Regioselective One-Pot Synthesis of Triptycenes via Triple-Cycloadditions of Arynes to Ynolates

Article abstract of DOI:10.1002/anie.201609111

We developed the novel one-pot synthetic method of substituted triptycenes by the reaction of ynolates and arynes. This four-step process involves three cycloadditions and electrocyclic ring opening of the strained Dewar anthracene. Each of the three related but structurally distinct classes of nucleophiles (ynolate, enolate, and anthracenolate) reacts with o-benzyne in the same predictable manner controlled by chelation and negative hyperconjugation. The resulting functionalized C₃-symmetrical triptycenes hold promise in the design of functional materials.

Full text of DOI:10.1002/anie.201609111

Angewandte
Communications
Chemie
International Edition: DOI: 10.1002/anie.201609111
German Edition: DOI: 10.1002/ange.201609111
Synthetic Methods
Regioselective One-Pot Synthesis of Triptycenes via Triple-
Cycloadditions of Arynes to Ynolates
Satoshi Umezu, Gabriel dos Passos Gomes, Tatsuro Yoshinaga, Mikei Sakae, Kenji Matsumoto,
Takayuki Iwata, Igor Alabugin, and Mitsuru Shindo*
Abstract: We developed the novel one-pot synthetic method of
substituted triptycenes by the reaction of ynolates and arynes.
This four-step process involves three cycloadditions and
electrocyclic ring opening of the strained Dewar anthracene.
Each of the three related but structurally distinct classes of
nucleophiles (ynolate, enolate, and anthracenolate) reacts with
o-benzyne in the same predictable manner controlled by
chelation and negative hyperconjugation. The resulting func-
tionalized C3-symmetrical triptycenes hold promise in the
design of functional materials.
Y
nolates 1 are compact energy-rich nucleophiles with great
potential in synthetic organic chemistry.[1] As dianion equiv-
alents, ynolates are useful as nucleophilic initiators of one-pot
sequences leading to rapid preparation of useful products.[2]
Scheme 1. Cycloadditions of ynolates to polar and non-polar multiple
bonds.
=
Formal cycloaddition reactions of ynolates with polar C X
(X = O, N) double bonds have been reported by us and others
to yield unsaturated four-membered heterocycles 2 such as b-
lactone or b-lactam enolates leading to various reactions and
products (Scheme 1, Equation (1)).[2b,3] In comparison with
cycloadditions to the polar bonds, examples of synthetic
will show that their electronic properties lead to new rich
reactivity features.
We adopted 2-bromophenol triflate 7 as a precursor of
benzyne.[8] Treatment of the precursor 7, added to an in situ
prepared ynolate solution in THF (Scheme 2),[9] with n-BuLi
at ꢀ788C, led to the generation of the anticipated o-benzyne.
As expected, the latter was trapped by the ynolate. Surpris-
ingly, however, the reaction involved three moles of o-
benzyne, leading to 9-hydroxy-10-methyltriptycene (5a) as
the major product in 30% yield.
ꢀ
reactions with nonpolar multiple C C bonds remain, to the
best of our knowledge, relatively scarce.[4] Based on the high
[5]
ꢀ
electrophilicity of the non-polar C C triple bond of arynes,
these strained alkynes can be expected to readily participate
in cycloadditions with nucleophilic ynolates. Herein, we
report a one-pot sequence of three efficient and regioselective
cycloadditions, initiated by the reaction between ynolates and
arynes (Scheme 1, Equation (3)). This sequence provides
substituted triptycenes 5 in a highly regioselective head-to-
head-to-head manner.
In analogy with the known reactions of enolates and
arynes (Scheme 1, Equation (2)),[6] one could expect that
reaction of ynolates 1 and arynes 3 will lead to the formation
of benzocyclobutenone enolates 4. Although these synthetic
intermediates[7] would be destabilized by antiaromaticity, we
Scheme 2. Reaction of ynolate with benzyne to provide 9-hydroxy-10-
methyltriptycene 5a.
[*] S. Umezu, T. Yoshinaga, M. Sakae
Interdisciplinary Graduate School of Engineering Sciences
Kyushu University
The suggested mechanism for the formation of this
unexpected product is shown in Scheme 3. Ynolate 1a adds
to benzyne to give a benzocyclobutenone enolate 4a, which is
sufficiently nucleophilic to add to another benzyne to form
the Dewar anthracene 8a.[10] Relief of antiaromaticity is likely
to contribute to the efficiency of this process. The fused [2.2.0]
core of the product is highly strained and can undergo
spontaneous ring-opening with the formation of electron-rich
anthracene alkoxide 9a.[11] This penultimate intermediate
engages the third benzyne molecule in the final [4+2]
cycloaddition step that furnishes the isolated triptycene
6-1 Kasuga-koen, Kasuga, 816-8580 (Japan)
Dr. K. Matsumoto, Dr. T. Iwata, Prof. Dr. M. Shindo
Institute for Materials Chemistry and Engineering, Kyushu University
6-1 Kasuga-koen, Kasuga, 816-8580 (Japan)
E-mail: shindo@cm.kyushu-u.ac.jp
G. dos Passos Gomes, Prof. Dr. I. Alabugin
Department of Chemistry and Biochemistry, Florida State University
Tallahassee, FL 32310 (USA)
Supporting information for this article can be found under:
http://dx.doi.org/10.1002/anie.201609111.
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Table 1: Synthesis of triptycenes from several ynolates.[a]
Entry Ynolate
R
13/14 Conditions Product Yield [%]
1
2
3
4
5
6
7
8
9
10
1a
1b
1c
1d
1e
1a
1b
1c
1 f
1e
Me
13
13
13
13
13
14
14
14
A
A
A
A
A
B
A
B
B
A
5a
5b
5c
5d
42
35
52
39
27
69
39
48
37
37
i-Pr
n-Bu
t-Bu
Ph
Me
i-Pr
n-Bu
5e
15a
15b
15c
15 f
15e
hexyl 14
Ph 14
Scheme 3. Triple cycloaddition of benzyne to ynolate leads to tripty-
cene.
[a] Reaction conditions: 6 (0.5 mmol), t-BuLi (2.0 mmol), THF, ꢀ788C to
08C; then condition A: 13 or 14 (3.0 mmol), n-BuLi (2.5 mmol, addition
for 1 h), RT, condition B: 14 (2.0 mmol), n-BuLi (2.0 mmol, addition for
5 min), ꢀ208C.
product 5a. It is noteworthy that the overall cascade
disassembles the triple bond into two one-carbon units that
“glue” the three aromatic rings together. This is a conceptually
unique application of alkynes in synthesis.
We then investigated reactivity of substituted benzynes. 3-
Methoxybenzyne, derived from 3-fluoroanisole 14 and butyl-
lithium, reacts with ynolate 1 at ꢀ208C to afford triptycene 15
in good yield. It is noteworthy that the major product had all
oxygen functionalities, i.e., the three methoxy groups and one
hydroxy group, at the same side of the triptycene.[15] This high
regioselectivity of reaction is consistent with previous reports
of selective nucleophilic attack at the C1 position of similar
alkynes, rationalized via charge distribution, or distortion
models.[5c,16] We will discuss the question of regioselectivity in
the computational part of this paper.
Triptycenes, which have three benzene rings fixed by
a rigid barrelene skeleton, are useful structural units for the
preparation of functional materials and supramolecular
systems.[12] Generally, triptycenes are synthesized with the
Diels–Alder reaction of benzyne with anthracene,[13] but this
method often suffers from poor efficiency. Furthermore,
access to substituted functionalized triptycenes is limited
because of the relative scarcity and occasional instability of
substituted anthracene precursors. These limitations
prompted us to investigate the new reaction as a practical
synthetic approach to the construction of triptycenes.
The low efficiency in the above reaction was due to
generation of numerous side products. Several of the side
products, detected by GC-MS analysis, provide mechanistic
information; 10-methylanthracen-9-ol originates from the
premature exit from the proposed reaction cascade,[14]
whereas formation of butylbenzene and 10-methylphenanth-
ren-9-ol is due to trapping of o-benzyne with species other
than the ynolate (see Figure SI-1 in the Supporting Informa-
tion). Benzyne reactions are usually conducted under the
excess of the trapping reagent in order to suppress the side
reactions. In our case, at least three equivalents of benzyne to
ynolate are required to yield the triptycene; however,
effective trapping of benzyne needs excess of ynolate. To
solve this discrepancy, benzyne should be gradually generated
in small amounts in the presence of ynolate.
Furthermore, disubstituted benzynes also react with
ynolate 1a regioselectively to provide the corresponding
multisubstituted triptycenes (17 and 19) (Scheme 4). Reac-
tions of aryl fluorides (16 and 18) with additional substituents
ꢀ
gave products consistent with deprotonation of C H bond
activated by two adjacent s-acceptors.
Calculations were used to gain insight into the origin of
high regioselectivity observed in the three reactions of o-
benzynes. We focused on the reactivity of the OMe-substi-
tuted benzyne. It is known that nucleophiles attack these
species at the meta-position relative to the OMe group. This
selectivity has been attributed to ground state polarization
and distortion of the LUMO. Despite the previous success of
By using the ortho lithiation as an aryne formation
method, the yield was improved to 42% when butyllithium
was added to fluorobenzene 13 at room temperature in one
hour. Using this method, we synthesized triptycenes from
several ynolates. Notably, even the sterically hindered yno-
lates provided produced the target polycyclic products
(Table 1).
Scheme 4. Synthesis of triptycenes using several benzyne precursors.
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such analysis, the ground state geometries have predictive
power only when they point out to an emerging electronic
effect that will be amplified in the TS. In a more precise
analysis of benzyne reactivity, the regioselectivity is con-
trolled by progressive evolution of negative hyperconjugation
*
from a moderate pin ! sCꢀO interaction in the reactant to
*
a strong nC ! sCꢀO interaction in the anionic product (see
Figure SI-2). Trends in the ground state geometry correctly
predict the observed reaction product only because the
ground state structural distortion and the dominant force of
TS stereoelectronic stabilization coincide.[17]
The observed structural distortion in the MeO-benzyne is
consistent with the importance of hyperconjugative
*
pin ! sCꢀO interaction. In particular, the greater bending at
the benzyne carbon adjacent to the OMe group reflects
increased electron density at this carbon where it interacts
*
with the vicinal sCꢀO acceptor (Scheme 5).
Figure 1. Top: Barrierless addition of ynolate to MeO-benzyne yields
the more stable isomer. Bottom: Evolution of chelated geometries
during addition of ynolate to MeO-benzyne.
Scheme 5. The ground state structural distortion and dominant force
of TS stereoelectronic stabilization are the same: ground state
geometry predicts correct reaction product.
Interestingly, no TS could be located for the reaction of o-
benzyne and lithium ynolate. Instead, the chelated O···LiO
complex is transformed into the product without any transient
penalty. This calculation paints a very different picture from
the reaction of benzyne with less reactive nucleophiles.
Addition of ynolate to benzyne is highly exergonic (> 60 kcal
molꢀ1) and, according to the Hammond–Leffler postulate, the
TS is expected to be very early. Furthermore, large reaction
exergonicity can lead to the disappearance of reaction
barriers.[18]
The key process at the barrierless stage is the change from
ꢀ
ꢀ
ꢀ
O Li to C Li coordination that precedes the C C bond
formation (Figure 1B). Both O···Li interactions are main-
tained throughout this stage, and O···Li···O chelation is likely
to play a substantial role in directing the initial stage of this
process.[19] The overall “cycloaddition” is distinctly non-
Figure 2. Computed energetics of the enolate (top) and the Diels–
Alder (bottom) stages of the cascade.
ꢀ
concerted: the barrierless C C bond formation leads to an
bond formation from the enolate is also barrierless (see the
SI) and leads to the formation of an aryl anion that undergoes
subsequent 4-exo cyclization. Again, the overall cycloaddition
acyclic ketene intermediate that undergoes fast 4-exo closure
in a separate step. Formation of the non-observed isomer is
less favorable due to the lack of chelation and lower
hyperconjugative stabilization.
is non-concerted. Due to the relief of antiaromaticity, the first
ꢀ1
ꢀ
C C bond formation with the o-benzyne is 2.6 kcalmol
Although formation of four-membered intermediate from
the two high-energy alkyne reactants is exergonic, it gives
a product that is destabilized by antiaromaticity as confirmed
by a positive NICS(1)[20] value and the ACID[21] plots (SI
part).
more exergonic for the fused enolate in comparison to the
ynolate. Because of accumulation of strain, the 4-exo cycliza-
tion barrier is considerably higher than the one in the ynolate
addition ( ꢁ 12 vs. 3 kcalmolꢀ1). Furthermore, the cyclization
is mildly endergonic and, hence, should be reversible.
In many ways, the reactions of ynolate and enolate with o-
The fragmentation of the Dewar intermediate provides
thermodynamic driving force for the overall enolate reaction
ꢀ
benzyne are similar (Figure 2). In particular, the initial C C
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with o-benzyne. The relatively low barrier is a consequence of
two factors: gain of aromaticity (the thermodynamic effect on
kinetics)[18] and the effect of anionic oxygen on pericyclic
reactions.[11]
The final Diels–Alder reaction is concerted (Figure 2,
bottom) but highly asynchronous: “phenolate” attack at C3 of
[1] Reviews: a) M. Shindo, K. Matsumoto in Pataiꢀs Chemistry of
Functional Groups, Metal Enolates (Eds.: J. Zabicky), Wiley,
Chichester, 2016, pp. 1 – 31; b) M. Shindo, K. Matsumoto in
Topics in Current Chemistry, Vol. 327 (Eds.: J. Wang), Springer,
Berlin, 2012, pp. 1 – 32; c) M. Shindo, Tetrahedron 2007, 63, 10 –
36.
[2] a) M. Shindo, Y. Sato, K. Shishido, J. Am. Chem. Soc. 1999, 121,
6507 – 6508; b) M. Shindo, Y. Sato, K. Shishido, J. Org. Chem.
2001, 66, 7818 – 7824; c) M. Shindo, K. Matsumoto, Y. Sato, K.
Shishido, Org. Lett. 2001, 3, 2029 – 2031.
[3] a) U. Schçllkopf, I. Hoppe, Angew. Chem. Int. Ed. Engl. 1975, 14,
765 – 765; Angew. Chem. 1975, 87, 814 – 815; b) M. Shindo, S.
Oya, R. Murakami, Y. Sato, K. Shishido, Tetrahedron Lett. 2000,
41, 5943 – 5946; c) M. Shindo, K. Matsumoto, S. Mori, K.
Shishido, J. Am. Chem. Soc. 2002, 124, 6840 – 6841; d) M.
Shindo, K. Itoh, C. Tsuchiya, K. Shishido, Org. Lett. 2002, 4,
3119 – 3121.
ꢀ
OMe-benzyne precedes formation of the second C C bond
(at C2). The calculated reaction barrier is remarkably low.
Significant negative charge accumulation at C2 in the TS
(NBO charge at C2 is ꢀ0.17e vs. + 0.12e on C3) benefits
*
strongly from the p ! sCꢀO hyperconjugative assistance.
Despite progressing through a panoply of unstable
intermediates, the overall cascade is > 260 kcalmolꢀ1 exer-
gonic. This large driving force highlights the power of alkynes
as the high-energy entry point into unusual chemical cas-
cades.[22]
[4] The Michael addition to alkylidene malonates: H. Kai, K.
Iwamoto, N. Chatani, S. Murai, J. Am. Chem. Soc. 1996, 118,
7634 – 7635.
In conclusion, we have developed a novel one-pot
approach to substituted triptycenes by the reaction of
ynolates and arynes. This process contains successive four
reactions. Each of the three nucleophiles reacts with o-
benzyne in the same predictable manner controlled by
chelation and negative hyperconjugation. In every case,
either the key intermediate or the transition state leading to
the observed product display significant negative charge
[5] Selected reviews on arynes: a) H. H. Wenk, M. Winkler, W.
Sander, Angew. Chem. Int. Ed. 2003, 42, 502 – 528; Angew.
Chem. 2003, 115, 518 – 546; b) H. Pellissier, M. Santelli, Tetrahe-
dron 2003, 59, 701 – 730; c) P. M. Tadross, R. M. Stoltz, Chem.
Rev. 2012, 112, 3550 – 3577; d) A. Bhunia, S. R. Yetra, A. T. Biju,
Chem. Soc. Rev. 2012, 41, 3140 – 3152; e) C. Wu, F. Shi, Asian J.
Org. Chem. 2013, 2, 116 – 125; f) A. V. Dubrovskiy, N. A.
Markina, R. C. Larock, Org. Biomol. Chem. 2013, 11, 191 – 218.
[6] a) M. C. Carre, B. Gregoire, P. Caubere, J. Org. Chem. 1984, 49,
2050 – 2052; b) M. A. Zouaoui, A. Mouaddib, B. Jamart-Gre-
goire, S. Ianelli, M. Nardelli, P. Caubere, J. Org. Chem. 1991, 56,
4078 – 4081.
ꢀ
accumulation next to a s-acceptor C O bond. The overall
cascade disassembles the triple bond in two one-carbon units
that regioselectively connect three o-benzynes.[23] This is
a conceptually unique application of alkynes in synthesis and
the first example of the formal insertion of three arynes into
a triple bond.[24] The resulting functionalized C3-symmetrical
triptycenes hold promise in the design of functional materi-
als.[25]
[7] Review: A. Flores-Gaspar, R. Martin, Synthesis 2013, 563 – 580.
[8] T. Matsumoto, T. Hosoya, M. Katsuki, K. Suzuki, Tetrahedron
Lett. 1991, 32, 6735 – 6736.
[9] a) M. Shindo, Y. Sato, K. Shishido, Tetrahedron 1998, 54, 2411 –
2422; b) M. Shindo, K. Matsumoto, K. Shishido, Org. Synth.
2007, 84, 11 – 21.
Acknowledgements
[10] a) D. E. Applequist, R. Searle, J. Am. Chem. Soc. 1964, 86, 1389 –
1391; b) W. Pritschins, W. Grimme, Tetrahedron Lett. 1979, 20,
4545 – 4548; c) W. Pritschins, W. Grimme, Tetrahedron Lett.
1982, 23, 1151 – 1154; d) M. A. Meador, H. Hart, J. Org. Chem.
1989, 54, 2336 – 2341; e) S. Grimme, S. D. Peyerimhoff, J. Phys.
Chem. 1994, 98, 12927 – 12932; f) M. Ohkita, K. Sano, S. Dohba,
Y. Fujita, T. Suzuki, T. Tsuji, J. Chem. Soc. Perkin Trans. 1 2000,
1971 – 1975.
We thank T. Matsumoto at Kyushu University for the X-ray
crystal structure analyses. This work was partially supported
by JSPS KAKENHI Grant Number (No. JP16H01157, No.
JP26293004), Science and Technology Research Promotion
Program for Agriculture, forestry, fisheries and food industry
(M.S.), the Asahi Glass Foundation (K.M.), and the Cooper-
ative Research Program of the Network Joint Research
Center for Materials and Devices. I.A. is grateful to the
National Science Foundation for support (CHE-1152491) and
NSF XSEDE (TG-CHE160006) and FSU RCC for computa-
tional resources. G.d.P.G. thanks IBM for its 2016 Ph.D.
Scholarship.
ꢀ
[11] Alkoxide moiety strongly facilitates C C bond cleavage:
a) D. A. Evans, A. M. Golob, J. Am. Chem. Soc. 1975, 97,
4765 – 4766; b) B. K. Carpenter, Tetrahedron 1978, 34, 1877 –
1884; c) R. Pal, R. J. Clark, M. Manoharan, I. V. Alabugin, J.
Org. Chem. 2010, 75, 8689 – 8692.
[12] Reviews: a) Y.-X. Ma, Z. Meng, C.-F. Chen, Synlett 2015, 6 – 30;
b) Y. Han, Z. Meng, Y.-X. Ma, C.-F. Chen, Acc. Chem. Res. 2014,
47, 2026 – 2040; c) Y. Jiang, C.-F. Chen, Eur. J. Org. Chem. 2011,
6377 – 6403; d) L. Zhao, Z. Li, T. Wirth, Chem. Lett. 2010, 39,
658 – 667; e) J. H. Chong, M. J. MacLachlan, Chem. Soc. Rev.
2009, 38, 3301 – 3315; f) J.-S. Yang, J.-L. Yan, Chem. Commun.
2008, 1501 – 1512; g) H. Hart, Pure Appl. Chem. 1993, 65, 27 – 34.
[13] a) W. Adcock, V. S. Iyer, J. Org. Chem. 1988, 53, 5259 – 5266;
b) E. de Barry Barnett, M. A. Matthews, J. Chem. Soc. Trans.
1923, 123, 2549 – 2557.
Conflict of interest
The authors declare no conflict of interest.
Keywords: aryne · directing effect · hyperconjugation ·
triptycene · ynolate
[14] Other intermediates, such as cyclobutenone and Dewar-anthra-
cene, were not detected.
[15] It is possible that a small amount of minor isomers was present in
the complex mixture of side products.
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[16] a) R. V. Stevens, G. S. Bisacchi, J. Org. Chem. 1982, 47, 2393 –
[21] R. Herges, D. Geuenich, J. Phys. Chem. A 2001, 105, 3214 – 3220;
2396; b) B. M. Bhawal, S. P. Khanapure, H. Zhang, E. R. Biehl, J.
Org. Chem. 1991, 56, 2846 – 2849; c) T. Hosoya, T. Hasegawa, Y.
Kuriyama, T. Matsumoto, K. Suzuki, Synlett 1995, 177 – 179; d) F.
Leroux, M. Schlosser, Angew. Chem. Int. Ed. 2002, 41, 4272 –
4274; Angew. Chem. 2002, 114, 4447 – 4450; e) T. Hamura, T.
Hosoya, H. Yamaguchi, Y. Kuriyama, M. Tanabe, M. Miyamoto,
Y. Yasui, T. Matsumoto, K. Suzuki, Helv. Chim. Acta 2002, 85,
3589 – 3604; f) P. Maurin, M. Ibrahim-Ouali, J.-L. Parrain, M.
Santelli, J. Mol. Struct. Theochem. 2003, 637, 91 – 100; g) P. M.
Tadross, C. D. Gilmore, P. Bugga, S. C. Virgil, B. M. Stoltz, Org.
Lett. 2010, 12, 1224 – 1227; h) T. Truong, O. Daugulis, Org. Lett.
2011, 13, 4172 – 4175; i) J. M. Medina, J. L. Mackey, N. K. Garg,
K. N. Houk, J. Am. Chem. Soc. 2014, 136, 15798 – 15805.
[17] I. V. Alabugin, Stereoelectronic Effects in Reaction Design in
Stereoelectronic Effects: A Bridge Between Structure and Reac-
tivity, Wiley, Chichester, 2016, pp. 257 – 274.
ACID calculations performed at the CGST-M06-2X/6-311 ++
G(d,p) level at the AICD 2.0.0 software.
[22] I. V. Alabugin, B. Gold, J. Org. Chem. 2013, 78, 7777 – 7784.
[23] For other examples of metal-free cascades that disassemble
alkynes into one-carbon synthons, see: a) S. Roy, M. P. Davy-
dova, R. Pal, K. Gilmore, G. A. Tolstikov, S. F. Vasilevsky, I. V.
Alabugin, J. Org. Chem. 2011, 76, 7482 – 7490; b) S. F. Vasilevsky,
D. S. Baranov, V. I. Mamatyuk, Y. V. Gatilov, I. V. Alabugin, J.
Org. Chem. 2009, 74, 6143 – 6150.
=
[24] Insertion of two arynes into C O double bonds: a) H. Yoshida,
M. Watanabe, H. Fukushima, J. Ohshita, A. Kunai, Org. Lett.
2004, 6, 4049 – 4051; Reviews: b) D. PeÇa, D. Perez, E. Guitian,
Angew. Chem. Int. Ed. 2006, 45, 3579 – 3581; Angew. Chem. 2006,
118, 3659 – 3661; c) H. Miyabe, Curr. Org. Chem. 2015, 19, 1222 –
1241; d) H. Yoshida, K. Takaki, Synlett 2012, 1725 – 1732; See
also ref. [5d].
[18] I. V. Alabugin, M. Manoharan, B. Breiner, F. D. Lewis, J. Am.
Chem. Soc. 2003, 125, 9329 – 9342.
[25] A recent example: a) N. Seiki, Y. Shoji, T. Kajitani, F. Ishiwari,
A. Kosaka, T. Hikima, M. Takata, T. Someya, T. Fukushima,
Science 2015, 348, 1122 – 1126; A review: b) T. M. Swager, Acc.
Chem. Res. 2008, 41, 1181 – 1189.
[19] An interesting analogy to the directing role of MeO···Li
interaction is provided by MeO···Sn interactions in radical
addition to propargylic ethers: a) K. Pati, G. d. P. Gomes, T.
Harris, A. Hughes, H. Phan, T. Banerjee, K. Hanson, I. V.
Alabugin, J. Am. Chem. Soc. 2015, 137, 1165 – 1180; b) T. Harris,
G. d. P. Gomes, R. J. Clark, I. V. Alabugin, J. Org. Chem. 2016,
81, 6007 – 6017.
Manuscript received: September 17, 2016
Revised: November 11, 2016
Final Article published: && &&, &&&&
[20] Z. Chen, C. S. Wannere, C. Corminboeuf, R. Puchta, P. v. R.
Schleyer, Chem. Rev. 2005, 105, 3842 – 3888.
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Communications
Synthetic Methods
S. Umezu, G. dos Passos Gomes,
T. Yoshinaga, M. Sakae, K. Matsumoto,
T. Iwata, I. Alabugin,
M. Shindo*
&&&& — &&&&
Regioselective One-Pot Synthesis of
Triptycenes via Triple-Cycloadditions of
Arynes to Ynolates
Three alkynes and one triple bond: The
title reaction constitutes a four-step pro-
cess involving three cycloadditions and
electrocyclic ring opening of the strained
Dewar anthracene. Each of the three
related but structurally distinct classes of
nucleophiles (ynolate, enolate, and
anthracenolate) reacts with o-benzyne in
the same predictable manner controlled
by chelation and negative hyperconjuga-
tion.
6
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Angew. Chem. Int. Ed. 2016, 55, 1 – 6
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