Unexpected iron(iii) chloride-catalysed dimerisation of 1,1,3-trisubstituted-prop-2-yn-1-ols as an expedient route to highly conjugated indenes

Article abstract of DOI:10.1039/c003522j

A method to prepare highly conjugated indenes efficiently by iron(iii) chloride-catalysed dimerisation of trisubstituted propargylic alcohols under very mild conditions at room temperature is described. The reactions are rapid and operationally straightfo

Full text of DOI:10.1039/c003522j

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Unexpected iron(III) chloride-catalysed dimerisation of
1,1,3-trisubstituted-prop-2-yn-1-ols as an expedient route to highly
conjugated indenes†
Weidong Rao and Philip Wai Hong Chan*
Received 25th February 2010, Accepted 8th June 2010
First published as an Advance Article on the web 20th July 2010
DOI: 10.1039/c003522j
A method to prepare highly conjugated indenes efficiently by iron(III) chloride-catalysed dimerisation
of trisubstituted propargylic alcohols under very mild conditions at room temperature is described. The
reactions are rapid and operationally straightforward, giving the indene products in good yields and
regioselectivity.
structures of 2 and 3 are unprecedented. Additionally, while 1,2-
Introduction
and 1,3-migrations of acetoxy,8 indole,2h silyl7h and sulfide9 groups
in the respective propargylic derivatives have been reported, the
apparent 1,3-alkyl group migration observed in this reaction is not
known. Herein, we report the discovery of this new iron-catalysed
method for the synthesis of ethynyl-2-vinyl-1H-indenes from
dimerisation of a variety of trisubstituted propargylic alcohols.
In addition to their versatility as building blocks in organic
synthesis, indenes are an important class of carbocycles found
in a myriad of compounds of biological and material interest.1
Although this has led to many synthetic methods to this important
carbocycle,2 the number of literature examples still remains
far fewer than those for structurally related heterocycles such
as indoles and benzofurans. Moreover, many of the reported
reactions have been shown to require high temperatures and/or
prolonged reaction times. In this regard, the development of mild
and efficient synthetic strategies that can make use of inexpensive
and ecologically benign starting materials and catalysts for the
synthesis of this class of compounds would be desirable.
Iron complexes have re-emerged as efficient Lewis acid catalysts
in a variety of stereoselective C–X (X = C, N, O, S) bond
formations in recent years.3–5 When the electrophile in these
reactions is an alcohol, they were shown not only to benefit from
the nontoxic and inexpensive nature of the ubiquitous Group 8
metal but also the low cost of the substrate and formation of
H2O as potentially the only byproduct.4,5 Added to this is the ease
of preparing the starting alcohol that provided the possibility to
introduce a wide variety of substitution patterns and a quaternary
carbon centre through the use of a tertiary alcohol. As part of an
ongoing program to develop such reactions,5a,6 we unexpectedly
found propargylic alcohols of the type 1 dimerised and gave the
indene products 2 and 3 when treated with FeCl3 under the mild
conditions shown in route 1 in Scheme 1. The reactions were also
shown to proceed with complete regioselectivity for substrates
containing a sterically bulky alkyl group on the carbinol carbon,
and such selectivities were dependent on the structural nature of
this functional group. Interestingly, although indene formation
from propargylic alcohols such as 1 has been described twice
before in the literature, as shown in routes 2 and 3 in Scheme 1,7 the
Results and discussion
˚
We found that treating a solution of 1a in CH2Cl2 and 4 A MS
with 5 mol% of FeCl3 at room temperature for 0.5 h gave the
best result (Table 1, entry 1). Under these conditions, the indenes
2a and 3a were obtained in respective yields of 65% and 7%,
comparable to the yields and regioselectivities obtained for the
analogous Au-catalysed reactions with propargylic acetates and
indoles.2h,2n The regiochemistries of both indene products were
determined by X-ray single crystal structure analysis (Fig. 1a and
1d).† Although requiring a longer reaction time of 2 h, the same
yields of 2a and 3a were reproduced when the experiment was
◦
repeated at -78 C (entry 2). In contrast, repeating the reaction
in other solvents was found to be markedly less effective (entries
3–5). When toluene was employed as the solvent, the conjugated
enyne side-product 7a was furnished as the major product in 38%
yield and the indene adducts as the minor products (entry 3).
Similarly, performing the reaction in either THF or MeCN was
found to result in only recovery of the starting alcohol in yields
of 85–95%, along with 7a in 7% yield when THF was used as the
solvent (entries 4–5). On the other hand, an examination of other
Lewis and Brønsted acid catalysts revealed that InCl3, ZnCl2 and
AuCl3 could also mediate the dimerisation of 1a and give 2a and
3a, albeit in lower yields of 46–61 and 8–14%, respectively (entries
6–8). Formation of 7a in yields of 3–8% was also afforded by
the ZnCl2- and AuCl3-catalysed reactions. However, the absence
of a catalyst, or switching to the metal triflates Cu(OTf)2 and
Yb(OTf)3, or Brønsted acids p-TsOH or TfOH, was found to lead
to no reaction based on 1H NMR and TLC analysis of the crude
mixtures (entries 9–13).
Division of Chemistry and Biological Chemistry, School of Physical
and Mathematical Sciences, Nanyang Technological University, Singapore
637371, Singapore. E-mail: waihong@ntu.edu.sg; Fax: +65 6791 1961;
Tel: +65 6316 8760
† Electronic supplementary information (ESI) available: 1H and 13C NMR
data and spectra for compounds 1, 7 and 8, 1H and 13C NMR spectra
for compounds 2 and 3 and HPLC measurements for the reaction of 1f.
CCDC reference numbers 726882–726885. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c003522j
To define the scope of the present indene-forming procedure,
we next turned our attentions to the reactions of a variety of
propargylic alcohols 1 (Table 2). This revealed indene products
2b and 3b, and 2c and 3c, could be furnished in good overall
4016 | Org. Biomol. Chem., 2010, 8, 4016–4025
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Scheme 1 FeCl3-catalysed formation of ethynyl-2-vinyl-1H-indenes from trisubstituted propargylic alcohols.
Table 1 Optimisation of the reaction conditionsa
found to play a role since a more bulky i-Pr or cyclopentane unit
in place of the cyclobutane group at the carbinol position in the
starting alcohol were found to lead to no reaction. On the other
hand, propargylic alcohols with a pendant (CH2)nCH3 side chain
where n = 1, 3 or 5 at the carbinol position as in 1f–h and 1k
gave the corresponding indene products in good to excellent yields
under the standard conditions. The enyne byproduct 7 was also
obtained in yields of 3–26% for the reactions of 1b and 1d–g shown
in Table 2. More notably, dimerisation of propargylic alcohols
containing an i-Bu, Bn or phenethyl moiety at the carbinol
position was shown to proceed with complete regioselectivity. A
similar regioselective outcome was also found when we conducted
the dimerisation of 1n bearing a homoallylic functional group at
the carbinol position of the starting alcohol. In each of these latter
reactions, the indene adducts 2i–j and 2l–n were cleanly afforded
as the sole product in yields of 61–78%. The structure of 2m was
also characterized by X-ray crystallographic analysis (Fig. 1c).†
No minor products that could be attributed to either the indene
regioisomer 3 or enyne byproduct 7 were detected based on TLC
Yield (%)
Entry
Catalyst
Solvent
Time/h
2a
3a
7a
1
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
AuCl3
InCl3
CH2Cl2
CH2Cl2
PhMe
MeCN
THF
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
0.5
2
65
65
23
—
—
50
61
46
—
—
—
—
—
7
7
7
—
—
38
—
7
3
—
8
—
—
—
—
—
2b
3
15
15
15
0.5
0.5
15
15
15
15
15
15
c
4
5
6
7
8
9
10
11
12
13
—
—
8
11
14
—
—
—
—
—
ZnCl2
c
c
c
c
c
Cu(OTf)2
Yb(OTf)3
p-TsOH
TfOH
1
and H NMR analysis of the crude mixtures. Varying the alkyl
substituent at the carbinol position with a methyl group in place
of the cyclobutane group was found to lead to oligomerization of
the starting alcohol. Further control experiments also showed that
no product formation could be detected for reactions with a proton
or phenyl group instead of an alkyl group at the carbinol position
of the starting material. In these reactions, either a mixture of
decomposition products that could be identified by 1H NMR
analysis or recovery of the starting alcohol in addition to the
Meyer–Schuster rearrangement product in respective yields of 41
and 26% was obtained.10
On the basis of the above results, it appears that the chemo-
and regioselective outcomes of the reaction are dependent on the
behaviour of the Lewis acid catalyst and the alkyl substitution
pattern at the carbinol position. Although highly speculative, the
apparent 1,3-alkyl group migration in products of the type 2
and 3,11 and the formation of the enyne byproduct 7 led us to
d
—
a
˚
All reactions were performed at room temperature with 4 A MS and
◦
catalyst : 1a ratio of 1 : 20. b Reaction conducted at -78 C. c No reaction
based on 1H NMR analysis of the crude reaction mixture. d Reaction
conducted in the absence of a catalyst.
yields from 1-cyclobutylprop-2-yn-1-ols containing an electron-
donating group at the acetylenic position. Although requiring a
longer reaction time and catalyst loading of 10 mol% at 40 ◦C, the
dimerisation process was also shown to be applicable to starting
alcohols bearing an electron-withdrawing or thiophene group at
this position. Under these slightly modified conditions, the indene
adducts 2d and 2e, which was also structurally characterized by
X-ray crystal analysis (Fig. 1b),† were afforded in lower yields
of 22 and 24%, respectively. Interestingly, steric effects were also
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Fig. 1 ORTEP drawings of (a) 2a, (b) 2e, (c) 2m and (d) 3a with thermal ellipsoids at 50% probability levels.†
propose the mechanism outlined in Scheme 2 for the reaction
of 1k. This could involve activation of the alcohol substrate
through coordination of the hydroxyl functional group to the
FeCl3 catalyst. This delivers the Fe(III)-coordinated intermediate
A which undergoes elimination to give the putative alkynyl cation
species B and its allenic resonance form C. Alkoxylation of
carbocation B/C at the sterically less hindered carbon center
by another molecule of 1k and intramolecular Friedel–Crafts
reaction would give the dimer E.12 The reaction then proceeds via a
second putative carbocation species G resulting from activation of
the hydroxyl group of this newly formed dimer due to coordination
to the metal catalyst and elimination of [Fe]–OH. This leads to
intramolecular cyclization of the alkyne moiety to the resultant
carbocation centre generated and concomitant 1,3-alkyl shift to
furnish the cationic allylindene H.13 We surmise that this C–C
bond formation and 1,3-migration process could be concerted
in character so as to avoid the possible formation of a highly
reactive and unstable vinylic cation species.14 Deprotonation at
the methylene carbon center of the 1,3-migrated alkyl group in
this indenyl cation species as shown in Scheme 2 would provide
the indene regiosiomer 2k. Alternatively, the aryl group in H could
undergo a 1,4-migration to give the cationic indenyl regioisomer
I, which deprotonates in a similar manner to that described above
to provide the indene product 3k.
1f. Under the experimental conditions described in Scheme 3,
the indene products 2f and 3f were both obtained as a racemic
mixture in 35% yield. What remains unclear is the origin of
the product regioselectivities obtained in the present propargylic
alcohol dimerisation process. One possible reason for the complete
regioselectivities obtained for reactions of substrates containing
an alkyl group with a bulky iPr or Ph group or terminal
=
C C bond could be to prevent any unfavourable steric and/or
stereoelectronic interactions arising between this group and the
migrating aryl group in H. However, this is highly speculative and
the exact reason(s) responsible for the unique regioselectivities
observed require future theoretical and experimental studies.
Conclusions
In summary, a novel iron-catalysed route to highly conjugated
indenes based on dimerisation of trisubstituted propargylic alco-
hols has been reported. This chemoselective carbocycle forming
method was shown to proceed under very mild conditions at
room temperature and provide product yields and regioselectivities
comparable to those reported for the analogous reactions with
propargylic acetates and indoles catalysed by gold salts.2h,2n In
reactions where the substrate contained a sterically bulky alkyl
group at the carbinol carbon, the indene-forming process was
also shown to proceed with complete regioselectivity. Moreover,
it makes use of alcohol substrates and an iron catalyst that are
The possible involvement of carbocation intermediates is also
supported by our results for the dimerisation of enantioenriched
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Table 2 Iron(III) chloride-catalyzed dimerisation of 1b–na
Substrate
Product
a
˚
All reactions were performed at room temperature for 0.5 h with 4 A MS and FeCl3 : 1 ratio = 1 : 20; values denoted in parenthesis are isolated yields.
b Reaction with 10 mol% FeCl3 at 40 ◦C for 24 h. c Reaction with 10 mol% FeCl3 at 40 ◦C for 2 h.
inexpensive, easily accessible and ecologically benign. Efforts are
currently underway to explore the detailed mechanistic aspects of
this reaction and how the method can be applied to natural product
synthesis and as potential advanced functional materials in view
of the nature of the substituents and high degree of conjugation
in the indene products obtained.
were purified following standard literature procedures; CH2Cl2
was purified prior to use by passing through a PURESOLVTM
Solvent Purification System. Analytical thin layer chromatography
(TLC) was performed using Merck 60 F254 pre-coated silica gel
plate. Visualization was achieved by UV light(254 nm). Flashchro-
matography was performed using Merck silica gel 60 with freshly
distilled solvents. Unless otherwise stated, 1H and 13C NMR
spectra were measured on Bruker Avance 400 MHz spectrometer.
Chemical shifts (ppm) were recorded with respect to TMS in
CDCl3. Multiplicities were given as: s (singlet), bs (broad singlet),
d (doublet), t (triplet), dd (doublet, doublet) or m (multiplets).
The number of protons (n) for a given resonance is indicated by
nH. Coupling constants are reported as a J value in Hz. Infrared
Experimental section
General details
Unless specified, all reagents and starting materials were pur-
chased from commercial sources and used as received. Solvents
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Scheme 2 Tentative mechanism for FeCl3-catalysed formation of ethynyl-2-vinyl-1H-indenes from trisubstituted propargylic alcohols.
spectra were recorded on Shimadzu IR Prestige-21 FTIR Spec-
trometer. High Resolution Mass (HRMS) spectra were obtained
using Finnigan MAT95XP LC/HRMS. Mass spectral data were
reported in units of mass to charge (m/z). Enantioselectivities
were determined by high performance liquid chromatography
(HPLC) analysis on a Shimadzu (DGU-20A5/LC-20AD/SPD-
M20A/RID-10(A) spectrometer employing a Daicel Chirapak
AD-H or OJ-H column.
Scheme 3 FeCl3-catalysed dimerisation of enantioenriched 1f.
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Representative experimental procedure for FeCl3-catalysed
preparation of vinyl-1H-indenes 2 and/or 3
25.1 (CH2), 31.0 (CH2), 31.2 (CH2), 31.5 (CH2), 31.6 (CH2), 32.1
(CH2), 32.3 (CH2), 35.7 (CH2), 35.9 (CH2), 38.4 (CH), 66.2 (Ph-
≡
≡
C-CH), 83.9 (C C), 94.5 (C C), 120.2 (Ar–C), 120.9 (Ar–C),
˚
To a solution of CH2Cl2 (3 mL) containing 1 (0.3 mmol) and 4 A
molecular sieves (200 mg), was added FeCl3 (5 mol%). The mixture
was stirred at room temperature and monitored by TLC analysis.
=
122.1 (C C), 124.9 (Ar–C), 125.6 (Ar–C), 126.0 (Ar–C), 126.7
(Ar–C), 127.2 (Ar–C), 127.6 (Ar–C), 128.1 (Ar–C), 128.3 (Ar–C),
128.5 (Ar–C), 131.7 (Ar–C), 135.8 (Ar–C), 140.3 (C C), 141.1
(Ar–C), 143.3 (Ar–C), 144.4 (C C), 145.0 (Ar–C), 149.2 (Ar–C),
=
R
On completion, the reaction mixture was filtered through Celiteꢀ
=
and washed with CH2Cl2 (20 mL). The solvent was removed under
reduced pressure and the residue was subjected to purification
by flash column chromatography on silica gel (eluent: n-hexane–
CH2Cl2 = 20 : 1 to 10 : 1) to give the title compound.
=
158.2 (C C); IR (NaCl, neat) v: 2953, 2928, 1647, 1508, 1456,
752, 696 cm-1; MS (ESI) m/z 629 [M + 1]+; HRMS (ESI) calcd.
for C48H53 (M+ + H): 629.4147, found: 629.4154.
2-((4-Chlorophenyl)(cyclobutylidene)methyl)-3-((4-chlorophe-
nyl)ethynyl)-1-cyclobutyl-1-phenyl-1H-indene (2d). Pale yellow
solid; Rf 0.50 (eluent: n-hexane–CH2Cl2 = 6 : 1); m.p. 167–168 ◦C;
1H NMR (CDCl3, 400 MHz): d 0.94–1.02 (m, 1H, CH2), 1.45–
1.66 (m, 3H, CH2), 1.71–1.88 (m, 2H, CH2), 2.06–2.23 (m, 3H,
CH2), 2.51–2.77 (m, 3H, CH2), 3.16–3.22 (m, 1H, CH), 6.73 (d,
2H, J = 7.4 Hz, Ar-H), 6.88–7.06 (m, 7H, Ar-H), 7.25–7.46 (m,
8H, Ar-H), 7.64 (d, 2H, J = 7.4 Hz, Ar-H); 13C NMR (CDCl3,
100 MHz): d 17.1 (CH2), 17.2 (CH2), 23.4 (CH2), 25.0 (CH2), 32.2
1 - Cyclobutyl - 2 - (cyclobutylidene(phenyl)methyl) - 1 - phenyl - 3-
(phenylethynyl)-1H-indene (2a). White solid; Rf 0.59 (eluent: n-
hexane–CH2Cl2 = 6 : 1); m.p. 180–181 ◦C; 1H NMR (CDCl3, 400
MHz): d 0.96–0.99 (m, 1H, CH2), 1.40–1.59 (m, 3H, CH2), 1.72–
1.86 (m, 2H, CH2), 2.04–2.09 (m, 3H, CH2), 2.49–2.57 (m, 1H,
CH2), 2.71 (t, 2H, J = 7.6 Hz, CH2), 3.13-3.19 (m, 1H, CH), 6.79
(d, 2H, J = 5.8 Hz, Ar-H), 7.00–7.13 (m, 8H, Ar-H), 7.23–7.52
(m, 8H, Ar-H), 7.68 (d, 2H, J = 7.4 Hz, Ar-H); 13C NMR (CDCl3,
100 MHz): d 17.1 (CH2), 17.3 (CH2), 23.5 (CH2), 25.0 (CH2), 32.0
≡
(CH2), 32.3 (CH2), 38.2 (CH), 66.2 (Ph-C-CH), 85.2 (C C), 93.4
≡
(CH2), 32.3 (CH2), 38.3 (CH), 66.4 (Ph-C-CH), 84.4 (C C), 94.3
≡
=
(C C), 120.2 (Ar–C), 121.9 (Ar–C), 122.1 (C C), 125.0 (Ar–C),
125.8 (Ar–C), 125.9 (Ar–C), 126.2 (Ar–C), 127.3 (Ar–C), 127.7
(Ar–C), 127.7 (Ar–C), 128.2 (Ar–C), 128.7 (Ar–C), 129.4 (Ar–C),
≡
=
(C C), 120.3 (Ar–C), 122.1 (C C), 123.7 (Ar–C), 125.0 (Ar–C),
125.7 (Ar–C), 125.9 (Ar–C), 126.2 (Ar–C), 126.7 (Ar–C), 127.2
(Ar–C), 127.6 (Ar–C), 127.7 (Ar–C), 128.2 (Ar–C), 128.3 (Ar–C),
=
131.5 (Ar–C), 132.9 (Ar–C), 134.3 (Ar–C), 136.8 (C C), 140.6
=
128.4 (Ar–C), 131.8 (Ar–C), 138.5 (C C), 140.9 (Ar–C), 144.3
=
=
(Ar–C), 143.8 (Ar–C), 146.6 (C C), 149.1(Ar–C), 158.2 (C C);
IR (NaCl, neat) v: 2998, 2931, 1498, 1321, 1108, 835 cm-1; MS
(ESI) m/z 557 [M + 1]+; HRMS (ESI) calcd. for C38H31Cl2 (M+ +
H): 557.1803, found: 557.1812.
=
=
(C C), 145.9 (Ar–C), 149.1 (Ar–C), 158.4 (C C); IR (NaCl, neat)
n: 2980, 2943,1653, 1597, 1511, 1443, 1265, 754 cm-1; MS (ESI)
m/z 489 [M + H]+; HRMS (ESI) calcd. for C38H33 (M+ + H):
489.2582, found: 489.2567.
3-((1-Cyclobutyl-1-phenyl-3-(thiophen-3-ylethynyl)-1H-inden-
2-yl)(cyclobutylidene) methyl)thiophene (2e). Pale yellow solid;
1-Cyclobutyl-2-(cyclobutylidene(p-tolyl)methyl)-1-phenyl-3-
(p-tolylethynyl)-1H-indene (2b). White solid; Rf 0.50 (eluent: n-
◦
1
◦
1
Rf 0.36 (eluent: n-hexane–CH2Cl2 = 6 : 1); m.p. 127–129 C; H
NMR (CDCl3, 400 MHz): d 0.95–1.01 (m, 1H, CH2), 1.45–1.64
(m, 1H, CH2), 1.75–1.86 (m, 4H, CH2), 2.05–2.11 (m, 2H, CH2),
2.45–2.47 (m, 1H, CH2), 2.71–2.79 (m, 1H, CH2), 3.24–3.28 (m,
1H, CH), 6.70 (dd, 1H, J = 5.0, 1.1 Hz, Ar-H), 6.76 (dd, 1H, J =
2.8, 1.0 Hz, Ar-H), 6.80 (dd, 1H, J = 8.1, 2.0 Hz, Ar-H), 6.98-7.05
(m, 4H, Ar-H), 7.17 (dd, 1H, J = 5.0, 1.0 Hz, Ar-H), 7.27-7.49
(m, 5H, Ar-H), 7.64 (d, 2H, J = 7.5 Hz Ar-H); 13C NMR (CDCl3,
100 MHz): d 17.2 (CH2), 17.2 (CH2), 23.6 (CH2), 25.1 (CH2), 31.8
hexane–CH2Cl2 = 6 : 1); m.p. 87–89 C; H NMR (CDCl3, 400
MHz): d 0.90–0.96 (m, 1H, CH2), 1.38–1.57 (m, 3H, CH2), 1.67–
1.82 (m, 2H, CH2), 1.95–2.05 (m, 3H, CH2), 2.26 (s, 3H, Ar–CH3),
2.33 (s, 3H, Ar–CH3), 2.41–2.49 (m, 1H, CH2), 2.68 (s, 2H, CH2),
3.08–3.16 (m, 1H, CH2), 6.77 (d, 2H, J = 7.2 Hz, Ar-H), 6.90–
7.03 (m, 7H, Ar-H), 7.11 (d, 2H, J = 7.8 Hz, Ar-H), 7.23-7.43
(m, 5H, Ar-H), 7.64 (d, 2H, J = 7.5 H, Ar-H); 13C NMR (CDCl3,
75 MHz): d 17.1 (CH2), 17.3 (CH2), 21.2 (CH3), 21.5 (CH3), 23.5
(CH2), 25.0 (CH2), 32.0 (CH2), 32.2 (CH2), 38.3 (CH), 66.3 (Ph-C-
≡
(CH2), 32.5 (CH2), 38.4 (CH), 66.3 (Ph-C-CH), 83.8 (C C), 89.6
≡
≡
=
CH), 83.8 (C C), 94.4 (C C), 120.2 (Ar–C), 120.6 (C C), 122.1
(Ar–C), 124.9 (Ar–C), 125.6 (Ar–C), 126.0 (Ar–C), 126.5 (Ar–C),
127.2 (Ar–C), 127.6 (Ar–C), 128.1 (Ar–C), 128.3 (Ar–C), 129.1
≡
=
(C C), 120.3 (Ar–C), 121.2 (Ar–C), 121.5 (C C), 122.0 (Ar–C),
122.6 (Ar–C), 123.7 (Ar–C), 125.0 (Ar–C), 125.3 (Ar–C), 125.7
(Ar–C), 126.2 (Ar–C), 127.2 (Ar–C), 127.7 (Ar–C), 127.9 (Ar–C),
=
(Ar–C), 131.7 (Ar–C), 135.3 (Ar–C), 135.6 (Ar–C), 138.3 (C C),
=
128.3 (Ar–C), 128.6 (Ar–C), 130.1 (Ar–C), 139.4 (C C), 141.0
=
141.1 (Ar–C), 144.4 (C C), 145.2 (Ar–C), 149.1(Ar–C), 158.2
-1
=
=
(Ar–C), 144.2 (C C), 145.7 (Ar–C), 149.0 (Ar–C), 157.9 (C C);
IR (NaCl, neat) v: 2977, 2941, 1653, 1636, 777, 696 cm-1; MS
(ESI) m/z 501 [M + 1]+; HRMS (ESI) calcd. for C34H29S2 (M+ +
H): 501.1711, found: 501.1708.
=
(C C); IR (NaCl, neat) v: 2978, 2941,1651, 1506, 816, 896 cm ;
MS (ESI) m/z 517 [M + 1]+; HRMS (ESI) calcd. for C40H37 (M+
+ H): 517.2895, found: 517.2894.
1-Cyclobutyl-2-(cyclobutylidene(4-pentylphenyl)methyl)-3-((4-
pentylphenyl)ethynyl)-1-phenyl-1H-indene (2c). Yellow oil; Rf
(E)-1-Ethyl-1-phenyl-3-(phenylethynyl)-2-(1-phenylprop-1-
enyl)-1H-indene (2f). Yellow oil; Rf 0.49 (eluent: n-hexane–
1
0.57 (eluent: n-hexane–CH2Cl2 = 4 : 1); H NMR (CDCl3, 400
1
MHz): d 0.87–1.00 (m, 7H, CH3, CH2), 1.26-1.44 (m, 10H, CH2),
1.32–1.49 (m, 9H, CH2), 1.55-1.62 (m, 6H, CH2), 1.75–1.85 (m,
2H, CH2), 2.05–2.14 (m, 3H, CH2), 2.48-2.73 (m, 7H, CH2), 3.08–
3.19 (m, 1H, CH), 6.77 (d, 2H, J = 6.6 Hz, Ar-H), 6.88–6.99 (m,
7H, Ar-H), 7.12–7.44 (m, 7H, Ar-H), 7.66 (d, 1H, J = 7.4 Hz,
Ar-H); 13C NMR (CDCl3, 100 MHz): d 14.1 (CH3), 14.1 (CH3),
17.2 (CH2), 17.3 (CH2), 22.6 (CH2), 22.6 (CH2), 23.6 (CH2),
CH2Cl2 = 6 : 1); H NMR (CDCl3, 400 MHz): d 1.07 (t, 3H, J
= 7.6 Hz, CH3CH2), 1.57 (d, 1H, J = 7.8 Hz, CH3CH), 2.37-2.44
(m, 2H, CH2CH3), 5.75 (q, 1H, J = 7.0 Hz, CHCH3), 7.09–7.35
(m, 19H, Ar-H); 13C NMR (CDCl3, 100 MHz): d 13.3 (CH3), 15.2
≡
≡
(CH3), 19.6 (CH2), 58.4 (Ph-C-CH2), 84.5 (C C), 89.8 (C C),
=
=
119.7 (C C), 123.7 (C C), 126.3 (Ar–C), 126.5 (Ar–C), 126.6
(Ar–C), 126.6 (Ar–C), 127.3 (Ar–C), 127.7 (Ar–C), 127.7 (Ar–C),
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128.0 (Ar–C), 128.2 (Ar–C), 128.3 (Ar–C), 129.6 (Ar–C), 131.8
(Ar–C), 136.0 (Ar–C), 139.9 (Ar–C), 140.8 (Ar–C), 141.5 (Ar–
(E)-1-Benzyl-2-(1,2-diphenylvinyl)-1-phenyl-3-(phenylethynyl)-
1H-indene (2j). Grey oil; Rf 0.24 (eluent: n-hexane–CH2Cl2 =
1
=
=
C), 143.8 (C C), 147.9 (Ar–C), 151.3 (C C); IR (NaCl, neat) v:
2993, 2921, 1654, 1490, 757, 693 cm-1; MS (ESI) m/z 437 [M +
1]+; HRMS (ESI) calcd. for C34H29 (M+ + H): 437.2269, found:
437.2243.
6 : 1); H NMR (CDCl3, 400 MHz): d 3.89 (q, 2H, J = 15.8 Hz,
CH2), 6.64 (s, 1H, CH), 6.75-7.36 (m, 29H, Ar-H); 13C NMR
≡
(CDCl3, 100 MHz): d 32.6 (CH2), 58.9 (C-CH2Ph), 84.8 (C C),
≡
=
89.3 (C C), 121.0 (Ar–C), 123.5 (C C), 123.7 (Ar–C), 126.1 (Ar–
C), 126.7 (Ar–C), 126.8 (Ar–C), 126.9 (Ar–C), 126.9 (Ar–C), 127.2
(Ar–C), 127.5 (Ar–C), 127.8 (Ar–C), 127.9 (Ar–C), 127.9 (Ar–C),
128.1 (Ar–C), 128.2 (Ar–C), 128.4 (Ar–C), 128.5 (Ar–C), 129.6
(Ar–C), 130.0 (Ar–C), 131.9 (Ar–C), 132.4 (Ar–C), 136.5 (Ar–
(E)-1-Butyl-1-phenyl-3-(phenylethynyl)-2-(1-phenylpent-1-enyl)-
1H-indene (2g). Yellow oil; Rf 0.46 (eluent: n-hexane–CH2Cl2
= 6 : 1); 1H NMR (CDCl3, 400 MHz): d 0.70 (t, 3H, J = 7.4 Hz,
CH3), 0.86 (t, 3H, J = 7.4 Hz, CH3), 1.16–1.30 (m, 4H, CH2),
1.38–1.50 (m, 2H, CH2), 1.87–1.99 (m, 2H, CHCH2), 2.27–2.32
(m, 2H, CH2CH2CH2CH3), 5.68 (t, 1H, J = 7.4 Hz, CH2CH),
7.08-7.33 (m, 19H, Ar-H); 13C NMR (CDCl3, 100 MHz): d
13.6 (CH3), 14.0 (CH3), 23.0 (CH2), 23.2 (CH2), 26.3 (CH2),
31.1 (CH2CH), 31.1 (CH2CH2CH2CH3), 58.6 (Ph-C-CH2), 84.4
=
=
C), 137.1 (C C), 139.1 (Ar–C), 139.5 (Ar–C), 140.4 (C C), 143.9
=
(Ar–C), 150.7 (Ar–C), 151.2 (C C); IR (NaCl, neat) v: 2991, 2918,
2089, 1636, 690 cm-1; MS (ESI) m/z 561 [M + 1]+; HRMS (ESI)
calcd. for C44H33 (M+ + H): 561.2582, found: 561.2592.
(E)-5-(Benzo[d][1,3]dioxol-5-yl)-5-ethyl-7-(phenylethynyl)-6-
(1-phenylprop-1-enyl)-5H-indeno[5,6-d][1,3]dioxole (2k). White
solid; Rf 0.28 (eluent: n-hexane–CH2Cl2 = 3 : 1); m.p. 68–70 ◦C;1H
NMR (CDCl3, 400 MHz): d 1.03 (t, 3 H, J = 7.5 Hz, CH2CH3),
1.60 (d, 3H, J = 7.0 Hz, CHCH3), 2.33 (q, 2H, J = 7.4 Hz,
CH3CH2), 5.77 (q, 1H, J = 7.0 Hz, CH3CH), 5.88 (d, 2H, J =
8.1 Hz, OCH2O), 5.92 (s, 2H, Ar-H), 6.59 (s, 1H, Ar-H), 6.65 (d,
1H, J = 8.1 Hz, Ar-H), 6.74 (s, 1H, Ar-H), 6.80 (s, 1H, Ar-H),
6.93 (d, 1H, J = 8.0 Hz, Ar-H), 7.09-7.30 (m, 10H, Ar-H); 13C
NMR (CDCl3, 100 MHz): d 13.3 (CH2CH3), 15.2 (CHCH3), 19.7
≡
≡
=
=
(C C), 90.0 (C C), 119.7 (C C), 123.6 (C C), 123.7 (Ar–C),
126.3 (Ar–C), 126.4 (Ar–C), 126.7 (Ar–C), 127.3 (Ar–C), 127.7
(Ar–C), 127.8 (Ar–C), 128.0 (Ar–C), 128.2 (Ar–C), 129.6 (Ar–C),
131.8 (Ar–C), 134.5 (Ar–C), 135.0 (Ar–C), 140.3 (Ar–C), 140.5
=
=
(Ar–C), 140.9 (Ar–C), 144.3 (C C), 147.9 (Ar–C), 151.3 (C C);
IR (NaCl, neat) v: 3057, 2957, 2928, 2859, 1597, 1489, 1445, 1022,
754, 696 cm-1; MS (ESI) m/z 493 [M + 1]+; HRMS (ESI) calcd.
for C38H37 (M++H): 493.2895, found: 493.2887.
(E)-1-Hexyl-1-phenyl-3-(phenylethynyl)-2-(1-phenylhept-1-
enyl)-1H-indene (2h). Yellow oil; Rf 0.48 (eluent: n-hexane–
≡
≡
=
(CH3CH2), 57.6 (C-CH2), 84.4 (C C), 89.7 (C C), 100.8 (C C),
100.9 (OCH2O), 101.1 (OCH2O), 105.0 (Ar–C), 106.9 (Ar–C),
1
CH2Cl2 = 6 : 1); H NMR (CDCl3, 400 MHz): d 0.75(t, 3H, J
=
107.7 (Ar–C), 120.0 (Ar–C), 123.5 (C C), 126.4 (Ar–C), 127.6
= 7.2 Hz, CH3), 0.88 (t, 3H, J = 7.1 Hz, CH3), 1.02-1.51 (m, 18H,
CH2), 1.83-2.02 (m, 2H, CHCH2CH2), 2.29 (t, 2H, J = 7.6 Hz,
CH2), 5.68 (t, 1H, J = 7.5 Hz, CH2CH), 7.08-7.33 (m, 19H, Ar-
H); 13C NMR (CDCl3, 100 MHz): d 13.9 (CH3), 14.1 (CH3),
22.5 (CH2), 22.7 (CH2), 26.6 (CH2), 28.9 (CH2), 29.0 (CH2), 29.5
(CH2), 29.8 (CH2), 31.1 (CH2), 31.7 (CH2), 58.5 (Ph-C-CH2), 84.5
(Ar–C), 127.8 (Ar–C), 127.9 (Ar–C), 128.0 (Ar–C), 129.6 (Ar–C),
131.8 (Ar–C), 134.6 (Ar–C), 136.0 (Ar–C), 137.4(Ar–C), 139.9
=
(Ar–C), 141.0 (Ar–C), 145.1(C C), 146.3 (Ar–C), 146.5(Ar–C),
=
147.0 (C C), 147.3 (Ar–C), 147.4 (Ar–C); IR (NaCl, neat) v:
2982, 2937, 1672, 1513, 1235, 824 cm-1; MS (ESI) m/z 525 [M +
1]+; HRMS (ESI) calcd. for C36H29O4 (M+ + H): 525.2066, found:
525.2057.
≡
≡
=
=
(C C), 90.0 (C C), 119.7 (C C), 123.6 (Ar–C), 123.7(C C),
126.3 (Ar–C), 126.4 (Ar–C), 126.7 (Ar–C), 127.3 (Ar–C), 127.7
(Ar–C), 127.7 (Ar–C), 128.0 (Ar–C), 128.2 (Ar–C), 129.6 (Ar–C),
131.8 (Ar–C), 134.8 (Ar–C), 134.8 (Ar–C), 140.3 (Ar–C), 140.5
(E)-1-Phenethyl-1-phenyl-2-(3-phenyl-1-p-tolylprop-1-enyl)-3-
(p-tolylethynyl)-1H-indene (2l). Pale yellow oil; Rf 0.44 (eluent:
n-hexane–CH2Cl2 = 6 : 1); 1H NMR (CDCl3, 400 MHz): d 2.26 (s,
3H, Ar–CH3), 2.30 (s, 3H, Ar–CH3), 2.65-2.88 (m, 4H, CH2), 3.17-
3.35 (m, 2H, CH2CH2), 5.72 (t, 1H, J = 7.7 Hz, CHCH2), 6.84-7.43
(m, 27H, Ar-H); 13C NMR (CDCl3, 100 MHz): d 21.2 (Ar-CH3),
21.5 (Ar-CH3), 28.9 (CH2CH2), 34.9 (CHCH2), 35.1 (CH2CH2),
=
=
(Ar–C), 140.9 (Ar–C), 144.3 (C C), 147.9 (Ar–C), 151.2 (C C);
IR (NaCl, neat) v: 2955, 2926, 2855, 1597, 1489, 1028, 696 cm-1;
MS (ESI) m/z 549 [M]+; HRMS (ESI) calcd. for C42H45 (M+ + H):
549.3521, found: 549.3523.
(E)-1-iso-Butyl-2-(3-methyl-1-phenylbut-1-enyl)-1-phenyl-3-
(phenylethynyl)-1H-indene (2i). Pale yellow oil; Rf 0.46 (eluent:
n-hexane–CH2Cl2 = 6 : 1); 1H NMR (CDCl3, 400 MHz): d 0.78 (d,
3H, J = 6.5 Hz, CH3), 0.82 (d, 3H, J = 6.5 Hz, CH3), 0.87 (d, 3H,
J = 6.5 Hz, CH3), 0.92 (d, 3H, J = 6.5 Hz, CH3), 1.99-2.09 (m,
1H, CH3CHCH), 2.18 (d, 2H, J = 7.3 Hz, CH2), 2.34-2.43 (m, 1H,
CH3CH), 5.44 (d, 1H, J = 10.3 Hz, CHCH), 7.07-7.32 (m, 19H,
Ar-H); 13C NMR (CDCl3, 100 MHz): d 23.0 (CH3), 23.1 (CH3),
23.1 (CH3), 23.2 (CH3), 28.0 (CH), 28.5 (CH), 35.0 (CHCH2),
≡
≡
=
58.5 (Ph-C-CH2), 84.8 (C C), 88.7 (C C), 119.8 (C C), 120.5
=
(Ar–C), 123.9 (C C), 125.7 (Ar–C), 126.0 (Ar–C), 126.6 (Ar–C),
126.7 (Ar–C), 126.8 (Ar–C), 127.4 (Ar–C), 128.3 (Ar–C), 128.3
(Ar–C), 128.4 (Ar–C), 128.6 (Ar–C), 128.7 (Ar–C), 128.7 (Ar–C),
129.4 (Ar–C), 131.7 (Ar–C), 131.9 (Ar–C), 135.9 (Ar–C), 136.5
(Ar–C), 136.6 (Ar–C), 137.7 (Ar–C), 139.2 (Ar–C), 140.7 (Ar–C),
=
140.9 (Ar–C), 141.9 (Ar–C), 143.8 (C C), 149.1 (Ar–C), 151.4
-1
=
(C C); IR (NaCl, neat) v: 2962, 2933, 1603, 1588, 1025, 717 cm ;
MS (ESI) m/z 617 [M + H]+; HRMS (ESI) calcd. for C48H41 (M+
≡
≡
=
58.8 (Ph-C-CH2), 84.8 (C C), 90.0 (C C), 120.0 (C C), 123.7
+ H): 617.3208, found: 617.3201.
=
(Ar–C), 123.7 (C C), 126.2 (Ar–C), 126.4 (Ar–C), 126.7 (Ar–C),
126.9 (Ar–C), 127.3 (Ar–C), 127.7 (Ar–C), 127.7 (Ar–C), 128.0
(Ar–C), 128.1 (Ar–C), 129.4 (Ar–C), 131.8 (Ar–C), 132.2 (Ar–C),
139.5 (Ar–C), 140.2 (Ar–C), 140.8 (Ar–C), 142.2 (Ar–C), 144.9
(E)-1-Benzyl-6-ethoxy-1-(4-ethoxyphenyl)-2-(2-phenyl-1-p-
tolylvinyl)-3-(p-tolylethynyl)-1H-indene (2m). Pale yellow solid;
Rf 0.38 (eluent: n-hexane–CH2Cl2 = 3 : 1); m.p. 191–192 C; H
NMR (CDCl3, 400 MHz): d 1.38-1.52 (m, 6 H, CH3CH2), 2.25
(s, 3H, Ar–CH3), 3.79 (d, 1H, J = 12.9 Hz, CH2Ph), 3.98–4.05
(m, 5H, CH3CH2O, CH2Ph), 6.51 (s, 1H, Ph-CH), 6.66–7.31(m,
◦
1
=
=
(C C), 149.2(Ar–C), 150.9 (C C); IR (NaCl, neat) v: 2957, 2864,
1636, 1456, 752, 696 cm-1; MS (ESI) m/z 493 [M + 1]+; HRMS
(ESI) calcd. for C38H37 (M+ + H): 493.2895, found: 493.2884.
4022 | Org. Biomol. Chem., 2010, 8, 4016–4025
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25H, Ar-H); 13C NMR (CDCl3, 100 MHz): d 14.9 (CH3CH), 15.0
(CH3CH), 21.3 (Ar-CH3), 21.5 (Ar-CH3), 42.5 (Ph-CH2), 61.4
7.38 (m, 10H, Ar-H), 7.58 (d, 2H, J = 7.6 Hz, Ar-H); 13C NMR
(CDCl3, 100 MHz): d 17.2 (CH2), 19.2 (CH2), 21.0 (Ar-CH3),
21.4 (Ar-CH3), 27.4 (CH2), 27.9 (CH2), 31.5 (CH2), 32.3 (CH2),
≡
(CH2Ph), 63.4 (CH3CH2O), 63.7 (CH3CH2O), 83.5 (C C), 101.0
≡
=
≡
≡
(C C), 109.4 (Ar–C), 113.1 (Ar–C), 114.9 (Ar–C), 120.4 (C C),
35.3 (CH), 58.4 (C-Ph), 84.3 (C C), 89.0 (C C), 120.5 (Ar–C),
120.6 (Ar–C), 124.3 (Ar–C), 125.9 (Ar–C), 126.0 (Ar–C), 126.5
=
121.4 (Ar–C), 125.5 (Ar–C), 126.4 (C C), 126.5 (Ar–C), 126.7
=
(Ar–C), 127.6 (Ar–C), 127.8 (Ar–C), 128.6 (Ar–C), 128.9 (Ar–C),
129.6 (Ar–C), 129.7 (Ar–C), 130.8 (Ar–C), 130.9 (Ar–C), 131.8
(Ar–C), 136.3 (Ar–C), 136.4 (Ar–C), 136.6 (Ar–C), 136.9 (Ar–C),
137.0 (Ar–C), 137.6 (Ar–C), 137.7 (Ar–C), 137.9 (Ar–C), 152.2
(Ar–C), 127.3 (Ar–C), 127.4 (Ar–C), 127.6 (C C), 128.1 (Ar–C),
128.4 (Ar–C), 128.4 (Ar–C), 131.6 (Ar–C), 135.2 (Ar–C), 136.5
=
=
(Ar–C), 137.3 (Ar–C), 140.9 (C C), 141.1 (C C), 144.0 (Ar–C),
=
144.1 (C C), 144.5 (Ar–C), 150.4 (Ar–C); IR (NaCl, neat) v: 2977,
(C C), 154.1(C C), 157.6 (Ar–C), 158.8 (Ar–C); IR (NaCl, neat)
v: 2978, 1651, 1506, 1246, 1045, 816, 694 cm-1; MS (ESI) m/z 677
[M + 1]+; HRMS (ESI) calcd. for C50H45O2 (M+ + H): 677.3420,
found: 677.3411.
2916, 2237, 1664, 1089, 751, 692 cm-1; MS (ESI) m/z 517 [M +
1]+; HRMS (ESI) calcd. for C40H37 (M+ + H): 517.2895, found:
517.2902.
=
=
3-Cyclobutyl-2-(cyclobutylidene(4-pentylphenyl)methyl)-1-((4-
pentylphenyl)ethynyl)-1-phenyl-1H-indene (3c). White solid; Rf
0.52 (eluent: n-hexane–CH2Cl2 = 4 : 1); m.p. 90–91 ◦C; 1H NMR
(CDCl3, 400 MHz): d 0.85–0.92 (m, 6H, CH2CH3), 1.25–1.34 (m,
9H, CH2), 1.54–1.67 (m, 5H, CH2), 1.75–1.96 (m, 2H, CH2), 2.04–
2.37 (m, 4H, CH2), 2.47–2.70 (m, 7H, CH2), 2.85–2.87 (m, 1H,
CH2), 3.63–3.72 (m, 1H CH), 6.85 (d, 2H, J = 7.8 Hz, Ar-H),
6.92–7.36 (m, 14H, Ar-H), 7.59 (d, 2H, J = 7.6 Hz, Ar-H); 13C
NMR (CDCl3, 100 MHz): d 14.0 (CH3), 14.1 (CH3), 17.3 (CH2),
19.2 (CH2), 22.5 (CH2), 22.6 (CH2), 27.4 (CH2), 27.8 (CH2), 30.9
(CH2), 31.2 (CH2), 31.4 (CH2), 31.6 (CH2), 31.8 (CH2), 32.4
(CH2), 35.2 (CH2), 35.7 (CH2), 35.8 (CH), 58.4 (CH-Ph), 84.2
(E)-1-(But-3-enyl)-6-ethoxy-1-(4-ethoxyphenyl)-3-(p-toly-
lethynyl)-2-(1-p-tolylpenta-1,4-dienyl)-1H-indene
(2n). Pale
1
brown oil; Rf 0.30 (eluent: n-hexane–CH2Cl2 = 3 : 1); H NMR
(CDCl3, 400 MHz): d 1.33–1.40 (m, 6H, CH3CH2O), 1.84–1.91
(m, 1H, CH2), 2.19–2.613 (m, 11H, CH2, Ar–CH3), 3.91–4.00 (m,
4H, CH3CH2O), 4.72–4.92 (m, 4H, CHCH2), 5.60–5.75 (m, 3H,
CH), 6.53 (d, 1H, J = 2.2 Hz, Ar-H), 6.72–6.80 (m, 3H, Ar-H),
6.98–7.24 (m, 10H, Ar-H), 7.39 (m, 1H, J = 8.2 Hz, Ar-H); 13C
NMR (CDCl3, 100 MHz): d 14.9 (CH3CH2O), 14.9 (CH3CH2O),
21.2 (Ar-CH3), 21.5 (Ar-CH3), 27.9 (CH2), 33.3 (CH2), 35.6
(CH2), 60.8 (C-CH2), 63.4 (CH3CH2O), 63.6 (CH3CH2O), 83.6
≡
≡
=
≡
≡
(C C), 98.2 (C C), 109.0 (C C), 112.6 (Ar–C), 114.3 (Ar–C),
(C C), 89.0 (C C), 120.6 (Ar–C), 120.8 (Ar–C), 124.3 (Ar–C),
125.9 (Ar–C), 126.5 (Ar–C), 127.2 (Ar–C), 127.4 (Ar–C), 127.5
=
114.4 (Ar–C), 114.7 (C C), 120.5 (Ar–C), 121.0 (Ar–C), 122.6
=
(Ar–C), 127.1 (Ar–C), 128.5 (Ar–C), 128.8 (Ar–C), 129.9 (Ar–C),
(Ar–C), 127.6 (Ar–C), 127.8 (Ar–C), 127.9 (C C), 131.5 (Ar–C),
=
=
=
=
=
131.0 (C C), 131.8 (C C), 136.0 (Ar–C), 136.1 (C C), 136.5
136.6 (C C), 140.3 (Ar–C), 140.9 (Ar–C), 141.1 (C C), 142.4
=
=
(C C), 136.7 (Ar–C), 137.4 (Ar–C), 138.0 (Ar–C), 138.8 (Ar–C),
(Ar–C), 144.0 (Ar–C), 144.1 (C C), 144.5 (Ar–C), 150.5 (Ar–C);
=
=
153.6 (C C), 153.8 (C C), 157.4 (Ar–C), 158.6 (Ar–C); IR
(NaCl, neat) v: 2978, 1607, 1508, 1248, 756 cm-1; MS (ESI)
m/z 605 [M + 1]+; HRMS (ESI) calcd. for C44H45O2 (M+ + H):
605.3420, found: 605.3413.
IR (NaCl, neat) v: 2979, 2918, 2089, 1634, 744, 696 cm-1; MS
(ESI) m/z 629 [M + 1]+; HRMS (ESI) calcd. for C48H53 (M+ + H):
629.4147, found: 629.4145.
(E)-3-Ethyl-1-phenyl-1-(phenylethynyl)-2-(1-phenylprop-1-
enyl)-1H-indene (3f). Yellow oil; Rf 0.45 (eluent: n-hexane–
3 - Cyclobutyl - 2 - (cyclobutylidene(phenyl)methyl) - 1 - phenyl - 1-
(phenylethynyl)-1H-indene (3a). White solid; Rf 0.41 (eluent: n-
hexane–CH2Cl2 = 6 : 1); m.p. 161–163 ◦C; 1H NMR (CDCl3, 400
MHz): d 1.59–1.85 (m, 3H, CH2), 1.90–1.97 (m, 1H, CH2), 2.03–
2.15 (m, 1H, CH2), 2.23–2.38 (m, 3H, CH2), 2.54–2.72 (m, 3H,
CH2), 2.84–2.89 (m, 1H, CH2), 3.64–3.73 (m, 1H, CH), 6.93 (d,
2H, J = 7.2 Hz, Ar-H), 7.04–7.25 (m, 14H, Ar-H), 7.36–7.39 (m,
2H, Ar-H), 7.60 (d, 2H, J = 7.5 Hz, Ar-H); 13C NMR (CDCl3,
100 MHz): d 17.3 (CH2), 19.2 (CH2), 27.4 (CH2), 27.8 (CH2),
1
CH2Cl2 = 6 : 1); H NMR (CDCl3, 400 MHz): d 0.55 (t, 3H, J
= 7.2 Hz, CH2CH3), 1.49 (d, 1H, J = 7.1 Hz, CHCH3), 2.37–2.45
(m, 1H, CH2CH3), 2.54–2.62 (m, 1H, CH2CH3), 5.82 (q, 1H, J =
7.1 Hz, CH3CH), 6.95 (m, 1H, J = 7.4 Hz, Ar-H), 7.11–7.33 (m,
17H, Ar-H), 7.52 (m, 1H, J = 7.4 Hz, Ar-H); 13C NMR (CDCl3,
100 MHz): d 8.1 (CH3CH2), 15.6 (CH3CH), 28.6 (CH2), 62.2 (C-
≡
≡
=
CH2), 84.2 (C C), 98.3 (C C), 120.2 (C C), 122.1 (Ar–C), 122.8
(Ar–C), 123.5 (Ar–C), 126.0 (Ar–C), 126.2 (Ar–C), 126.5 (Ar–C),
126.8 (Ar–C), 127.0 (Ar–C), 127.8 (Ar–C), 127.9 (Ar–C), 128.0
≡
31.6 (CH2), 32.5 (CH2), 35.2 (C-CH), 58.4 (C-Ph), 84.2 (C C),
≡
=
89.8 (C C), 120.7 (Ar–C), 123.5 (Ar–C), 124.3 (Ar–C), 125.7
(Ar–C), 128.5 (Ar–C), 130.1 (Ar–C), 130.3 (Ar–C), 132.0 (C C),
=
(Ar–C), 126.0 (Ar–C), 126.6 (Ar–C), 127.3 (Ar–C), 127.4 (Ar–C),
137.5 (Ar–C), 139.2 (Ar–C), 143.3 (C C), 144.3 (Ar–C), 151.7
=
=
127.5 (Ar–C), 127.6 (C C), 127.7 (Ar–C), 128.0 (Ar–C), 131.7
(C C), 155.3 (Ar–C); IR (NaCl, neat) v: 3055, 2968, 1597, 1489,
=
=
=
(Ar–C), 139.2 (C C), 140.8 (Ar–C), 141.2 (C C), 144.1 (C C),
144.2 (Ar–C), 145.0 (Ar–C), 150.4 (Ar–C); IR (NaCl, neat) n:
2983, 2933,1651, 1489, 754, 694 cm-1; MS (ESI) m/z 489 [M +
1]+; HRMS (ESI) calcd. for C38H33 ([M + H]+): 489.2582, found:
489.2579.
1443, 1265, 756, 698 cm-1; MS (ESI) m/z 437 [M + 1]+; HRMS
(ESI) calcd. for C34H29 (M+ + H): 437.2269, found: 437.2261.
(E)-3-Butyl-1-phenyl-1-(phenylethynyl)-2-(1-phenylpent-1-enyl)-
1H-indene (3g). Yellow oil; Rf 0.42 (eluent: n-hexane–CH2Cl2
= 6 : 1); 1H NMR (CDCl3, 400 MHz): d 0.57–0.88 (m, 7H,
CH3, CH2), 1.15–1.53 (m, 5H, CH2), 1.82–1.86 (m, 2H, CH2),
2.28–2.37 (m, 1H, CH2), 2.43–2.50 (m, 1H, CH2), 5.73 (t, 1H, J =
7.6 Hz, CHCH2), 6.96 (d, 1H, J = 7.4 Hz, Ar-H), 7.10–7.31 (m,
17H, Ar-H), 7.52 (d, 1H, J = 7.5 Hz, Ar-H); 13C NMR (CDCl3,
100 MHz): d 13.5 (CH3), 14.0 (CH3), 22.8 (CH2), 23.1 (CH2),
25.4 (CH2), 31.3 (CHCH2), 35.7 (CCH2), 61.7 (CCH2), 84.2
3- Cyclobutyl- 2- (cyclobutylidene(p-tolyl)methyl)-1-phenyl-1-
(p-tolylethynyl)-1H-indene (3b). Pale yellow oil; Rf 0.46 (eluent:
n-hexane–CH2Cl2 = 6 : 1); 1H NMR (CDCl3, 400 MHz): d 1.61–
1.96 (m, 5H, CH2), 2.02–2.39 (m, 9H, CH2, Ar–CH3), 2.51–2.66
(m, 3H, CH2), 2.83–2.89 (m, 1H, CH2), 3.63–3.72 (m, 1H, CH),
6.78 (d, 2H, J = 7.9 Hz, Ar-H), 6.93–7.00 (m, 4H, Ar-H), 7.10–
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≡
≡
=
(C C), 98.1 (C C), 120.2 (C C), 122.0 (Ar–C), 122.4 (Ar–C),
123.5 (Ar–C), 126.1 (Ar–C), 126.2 (Ar–C), 126.4 (Ar–C), 126.7
(Ar–C), 127.0 (Ar–C), 127.7 (Ar–C), 127.9 (Ar–C), 128.0 (Ar–C),
Notes and references
1 For a review, see: (a) H. Gao, J. A. Katzenellenbogen, R. Garg and C.
Hansch, Chem. Rev., 1999, 99, 723; (b) For selected examples, see: N. J.
Clegg, S. Paruthiyil, D. C. Leitman and T. S. Scanlan, J. Med. Chem.,
2005, 48, 5989; (c) A. Korte, J. Legros and C. Bolm, Synlett, 2004, 2397;
(d) I.-M. Karaguni, K.-H. Glu¨senkamp, A. Langerak, C. Geisen, V.
Ullrich, G. Winde, T. Mo¨ro¨y and O. Mu¨ller, Bioorg. Med. Chem. Lett.,
2002, 12, 709; (e) J. Yang, M. V. Lakshmikantham, M. P. Cava, D.
Lorcy and J. R. Bethelot, J. Org. Chem., 2000, 65, 6739; (f) O. J. Barber,
O. A. Rakitin, M. B. Ros and T. Torroba, Angew. Chem., Int. Ed.,
1998, 37, 296; (g) S. Hagishita, M. Yamada, K. Shirahase, T. Okada, Y.
Murakami, Y. Ito, T. Matsuura, M. Wada and T. Kato, J. Med. Chem.,
1996, 39, 3636; (h) J. Palm, K. P. Boegesoe and T. Liljefors, J. Med.
Chem., 1993, 36, 2878; (i) D. T. Witiak, S. V. Kakodkar, G. E. Brunst,
J. R. Baldwin and R. G. Rahwan, J. Med. Chem., 1978, 21, 1313.
2 For recent selected examples, see: (a) Z. A. Khan and T. Wirth, Org.
Lett., 2009, 11, 229; (b) X. B. Zhou, H. M. Zhang, X. Xie and Y. Z. Li,
J. Org. Chem., 2008, 73, 3958; (c) Z. B. Zhu and M. Shi, Chem.–Eur. J.,
2008, 14, 10219; (d) F. R. Gou, H. P. Bi, L. N. Guo, Z. H. Guan, X. Y.
Liu and Y. M. Liang, J. Org. Chem., 2008, 73, 3837; (e) W. L. Chen,
J. Cao and X. Huang, Org. Lett., 2008, 10, 5537; (f) Y. T. Wu, M. Y.
Kuo, Y. T. Chang, C. C. Shin, T. C. Wu, C. C. Tai, T. H. Cheng and
W. S. L i u , Angew. Chem., Int. Ed., 2008, 47, 9891; (g) M. Miyamoto, Y.
Harada, M. Tobisu and N. Chatani, Org. Lett., 2008, 10, 2975; (h) R.
Sanz, D. Miguel and F. Rodriguez, Angew. Chem., Int. Ed., 2008, 47,
7354; (i) C. C. Liu, R. P. Korivi and C. H. Cheng, Chem.–Eur. J., 2008,
14, 9503; (j) H. P. Bi, X. Y. Liu, F. R. Gou, L. N. Guo, X. H. Duan and
Y. M. Liang, Org. Lett., 2007, 9, 3527; (k) D. Zhang, Z. Liu, E. K. Yum
and R. C. Larock, J. Org. Chem., 2007, 72, 251; (l) H. Tsukamoto, T.
Ueno and Y. Kondo, Org. Lett., 2007, 9, 3033; (m) L. N. Guo, X. H.
Duan, H. P. Bi, X. Y. Liu and Y. M. Liang, J. Org. Chem., 2007, 72,
1538; (n) N. Marion, S. Diez-Gonzalez, P. de Fremont, A. R. Noble
and S. P. Nolan, Angew. Chem., Int. Ed., 2006, 45, 3647; (o) G. B.
Bajracharya, N. K. Pahadi, I. D. Gridnev and Y. Yamamoto, J. Org.
Chem., 2006, 71, 6204; (p) X. H. Duan, L. N. Guo, H. P. Bi, X. Y. Liu
and Y. M. Liang, Org. Lett., 2006, 8, 5777; (q) Y. Kuninobu, A. Kawata
and K. Takai, J. Am. Chem. Soc., 2005, 127, 13498; (r) I. Nakamura,
G. B. Bajracharya, Y. Mizushima and Y. Yamamoto, Angew. Chem.,
Int. Ed., 2002, 41, 4328.
=
128.4 (Ar–C), 130.2 (Ar–C), 132.0 (C C), 136.3 (Ar–C), 136.4
=
=
(Ar–C), 139.3(Ar–C), 143.2 (Ar–C), 144.2 (C C), 152.1 (C C),
156.1(Ar–C); IR (NaCl, neat) v: 2957, 2859, 1645, 1488, 1456,
754, 698 cm-1; MS (ESI) m/z 493 [M + 1]+; HRMS (ESI) calcd.
for C38H37 (M+ + H): 493.2895, found: 493.2894.
(E)-3-Hexyl-1-phenyl-1-(phenylethynyl)-2-(1-phenylhept-1-
enyl)-1H-indene (3h). Yellow oil; Rf 0.42 (eluent: n-hexane–
1
CH2Cl2 = 6 : 1); H NMR (CDCl3, 400 MHz): d 0.76 (t, 3H,
J = 7.3 Hz, CH3), 0.83 (t, 3H, J = 7.1 Hz, CH3), 0.98–1.26
(m, 14H, CH2), 1.84 (q, 2H, J = 7.2 Hz, CH2), 2.29–2.37 (m,
1H, CH2), 2.44–2.50 (m, 1H, CH2), 5.72 (t, 1H, J = 7.6 Hz,
CHCH2), 6.96 (d, 1H, J = 7.4 Hz, Ar-H), 7.10–7.31 (m, 17H, Ar-
H), 7.52 (d, 1H, J = 7.5 Hz, Ar-H); 13C NMR (CDCl3, 100 MHz):
d 13.9 (CH3), 14.1 (CH3), 22.5 (CH2), 22.6 (CH2), 23.1 (CH2),
29.2 (CH2), 29.3 (CH2), 29.8 (CH2), 31.0 (CH2), 31.6 (CH2), 36.0
≡
≡
=
(CCH2), 61.7 (CCH2), 84.2 (C C), 98.1 (C C), 120.2 (C C),
122.0 (Ar–C), 122.4 (Ar–C), 123.5 (Ar–C), 126.0 (Ar–C), 126.2
(Ar–C), 126.4 (Ar–C), 126.7 (Ar–C), 127.0 (Ar–C), 127.7 (Ar–C),
127.9 (Ar–C), 128.0 (Ar–C), 128.4 (Ar–C), 130.2 (Ar–C), 132.0
=
=
(C C), 136.2 (Ar–C), 136.5 (Ar–C), 139.3 (Ar–C), 143.2 (C C),
=
144.3 (C C), 152.1 (Ar–C), 156.2 (Ar–C); IR (NaCl, neat) v: 2953,
2926, 2855, 1597, 1493, 1443, 754, 698 cm-1; MS (ESI) m/z 549 [M
+ 1]+; HRMS (ESI) calcd. For C42H45 (M+ + H): 549.3521, found:
549.3506.
(E)-5-(Benzo[d][1,3]dioxol-5-yl)-7-ethyl-5-(phenylethynyl)-6-(1-
phenylprop-1-enyl)-5H-indeno[5,6-d][1,3]dioxole
(3k). Yellow
3 For reviews on iron catalysis, see: (a) B. D. Sherry and A. Fu¨rstner, Acc.
Chem. Res., 2008, 41, 1500; (b) A. Fu¨rstner, Angew. Chem., Int. Ed.,
2009, 48, 1364; (c) S. Enthaler, K. Junge and M. Beller, Angew. Chem.,
Int. Ed., 2008, 47, 3317; (d) E. B. Bauer, Curr. Org. Chem., 2008, 12,
1341; (e) A. Correa, O. Garcia Mancheno and C. Bolm, Chem. Soc.
Rev., 2008, 37, 1108; (f) C. Bolm, J. Legros, J. Le Paih and L. Zani,
Chem. Rev., 2004, 104, 6217.
4 For reviews on the use of alcohols as pro-electrophiles, see: (a) M
Bandini and M. Tragni, Org. Biomol. Chem., 2009, 7, 1501; (b) N
Ljungdahl and N. Kann, Angew. Chem., Int. Ed., 2009, 48, 642; (c) J.
Muzart, Tetrahedron, 2008, 64, 5815; (d) J. Muzart, Eur. J. Org. Chem.,
2007, 3077; (e) J. Muzart, Tetrahedron, 2005, 61, 4179; (f) Y. Tamaru,
Eur. J. Org. Chem., 2005, 2647.
solid; Rf 0.24 (eluent: n-hexane–CH2Cl2 = 3 : 1); m.p. 82–83 ◦C;1H
NMR (CDCl3, 400 MHz): d 0.55 (t, 3 H, J = 7.1 Hz, CH3CH2),
1.50 (d, 3H, J = 7.1 Hz, CH3CH), 2.27–2.43 (m, 2H, CH3CH2),
5.80 (q, 1H, J = 7.0 Hz, CH3CH), 5.87–5.93 (m, 4H, OCH2O),
6.45 (s, 1H, Ar-H), 6.52 (s, 1H, Ar-H), 6.67 (d, 1H, J = 8.2 Hz,
Ar-H), 6.73 (d, 1H, J = 7.8 Hz, Ar-H), 6.98 (s, 1H, Ar-H),
7.16–7.33 (m, 10H, Ar-H); 13C NMR (CDCl3, 100 MHz): d
≡
8.0 (CH3CH2), 15.6 (CH3CH), 29.0 (CH3CH2), 61.4 (C-C C),
84.0 (C C), 98.1 (C C), 100.8 (Ar–C), 101.0 (OCH2O), 101.1
(OCH2O), 103.2 (Ar–C), 106.9 (Ar–C), 108.0 (Ar–C), 118.5
≡
≡
5 (a) X. Zhang, W. Rao, Sally and Philip W. H. Chan, Org. Biomol. Chem.,
2009, 7, 4186; (b) J. Wang, W. Huang, Z. Zhang, X. Xiang, R. Liu and
X. Zhou, J. Org. Chem., 2009, 74, 3299; (c) J. Fan, C. Wan, G. Sun and
Z. Wang, J. Org. Chem., 2008, 73, 8608; (d) W. Huang, P. Zheng, Z.
Zhang, R. Liu, Z. Chen and X. Zhou, J. Org. Chem., 2008, 73, 6845;
(e) W. Huang, Q. Shen, J. Wang and X. Zhou, J. Org. Chem., 2008, 73,
1586; (f) U. Jana, S. Maiti and S. Biswas, Tetrahedron Lett., 2007, 48,
7160; (g) D. Zhang and J. M. Ready, J. Am. Chem. Soc., 2006, 128,
15050; (h) Z.-P. Zhan, J.-L. Yu, H.-J. Liu, Y.-Y. Cui, R.-F. Yang, W.-Z.
Yang and J.-P. Li, J. Org. Chem., 2006, 71, 8298; (i) P. O. Miranda,
M. A. Ramirez, J. I. Padron and V. S. Martin, Tetrahedron Lett., 2006,
47, 283; (j) M. M. Heravi, F. K. Behbahani, R. H. Shoar and H. A.
Oskooie, Catal. Commun., 2006, 7, 136; (k) P. R. Krishna, B. Lavanya,
A. K. Mahalingam, V. V. R. Reddy and G. V. M. Sharma, Lett. Org.
Chem., 2005, 2, 360; (l) I. Iovel, K. Mertins, J. Kischel, A. Zapf and M.
Beller, Angew. Chem., Int. Ed., 2005, 44, 3913.
=
(Ar–C), 122.2 (Ar–C), 123.3 (C C), 127.0 (Ar–C), 127.8 (Ar–C),
127.9 (Ar–C), 129.0 (Ar–C), 130.3 (Ar–C), 132.0 (Ar–C), 136.9
=
=
(C C), 137.4 (Ar–C), 138.1 (Ar–C), 139.2 (Ar–C), 145.9 (C C),
=
145.9 (Ar–C), 146.8 (C C), 147.0 (Ar–C), 147.8 (Ar–C), 154.4
(Ar–C); IR (NaCl, neat) v: 2975, 2915, 1654, 1527, 1033, 796 cm-1;
MS (ESI) m/z 525 [M + 1]+; HRMS (ESI) calcd. for C36H29O4
(M+ + H): 525.2066, found: 525.2062.
Acknowledgements
This work is supported by a University Research Committee Grant
(RG55/06) from Nanyang Technological University, and Science
and Engineering Research Council Grant (092 1010 053) from
A*STAR, Singapore. Prof. Koichi Narasaka of this division is also
gratefully acknowledged for his helpful insights on the possible
mechanism of the reaction.
6 (a) P. Kothandaraman, W. Rao, S. J. Foo and P. W. H. Chan, Angew.
Chem., Int. Ed., 2010, 49, 4619; (b) X. Zhang, W. T. Teo and P. W. H.
Chan, Org. Lett., 2009, 11, 4990; (c) P. Kothandaraman, S. J. Foo and
P. W. H. Chan, J. Org. Chem., 2009, 74, 5947; (d) S. R. Mothe and
P. W. H. Chan, J. Org. Chem., 2009, 74, 5887; (e) W. Rao, X. Zhang,
E. M. L. Sze and P. W. H. Chan, J. Org. Chem., 2009, 74, 1740; (f) P.
4024 | Org. Biomol. Chem., 2010, 8, 4016–4025
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Kothandaraman, W. Rao, X. Zhang and P. W. H. Chan, Tetrahedron,
2009, 65, 1833; (g) W. Rao and P. W. H. Chan, Chem.–Eur. J., 2008, 14,
10486; (h) W. Wu, W. Rao, Y. Q. Er, K. J. Loh, C. Y. Poh and P. W. H.
Chan, Tetrahedron Lett., 2008, 49, 2620; W. Wu, W. Rao, Y. Q. Er, K. J.
Loh, C. Y. Poh and P. W. H. Chan, Tetrahedron Lett., 2008, 49, 4981;
(i) W. Rao and P. W. H. Chan, Org. Biomol. Chem., 2008, 6, 2426; (j) X.
Zhang, W. Rao, and P. W. H. Chan, Synlett 2008, Special Issue, 2204.;
(k) W. Rao, A. H. L. Tay, P. J. Goh, J. M. L. Choy, J. K. Ke and P. W. H.
Chan, Tetrahedron Lett., 2008, 49, 122; W. Rao, A. H. L. Tay, P. J. Goh,
J. M. L. Choy, J. K. Ke and P. W. H. Chan, Tetrahedron Lett., 2008, 49,
5115.
and K. J. Haller, J. Org. Chem., 1993, 58, 6493; (d) X. Coqueret, F.
Bourelle-Wargnier and J. Chuche, J. Org. Chem., 1985, 50, 909; (e) M.
Takahashi, N. Ishii, H. Suzuki, Y. Moro-Oka and T. Ikawa, Chem.
Lett., 1981, 1361; (f) H. Suzuki, H. Yashima, T. Hirose, M. Takahashi,
Y. Moro-Oka and T. Ikawa, Tetrahedron Lett., 1980, 21, 4927; (g) K.
Takagi and Y. Ogata, J. Chem. Soc., Perkin Trans. 2, 1977, 1410.
12 For examples of Lewis acid-catalysed formation of propargylic cations
and similar regioselectivities observed in these reactions, see ref. 4–7
and: (a) M. Yoshimatsu, T. Yamamoto, A. Sawa, T. Kato, G. Tanabe
and O. Muraoka, Org. Lett., 2009, 11, 2952; (b) M. Yoshimatsu, T.
Otani and A. Sawa, Org. Lett., 2008, 10, 4251; (c) T. Ishikawa, T.
Aikawa, Y. Mori and S. Saito, Org. Lett., 2003, 5, 51; (d) T. Ishikawa,
M. Okano, T. Aikawa and S. Saito, J. Org. Chem., 2001, 66, 4635.
13 The addition of an acetylenic moiety to a carbocation centre has also
been proposed in other reactions, for selected examples see ref. 7a and
(a) K. Kohno, K. Nakagawa, T. Yahagi, J.-C. Choi, H. Yasuda and T.
Sakakura, J. Am. Chem. Soc., 2009, 131, 2784; (b) M.-L. Yao, T. R.
Quick, Z. Wu, M. P. Quinn and G. W. Kabalka, Org. Lett., 2009, 11,
2647; (c) Z. Liu, J. Wang, Y. Zhao and B. Zhou, Adv. Synth. Catal.,
2009, 351, 371; (d) T. Xu, Z. Yu and L. Wang, Org. Lett., 2009, 11,
2113; (e) S. Biswas, S. Maiti and U. Jana, Eur. J. Org. Chem., 2009,
2354; (f) U. Jana, S. Biswas and S. Maiti, Eur. J. Org. Chem., 2008,
5798; (g) R. Marcuzzi, G. Modena and G. Melloni, J. Org. Chem.,
1982, 47, 4577; (h) R. Maroni, G. Melloni and G. Modena, J. Chem.
Soc., Perkin Trans. 1, 1973, 2491.
14 For a review, see: (a) P. J. Stang, J. Org. Chem., 2009, 74, 2; (b) For
selected examples, see: M. Slegt, R. Gronheid, D. Van der Vlugt, M.
Ochiai, T. Okuyama, H. Zuilhof, H. S. Overkleeft and G. Lodder, J. Org.
Chem., 2006, 71, 2227; (c) K. van Alem, G. Belder, G. Lodder and H.
Zuilhof, J. Org. Chem., 2005, 70, 179; (d) M. Fujita, Y. Sakanishi, M.
Nishii, H. Yamataka and T. Okuyama, J. Org. Chem., 2002, 67, 8130;
(e) R. Pellicciari, B. Natalini, B. M. Sadeghpour, M. Marinozzi, J. P.
Snyder, B. L. Williamson, J. T. Kuethe and A. Padwa, J. Am. Chem.
Soc., 1996, 118, 1; (f) E. S. Krijnen and G. Lodder, Tetrahedron Lett.,
1993, 34, 729; (g) S. Kobayashi, T. Nishi, I. Koyama and H. Taniguchi,
J. Chem. Soc., Chem. Commun., 1980, 103; (h) M. F. Ruasse and J.-E.
Dubois, J. Org. Chem., 1977, 42, 2689.
7 (a) V. Maraval, C. Duhayon, Y. Coppel and R. Chauvin, Eur. J. Org.
Chem., 2008, 5144; (b) A.-H. Feng, J.-Y. Chen, L.-M. Yang, G.-H. Lee,
Y. Wang and T.-Y. Luh, J. Org. Chem., 2001, 66, 7922.
8 For a review, see: (a) N. Marion and S. P. Nolan, Angew. Chem., Int. Ed.,
2007, 46, 2750; For selected examples, see ref. 2n and: (b) P. Mauleon,
J. L. Krinsky and F. D. Toste, J. Am. Chem. Soc., 2009, 131, 4513; (c) M.
Uemura, L. D. Watson, M. Katsukawa and F. D. Toste, J. Am. Chem.
Soc., 2009, 131, 3464; (d) L. D. Watson, S. Ritter and F. D. Toste, J. Am.
Chem. Soc., 2009, 131, 2056; (e) N. D. Shapiro and F. D. Toste, J. Am.
Chem. Soc., 2008, 130, 9244; (f) G. Li, G. Zhang and L. Zhang, J. Am.
Chem. Soc., 2008, 130, 3740; (g) A. Correa, N. Marion, L. Fensterbank,
M. Malacria, S. P. Nolan and L. Cavallo, Angew. Chem., Int. Ed., 2008,
47, 718; (h) C. H. M. Amijs, V. Lo´pez-Carrillo and A. M. Echavarren,
Org. Lett., 2007, 9, 4021; (i) J. Marco-Contelles and E. Soriano, Chem.–
Eur. J., 2007, 13, 1350; (j) X. Shi, D. J. Gorin and F. D. Toste, J. Am.
Chem. Soc., 2005, 127, 5802; (k) V. Mamane, T. Gress, H. Krause and
A. Fu¨rstner, J. Am. Chem. Soc., 2004, 126, 8654.
9 (a) X. Zhao, Z. Zhong, L. Peng, W. Zhang and J. Wang, Chem.
Commun., 2009, 2535; (b) L. Peng, X. Zhang, S. Zhang and J. Wang,
J. Org. Chem., 2007, 72, 1192.
10 Please see the Electronic Supplementary Information for details†.
11 Apparent 1,3-alkyl migrations have also been proposed in other
reactions, for selected examples see: (a) H.-H. Chou, H.-M. Wu, J.-
D. Wu, T. W. Ly, N.-W. Jan, K.-S. Shia and H.-J. Liu, Org. Lett., 2008,
10, 121; (b) N. Dieltiens and C. V. Stevens, Org. Lett., 2007, 9, 465;
(c) B. D. Smith, D. E. Alonso, J. T. Bien, J. D. Zielinski, S. L. Smith
This journal is
The Royal Society of Chemistry 2010
Org. Biomol. Chem., 2010, 8, 4016–4025 | 4025
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