Titanocene-Mediated Dinitrile Coupling: A Divergent Route to Nitrogen-Containing Polycyclic Aromatic Hydrocarbons

Article abstract of DOI:10.1021/jacs.7b13823

A general synthetic strategy for the construction of large, nitrogen-containing polycyclic aromatic hydrocarbons (PAHs) is reported. The strategy involves two key steps: (1) a titanocene-mediated reductive cyclization of an oligo(dinitrile) precursor to form a PAH appended with di(aza)titanacyclopentadiene functionality; (2) a divergent titanocene transfer reaction, which allows final-step installation of one or more o-quinone, diazole, or pyrazine units into the PAH framework. The new methodology enables rational, late-stage control of HOMO and LUMO energy levels and thus photophysical and electrochemical properties, as revealed by UV/vis and fluorescence spectroscopy, cyclic voltammetry, and DFT calculations. More generally, this contribution presents the first productive use of di(aza)metallacyclopentadiene intermediates in organic synthesis, including the first formal [2 + 2 + 2] reaction to form a pyrazine ring.

Full text of DOI:10.1021/jacs.7b13823

Subscriber access provided by University of Leicester
Communication
Titanocene-Mediated Dinitrile Coupling: A Divergent Route
to Nitrogen-Containing Polycyclic Aromatic Hydrocarbons
Gavin R. Kiel, Adrian E. Samkian, Amelie Nicolay, Ryan J. Witzke, and T. Don Tilley
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b13823 • Publication Date (Web): 31 Jan 2018
Downloaded from http://pubs.acs.org on January 31, 2018
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of the American Chemical Society is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 5
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Titanocene-Mediated Dinitrile Coupling: A Divergent Route to Nitro-
gen-Containing Polycyclic Aromatic Hydrocarbons
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Gavin R. Kiel, Adrian E. Samkian, Amélie Nicolay, Ryan J. Witzke, and T. Don Tilley*
Department of Chemistry, University of California, Berkeley, Berkeley, California, 94720, United States
Supporting Information Placeholder
lacyclopentadiene ring. Rosenthal and coworkers recently re-
ported a breakthrough in this regard, demonstrating the compe-
tence of Cp* M(Me SiCCSiMe ) (M = Ti or Zr) for the formation
2 3 3
ABSTRACT: A general synthetic strategy for the construction of
large, nitrogen-containing polycyclic aromatic hydrocarbons
(
PAHs) is reported. The strategy involves two key steps: 1) a titan-
of several 2,5-di(aza)metallacyclopentadienes (the first unambig-
ocene-mediated reductive cyclization of an oligo(dinitrile) precur-
sor to form a PAH appended with di(aza)titanacyclopentadiene
functionality; and 2) a divergent titanocene transfer reaction,
which allows final-step installation of one or more o-quinone, dia-
zole, or pyrazine units into the PAH framework. The new method-
ology enables rational, late-stage control of HOMO and LUMO en-
ergy levels and thus photophysical and electrochemical proper-
ties, as revealed by UV/Vis and fluorescence spectroscopy, cyclic
voltammetry, and DFT calculations. More generally, this contribu-
tion presents the first productive use of di(aza)metallacyclopenta-
diene intermediates in organic synthesis, including the first formal
7
uous examples with any transition metal).
This report describes a cheaper and more accessible coupling rea-
8
2 3 3
gent, Cp Ti(Me SiCCSiMe ), that efficiently cyclizes tethered di-
nitrile compounds of general structure 2. Furthermore, treatment
of the resulting π-extended di(aza)titanacycles 3 with aqueous
acid, main-group dihalides, or acetylene dicarboxylates provides a
divergent route to π-extended o-quinones (4a), diazoles (4b), or
pyrazines (4c), respectively. These transformations represent the
6c-d
first development of metallacycle-transfer chemistry
for
di(aza)metallacyclopentadienes (to prepare 4b) and the first ex-
amples of formal [2+2+2] reactions to form pyrazine rings. This
chemistry was initially developed in the model system of Scheme
[
2+2+2] reaction to form a pyrazine ring.
2, and then applied to divergently tune the HOMO-LUMO gap in
two different PAH systems via installation of a range of substitu-
ents and heterocyclic rings.
Heterocyclic rings have a profound impact on the electronic, pho-
tophysical, and supramolecular properties of polycyclic aromatic
Scheme 1.
1
,2
hydrocarbons (PAHs) and related carbon nanostructures. In par-
ticular, nitrogen-containing PAHs have attracted tremendous in-
terest in organic electronics, as they often are good electron-ac-
2
ceptors and have increased stability. Such compounds are also
models or building blocks for nitrogen-doped graphene, which is
currently under intense investigation for its applications in elec-
3
tronics and catalysis. The general, directed incorporation of nitro-
gen and other heteroatoms into PAHs is a significant challenge.
Many synthetic methods have emerged, but few are divergent,
which provide access to libraries of analogous compounds and fa-
4
cilitate the identification of structure-property relationships. In-
deed, the future success of PAHs as components in functional ma-
terials will critically depend on the availability of reliable synthetic
methods that can be used to rationally tune properties in this way.
As part of an effort to expand the utility of [2+2+n] cycloadditions
in PAH synthesis, we recently developed a general strategy for the
synthesis of large PAHs, exemplified by the quantitative cyclization
of oligo(diyne) compounds like 1 (Scheme 1a) with a zirconocene
The model system of Scheme 2 formed the basis of our investiga-
tions. Based on our favorable experience with biaryl-tethered
diynes (e.g. 1), we hypothesized that the required intramolecular
5
5
reagent or Ir catalyst. The extension of this approach to include
coupling of tethered dinitrile 5 might proceed with readily-acces-
analogous precursors of general structure 2 (Scheme 1b), contain-
ing one or more tethered dinitrile units, would provide access to
nitrogen-containing or other electron-deficient analogues. Nota-
sible Cp
2
Ti(Me
3
SiC≡CSiMe
3
), despite the failure of this reagent in
7a
an analogous intermolecular coupling. Furthermore, it seemed
that the relatively small Cp ligands would provide a reactive titana-
cycle better poised for further transformations. Indeed, treatment
6
bly, in contrast to diyne coupling, there is little precedent for the
reductive coupling of two nitrile units to form a 2,5-di(aza)metal-
of 5 with 1.1 equiv of Cp
2 3 3
Ti(Me SiC≡CSiMe ) gave the phenan-
threne-annulated di(aza)titanacyclopentadiene 6 in 75% isolated
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 5
yield. The structure of this compound was verified by X-ray crys-
tallography (see SI, Figure S82) and its isolation allowed stream-
lined reactivity studies (vide infra).
Lewis acid-base adducts,15 but the short bonds in the central Sn–
N–Sn–N ring of 13 suggest that this dimeric compound is associ-
ated through normal covalent bonding.
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
The first transformation employed 6 in situ as a synthetic interme-
diate. A one-pot procedure involving coupling of 5, protodemetal-
lation of 6, and hydrolysis of the resulting bis-imine gave 9,10-phe-
nanthrenequinone 7 in 61% isolated yield. This represents a new
way to access π-extended o-quinones, which are most commonly
obtained by functionalization of one of the few commercially
available o-quinones, or via oxidation of the parent PAH. These
compounds are attractive for their electronic properties (most no-
The formal [2+2+2] products 14 and 15 were produced in good
yields by treatment of 6, generated in situ from 5, with excess
di(alkyl)acetylene dicarboxylate. An interesting feature of this
transformation is its occurrence in the absence of additives, as it
1
8
formally requires the extrusion of thermally unstable “Cp
2
Ti”. It
is possible that the excess alkyne plays a role in this extrusion, as
19
1
metallacyclopentadiene 16 is observed (by H NMR spectros-
copy) as a byproduct in the synthesis of 14. Furthermore, the yield
drops to 63% when 1.1 equiv of acetylene is used. No reaction oc-
curred with 3-hexyne and diphenylacetylene, even at elevated
temperature, suggesting that an electron deficient alkyne is re-
quired. Surprisingly, this appears to be the first example of a
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
9
tably, their ability to reversibly accept electrons), as ligands for
1
0
2e,11
transition metal complexes, and as synthetic precursors.
Scheme 2. Investigations of a model system
[
2+2+2] reaction to form a pyrazine ring, despite the extensive lit-
2
0
erature on [2+2+2] reactions involving nitriles.
An appealing feature of the dinitrile precursors is the ease with
which functionalized derivatives can be accessed. For example,
the cyano group is a good activating group in nucleophilic aromatic
21
substitution (S
available 2-bromo-4-fluorobenzonitrile to the simple three-step
sequence of S Ar, aryl-aryl coupling, and the [2+2+2] conditions
N
Ar) reactions. By subjection of commercially-
N
described above, a range of 7,10-substituted dibenzo[f,h]quinox-
alines 17–21 were produced (Scheme 3). The 57–70% yields for
the [2+2+2] reactions are for the two-step, one-pot procedure.
N
The S Ar reactions are notable for their scalability and simplicity.
For example, introduction of the amino substituent requires sim-
ple heating of a concentrated mixture of secondary amine (2.2
equiv) and 2-bromo-4-fluorobenzonitrile in DMF.
A critical feature of the new synthetic strategy is that the interme-
diate di(aza)titanacyclopentadienes (22) can be subjected to any
of the reactions described in Scheme 2. This is shown in the syn-
thesis of thiadiazole-oxide 23, which was targeted for its expected
small HOMO-LUMO gap due to its donor-acceptor (D-A) structure.
In analogy to Fagan and Nugent’s versatile and well-established
6c-d
zirconacyclopentadiene-transfer chemistry,
2
the “Cp Ti” frag-
Scheme 3. Functionalized derivatives via an S
coupling / [2+2+n] sequence
N
Ar / aryl-aryl
ment in 6 can be exchanged for a range of heteroatoms. For ex-
ample, this compound provided divergent access to chalcogenadi-
azoles 8–11. Phenanthrene-annulated thiadiazole 8 and thiadia-
zole-oxide 9 were isolated in good yields by treatment of 6 with
12
2 2 2 2 2
S Cl and SOCl , respectively. The reaction of 6 with SO Cl failed
to yield the corresponding thiadiazole-dioxide, resulting primarily
in decyclization to re-form 5. The heavier chalcogen analogues 10
and 11 were similarly synthesized by treatment of 6 with the iso-
1
3
lable, base-stabilized chalcogen dihalides SeCl
TeCl (bipy),
2
2
(bipy) and
13,14
respectively. Benzannulated chalcogenadiazole
heterocycles are heavily-used as electron acceptors in conducting
polymers and their unique self-assembly properties are well-doc-
1
5
umented. These two features make them attractive for incorpo-
15d-f, 16
ration into PAHs;
however, this typically requires o-quinone
or o-diamine functionality, which can be difficult to install.
The chemistry was extended to other main group diazole hetero-
17
cycles, such as the π-extended phosphadiazole 12, which was
1
produced in 79% yield (by H NMR spectroscopy) upon treatment
of titanacycle 6 with POCl Ph. Unfortunately, compound 12 could
not be isolated due to the difficulty in separating the Cp TiCl by-
product, which was complicated by the hydrolytic lability of the P–
N bond in this compound. Treatment of a CH Cl solution of 6 with
equiv of SnMe Cl resulted in precipitation of dimeric 13, as re-
2
The advantages of this strategy are more apparent in the construc-
tion of larger PAHs, such as those resulting from multifold coupling
reactions and containing two or more quinones, pyrazines, or dia-
zoles. The focus here is on the series of large, angular PAHs 24–26
(Scheme 4), which were targeted in the context of our general in-
2
2
2
2
2
2
2
vealed by single crystal X-ray crystallography (Figure S83). It is well
known that diazole heterocycles (e.g., 10 and 11) associate non-
covalently by formation of cyclic E–N–E–N linkages viewed as
5b
terest in expanded helicenes. These compounds possess an al-
ternation of donor and acceptor units, which might give rise to
ambipolar charge transport and/or novel self-assembly. The
ACS Paragon Plus Environment

Page 3 of 5
Journal of the American Chemical Society
bis(dinitrile) precursors 27–29 were obtained via Suzuki cross-cou-
pling of compound 30 with the appropriate boronic ester. The
modification of the heterocyclic ring,16a as shown for thiadiazole-
22
1
2
3
4
5
6
7
8
9
oxide-annulated PAH 23. Compared to pyrazine-annulated 17, this
compound exhibits a further bathochromic shift in absorption (λon-
set) of 84 nm and in emission (λmax) of 91 nm. The total shifts in
absorption and emission (from 20 to 23) are 213 and 249 nm, re-
spectively. Thus, a large decrease in the optical HOMO-LUMO
gaps, from 3.20 eV for 20 to 2.06 eV for 23, can be achieved from
rational and independent perturbations of HOMO and LUMO en-
ergy levels in this PAH system.
former was easily prepared on a gram scale using a Pd-catalyzed
23
cyanation reaction and the latter were produced via another ex-
ploitation of S Ar chemistry (see SI).
N
The first targets were the pyrazine-annulated 24–26-pyr, which
differ only in the electron-donating ability of the “Nu” substituent,
by employment of the [2+2+2] conditions described above. These
compounds were isolated in 39–47% yields for the two-step, one-
pot reaction, which are consistent with the yields expected based
on the one-fold couplings described above. The side products
were easily separated by column chromatography. Monitoring of
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
the reactions by H NMR spectroscopy revealed formation of the
intermediate bis(di(aza)titanacyclopentadiene)s 24–26-Ti in 58,
76, and 67% yields, respectively. The NEt
2
-substituted bis(dinitrile)
2
8 was next subjected to the titanocene-coupling / chalcogen
transfer reactions described above, which produced bis(chalco-
genadiazoles) 25-S, 25-SO, and 25-Se in 34, 47, and 52% yields, re-
spectively. Compound 25-SO is an inseparable mixture of two dia-
stereomers, resulting from the chiral S=O centers. It is important
to note that, in contrast to the model system (Scheme 2), these
compounds were produced in a one-pot reaction from bis(dini-
trile) 28. An attempt to produce the bis(o-quinone) 25-Q using the
conditions presented for 7 gave a complex mixture, probably due
Figure 1. Normalized a) absorption and b) emission spectra
(CH
2 2
Cl ) for PAHs 14, 17–21, and 23.
The expected red-shift in absorption and emission is again seen on
to the basicity of the NEt
2
group; however, synthesis of bis(o-qui-
going from unsubstituted 24-pyr to NEt -substituted 25-pyr (Fig-
2
none) 26-Q using these conditions proceeded without difficulty.
ures 2a and 2b); however, the effect of the substituent is attenu-
ated since the HOMO is partially distributed onto the central phe-
nanthrene unit, which also contains electron-donating groups. In-
troduction of the thia- and selenadiazole rings in compounds 25-S
and 25-Se results in blue-shifted absorption and emission maxima
Scheme 4. Large, angular PAHs via twofold coupling
(λmax) compared to compound 25-Pyr; however, the absorption
and emission (λmax) of bis(thiadiazole-oxide) 25-SO exhibit large
red-shifts and a concomitant decrease in optical HOMO-LUMO
gap of 0.35 eV (from 2.31 to 1.96 eV) compared to 25-pyr. Bis(qui-
none) 26-Q exhibits a weak, red-shifted absorption band and this
compound is non-fluorescent.
Figure 2. Normalized a) absorption and b) emission spectra
(
2 2
CH Cl ) for 24–26
Given the facility with which o-quinones accept electrons, the rare
bis(o-quinone) 26-Q was analyzed by CV in THF with 0.1 M
n
4
N Bu PF
6
as supporting electrolyte (Figure S81). This compound
A high level of control over HOMO and LUMO energy levels, and
thus photophysical and electronic properties, can be achieved us-
ing the chemistry developed above. In the series of pyrazine-an-
nulated PAHs 14 and 17–21, a bathochromic shift in the absorp-
tion onset (λonset) value of 129 nm results on going from F-substi-
tuted 20 to NEt -substituted 17 (Figure 1a), with intermediate
2
shifts for less-donating substituents. This results from an increase
in the HOMO energy level, as supported by cyclic voltammetry
exhibits four reduction events (three reversible and one irreversi-
ble) with E1/2 values of –1.16, –1.32, –1.91, and –3.01 V vs. Fc/Fc .
No oxidation events could be observed within the solvent window.
+
In conclusion, a general, divergent synthetic strategy to rationally
control the electronic and optical properties of nitrogen-substi-
tuted PAHs has been disclosed. The initial focus is on application
of this strategy to PAHs and graphene nanostructures; however,
this chemistry should find applications in other fields where o-qui-
none, diazole, or pyrazine functionalities are desirable. Metallacy-
clopentadiene intermediates have long been employed to access
(
CV) and DFT calculations (see Figures S80 and S84 and Table S2).
Emission λmax values span a range of 158 nm in this series of com-
pounds (Figure 1b). The LUMO energy level can be manipulated by
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 5
highly-substituted benzenes and metallole heterocycles (e.g., thi-
ophenes, phospholes, and stannoles). This strategy has now been
extended to seven di(aza)-analogues. Current efforts involve ap-
plication of the method to synthesis of more complex electron-
deficient PAHs (e.g. expanded helicenes), especially those contain-
ing multiple redox centers.
(6)
(a) Müller, E. Synthesis 1974, 1974, 761. (b) Vollhardt, K. P. C. Acc.
Chem. Res. 1977, 10, 1. (c) Fagan, P. J.; Nugent, W. A. J. Am.
Chem. Soc. 1988, 110, 2310. (d) Yan, X.; Xi, C. Acc. Chem. Res.
6
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
015, 48, 935. (e) Agenet, N.; Buisine, O.; Slowinski, F.; Gandon,
V.; Aubert, C.; Malacria, M. In Organic Reactions; Overman, L. E.,
Ed.; John Wiley & Sons: Hoboken, NJ, 2007, Vol. 68, pp. 1–302.
(f) Transition-Metal-Mediated Aromatic Ring
Construction; Tanaka, K., Ed.; John Wiley & Sons, Inc.: Hoboken,
NJ, 2013.
ASSOCIATED CONTENT
Supporting Information
(
7)
Initial report: (a) Becker, L.; Arndt, P.; Jiao, H.; Spannenberg, A.;
Rosenthal, U. Angew. Chem. Int. Ed. 2013, 52, 11396. Follow-up
reports: (b) Becker, L.; Arndt, P.; Spannenberg, A.; Jiao, H.;
Rosenthal, U. Angew. Chem. Int. Ed. 2015, 54, 5523. (c) Becker,
L.; Reiß, F.; Altenburger, K.; Spannenberg, A.; Arndt, P.; Jiao, H.;
Rosenthal, U. Chem. Eur. J. 2016, 22, 10826.
(a) Review: Rosenthal, U.; Burlakov, V. V.; Arndt, P.; Baumann,
W.; Spannenberg, A. Organometallics 2003, 22, 884. (b) This re-
agent has also been used to construct hexaazatriphenylenes via
an intermolecular, dehydrogenative C-C bond forming reaction:
J. Am. Chem. Soc. 2005, 127, 14190.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
The Supporting Information is available free of charge on the ACS
Publications
website.
(
8)
9)
Experimental procedures and characterization data for all new
compounds (PDF)
Crystallographic information file for 6 and 13 (CIF)
(
(a) Schweinfurth, D.; Zalibera, M.; Kathan, M.; Shen, C.; Mazzo-
lini, M.; Trapp, N.; Crassous, J.; Gescheidt, G.; Diederich, F. J. Am.
Chem. Soc. 2014, 136, 13045. (b) Urakawa, K.; Sumimoto, M.;
Arisawa, M.; Matsuda, M.; Ishikawa, H. Angew. Chem. Int. Ed.
AUTHOR INFORMATION
Corresponding Author
tdtilley@berkeley.edu
2
016, 128, 7558.
(
(
10)
11)
Pierpont, C. G.; Buchanan, R. M. Coord. Chem. Rev. 1981, 38, 45.
Wasserfallen, D.; Kastler, M.; Pisula, W.; Hofer, W. A.; Fogel, Y.;
Wang, Z.; Müllen, K. J. Am. Chem. Soc. 2006, 128, 1334.
Notes
The authors declare no competing financial interests.
(12)
One thiadiazole-oxide has been synthesized by treatment of a
ACKNOWLEDGMENT
2
di(aza)titanacyclopentadiene with SOCl , but the yield was low
(ref 7c). To the best of our knowledge, this is the only previous
This work was funded by the National Science Foundation under
Grant No. CHE-1708210. Crystallographic analysis of compound 6
was performed at The Advanced Light Source, which is supported
by the Director, Office of Science, Office of Basic Energy Sciences,
of the U.S. Department of Energy under Contract No. DE-AC02-
05CH11231. Crystallographic analysis of compound 13 was per-
formed at the ChexRay X-ray crystallographic facility (UC Berke-
ley), which is funded by the National Institutes of Health under
grant no. S10-RR027172. DFT calculations were performed at the
Molecular Computation and Graphics Facility at UC Berkeley,
which is funded by the National Institutes of Health under grant
number S10OD023532.
example of metallacycle-transfer chemistry with a di(aza)metal-
lacyclopentadiene.
Dutton, J. L.; Farrar, G. J.; Sgro, M. J.; Battista, T. L.; Ragogna, P. J.
Chem. Eur. J. 2009, 15, 10263.
He, G.; Kang, L.; Torres Delgado, W.; Shynkaruk, O.; Ferguson, M.
J.; McDonald, R.; Rivard, E. J. Am. Chem. Soc. 2013, 135, 5360.
(a) Cozzolino, A. F.; Vargas-Baca, I.; Mansour, S.; Mahmoudkhani,
A. H. J. Am. Chem. Soc. 2005, 127, 3184. (b) Ono, K.; Tanaka, S.;
Yamashita, Y. Angew. Chem. Int. Ed. Engl. 1994, 33, 1977. (c)
Langis-Barsetti, S.; Maris, T.; Wuest, J. D. J. Org. Chem. 2017, 82,
(13)
(
14)
15)
(
5
1
034. (d) Neidlein, R.; Knecht, D.; Endres, H. Z. f. Naturforsch.
987, 42, 84. (e) Appleton, A. L.; Miao, S.; Brombosz, S. M.; Ber-
ger, N. J.; Barlow, S.; Marder, S. R.; Lawrence, B. M.; Hardcastle,
K. I.; Bunz, U. H. F. Org. Lett. 2009, 11, 5222. (f) Xia, D.; Wang, X.-
Y.; Guo, X.; Baumgarten, M.; Li, M.; Müllen, K. Cryst. Growth Des.
REFERENCES
2
2
016, 16, 7124. (g) Wang, Y.; Michinobu, T. J. Mater. Chem. C
016, 4, 6200.
(1)
(a) Jiang, W.; Li, Y.; Wang, Z. Chem. Soc. Rev. 2013, 42, 6113. (b)
Stępień, M.; Gońka, E.; Żyła, M.; Sprutta, N. Chem. Rev. 2017,
(16)
(a) Linder, T.; Badiola, E.; Baumgartner, T.; Sutherland, T. C. Org.
Lett. 2010, 12, 4520. (b) Xie, Y.; Shuku, Y.; Matsushita, M. M.;
Awaga, K. Chem. Commun. 2014, 50, 4178. (c) Xiao, J.; Xiao, X.;
Zhao, Y.; Wu, B.; Liu, Z.; Zhang, X.; Wang, S.; Zhao, X.; Liu, L.; Jiang,
L. Nanoscale 2013, 5, 5420.
1
17, 3479. (c) Anthony, J. E. Chem. Rev., 2006, 106, 5028. (d) Vos-
trowsky, O.; Hirsch, A. Chem. Rev. 2006, 106, 5191. (e) Polycyclic
Arenes and Heteroarenes; Miao, Q., Ed.; Wiley-VCH Verlag GmbH
&
Co. KGaA: Weinheim, Germany, 2015. (f) Narita, A.; Wang, X.-
(
17)
18)
Linder, T.; Sutherland, T. C.; Baumgartner, T. Chem. Eur. J. 2010,
16, 7101.
Y.; Feng, X.; Müllen, K. Chem. Soc. Rev. 2015, 44, 6616.
(2)
(a) Bunz, U. H. F.; Engelhart, J. U.; Lindner, B. D.; Schaffroth, M.
Angew. Chem. Int. Ed. 2013, 52, 3810. (b) Bunz, U. H. F. Acc.
Chem. Res. 2015, 48, 1676. (c) Miao, Q. Adv. Mater. 2014, 26,
(
In contrast, the reaction between a zirconacyclopentadiene and
a di(alkyl)acetylene dicarboxylate requires an initial transmetal-
lation to Cu: Takahashi, T.; Xi, Z.; Yamazaki, A.; Liu, Y.; Nakajima,
K.; Kotora, M. J. Am. Chem. Soc. 1998, 120, 1672.
Demerseman, B.; H. Dixneuf, P. J. Chem. Soc. Chem. Commun.
1981, 665.
5
2
541. (d) Li, J.; Zhang, Q. ACS Appl. Mater. Interfaces 2015, 7,
8049. (e) Mateo-Alonso, A. Chem. Soc. Rev. 2014, 43, 6311.
(19)
(
3)
4)
(a) Wang, H.; Maiyalagan, T.; Wang, X. ACS Catal. 2012, 2, 781.
b) Kong, X.-K.; Chen, C.-L.; Chen, Q.-W. Chem. Soc. Rev. 2014, 43,
2841.
(
(20)
A closely related transformation is a 1,2,4-triazine synthesis via a
[
2+2+2] reaction between a dinitrile and a nitrile: Gesing, E. R. F.;
Groth, U.; Vollhardt, K. P. C. Synthesis, 1984, 351. For a review of
2+2+2] reactions involving nitriles, see: Varela, J. A.; Saá, C.
(
Many of the methods employed to date are summarized in refs
1
and 2. Notable examples of divergent approaches: (a) Jiang, W.;
[
Qian, H.; Li, Y.; Wang, Z. J. Org. Chem. 2008, 73, 7369. (b) He, B.;
Dai, J.; Zherebetskyy, D.; L. Chen, T.; A. Zhang, B.; J. Teat, S.;
Zhang, Q.; Wang, L.; Liu, Y. Chem. Sci. 2015, 6, 3180.
Chem. Rev. 2003, 103, 3787.
(
(
21)
22)
Bunnett, J. F.; Zahler, R. E. Chem. Rev. 1951, 49, 273.
Urawa, Y.; Naka, H.; Miyazawa, M.; Souda, S.; Ogura, K. J. Organ-
omet. Chem. 2002, 653, 269.
Tschaen, D. M.; Desmond, R.; King, A. O.; Fortin, M. C.; Pipik, B.;
King, S.; Verhoeven, T. R. Synth. Commun. 1994, 24, 887.
(5)
(a) Kiel, G. R.; Ziegler, M. S.; Tilley, T. D. Angew. Chem. Int. Ed.
2
017, 56, 4839. (b) Kiel, G. R.; Patel, S. C.; Smith, P. W.; Levine, D.
(23)
S.; Tilley, T. D. J. Am. Chem. Soc. 2017, 139, 18456.
ACS Paragon Plus Environment

Page 5 of 5
Journal of the American Chemical Society
For Table of Contents Only:
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
ACS Paragon Plus Environment