H), 3.43 (s, 2H), 2.43–2.38 (m, 2H), 2.30–2.22
(m, 4H), 1.84–1.74 (m, 2H), 1.08 (t, J¼7.5 Hz, 3H); 13C
NMR (CDCl3, 75 MHz): d¼140.7, 138.5, 132.9, 128.5,
128.2, 125.6, 36.9, 35.3, 34.7, 21.6, 13.1; MS (EI): 186 (100,
Mþ), 157 (87), 129 (43), 91 (53); HRMS calcd for C14H18:
186.1409, found: 186.1404.
1
2867, 2842, 1602, 1494, 1452, 1030, 720, 698 cm21; H
NMR (CDCl3, 300 MHz): d¼7.33–7.28 (m, 4H), 7.24–
7.19 (m, 6H), 3.56 (s, 4H), 2.29 (t, J¼7.3 Hz, 4H), 1.80–
1.70 (m, 2H); 13C NMR (CDCl3, 75 MHz): d¼140.3, 135.4,
128.6, 128.3, 125.8, 35.9, 34.9, 21.5; MS (EI): 248 (15,
Mþ), 157 (100), 129 (31), 91 (32); HRMS calcd for C19H20:
248.1565, found: 248.1587.
4.3.8. 2-Ethyl-1,1-diphenylbut-1-ene (24). To a solution of
Ti(IV)-chloride (40.98 g, 216 mmol) in Et2O (300 mL) at
08C was added Zn-dust (26.15 g, 400 mmol) and pyridine
(16 mL). After addition of benzophenone (18.22 g,
100 mmol) and 3-pentanone (8.61 g, 100 mmol), the
solution was refluxed for 24 h. The resulting solution was
carefully quenched by slowly adding to an aqueous solution
of Na2CO3 (800 mL, 5%) and then filtered through celite,
which was washed with Et2O (400 mL). The phases were
separated and the organic phase washed with aqueous HCl
(2 M) and brine. After evaporation of the solvent, the crude
product was purified by column chromatography (pentane),
yielding 24 (21.38 g, 90%) as a colourless oil. IR (film):
3077, 3056, 2967, 2873, 1945, 1875, 1598, 1491, 758, 701,
625, 568 cm21; 1H NMR (CDCl3, 200 MHz): d¼7.58–7.13
(m, 10H), 2.16 (q, J¼7.6 Hz, 4H), 1.00 (t, J¼7.5 Hz, 6H);
13C NMR (CDCl3, 50 MHz): d¼143.4, 142.2, 137.2, 129.3,
128.0, 126.0, 24.4, 13.3; MS (EI): 236 (28, Mþ), 207 (41),
179 (37), 129 (100), 91 (62). Anal. calcd for C18H20: C
91.47, H 8.53; found: C 91.28, H 8.66.
4.3.5. 1-tert-Butyl-2-methylcyclopentene (1f). A solution
of 2-tert-butylcyclopentanone15 (10.5 g, 75 mmol) in Et2O
(50 mL) was added dropwise to a solution of MeLi (50 mL,
80 mmol, 1.6 M in Et2O) in Et2O (50 mL) at 2788C. The
mixture was allowed to warm up to 08C and then added to
cold aqueous hydrochloric acid (200 mL, 20% in water) and
stirred for 2 h at room temperature. The aqueous phase was
extracted with pentane (2£50 mL). The combined organic
phases were washed with water and brine and dried over
MgSO4. Distillation gave 6.73 g (65%) of a mixture,
containing 67% of 1-tert-butyl-2-methylcyclopentene,
15% of 1-methyl-5-tert-butylcyclopentene and 18% of
2-tert-butylcyclopentanone. This mixture was then reacted
with diethylborane, prepared from BH3·Me2S (0.46 g,
6 mmol) and Et3B (1.18 g, 12 mmol), in THF (40 mL) at
room temperature for 24 h in order to remove undesired
alkene and starting ketone. After the solution was cooled to
08C, NaOH (10 mL, 2 M in H2O) and H2O2 (10 mL, 30% in
H2O) were added carefully and the mixture was stirred for
30 min at room temperature. Usual workup, followed by
purification on a short column (pentane) and distillation,
gave 3.7 g (36% based on 2-tert-butylcyclopentanone) of
desired alkene 1f as a colourless oil, bp 54–568C/20 mbar.
4.4. General procedure III. Formation of the alcohols
To a solution of the corresponding olefin (1 mmol) in THF
(4 mL) was slowly added BH3·THF (3 mL, 3 mmol, 1 M in
THF) at 08C. The resulting solution was stirred for the time
and at the temperature stated. After the solution was cooled
to 08C, NaOH (4 mL, 2 M in H2O) and H2O2 (4 mL, 30% in
H2O) were slowly added. The resulting solution was stirred
for 2 h at 258C. After usual workup, the crude alcohols were
purified by column chromatography (pentane/Et2O).
1
IR (film): 2953, 2868, 2841, 1463, 1362 cm21; H NMR
(CDCl3, 300 MHz): d¼2.42–2.36 (m, 2H), 2.33–2.26
(m, 2H), 1.77–1.75 (m, 3H), 1.70–1.60 (m, 2H), 1.12 (s,
9H); 13C NMR (CDCl3, 75 MHz): d¼141.5, 129.2, 41.5,
35.5, 33.3, 30.3, 21.4, 16.0; MS (EI): 138 (34, Mþ), 123

E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
9193
4.4.1. 2,3-Diphenylcyclopentanol (2a). According to
general procedure III, 1,2-diphenylcyclopentene 1a16
(0.220 g, 1 mmol) was reacted with BH3·THF at 508C for
3 h. After oxidative workup, the desired alcohol 2a was
obtained as one diastereoisomer (0.195 g, 82%, column
chromatography with pentane/Et2O¼1:1). IR (film): 3351,
3028, 2956, 1603, 1497, 1451, 698 cm21; 1H NMR (CDCl3,
300 MHz): d¼7.13–7.02 (m, 6H), 6.84–6.76 (m, 4H),
4.70–4.63 (m, 1H), 3.75–3.67 (m, 1H), 3.35 (dd, J¼8.0,
6.2 Hz, 1H), 2.58–2.47 (m, 1H), 2.38–2.26 (m, 1H), 2.18–
2.05 (m, 1H), 1.96–1.84 (m, 1H), 1.72 (s, 1H); 13C NMR
(CDCl3, 75 MHz): d¼141.9, 139.4, 128.7, 128.4, 127.7,
127.6, 126.1, 125.8, 77.2, 59.6, 48.5, 33.6, 28.3; MS (EI):
238 (17, Mþ), 220 (100), 147 (38), 129 (47), 91 (44); HRMS
calcd for C17H18O: 238.1358, found: 238.1362.
4.4.5. 2,3-Dibenzylcyclopentanol (2e). According to gen-
eral procedure III, 1,2-dibenzylcyclopentene 1e (0.248 g,
1 mmol) was reacted with BH3·THF at 508C for 3 h. After
oxidative workup, the desired alcohol 2e was obtained as
one diastereoisomer (0.213 g, 80%, column chromatog-
raphy with pentane/Et2O¼1:1). IR (film): 3360, 3350, 3025,
2934, 1602, 1495, 1454, 738, 699 cm21; 1H NMR (CDCl3,
600 MHz): d¼7.32–7.28 (m, 4H), 7.23–7.19 (m, 6H),
4.06–4.04 (m, 1H), 2.92–2.86 (m, 2H), 2.63–2.57 (m, 1H),
2.52 (dd, J¼13.5, 9.8 Hz, 1H), 2.41 (dd, J¼14.1, 10.6 Hz,
1H), 2.21–2.13 (m, 2H), 1.84–1.78 (m, 1H), 1.57–1.51 (m,
1H), 1.46–1.40 (m, 1H), 1.23 (brs, 1H); 13C NMR (CDCl3,
150 MHz): d¼141.6, 141.0, 128.8, 128.7, 128.5, 128.3,
126.0, 125.8, 76.9, 52.5, 42.0, 36.4, 33.6, 32.4, 27.8; MS
(EI): 266 (1, Mþ), 248 (9), 157 (100), 117 (43); HRMS
calcd for C19H22O: 266.1671, found: 266.1690.
4.4.2. 2,3-Diethylcyclopentanol (2b). According to general
procedure III, 1,2-diethylcyclopentene 1b (0.186 g,
1.5 mmol) in THF (6 mL) was reacted with BH3·THF
(4.5 mL, 4.5 mmol, 1 M in THF) at 508C for 3 h. After
oxidative workup (6 mL 2 M NaOH, 6 mL 30% H2O2), the
desired alcohol 2b was obtained as one diastereoisomer
(0.151 g, 71%, column chromatography with pentane/
Et2O¼3:1). IR (film): 3342, 2959, 2934, 2874,
4.4.6. 3-tert-Butyl-2-methylcyclopentanol (2f). According
to general procedure III, 1-tert-butyl-2-methylcyclopentene
1f (0.207 g, 1.5 mmol) in THF (6 mL) was reacted with
BH3·THF (4.5 mL, 4.5 mmol, 1 M in THF) at 508C for 3 h.
After oxidative workup (6 mL 2 M NaOH, 6 mL 30%
H2O2), the desired alcohol 2f was obtained as one
diastereoisomer (0.164 g, 70%, column chromatography
with pentane/Et2O¼3:1). IR (film): 3326, 2958, 2903, 2877,
1471, 1364, 1023 cm21 1H NMR (CDCl3, 600 MHz):
;
d¼3.83–3.82 (m, 1H), 2.06–1.95 (m, 4H), 1.70–1.64 (m,
1H), 1.51–1.44 (m, 2H), 0.92 (s, 9H), 0.78 (d, J¼7.2 Hz,
3H); 13C NMR (CDCl3, 75 MHz): d¼80.8, 50.2, 44.9, 31.9,
31.7, 29.3, 21.8, 14.4; MS (EI): 154 (0.3, [M22H]þ), 139
(2), 123 (59), 99 (36), 81 (100); HRMS calcd for C10H18O:
154.1358, found: 154.1360.
1462 cm21
;
1H NMR (CDCl3, 600 MHz): d¼4.00–3.98
(m, 1H), 2.04–1.98 (m, 2H), 1.86–1.80 (m, 1H), 1.63–1.58
(m, 1H), 1.50–1.45 (m, 1H), 1.42–1.32 (m, 2H), 1.27–1.19
(m, 1H), 1.14–1.02 (m, 2H), 0.92 (t, J¼7.3 Hz, 3H), 0.87 (t,
J¼7.3 Hz, 3H); 13C NMR (CDCl3, 150 MHz): d¼77.5,
52.8, 42.0, 33.0, 27.7, 22.6, 19.6, 13.0, 12.7; MS (EI): 142
(1, Mþ), 124 (7), 98 (45), 95 (100); HRMS calcd for
C9H18O: 142.1358, found: 142.1369.
4.4.3. 2,3-Dipropylcyclopentanol (2c). According to
general procedure III, 1,2-propylcyclopentene 1c (0.152 g,
1 mmol) was reacted with BH3·THF at 508C for 3 h. After
oxidative workup, the desired alcohol 2c was obtained as
one diastereoisomer (0.105 g, 62%, column chromatog-
raphy with pentane/Et2O¼3:1). IR (film): 3340, 2956, 2929,
4.4.7. 3-tert-Butyl-4-methylcyclopentanol (2g). According
to general procedure III, 1-tert-butyl-2-methylcyclopentene
1f (0.207 g, 1.5 mmol) in THF (6 mL) was reacted with
BH3·THF (4.5 mL, 4.5 mmol, 1 M in THF) at 658C for 96 h.
After oxidative workup (6 mL 2 M NaOH, 6 mL 30%
H2O2), the desired alcohol 2g was obtained as one dia-
stereoisomer (0.150 g, 64%, column chromatography with
pentane/Et2O¼3:1). IR (film): 3340, 2956, 2870, 1476,
1
2871, 1466, 1020 cm21; H NMR (CDCl3, 600 MHz): d¼
4.02–4.00 (m, 1H), 2.17–2.11 (m, 1H), 2.08–2.02 (m, 1H),
1.88–1.82 (m, 1H), 1.73–1.69 (m, 1H), 1.52–1.47 (m, 2H),
1.44–1.21 (m, 6H), 1.16–1.02 (m, 2H), 0.95–0.91 (m, 6H);
13C NMR (CDCl3, 150 MHz): d¼77.9, 50.9, 39.8, 33.0,
32.2, 29.2, 28.1, 21.7, 21.4, 14.5, 14.4; MS (EI): 169 (1,
[M2H]þ), 109 (100), 84 (96), 56 (89), 41 (50); HRMS calcd
for C11H21O: 169.1592, found: 169.1607.
1365 cm21
;
1H NMR (CDCl3, 600 MHz): d¼3.73–3.71
(m, 1H), 1.76–1.70 (m, 1H), 1.64–1.55 (m, 3H), 1.54–1.49
(m, 1H), 1.42 (brs, 1H), 1.32–1.28 (m, 1H); 13C NMR
(CDCl3, 150 MHz): d¼81.2, 56.5, 43.7, 33.9, 32.7, 27.9,
25.2, 21.4; MS (EI): 124 (7, [M2CH3OH]þ), 123 (93), 99
(70), 83 (100); HRMS calcd for C9H16: 124.1252, found:
124.1206.
4.4.4. 2,3-Dibutylcyclopentanol (2d). According to general
procedure III, 1,2-dibutylcyclopentene 1d (0.180 g,
1 mmol) was reacted with BH3·THF at 508C for 3 h. After
oxidative workup, the desired alcohol 2d was obtained as
one diastereoisomer (0.101 g, 51%, column chroma-
tography with pentane/Et2O¼3:1). IR (film): 3338, 2956,
;
1H NMR (CDCl3,
300 MHz): d¼4.02–3.97 (m, 1H), 2.15–1.97 (m, 2H),
1.89–1.77 (m, 1H), 1.71–1.63 (m, 1H), 1.53–1.42 (m,
2H), 1.39–1.02 (m, 12H), 0.92–0.87 (m, 6H); 13C NMR
(CDCl3, 75 MHz): d¼77.9, 51.1, 40.1, 33.0, 30.8,
30.5, 29.6, 28.1, 26.6, 23.1, 23.0, 14.1, 14.1; MS (EI):
197 (0.3, [M2H]þ), 180 (4), 123 (100), 81 (59), 56 (68),
41 (57); HRMS calcd for C13H25O: 197.1905, found:
197.1931.
4.4.8. 3-Methyl-4-(triisopropylsilyl)cyclopentanol (2h).
According to general procedure III, 1-(triisopropylsilyl)-2-
methylcyclopentene 1g (0.238 g, 1 mmol) was reacted with
BH3·THF at 508C for 24 h. After oxidative workup, the
desired alcohol 2h was obtained as one diastereoisomer
(0.154 g, 60%, column chromatography with pentane/
Et2O¼3:1). IR (film): 3328, 2945, 2867, 1464, 1028, 883,
833, 663 cm21; 1H NMR (CDCl3, 300 MHz): d¼4.47–4.42
(m, 1H), 2.55–2.47 (m, 1H), 2.06–1.95 (m, 1H), 1.79–1.70
(m, 3H), 1.67–1.58 (m, 1H), 1.47 (s, 1H), 1.16–1.05 (m,
21H), 0.92 (d, J¼7.1 Hz, 3H); 13C NMR (CDCl3, 75 MHz):
d¼73.2, 46.2, 37.7, 35.5, 26.3, 20.7, 19.5, 19.4, 12.2; MS
(EI): 213 (41, [M2C3H7]þ), 131 (22), 81 (100); HRMS
calcd for C12H25OSi: 213.1675, found: 213.1649.
2927, 2859, 1466, 1022 cm21

9194
E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
4.4.9. 3-Benzyl-2-ethylcyclopentanol (2i). According to
general procedure III, 1-benzyl-2-ethylcyclopentene 1h
(0.186 g, 1 mmol) was reacted with BH3·THF at 508C for
3 h. After oxidative workup, the desired alcohol 2i was
obtained as one diastereoisomer (0.118 g, 58%, column
chromatography with pentane/Et2O¼1:1). IR (film): 3342,
3026, 2958, 2933, 2873, 1603, 1496, 1454, 1030, 737,
699 cm21; 1H NMR (CDCl3, 600 MHz): d¼7.36–7.33 (m,
2H), 7.26–7.23 (m, 3H), 4.17–4.14 (m, 1H), 2.85 (dd,
J¼13.4, 5.3 Hz, 1H), 2.60–2.54 (m, 1H), 2.40 (dd, J¼13.4,
10.7 Hz, 1H), 2.20–2.14 (m, 1H), 1.82–1.75 (m, 2H),
1.63–1.54 (m, 2H), 1.46–1.37 (m, 2H), 1.36–1.29 (m, 1H),
1.07 (t, J¼7.2 Hz, 3H); 13C NMR (CDCl3, 150 MHz):
d¼141.9, 128.7, 128.2, 125.6, 77.5, 53.3, 41.9, 36.0, 33.0,
27.7, 20.1, 12.7; MS (EI): 204 (55, Mþ), 157 (71), 117
(100), 113 (82), 104 (27); HRMS calcd for C14H20O:
204.1514, found: 204.1515.
600 MHz): d¼7.31–7.28 (m, 2H), 7.20–7.18 (m, 3H),
4.08–4.06 (m, 1H), 3.57–3.53 (m, 1H), 2.30–2.26 (m, 1H),
2.22–2.17 (m, 1H), 2.16–2.10 (m, 1H), 2.01–1.94 (m, 1H),
1.71–1.65 (m, 2H), 0.58 (d, J¼7.4 Hz, 3H); 13C NMR
(CDCl3, 75 MHz): d¼142.5, 128.3, 128.0, 125.8, 79.7, 47.1,
46.0, 33.2, 26.4, 13.2; MS (EI): 176 (1, Mþ), 158 (61), 143
(100), 117 (44); HRMS calcd for C12H16O: 176.1201,
found: 176.1198.
4.5. General procedure IV. Formation of the amines
To a solution of the corresponding olefin (1 mmol) in THF
(4 mL) was slowly added BH3·THF (3 mL, 3 mmol, 1 M in
THF) at 08C. The resulting solution was stirred for the time
and at the temperature stated. The solvent and the excess of
borane were removed under reduced pressure (0.1 mm Hg,
1 h). The residue was dissolved in CH2Cl2 (2 mL) and BCl3
(5 mL, 5 mmol, 1 M in CH2Cl2) was added at 08C. After
stirring for 4 h at 258C, the solvent and an excess of BCl3
were removed under reduced pressure (0.1 mm Hg, 1 h).
The residue was dissolved in CH2Cl2 (2 mL) and benzyl
azide (0.399 g, 3 mmol) was added at 08C. The solution was
allowed to warm up to 258C overnight. The reaction mixture
was then quenched with NaOH (2 M in H2O) and worked up
as usual. The crude amines were purified by column
chromatography (pentane/Et2O).
4.4.10. 2-Benzyl-3-ethylcyclopentanol (2j). According to
general procedure III, 1-benzyl-2-ethylcyclopentene 1h
(0.186 g, 1 mmol) was reacted with BH3·THF at 508C for
3 h. After oxidative workup, the desired alcohol 2j was
obtained as one diastereoisomer (0.024 g, 12%, column
chromatography with pentane/Et2O¼1:1). IR (film): 3351,
3026, 2957, 2933, 2872, 1603, 1495, 1454, 1017, 740,
699 cm21; 1H NMR (CDCl3, 600 MHz): d¼7.30–7.28 (m,
2H), 7.20–7.18 (m, 3H), 3.99–3.97 (m, 1H), 2.77 (dd,
J¼13.9, 4.8 Hz, 1H), 2.24 (J¼13.9, 10.1 Hz, 1H), 2.17–
2.07 (m, 3H), 1.96–1.90 (m, 1H), 1.56–1.49 (m, 2H), 1.38–
1.33 (m, 1H), 1.32–1.26 (m, 1H), 1.17 (brs, 1H), 0.95 (t,
J¼7.2 Hz, 3H); 13C NMR (CDCl3, 150 MHz): d¼141.3,
128.8, 128.4, 125.9, 77.0, 52.3, 42.3, 33.3, 32.5, 27.9, 23.1,
13.0; MS (EI): 204 (20, Mþ), 186 (56), 157 (61), 117 (75),
113 (100); HRMS calcd for C14H20O: 204.1514, found:
204.1514.
4.5.1. N-2,3-Tribenzylcyclopentanamine (3a). According
to general procedure IV, 1,2-dibenzylcyclopentene 1e
(0.248 g, 1 mmol) was reacted with BH3·THF at 508C for
3 h. The desired amine 3a was obtained as one diastereo-
isomer (0.220 g, 62%, column chromatography with
pentane/Et2O¼1:3). IR (film): 3025, 2933, 2864, 1602,
1
1495, 1454, 738, 699 cm21; H NMR (CDCl3, 300 MHz):
d¼7.35–7.18 (m, 13H), 7.05–7.02 (m, 2H), 3.54–3.43 (m,
2H), 3.00–2.86 (m, 3H), 2.56–2.43 (m, 3H), 2.23–2.07 (m,
2H), 1.80–1.69 (m, 1H), 1.51–1.36 (m, 2H); 13C NMR
(CDCl3, 75 MHz): d¼141.8, 141.2, 140.4, 129.0, 128.7,
128.4, 128.2, 128.2, 128.0, 126.6, 125.9, 125.7, 62.5, 52.1,
50.0, 43.0, 36.3, 34.9, 31.1, 28.8; MS (EI): 356 (22), 355
(22, Mþ), 264 (43), 146 (96), 91 (100); HRMS calcd for
C26H29N: 355.2300, found: 355.2296.
4.4.11. 3-Methyl-2-phenylcyclopentanol (2k). According
to general procedure III, 1-phenyl-2-methylcyclopentene
1i17 (0.237 g, 1.5 mmol) in THF (6 mL) was reacted with
BH3·THF (4.5 mL, 4.5 mmol, 1 M in THF) at 508C for 3 h.
After oxidative workup (6 mL 2 M NaOH, 6 mL 30%
H2O2), the desired alcohol 2k was obtained as one
diastereoisomer (0.106 g, 40%, column chromatography
with pentane/Et2O¼1:1). IR (film): 3341, 3028, 2871, 1602,
;
1H NMR (CDCl3,
4.5.2. Octahydro-1H-inden-1-ol (8). According to general
procedure III, 2,3,4,5,6,7-hexahydro-1H-indene 618
(0.183 g, 1.5 mmol) in THF (6 mL) was reacted with
BH3·THF (4.5 mL, 4.5 mmol, 1 M in THF) at 508C for
3 h. After oxidative workup (6 mL 2 M NaOH, 6 mL 30%
H2O2), the desired alcohol 8 was obtained as one
diastereoisomer (0.172 g, 82%, column chromatography
with pentane/Et2O¼3:1). IR (film): 3339, 2923, 2853, 1448,
1061 cm21; 1H NMR (CDCl3, 600 MHz): d¼4.04–4.02 (m,
1H), 2.21–2.11 (m, 2H), 1.79–1.72 (m, 2H), 1.59 (s, 1H),
1.54–1.41 (m, 6H), 1.38–1.19 (m, 4H); 13C NMR (CDCl3,
150 MHz): d¼77.0, 48.1, 36.5, 32.9, 27.7, 26.9, 25.0, 23.6,
22.7; MS (EI): 140 (2, Mþ), 122 (53), 96 (66), 81 (100);
HRMS calcd for C9H16O: 140.1201, found: 140.1173.
1495, 1454, 834, 747, 701 cm21
600 MHz): d¼7.31 (t, J¼7.6 Hz, 2H), 7.24–7.20 (m, 1H),
7.18–7.16 (m, 2H), 4.58–4.55 (m, 1H), 3.04 (t, J¼7.6 Hz,
1H), 2.50–2.43 (m, 1H), 2.30–2.25 (m, 1H), 2.13–2.07 (m,
1H), 1.76 (brs, 1H), 1.72–1.66 (m, 1H), 1.43–1.37 (m, 1H),
0.63 (d, J¼7.0 Hz, 3H); 13C NMR (CDCl3, 150 MHz):
d¼140.4, 128.7, 128.2, 126.1, 76.6, 58.1, 36.6, 33.4, 31.1,
17.4; MS (EI): 176 (67, Mþ), 132 (74), 117 (100); HRMS
calcd for C12H16O: 176.1201, found: 176.1187.
4.4.12. 2-Methyl-3-phenylcyclopentanol (2l). According
to general procedure III, 1-phenyl-2-methylcyclopentene
1i17 (0.237 g, 1.5 mmol) in THF (6 mL) was reacted with
BH3·THF (4.5 mL, 4.5 mmol, 1 M in THF) at 508C for 3 h.
After oxidative workup (6 mL 2 M NaOH, 6 mL 30%
H2O2), the desired alcohol 2l was obtained as one
diastereoisomer (0.079 g, 30%, column chromatography
with pentane/Et2O¼1:1). IR (film): 3344, 3028, 2876, 1602,
;
1H NMR (CDCl3,
4.5.3. N-Benzyloctahydro-1H-inden-1-amine (9). Accord-
ing to general procedure IV, 2,3,4,5,6,7-hexahydro-1H-
indene 618 (0.183 g, 1.5 mmol) in THF (6 mL) was reacted
with BH3·THF (4.5 mL, 4.5 mmol, 1 M in THF) at 508C for
3 h. The residue was further reacted with BCl3 (7.5 mL,
1497, 1452, 834, 746, 700 cm21

E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
9195
7.5 mmol, 1 M in CH2Cl2) in CH2Cl2 (4 mL) and benzyl
azide (0.599 g, 4.5 mmol) in CH2Cl2 (6 mL). Evaporation
of solvents after treatment with BCl3 was performed at
50 mbar vacuum. The desired amine 9 was obtained as one
diastereoisomer (0.189 g, 55%, column chromatography
with pentane/Et2O¼1:3). IR (film): 3027, 2922, 2853, 1495,
(100), 57 (29). Anal. calcd for C8H16O: C 74.94, H 12.58;
found: C 75.12, H 12.67.
4.5.7. 2-Isopropyl-1-(N-benzylamino)-cyclopentane (14).
According to general procedure IV, (1-methylethylidene)-
cyclopentane 1220 (0.331 g, 3 mmol) in THF (23 mL) was
reacted with BH3·THF (9 mL, 9 mmol, 1 M in THF) at 508C
for 12 h. The residue was further reacted with BCl3 (12 mL,
12 mmol, 1 M in CH2Cl2) in CH2Cl2 (25 mL) and benzyl
azide (0.479 g, 3.6 mmol) in CH2Cl2 (20 mL). The desired
amine 14 was obtained as one diastereoisomer (0.449 g,
69%; column chromatography with pentane/Et2O¼2:1). IR
(film): 3086, 3063, 3027, 2870, 1603, 1453, 1343, 1066,
975, 699 cm21; 1H NMR (CDCl3, 300 MHz): d¼7.40–7.23
(m, 5H), 3.88 (d, J¼12.9 Hz, 1H), 3.81 (d, J¼12.9 Hz, 1H),
2.85 (q, J¼6.9 Hz, 1H), 1.88–1.24 (m, 8H), 0.94 (d,
J¼7.1 Hz, 3H), 0.89 (d, J¼6.3 Hz, 3H); 13C NMR (CDCl3,
75 MHz): d¼140.9, 128.3, 128.2, 126.7, 62.0, 53.4, 52.8,
33.1, 30.8, 28.1, 23.8, 21.7, 19.5; MS (EI): 217 (10, Mþ),
146 (100), 91 (94). Anal. calcd for C15H23N: C 82.89, H
10.67, N 6.44; found: C 82.68, H 10.85, N 6.70.
1
1453, 732, 698 cm21; H NMR (CDCl3, 300 MHz): d¼
7.33–7.21 (m, 5H), 3.83–3.71 (m, 2H), 2.98–2.92 (m, 1H),
2.16–2.03 (m, 2H), 1.80–1.66 (m, 2H), 1.56–1.25 (m,
10H); 13C NMR (CDCl3, 75 MHz): d¼140.8, 128.3, 128.1,
126.7, 61.6, 52.6, 45.3, 37.7, 31.0, 28.1, 28.0, 26.3, 23.5,
23.4; MS (EI): 229 (14, Mþ), 200 (17), 146 (100), 91 (61);
HRMS calcd for C16H23N: 229.1830, found: 229.1819.
4.5.4. Decahydro-1-naphthalenol (10). According to
general procedure III, 1,2,3,4,5,6,7,8-octahydronaphthalene
719(0.204 g, 1.5 mmol) in THF (6 mL) was reacted with
BH3·THF (4.5 mL, 4.5 mmol, 1 M in THF) at 508C for 3 h.
After oxidative workup (6 mL 2 M NaOH, 6 mL 30%
H2O2), the desired alcohol 10 was obtained as one
diastereoisomer (0.147 g, 72%, column chromatography
with pentane/Et2O¼3:1). IR (film): 3350, 2924, 2859, 1448,
1045 cm21
;
1H NMR (toluene-d8, 400 MHz, T¼373 K):
4.5.8. 2,3-Diphenylbutan-1-ol (syn-18). According to
general procedure III, Z-1,2-dimethyl-1,2-diphenylethylene
Z-1721,22 (0.208 g, 1 mmol) was reacted with BH3·THF
under reflux for 16 h. After oxidative workup, the desired
alcohol syn-18 was obtained as one diastereoisomer
(0.170 g, 75%; column chromatography with pentane/
Et2O¼2:1). IR (KBr): 3480, 3080, 3024, 2960, 2924,
d¼3.53–3.48 (m, 1H), 1.80–1.73 (m, 2H), 1.66–1.60 (m,
1H), 1.54–1.11 (m, 13H), 0.67 (brs, 1H); 13C NMR
(toluene-d8, 100 MHz, T¼373 K): d¼69.0, 44.6, 35.2,
33.9, 29.9, 29.8, 26.6, 25.2, 23.8, 21.1; MS (EI): 153 (0.4,
[M2H]þ), 136 (100), 121 (45), 94 (58); HRMS calcd for
C10H17O: 153.1279, found: 153.1265.
1
1342, 1055, 702 cm21; H NMR (CDCl3, 300 MHz): d¼
4.5.5. N-Benzyldecahydro-1-naphthalenamine (11).
According to general procedure IV, 1,2,3,4,5,6,7,8-octa-
hydronaphthalene 719 (0.204 g, 1.5 mmol) in THF (6 mL)
was reacted with BH3·THF (4.5 mL, 4.5 mmol, 1 M in THF)
at 508C for 3 h. The residue was further reacted with BCl3
(7.5 mL, 7.5 mmol, 1 M in CH2Cl2) in CH2Cl2 (4 mL) and
benzyl azide (0.599 g, 4.5 mmol) in CH2Cl2 (6 mL).
Evaporation of solvents after treatment with BCl3 was
performed at 50 mbar vacuum. The desired amine 11 was
obtained as one diastereoisomer (0.208 g, 57%, column
chromatography with pentane/Et2O¼1:3). IR (film): 3028,
2923, 2857, 1495, 1448, 746, 698 cm21; 1H NMR (toluene-
d8, 400 MHz, T¼373 K): d¼7.28–7.26 (m, 3H), 7.14 (t,
J¼7.6 Hz, 2H), 3.74–3.61 (m, 2H), 2.57–2.53 (m, 1H),
1.87–1.10 (m, 16H); 13C NMR (toluene-d8, 100 MHz,
T¼373 K): d¼139.1, 128.5, 128.5, 127.0, 56.0, 51.9, 42.7,
34.7, 30.4, 30.2, 29.6, 27.5, 27.7, 27.7, 21.5; MS (EI): 243
(9, Mþ), 200 (55), 146 (86), 91 (100); HRMS calcd for
C17H25N: 243.1987, found: 243.2005.
7.34–7.21 (m, 10H), 3.59–3.44 (m, 2H), 2.95–2.88 (m,
2H), 1.02 (d, J¼6.8 Hz, 3H); 13C NMR (CDCl3, 75 MHz):
d¼145.5, 141.5, 128.7, 128.6, 128.5, 127.2, 126.8, 126.3,
65.7, 55.5, 42.2, 20.8; MS (EI): 226 (3, Mþ), 121 (24), 105
(100), 91 (23); anal. calcd for C16H18O: C 84.91, H 8.02, O
7.07; found: C 84.43, H 7.58, O 6.89.
4.5.9. 2,3-Diphenylbutan-1-ol (anti-18). According to
general procedure III, E-1,2-dimethyl-1,2-diphenylethylene
E-1721,22 (0.208 g, 1 mmol) was reacted with BH3·THF
under reflux for 16 h. After oxidative workup, the desired
alcohol anti-18 was obtained as one diastereoisomer
(0.172 g, 76%; column chromatography with pentane/
Et2O¼2:1). IR (film): 3558, 3375, 3084, 3061, 3028,
2964, 2930, 1494, 1452, 1047, 763 cm21
;
1H NMR
(CDCl3, 300 MHz): d¼7.31–6.93 (m, 10H), 4.03–3.85
(m, 2H), 3.20–3.00 (m, 2H), 1.36 (d, J¼6.7 Hz, 3H); 13C
NMR (CDCl3, 75 MHz): d¼144.7, 140.4, 128.9, 128.1,
127.9, 127.8, 126.6, 125.9, 64.7, 54.8, 41.9, 19.7; MS (EI):
226 (51, Mþ), 105 (100), 91 (19), 28 (31); HRMS calcd for
C16H18O: 226.1358, found: 226.1354.
4.5.6. 2-Isopropyl-cyclopentanol (13). According to gen-
eral procedure III, (1-methylethylidene)cyclopentane 1220
(0.331 g, 3 mmol) in THF (23 mL) was reacted with
BH3·THF (9 mL, 9 mmol, 1 M in THF) at 508C for 8 h.
After oxidative workup (25 mL 2 M NaOH, 10 mL 30%
H2O2), the desired alcohol 13 was obtained as one
diastereoisomer (0.280 g, 73%; column chromatography
with pentane/Et2O¼3:1). IR (film): 3307, 3076, 3061, 3029,
4.5.10. N-Benzyl-2,3-diphenylbutan-1-amine (22a).
According to general procedure IV, Z-1,2-dimethyl-1,2-
diphenylethylene Z-1721,22 (0.208 g, 1 mmol) was reacted
with BH3·THF under reflux for 16 h. The desired amine 22a
was obtained as one diastereoisomer (0.251 g, 80%; column
chromatography with pentane/Et2O¼3:1). IR (film): 3308,
1
1
2872, 1632, 733, 688 cm21; H NMR (CDCl3, 300 MHz):
3084, 3026, 2966, 2026, 1494, 1452, 775, 756 cm21; H
d¼3.91 (m, 1H), 1.82–1.39 (m, 7H), 1.22–1.09 (m, 1H),
0.92 (d, J¼6.8 Hz, 3H), 0.83 (d, J¼6.7 Hz, 3H); 13C NMR
(CDCl3, 75 MHz): d¼76.7, 55.2, 35.7, 30.5, 27.9, 22.6,
21.4, 19.9; MS (EI): 128 (3, Mþ), 110 (11), 95 (53), 82
NMR (CDCl3, 300 MHz): d¼7.33–6.92 (m, 15H), 3.62 (d,
J¼13.4 Hz, 1H), 3.42 (d, J¼13.4 Hz, 1H), 3.00 (dt, J¼10.1,
4.3 Hz, 1H), 2.91–2.80 (m, 1H), 2.70 (dd, J¼11.7, 9.9 Hz,
1H), 2.59 (dd, J¼11.7, 4.3 Hz, 1H), 0.98 (d, J¼7.8 Hz, 3H);

9196
E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
13C NMR (CDCl3, 75 MHz): d¼145.9, 142.4, 139.8, 128.6,
128.5, 128.4, 128.2, 127.9, 127.4, 126.8, 126.7, 126.3, 53.5,
53.0, 52.9, 44.5, 21.0; MS (EI): 313 (3), 195 (3), 121 (18),
120 (100), 105 (20), 91 (97), 43 (9); HRMS calcd for
C23H23N: 313.1830, found: 313.1829.
2H), 7.46–7.12 (m, 13H), 3.51 (td, J¼10.2, 3.6 Hz, 1H),
3.24 (dd, J¼16.4, 10.1 Hz, 1H), 3.04–2.91 (m, 2H), 1.03 (d,
J¼6.9 Hz, 3H); 13C NMR (CDCl3, 75 MHz): d¼199.1,
145.8, 143.3, 137.3, 132.6, 128.6, 128.3, 127.7, 127.3,
126.5, 126.4, 48.4, 45.9, 44.1, 20.9; MS (EI): 210 (6), 194
(29), 105 (100), 77 (24); HRMS calcd for C15H14: 194.1096,
found: 194.1092.
4.6. General procedure V. Formation of the zinc-
reagents
4.6.4. N-Benzyl-N-[1-methyl-2-ethyl-3,3-diphenylpropyl]-
amine (26). According to general procedure IV, 2-ethyl-
1,1-diphenylbut-1-ene 24 (0.708 g, 3 mmol) in THF
(25 mL) was reacted with BH3·THF (9 mL, 9 mmol, 1 M
in THF) at 508C for 3 h. The residue was further reacted
with BCl3 (12 mL, 12 mmol, 1 M in CH2Cl2) in CH2Cl2
(25 mL) and benzyl azide (0.479 g, 3.6 mmol) in CH2Cl2
(15 mL). The desired amine 26 was obtained as a
diastereomeric mixture of 92:8 (GC–MS, method B,
6.74 min and 6.89 min) (0.587 g, 57%; column chroma-
tography with pentane/Et2O¼2:1). IR (film): 3061, 2961,
To a solution of Z-1,2-dimethyl-1,2-diphenylethylene
Z-1721,22 (0.416 g, 2 mmol) in THF (10 mL) was slowly
added BH3·THF (4 mL, 4 mmol, 1 M in THF). The resulting
solution was heated to reflux for 16 h. The solvent and the
excess of borane were removed under reduced pressure
(0.1 mm Hg, 1 h). The residue was dissolved in THF
(10 mL) and treated with ethylene for 0.5 h. After the
solvent was removed under reduced pressure (0.1 mm Hg,
1 h), Et2Zn (2.1 mL, 20 mmol) was added at 08C and stirring
was continued for 3 h at this temperature. The excess of
Et2Zn and the solvent were removed under reduced pressure
(0.1 mm Hg, 1 h) and the residue was diluted with THF
(10 mL). The resulting mixture was cooled to 2788C and a
solution of CuCN·2LiCl (0.4 mL, 0.4 mmol, 1 M in THF)
was slowly added. The mixture was allowed to warm to
2608C and the corresponding electrophile (10 mmol) was
added. The solution was allowed to warm up to 258C and
stirred at this temperature for 1 h. After usual workup, the
crude products were purified by column chromatography
(pentane/Et2O).
1
1597, 1493, 1451, 1380, 1029, 744, 703 cm21; H NMR
(CDCl3, 300 MHz): d¼7.26–6.98 (m, 15H), 3.63 (m, 3H),
2.68 (m, 1H), 2.38 (m, 1H), 1.49 (m, 1H), 1.25–0.79 (m,
2H), 0.86 (m, 3H), 0.63 (m, 3H); 13C NMR (CDCl3,
75 MHz): d¼144.6, 144.3, 128.5, 128.3, 128.3, 128.3,
128.0, 127.8, 126.7, 126.0, 125.9, 56.1, 53.5, 51.5, 46.2,
20.7, 15.2, 14.5; MS (EI): 343 (1, Mþ), 134 (100), 91 (51);
HRMS calcd for C25H30N: 344.2378, found: 344.2365.
4.6.5. 3-Benzhydrylpentan-2-ol (27). According to general
procedure III, 2-ethyl-1,1-diphenylbut-1-ene 24 (0.708 g,
3 mmol) in THF (23 mL) was reacted with BH3·THF (9 mL,
9 mmol, 1 M in THF) at 508C for 3 h. After oxidative
workup (25 mL 2 M NaOH, 10 mL 30% H2O2), the desired
alcohol 27 was obtained as a diastereomeric mixture of
72:28 (GC–MS, method B, 4.19 and 4.22 min) (0.556 g,
73%; column chromatography with pentane/Et2O¼3:1). IR
(film): 3321, 3067, 2922, 1939, 1860, 1557, 1490, 1377,
4.6.1. 5,6-Diphenyl-1-heptene (22b). According to general
procedure V, 22b was obtained after reaction with allyl
bromide (10 mmol, 1.21 g) as one diastereoisomer (0.361 g,
72%; column chromatography with pentane). IR (KBr):
1
3063, 3026, 2972, 2926, 1639, 1494, 1452, 756 cm21; H
NMR (CDCl3, 300 MHz): d¼7.36–7.12 (m, 10H), 5.64–
5.47 (m, 1H), 4.86–4.71 (m, 2H), 2.92–2.76 (m, 1H), 2.73–
2.58 (m, 1H), 1.80–1.41 (m, 4H), 0.96 (d, J¼6.8 Hz, 3H);
13C NMR (CDCl3, 75 MHz): d¼146.6, 143.9, 138.6, 128.4,
128.2, 127.6, 126.1, 126.0, 114.3, 52.4, 46.4, 33.5, 31.7,
21.1; MS (EI): 250 (2, Mþ), 145 (34), 105 (56), 91 (100);
HRMS calcd for C19H22: 250.1722, found: 250.1716.
1
1352, 986, 772, 698 cm21; H NMR (CDCl3, 300 MHz):
d¼7.26–7.06 (m, 10H), 3.79 (m, 1H), 3.65 (d, J¼10.8 Hz,
1H), 2.36 (m, 1H), 1.54–1.13 (m, 3H), 1.02 (d, J¼6.4 Hz,
3H), 0.72 (t, J¼7.6 Hz, 3H); 13C NMR (CDCl3, 75 MHz):
d¼144.0, 144.0, 128.3, 128.2, 128.0, 127.8, 126.1, 126.0,
69.1, 55.0, 49.4, 21.0, 18.3, 13.5; MS (EI): 254 (71, Mþ),
195 (59), 174 (66), 91 (100), 28 (37). Anal. calcd for
C18H22O: C 84.99, H 8.72; found: C 84.78, H 8.55.
4.6.2. 1,4,5-Triphenyl-1-hexyne (22c). According to gen-
eral procedure V, 22c was obtained after reaction with
(bromoethynyl)benzene (10 mmol, 1.81 g) as one dia-
stereoisomer (0.316 g, 51%; column chromatography with
pentane). IR (film): 3082, 3061, 3028, 2962, 2926, 1491,
4.6.6. N-Benzyl-N-[1,2-dimethyl-3,3-diphenylpropyl]-
amine (30). According to general procedure IV, 2-methyl-
1,1-diphenylbut-1-ene 2821,23 (0.667 g, 3 mmol) in THF
(25 mL) was reacted with BH3·THF (9 mL, 9 mmol, 1 M in
THF) at 508C for 3 h. The residue was further reacted with
BCl3 (12 mL, 12 mmol, 1 M in CH2Cl2) in CH2Cl2 (25 mL)
and benzyl azide (0.479 g, 3.6 mmol) in CH2Cl2 (15 mL).
The desired amine 30 was obtained as a diastereomeric
mixture of 92:8 (GC–MS, method B, 6.00 and 6.19 min)
(0.691 g, 70%; column chromatography with pentane/
Et2O¼2:1). IR (film): 3096, 3051, 3020, 2870, 1944,
1
1452, 756, 700 cm21; H NMR (CDCl3, 300 MHz): d¼
7.42–7.14 (m, 15H), 3.24–3.10 (m, 1H), 3.33–2.89 (m,
1H), 2.52–2.35 (m, 2H), 1.06 (d, J¼6.8 Hz, 3H); 13C NMR
(CDCl3, 75 MHz): d¼145.8, 143.0, 131.4, 131.4, 128.5,
128.4, 128.2, 128.1, 127.6, 127.4, 126.6, 126.4, 88.7, 82.4,
52.1, 44.2, 25.6, 20.7; MS (EI):310 (19, Mþ), 205 (100), 105
(90), 91 (75), 77 (22); HRMS calcd for C24H22: 310.1721,
found: 310.1721.
1
4.6.3. 1,3,4-Triphenylpentan-1-one (22d). According to
general procedure V, 22d was obtained after reaction with
benzoyl chloride (10 mmol, 1.41 g) as one diastereoisomer
(0.327 g, 52%; column chromatography with pentane/
Et2O¼9:1). IR (KBr): 3057, 3026, 2953, 2922, 1676,
744 cm21; 1H NMR (CDCl3, 300 MHz): d¼7.67–7.61 (m,
1746, 1495, 1384, 1123, 973, 914, 675 cm21; H NMR
(CDCl3, 300 MHz): d¼7.22–7.00 (m, 15H), 3.62 (m, 2H),
3.50 (d, J¼11.5 Hz, 1H), 2.61 (m, 2H), 0.85 (d, J¼6.1 Hz,
3H), 0.70 (d, J¼6.6 Hz, 3H); 13C NMR (CDCl3, 75 MHz):
d¼144.6, 143.8, 140.9, 128.5, 128.4, 128.3, 128.0, 127.9,
127.7, 126.7, 126.0, 56.6, 52.4, 51.3, 39.3, 13.9, 11.4; MS

E. Hupe et al. / Tetrahedron 59 (2003) 9187–9198
9197
(EI): 329 (20, Mþ), 258 (44), 251 (61), 91 (100). Anal. calcd
for C24H27N: C 87.49, H 8.26, N 4.25; found: C 87.37, H
8.40, N 4.04.
1H), 1.59–1.48 (m, 1H), 0.83 (d, J¼6.8 Hz, 3H), 0.73 (t,
J¼7.3 Hz, 3H); 13C NMR (CDCl3, 75 MHz): d¼143.5,
140.4, 137.8, 130.4, 129.0, 127.5, 127.0, 125.6, 125.5,
116.0, 54.8, 48.5, 40.3, 33.5, 26.8, 15.2, 12.1; MS (EI): 278
(5, Mþ), 159 (51), 119 (50), 118 (53), 91 (100). Anal. calcd
for C21H26: C 90.59, H 9.41; found: C 90.32, H 9.62.
4.6.7. N-Benzyl-3,4-diphenyl-2-hexanamine (syn-35).
According to general procedure IV, Z-3,4-diphenylhex-3-
ene Z-3321,22c (0.236 g, 1 mmol) was reacted with BH3·THF
under reflux for 14 h. The desired amine syn-35 was
obtained as one diastereoisomer (0.137 g, 40%; column
chromatography with pentane/Et2O¼1:1). IR (film): 3025,
2964, 1494, 1451, 1377, 751, 701 cm21; 1H NMR (CDCl3,
300 MHz): d¼7.43–7.18 (m, 15H), 3.79 (d, J¼13.2 Hz,
1H), 3.66 (d, J¼13.2 Hz, 1H), 3.28 (m, 1H), 2.95 (m, 1H),
2.63 (m, 1H), 1.52 (m, 1H), 1.33 (m, 1H), 0.90 (d, J¼6.6 Hz,
3H), 0.60 (t, J¼7.7 Hz, 3H); 13C NMR (CDCl3, 75 MHz):
d¼143.7, 140.9, 139.9, 129.9, 128.4, 128.2, 128.1, 127.9,
126.6, 126.4, 126.1, 54.8, 53.0, 50.8, 49.4, 27.9, 15.9, 12.0;
MS (CI): 344 (100, [MþH]þ), 119 (40), 105 (36), 91 (28).
Anal. calcd for C25H29N: C 87.41, H 8.51, N 4.08; found: C
87.36, H 8.73, N 4.24.
4.6.10. 3,4-Diphenylhexan-2-ol (anti-37). According to
general procedure III, E-3,4-diphenylhex-3-ene E-3321,22c
(0.236 g, 1 mmol) was reacted with BH3·THF under reflux
for 14 h. After oxidative workup, the desired alcohol anti-37
was obtained as a diastereomeric mixture of 75:25 (GC–
MS, method C, 4.39 and 4.43 min) (0.223 g, 82%; column
chromatography with pentane/Et2O¼2:1). IR (KBr): 3367,
3060, 3028, 2962, 2930, 1493, 1453, 1375, 1106, 757,
704 cm21; 1H NMR (CDCl3, 300 MHz): d¼7.22–7.08 (m,
6H), 6.99–6.88 (m, 2H), 6.77–6.71 (m, 2H), 4.07 (m, 1H),
3.37 (m, 1H), 2.92 (m, 1H), 1.79–1.51 (m, 3H), 1.02 (d,
J¼6.2 Hz, 3H), 0.82 (t, J¼7.0 Hz, 3H); 13C NMR (CDCl3,
75 MHz): d¼141.4, 138.8, 130.3, 129.7, 127.4, 126.3,
125.9, 67.9, 58.8, 47.0, 26.3, 21.9, 12.2; MS (EI): 236 (4,
Mþ), 118 (94), 91 (100). Anal. calcd for C18H22O: C 84.99,
H 8.72; found: C 84.81, H 8.52.
4.6.8. N-Benzyl-3,4-diphenyl-2-hexanamine (anti-35).
According to general procedure IV, E-3,4-diphenylhex-3-
ene E-3321,22c (0.236 g, 1 mmol) was reacted with BH3·THF
under reflux for 14 h. The desired amine anti-35 was
obtained as a diastereomeric mixture of 90:10 (GC–MS,
method A, 5.41 and 5.61 min) (0.227 g, 66%; column
chromatography with pentane/Et2O¼3:2). IR (film): 3083,
4.6.11. N-Benzyl-N-[1-methyl-2,3-diphenylbutyl]amine
(40). According to general procedure IV, Z-2,3-diphenyl-
pent-2-ene Z-3824 (0.222 g, 1 mmol) was reacted with
BH3·THF under reflux for 14 h. The desired amine 40 was
obtained as a diastereomeric mixture of 95:5 (GC–MS,
method A, 5.28 and 5.44 min) (0.151 g, 46%; column
chromatography with pentane/Et2O¼2:1). IR (KBr): 3306,
3083, 3026, 2964, 2924, 1493, 1452, 1375, 750, 731,
700 cm21; 1H NMR (CDCl3, 300 MHz): d¼7.28–6.99 (m,
15H), 3.67 (d, J¼13.2 Hz, 1H), 3.55 (d, J¼13.4 Hz, 1H),
3.07 (m, 2H), 2.56 (m, 1H), 0.96 (d, J¼6.6 Hz, 3H), 0.81
(d, J¼6.7 Hz, 3H); 13C NMR (CDCl3, 75 MHz): d¼146.1,
140.8, 139.7, 129.9, 128.5, 128.2, 127.9, 127.9, 127.3,
126.6, 126.4, 126.1, 56.0, 53.0, 50.8, 41.4, 21.5, 16.1; MS
(EI): 329 (58, Mþ), 134 (100), 91 (80). Anal. calcd for
C24H27N: C 87.49, H 4.25; found: C 87.30, H 4.09.
1
3060, 2961, 2928, 1493, 1452, 1147, 753, 701 cm21; H
NMR (CDCl3, 300 MHz): d¼7.39–7.12 (m, 5H), 7.07–
6.93 (m, 6H), 6.83–6.71 (m, 4H), 3.85 (d, J¼13.0 Hz, 1H),
3.77 (d, J¼12.7 Hz, 1H), 3.27 (m, 1H), 2.99 (m, 2H), 1.68
(m, 1H), 1.47 (m, 1H), 0.90 (d, J¼6.1 Hz, 3H), 0.68 (t, J¼
7.7 Hz, 3H); 13C NMR (CDCl3, 75 MHz): d¼142.6, 141.0,
139.6, 130.4, 129.4, 128.4, 128.2, 127.4, 127.2, 126.8,
126.0, 125.6, 56.0, 52.7, 50.9, 47.4, 26.6, 17.4, 12.1; MS
(CI): 344 (100, [MþH]þ). Anal. calcd for C25H29N: C
87.41, H 8.51, N 4.08; found: C 87.30, H 8.36, N 4.45.
4.6.9. (1-Ethyl-3-methyl-2-phenylhex-5-enyl)benzene
(syn-36). To a solution of Z-3,4-diphenylhex-3-ene Z-3321,
22(0.236 g, 1 mmol) in THF (5 mL) was slowly added
BH3·THF (3 mL, 3 mmol, 1 M in THF). The resulting
solution was heated to reflux for 14 h. The solvent and the
excess of borane were removed under reduced pressure
(0.1 mm Hg, 1 h). The residue was treated with i-Pr2Zn
(1 mL, 4 mmol, 4 M in Et2O) for 3 h at 258C. After the
solvents and the excess of i-Pr2Zn were removed under
reduced pressure (0.1 mm Hg, 1 h), the residue was diluted
with THF (2 mL). The resulting mixture was cooled to
2788C and a solution of CuCN·2LiCl (1 mL, 1 mmol, 1 M
in THF) was slowly added. The mixture was stirred at
2788C for 30 min. Allyl bromide (0.363 g, 3 mmol) in THF
(1 mL) was slowly added at this temperature. The solution
was allowed to warm up to 258C overnight. After usual
workup, the crude product syn-36 was purified by column
chromatography (pentane) and obtained in a 60:40 mixture
of diastereoisomers (1H NMR, e.g. 5.83 and 5.50 ppm)
(0.170 g, 61%). IR (film): 3061, 3027, 2962, 2928, 1492,
Acknowledgements
We thank the DFG (SPP 1118) and the Fonds der
´
Chemischen Industrie (Kekule-scholarship for E.H.) for
generous support. We thank also the BASF AG, Bayer AG,
Chemetall GmbH and Degussa AG for the generous gift of
chemicals.
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