Stereoselective tandem cascade furan cycloadditions

Article abstract of DOI:10.1021/jo4022265

Oligofurans linked by a rigid tether undergo tandem cycloaddition reactions with high stereoselectivity. The reaction of bisfurans with dimethyl acetylenedicarboxylate (DMAD) involves tandem [4 + 2]/[4 + 2] cycloadditions in a pincer mode. The reaction of oligofurans with arynes involves stereoselective tandem [4 + 2]/[4 + 2] cycloaddition reactions in a domino mode. The corresponding aryne adducts have been transformed into extended perylene derivatives by deoxygenation and aromatization with HCl/EtOH.

Full text of DOI:10.1021/jo4022265

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Article
Stereoselective Tandem Cascade Furan Cycloadditions
Alejandro Criado, Manuel Vilas, Agustín Cobas, Dolores Pérez, Diego Peña, and Enrique Guitian
J. Org. Chem., Just Accepted Manuscript • Publication Date (Web): 14 Nov 2013
Downloaded from http://pubs.acs.org on November 17, 2013
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Stereoselective Tandem Cascade Furan Cycloadditions
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Alejandro Criado, Manuel VilasꢀVarela, Agustín Cobas, Dolores Pérez, Diego Peña*, Enrique Guitián*
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Departamento de Química Orgánica and Centro de Investigación en Química Biolóxica e Materiais
Moleculares (CIQUS), Universidade de Santiago de Compostela, 15782 Santiago de Compostela,
Spain
Eꢀmail: enrique.guitian@usc.es, diego.pena@usc.es
Table of Contents
Abstract: Oligofurans linked by a rigid tether undergo tandem cycloaddition reactions with high
stereoselectivity. The reaction of bisfurans with dimethyl acetylenedicarboxylate (DMAD) involves
tandem [4+2]/[4+2] cycloadditions in a pincer mode. The reaction of oligofurans with arynes involves
stereoselective tandem [4+2]/[4+2] cycloaddition reactions in a domino mode. The corresponding
aryne adducts have been transformed into extended perylene derivatives by deoxygenation and
aromatization with HCl/EtOH.
Keywords: Tandem cycloadditions • Arynes • Oligofurans • Polycyclic Aromatic Hydrocarbons
(PAHs)
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Introduction
Tandem cycloadditions, in which several processes take place without the isolation of intermediary
[
1,2]
products, play a very important role in organic synthesis.
Tandem cascade cycloadditions, defined
[2]
as those in which two or more cycloadditions take place without additional components or reagents,
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are particularly efficient from the point of view of atom and step economy. Tandem cascade
cycloadditions have been extensively used in organic synthesis, but they have been scarcely employed
for the synthesis of molecules of interest in materials science. We have devised a new strategy for the
[
3]
controlled synthesis of nanographenes, two dimensional sheets of benzenoid rings, based on tandem
[
4]
cascade oligofuran cycloadditions, as depicted in Scheme 1. The key feature of this strategy is the
use of tethered oligofuran chains, to favour the reaction cascades. One dimension of the graphene
[
5]
would be determined by the length of the oligofuran chain, the second by the number of chains. The
parallel series of [4+2] cycloadditions would afford a graphene oxide, which could be transformed into
the final graphene by reduction.
Scheme 1. Proposed strategy for the synthesis of nanographenes
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Results and Discussion
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As a proof of concept of this approach we decided to start the study with simple bisfurans, such as 1
(Scheme 2), in which the furan rings are linked through a rigid naphthalene tether. These bisfurans
should be available by crossꢀcoupling reactions between 1,8ꢀdiiodonaphthalene (2) and furan
derivatives 3, as shown in Scheme 2. Furanꢀderivatives 3 in turn should be obtained by metalation of
the corresponding furans. We thought that substituents R, such as tolyl or mesityl, placed at the edge of
the “nanographene” might enhance its kinetic stability, particularly against photooxidation, improve its
solubility and modify its solidꢀphase packing.
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Scheme 2. Retrosynthetic disconnection of tethered bisfurans 1
Synthesis of tethered oligofurans 1a-c and 7
First of all, substituted furans 4b and 4c were prepared. To this aim, we screened different cross
coupling conditions between 2ꢀfuryl metal derivatives and appropriate aryl halides (Scheme 3).
Metalation of furan (4a) with BuLi, transmetalation with ZnCl to (2ꢀfuryl)ZnCl [3a(Zn)] and
2
palladiumꢀcatalyzed coupling with pꢀiododotoluene afforded the desired 2ꢀ(pꢀtolyl)furan 4b in 75%
yield. However, the attempted coupling of 3a(Zn) with 2ꢀbromomesitylene in a similar reaction
condition afforded 4c in only 2% yield. This result could be attributed to the high steric hindrance
provided by the methyl groups of bromomesitylene (MesBr). To overcome this problem we decided to
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test the coupling method developed by Sarandeses and Sestelo based on the use of indium
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Scheme 3. Synthesis of substituted furans 4b,c
The desired coupling was performed using (2ꢀfuryl) In [3a(In)] and a catalyst generated in situ from
3
Pd (dba) and an adequate ligand. While ligands such as 1,1'ꢀbis(diphenylphosphino)ferrocene (dppf),
2
3
tricyclohexylꢀphosphine, triisopropylphosphine, and triꢀoꢀtolylphosphine failed to provide reasonable
[
7]
yields of 4c, the use of dicyclohexylphosphinoꢀ(2’,4’,6’ꢀtriisopropyl)biphenyl (XꢀPhos) proved to be
crucial, leading to the coupling product 4c in 90% yield. This is a remarkable result for a crossꢀ
coupling reaction involving two highly hindered reagents.
With furans 4a-c in hand we studied the synthesis of tethered bisfurans 1a-c as shown in Scheme 4 and
Table 1. Bisfuran 1a was obtained in moderate yield by Negishi coupling of (2ꢀfuryl)ZnCl [3a(Zn)] and
1,7ꢀdiiodonaphthalene (2) using NiCl (dppp) or PdCl (dppf) as catalyst (entries 1 and 2). Better yields
2
2
were obtained by Suzuki coupling of (2ꢀfuryl)B(OH) [3a(B)], 92% yield] or Stille coupling of (2ꢀ
2
furyl)SnBu [3a(Sn), 99% yield], but in the last case lower yields were obtained when scaling up the
3
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reaction (entries 3 and 4). For the preparation of the bisfuran 1b we planned to use the Suzuki reaction
but the preparation of the 2ꢀ[5ꢀ(pꢀtolyl)furyl)]boronic acid [3b(B)] was not fully reproducible.
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Scheme 4. Synthesis of furylnaphthalenes
To overcome these problems we decided to switch again to the use of indium organometallics. For the
optimization of the coupling reaction, we started with unsubstituted furan 4a. Firstly, we coupled 100
mol% of 2 with 40 mol% of the organoindium intermediate (2ꢀfuryl) In [3a(In)], the amount
3
corresponding to a 12% excess if all three furyl groups at indium were transferred, and PdCl (dppf) as
2
catalyst (entry 5). The major product 5a, obtained in 19% yield, resulting from the coupling of only one
equivalent of furan. When 100 mol% of indium derivative were used, a mixture of 1a (33% yield) and
5
a (32% yield) was obtained (entry 6). A higher excess of organomeallic reagent led to a 92% of
bisfuran 1a (entry 7). Under similar conditions bisfurans 1b and c were obtained in 75 and 99% yield,
respectively (entries 8 and 9).
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Table 1. Optimization of coupling reactions
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We realized that monocoupled product 5a could be a valuable intermediate for the synthesis of new
oligofurans. For example, it could be coupled with an indium derivative of 1a, such as 6, to afford a
trisfuran 7 (Scheme 5). To this aim, we treated 1a with butyl lithium and InCl as above, and coupled
3
the resulting indiumꢀderivative 6 with iodide 5, using PdCl (dppf) as catalyst. After the usual workꢀup
2
trisfuran 7 was obtained in 46% yield.
Scheme 5. Synthesis of trisfuran 7.
[8ꢀ10]
Tandem [4+2]/[4+2] cycloaddition with DMAD.
Firstly, to trigger the tandem cyclodditions we
choose dimethyl acetylenedicarboxylate (DMAD), because it is a very reactive, easyꢀtoꢀhandle
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dienophile. However, previous reports on tandem furan cycloadditions showed that the initial [4+2]
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adduct can undergo two modes of cycloaddition, leading to adducts termed domino and pincer (Scheme
[
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Scheme 6. Tandem [4+2] cycloadditions of furan and alkynes
When we carried out the reaction of bisfuran 4a and DMAD in ether at 20 ºC for 9 days, an adduct with
a molecular mass of 402 was isolated in 33 % yield. The same product was obtained in 57% yield, by
[
11]
heating bisfuran 4a and DMAD in toluene at 111 ºC for 6 days. This adduct was identified by NMR
[12]
spectroscopy and Xꢀray diffraction studies as exo,exo-8,
cycloaddition in a pincer mode (Scheme 7).
which results from the tandem cascade
Scheme 7. Tandem [4+2]/[4+2] cycloadditions of 1a and DMAD
In an effort to understand the reasons for this behaviour we carried out a computational study on the
formation of the seven isomers that could result from a tandem [4+2]/[4+2] cycloaddition in pincer or
in domino modes. Single point calculations were performed at the M062x/6ꢀ31++G(d,p) level on the
[
13]
corresponding B3LYP/6ꢀ31G(d) geometries (see Table 2).
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The formation of exo,exoꢀ8 (pincer mode) under kinetic control was predicted by the calculation, a
situation in good agreement with the experimental result. According to the calculations, exo,exoꢀ9
(domino mode) should be the thermodynamic product. However, we believe that under our
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[14]
experimental conditions, the process is irreversible and therefore proceeds under kinetic control.
In
fact, calculations show that the activation barrier for the retroꢀDiels–Alder reaction from exo,exoꢀ8
33.6 Kcal/mol) to 10 is high enough to make the process irreversible under the reaction conditions.
(
However, we found that if the exo,exoꢀ8 adduct is heated under argon at 180 ºC for 1 hour, phenol 11
was obtained, presumably formed by the mechanism outlined in Scheme 8.
Table 2. Structures and enthalpies for possible adducts 8 and 9
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Scheme 8. Thermal rearrangement of exo,exoꢀ8
[
15,16]
Tandem [4+2]/[4+2] Cycloadditions Triggered by Arynes.
To drive the tandem cycloadditions
towards the formation of “nanographene oxides” we chose arynes as dienophiles by several reasons:
they are very reactive species, they should react in tandem processes in a domino mode (pincer modes
are not possible) and they contain aromatic rings that will be incorporated in the final adducts,
affording, after deoxygenation and aromatization, large aromatic structures, namely “nanographenes”.
These arynes would be generated from the corresponding oꢀ(trimethylsilyl)aryl triflates as reported in
[
17]
the literature.
When benzyne (12) was generated, by treatment of oꢀ(trimethylsilyl)phenyl triflate (13) with cesium
fluoride, in the presence of bisfuran 1a, an adduct exo,exo-15a was isolated in 99% yield (Scheme 9).
Presumably, exo,exo-15a was formed through intermediate 14, by exo approximation of the diene to
the exo face of the dienophile. Remarkably, this is a highly stereoselective tandem cascade domino
[18]
[
4+2]/[4+2] cycloaddition, in which six adjacent stereocenters are formed with total stereocontrol.
The stereochemistry of adduct 15a was established by NMR (NOESY experiments and analysis of the
1
13
coupling constants in the H NMR spectrum). We carried out MO52x/6ꢀ31++(d,p) calculations,
[
4,13]
which showed that the exo,exo adduct is favoured under kinetic or thermodynamic control.
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Scheme 9. Tandem [4+2]/[4+2] cycloaddition of 1a with benzyne (12).
Similar cycloadditions between 1a and arynes 25-33, generated from the corresponding oꢀ
[
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(trimethylsilyl)aryl triflates 16-24,
yielded the corresponding adducts in moderate to good yields
(Table 3, entries 1ꢀ10). NMR analysis of these adducts shows the same stereochemical outcome as for
15a. Substituted benzynes 25-27 react with bisfuran 1a to afford the corresponding adducts 34a, 35 and
6, respectively, in moderate to good yields (Entries 1ꢀ3). Asymmetrically substituted benzyne 28
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reacts with complete regioselectivity to afford adduct 37 in 88% yield (Entry 4).
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Table 3. [4+2]/[4+2] Cascade cycloadditions of bisfuran 1a and arynes 25ꢀ33
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On the contrary, asymmetric 1ꢀnaphthyne (29) reacts with bisfuran 1a to give a mixture of regioisomers
8a and 39a in 55 and 34% yield, respectively (Entry 5). 2ꢀNaphthyne (30) reacts with 1a leading to
3
adduct 40a in 51% yield (Entry 6). 1ꢀPhenanthryne (31) reacts with 1a to afford a mixture of
regioisomers 41 and 42, in 42% and 50% yield, respectively (Entry 7). Symmetric arynes 32 and 33 led
to adducts 43 and 44, respectively (Entries 8 and 9). Cycloadducts 34-44 showed the same relative
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
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7
8
9
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7
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9
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7
8
9
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7
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9
0
4
stereochemistry, which was confirmed by Xꢀray diffraction analysis of compound 43.
We have also studied the reactivity of substituted bisfurans 1b,c against some arynes. Substituted
bisfuran 1b (R= pꢀTol) reacts with arynes 12, 25, 29 and 30 in a similar way as 1a, as shown in Table 4
(Entries 1ꢀ4). NMR analysis of these adducts shows the same stereochemical outcome as for 15a.
However, an unusually low yield was obtained from the reaction of benzyne (12) and bisfuran 1c (R=
Mes), probably due to the bulky mesityl groups, which hinder both cycloadditions in the tandem
process leading to 15c (Entry 5).
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Table 4. [4+2]/[4+2] Cascade cycloadditions of bisfuran 1b/1c and arynes 12, 25, 29 and 30.
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
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7
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3
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7
8
9
0
a
3
8b and 39b were obtained as an inseparable mixture. Yields determined by NMR
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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
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3
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4
4
4
4
4
4
4
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5
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5
5
5
5
6
Trisfuran 7 reacts with benzyne (12) in a tandem cascade [4+2]/[4+2]/[4+2] cycloaddition to afford
exo,exo,exo,exo-45 in an excellent 56% yield (Scheme 10). Remarkably, this transformation involves
the stereoselective formation of six new bonds and ten adjacent stereocenters! Again, we were able to
univocally confirm the stereochemical outcome of adduct 45 by Xꢀray diffraction studies.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
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7
8
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3
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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
Scheme 10. Tandem [4+2]/[4+2]/[4+2] cycloaddition of 7 with benzyne (12)
Deoxygenation/aromatization of aryne cycloadducts. Finally, to convert the obtained “nanographene
oxides” into the corresponding PAHs deoxygenation/aromatization processes are required. These
reactions were optimized with adduct 15a. All initial attempts to reduce adduct 15a to
benzo[a]perylene (46a) failed, due to the instability of this compound in the presence of oxygen and
light. After some experimentation we found that benzo[a]perylene (46a) can be obtained in 72 % yield
[
19]
by treatment of 15a with HCl in refluxing EtOH in the absence of light. Under the same conditions
adducts shown in Table 3 were transformed into the corresponding benzenoid hydrocarbons (Figure 1).
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6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. PAHs obtained by deoxygenation/aromatization
The deoxygenation of substituted derivatives 15b, 15c, 36b, 40b, 41b and 42b proved to be
more difficult under these conditions, leading to complex mixtures. To facilitate the formal
elimination of water from these adducts we planned to perform the aromatization in two
synthetic operations: the reduction of the olefinic double bond by a catalytic hydrogenation
followed by the deoxygenation by double endoxide opening and dehydration in acidic
conditions.[20] These alternative procedure was tested with substituted adducts 15b, 34b and
4
0b. Reduction of 15b, 34b and 40b with H (5 atm) and Ni Raney afforded intermediates 58, 59 and
2
6
0, which were transformed into benzoperylenes 46b (42% yield), 47b (27% yield) and 53b (19%
yield), respectively, by treatment with HCl/EtOH (Scheme 11).
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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
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4
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4
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4
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4
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5
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5
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5
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9
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0
1
2
3
4
5
6
7
8
9
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1
2
3
4
5
6
7
8
9
0
Scheme 11. Stepwise reduction of adducts 15b, 34b and 40b
[21]
Electronic properties of PAHs 46-57. All the prepared PAHs contain both perylene and acene units.
Acenes are the subject of a huge amount of work due to their interesting electronic properties and their
[
22]
potential use as organic semiconductors in electronic/photonic devices. The fundamental parameters
for the evaluation of acenes as potential candidates as semiconductors are the energies of frontier
orbitals (EHOMO, ELUMO), the HOMOꢀLUMO gap and the kinetic stability against atmospheric
conditions (O /light). For example, pentacene owns very interesting electronic properties (gap: 2.1 eV,
2
high mobility, etc), but is very unstable in the presence of oxygen and light.
We have studied the basic parameters of our acenes computationally as well as experimentally (Table
5). Most compounds in Table 4 show optical gaps close to that of pentacene (2.1 eV), with remarkable
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optical gaps of 2.01,1.90 and 1.85 eV for 53a, 53b and 57, respectively. All compounds in Figure 2,
with the exception of 56, in solution are sensitive to photooxidation in the presence of oxygen and
sunlight while, as expected, substituted derivatives 46b, 47b and 53b are much more stable.
While photooxidation of these compounds in the presence of air and light gives complex mixtures of
products, under these conditions, compound 56 underwent a clean cyclodehydrogenation to
quantitatively afford 61 (Scheme 12). Even the photon flux used to record its UV spectrum causes the
cyclodehydrogenation.
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
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5
5
5
5
5
5
5
6
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9
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3
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5
6
7
8
9
0
Scheme 12. Photochemical cyclodehydrogenation of 56.
Dibenzo[cd,n]naphtho[3,2,1,8ꢀpqra]perylene (61) is very insoluble in all solvents tested, preventing
1
3
from recording its C NMR spectrum. Remarkably, its structure has been recently confirmed by means
[
23,24]
of atomic force microscopy (AFM).
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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
Table 5. Photophysical and electrochemical data for compounds 46-57.
a)
a)
b)
c)
HOMO
b)
d)
LUMO
e)
f)
λonset
λem
518
557
573
599
524
528
531
537
506
604
643
541
521
544
661
E
ox
E
E
red
E
Gapopt
Gapelc
4
4
4
4
4
6a 507
0.28
0.19
0.32
0.36
0.17
0.29
0.20
0.38
0.45
0.03
0.12
0.33
0.36
0.45
0.06
ꢀ5.08
ꢀ4.99
ꢀ5.12
ꢀ5.16
ꢀ4.97
ꢀ5.09
ꢀ5.00
ꢀ5.17
ꢀ5.25
ꢀ4.83
ꢀ4.92
ꢀ5.14
ꢀ5.16
ꢀ5.25
ꢀ4.86
ꢀ1.97
ꢀꢀꢀꢀꢀ
ꢀ2.83
ꢀ2.80
ꢀ2.77
ꢀ2.89
ꢀ2.72
ꢀ2.75
ꢀ2.86
ꢀ2.87
ꢀ2.83
ꢀ3.04
ꢀ3.02
ꢀ2.90
ꢀ2.95
ꢀ2.88
ꢀ3.12
2.34
2.19
2.35
2.22
2.30
2.35
2.31
2.25
2.30
2.01
1.90
2.21
2.25
2.26
1.85
2.25
ꢀꢀꢀꢀꢀ
2.35
2.27
2.25
2.34
2.14
2.30
2.42
1.79
1.90
2.24
2.25
2.37
1.74
g)
6b 527
7a 501
7b 520
0
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h)
ꢀ2.03
ꢀ1.90
ꢀ2.08
ꢀ2.05
ꢀ1.94
ꢀ1.93
ꢀ1.97
ꢀ1.76
ꢀ1.78
ꢀ1.90
ꢀ1.85
ꢀ1.92
ꢀ1.68
8
510
500
537
550
540
49
5
5
0
1
52
5
5
5
5
3a 560
3b 610
4
5
560
550
548
643
56
5
7
a) nm, in CHCl ; b) V, determined by cyclic voltammetry (CV) in solution (CH Cl /0.1 M Bu NPF ),
3
2
2
4
6
working electrode: Pt, reference electrode: AgCl/Ag, counter electrode: platinum wire, internal standard:
ferrocene; c) eV, calculated from EHOMO= ꢀ(4.8 + Eox); d) eV, calculated from ELUMO= ꢀ(4.8 + E ); e) eV,
calculated from the UV onset; f) eV, calculated from CV data; h) there is an irreversible reduction at ꢀ1.63
V.
red
Conclusions
In summary, the tandem cascade cycloadditions reported here allow a rapid increase in the molecular
connectivity with complete control of the relative stereochemistry. Bisfuran 1a reacts with DMAD in a
tandem [4+2]/[4+2] cycloaddition in a pincer mode with the stereoselective formation of four bonds
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and six adjacent stereocenters. Bisfurans 1 react with arynes in tandem [4+2]/[4+2] cycloadditions in a
3
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5
6
7
8
9
1
1
1
1
1
1
1
1
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1
2
2
2
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2
2
2
2
2
2
3
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3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
domino mode with the stereoselective formation of four bonds and six adjacent stereocenters. Trisfuran
7
react with benzyne in a tandem [4+2]/[4+2]/[4+2] cycloaddition in a domino mode with the
stereoselective formation of six bonds and ten adjacent stereocenters. Extended PAHs combining cata-
and periꢀ ring fusion are easily obtained by treatmentt of the cycloadducts with HCl in EtOH.
Extension of this methodology to other oligofuran topologies for the synthesis of larger PAHs and
nanographenes is in progress.
0
1
2
3
4
5
6
7
8
9
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Experimental Section
General
All reactions were carried out under argon using ovenꢀdried glassware. TLC was performed on silica
gel 60 F254; chromatograms were visualized with UV light (254 and 360 nm). Flash column
chromatography was performed on silica gel 60 (ASTM 230ꢀ400 mesh). High resolution mass spectra
were obtained using a quadrupole mass analyzer.
[17b]
[17b,24]
[25]
[26]
[17b]
[17b,27]
[28]
[17b,29]
[17b,27]
[30]
Aryne precursors 13,
16,
17, 18, 19,
20,
21, 22,
23
and 24,
[31]
[32]
[33]
Pd(PPh ) , 1,8ꢀdiiodonaphthalene (2), furyl derivative 3a(Sn)
and tolylfuran 4b were prepared
3
4
following published procedures. Furyl derivative 7a (THF solution) was prepared in situ by reaction of
furan with n-BuLi and ZnCl . n-BuLi and Bu NF (TBAF) were used in solution in hexane (2.4 M) and
2
4
THF (1.0 M), respectively.
[34]
Synthesis of 2-mesitylfuran (4c). nꢀBuLi (6.20 mL, 2.43 M in hexane, 15.1 mmol) was added
dropwise to a stirred solution of furan (4a, 1.10 mL, 15.1 mmol) in THF (25 ml) at 0 ºC, and the
solution was stirred for further 30 min. The resulting solution was slowly added to a suspension of
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2
2
2
2
2
2
2
3
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3
3
3
3
4
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4
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4
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5
5
5
5
5
5
6
InCl (1.10 g, 5.02 mmol) in THF (25 ml) at ꢀ78 ºC and the mixture was stirred for 30 min. The cooling
3
bath was removed and when the solution reaches 25 ºC it was added to a refluxing solution of
bromomesitylene (380 ꢁL, 5.02 mmol), Pd (dba) (135 mg, 0.12 mmol) and dicyclohexylphosphinoꢀ
2
3
(2’,4’,6’ꢀtriisopropyl)biphenyl (XꢀPhos, 114 mg, 0.24 mmol) in THF (50 ml), and the mixture was
0
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4
5
6
7
8
9
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2
3
4
5
6
7
8
9
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9
0
refluxed for 15 h. Then MeOH (1 ml) was added, the solution was evaporated in vacuo and the residue
solved in Et O. The ethereal solution was successively washed with hydrochloric acid (5%), with a
2
saturated solution of NaHCO and with brine, dried over anhydrous Na SO and evaporated in vacuo.
3
2
4
The residue was purified by column chromatography (SiO , hexane) to yield 4c (840 mg, 99%) as a
2
1
colorless oil. H NMR (300 MHz, CDCl ) δ 7.54 (dd, J = 1.7, 0.6 Hz, 1H), 6.97 (s, 2H), 6.52 (dd, J =
3
3
.2, 1.8 Hz, 1H), 6.30 (dd, J = 3.1, 0.5 Hz, 1H), 2.36 (s, 3H), 2.22 (s, 6H) ppm; LRMS (EI) m/z (%):
+
186 (100, M ), 171 (15), 157 (54), 142 (49).
General procedure for the coupling of diiodonaphthalene (2) and furans (4a-c) via indium
derivatives
nꢀBuLi xM in hexane (10.2 equiv) was added dropwise to a stirred solution of furan 4 (10.2 equiv) in
THF (0.6 M) at 0 ºC. After 30 min the mixture was carefully added over a suspension of InCl (3.4
3
equiv) in THF (0.2M) a ꢀ78 ºC. The mixture was stirred for 30 min and the temperature was slowly
raised until 25ºC. This solution was was added to a refluxing solution of 1,8ꢀdifurylnaphthalene (9, 1
equiv) and PdCl (dppf) (0.10ꢀ0.05 equiv) in THF (0.03 M) and the mixture was refluxed for 18h.
2
MeOH (1 mL) was added, the mixture was evaporated in vacuo and solved in ether. The solution was
washed with hydrochloric acid (5%), with aqueous saturated solution of NaHCO and brine. The
3
organic phase was dried over Na SO , filtered and evaporated in vacuo. The residue was
2
4
chromatographed in column (Al O or SiO ).
2
3
2
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1
,8-Difurylnaphthalene (1a). 647 mg, 95% yield, oil; H NMR (300 MHz, CDCl ) δ 7.92 (dd, J =
3
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
8
.1, 1.4 Hz, 2H), 7.66 (dd, J = 7.1, 1.4 Hz, 2H), 7.54 (dd, J = 8.1, 7.1 Hz, 2H), 7.17 (dd, J = 1.8, 0.7
1
3
Hz, 2H), 6.22 (dd, J = 3.3, 0.7 Hz, 2H), 6.13 (dd, J = 3.3, 0.8 Hz, 2H) ppm; C NMR (75 MHz,
CDCl ) δ 154.4 (2C), 141.5 (2CH), 135.0 (C), 130.2 (2CH), 129.3 (2CH), 128.8 (2C), 128.7 (C), 125.1
3
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
+
(2CH), 110.9 (2CH), 107.3 (2CH) ppm; LRMS (IE), m/z (%): 260 (M , 82), 231 (50) 203 (100).
HRMS (EI) calcd. for C H O : 260.0837, found: 260.0830.
1
8
12
2
1
1,8-Bis(5-(p-tolyl)furan-2-yl)naphthalene (1b). 647 mg, 75% yield, orange solid; mp 124ꢀ125 ºC; H
NMR (300 MHz, CDCl ) δ 7.95 (dd, J = 8.2, 1.2 Hz, 2H), 7.77 (dd, J = 7.1, 1.3 Hz, 2H), 7.58 (dd, J =
3
8.0, 7.2 Hz, 2H), 7.26 (d, J = 8.2 Hz, 4H), 6.97 (d, J = 7.9 Hz, 4H), 6.28 (d, J = 3.4 Hz, 2H), 6.26 (d, J
13
=
3.4 Hz, 2H), 2.27 (s, 6H) ppm; C NMR (75 MHz, CDCl ) δ 153.7 (2C), 153.2 (2C), 136.1 (2C),
3
1
1
35.2(C), 130.2 (2CH), 129.3 (2CH), 129.1 (2C), 128.7 (4CH), 128.5 (C), 128.0 (2C), 125.2 (2CH),
+
23.5 (4CH), 109.5 (2CH), 105.51 (2CH), 21.2 (2CH ) ppm. LRMS (EI) m/z (%): 440 (75, M ), 321
3
(38), 119 (100); HRMS (EI) calcd. for C H O : 440.1776, found: 440.1788.
32 24 2
1
1
,8-Bis(5-mesitylfuran-2-yl)naphthalene (1c). 196 mg, 99% Yield, orange solid, mp 173ꢀ175 ºC; H
NMR (300 MHz, CDCl ) δ 7.91 (dd, J = 8.2, 1.2 Hz, 2H), 7.79 (dd, J = 7.2, 1.2 Hz, 2H), 7.65ꢀ7.55
3
(dd, J = 8.0, 7.3 Hz, 2H), 7.01 (s, 4H), 6.16 (d, J = 3.3 Hz, 2H), 6.06 (d, J = 3.2 Hz, 2H), 2.38 (s, 6H),
13
2
.36 (s, 12H) ppm; C NMR (75 MHz, CDCl ) δ 152.5 (3C), 150.1 (3C), 138.1 (6C), 135.2 (2C),
3
129.2 (2CH), 128.4 (6CH), 128.2 (C), 128.0 (C), 125.2 (2CH), 111.3 (2CH), 110.2 (2CH), 21.1
+
(2CH ), 21.0 (4CH ) ppm; LRMS (EI) m/z (%): 496 (79, M ), 349 (11), 147 (100); HRMS (EI) calcd.
3
3
for C H O : 496.2402, found: 496.2399.
36 32
2
Synthesis of 1-iodo-8-furylnaphthalene (5). Using the general procedure for the indiumꢀpromoted
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couplings, but with a 1:1 molar ratio of furan (4a) and diiodonaphthalene (2) a mixture of 1a (33%
1
yield) and 5 (yellow oil, 103 mg, 32% yield) was obtained. H NMR (300 MHz, CDCl ) δ δ 8.26 (dd, J
3
= 7.3, 1.1 Hz, 1H), 7.90 (dd, J = 8.2, 1.6 Hz, 2H), 7.63 (dd, J = 5.7, 1.5 Hz, 2H), 7.49 (dd, J = 8.0, 7.3
13
Hz, 1H), 7.16ꢀ7.08 (m, 1H), 6.58 (dd, J = 3.2, 1.8 Hz, 1H), 6.49 (dd, J = 3.2, 0.6 Hz, 1H) ppm; C
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8
9
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8
9
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8
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0
1
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4
5
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7
8
9
0
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3
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8
9
0
NMR (75 MHz, CDCl ) δ 151.5 (C), 142.0 (CH), 141.8 (CH), 135.4 (C), 132.8 (C), 132.4 (CH), 131.0
3
(CH), 130.4 (C), 129.6 (CH), 126.8 (CH), 125.1 (CH), 112.1 (CH), 111.2 (CH), 91.4 (C) ppm; LRMS
+
(
EI) m/z (%): 320 (69, M ), 193 (29), 165 (100); HRMS (EI) calcd. for C H IO: 319.9698, found:
1
4
9
319.9699.
Synthesis of 2,5-bis(8-(furan-2-yl)naphthalen-1-yl)furan (7). nꢀBuLi (840 ꢁL, 2.43 M in hexane,
2.04 mmol) was added dropwise to a stirred solution of 1,8ꢀdifurylnaphthalene (1a, 530 mg, 2.04
mmol) in THF (10 ml) at 0 ºC, and the solution was stirred for further 30 min. The resulting solution
was slowly added to a suspension of InCl (149 mg, 2.04 mmol) in THF (5 ml) at ꢀ78 ºC and the
3
mixture was stirred for 30 min. The cooling bath was removed and when the solution reaches 25 ºC it
was added to a refluxing solution of 1ꢀiodoꢀ8ꢀfurylnaphthalene (5, 128 mg, 0.40 mmol) and
PdCl (dppf) (16 mg, 0.02 mmol) in THF (15 ml), and the mixture was refluxed for 15 h. Then MeOH
2
(
1 ml) was added, the solution was evaporated in vacuo and the residue solved in Et O. The ethereal
2
solution was successively washed with hydrochloric acid (5%), with a saturated solution of NaHCO3
and with brine, dried over anhydrous Na SO and evaporated in vacuo. The residue was purified by
2
4
column chromatography (Al O , hexano/CH Cl 9:1 a 1:1) to yield 7 (83 mg, 46%) as a white solid, mp
2
3
2
2
1
5
3ꢀ55 ºC. H NMR (300 MHz, CDCl ) δ 7.91ꢀ7.86 (m, 4H), 7.62ꢀ7.54 (m, 6H), 7.49 (dd, J = 8.0, 7.2
3
Hz, 2H), 7.08 (dd, J = 1.8, 0.8 Hz, 2H), 6.13 (dd, J = 3.3, 1.8 Hz, 2H), 6.06 (dd, J = 3.3, 0.8 Hz, 2H),
1
3
5
1
.94 (s, 2H) ppm; C NMR (75 MHz, CDCl ) δ 154.4 (2C), 153.0 (2C), 141.0 (2CH), 135.1 (2C),
3
30.1 (2CH), 129.9 (2CH), 129.1 (2CH), 128.9 (2CH), 125.1 (4CH), 110.7 (2CH), 109.4 (2CH), 107.6
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(
2CH) ppm; LRMS (EI), m/z (%): 452 (12, M ), 259 (31), 218 (58); HRMS (EI) calcd. for C H O :
3
2
20
3
3
4
5
6
7
8
9
1
1
1
1
1
1
1
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4
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4
4
5
5
5
5
5
5
5
5
5
5
6
4
52.1412, found: 452.1412.
Tandem [4+2]/[4+2] cycloadditions of bisfuran 1a and DMAD.
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Dimethylacetylenedicarboxylate (DMAD, 0.048 mL, 0.38 mmol) was added to a solution of 1,8ꢀ
difurylnaphthalene (1a, 100 mg, 0.38 mmol) in toluene (6 mL), and the mixture was refluxed for 6
days. Then the mixture was concentrated under reduced pressure. The residue was purified by column
chromatography (SiO , 9:1 to 1:1 hexane/EtOAc) to obtain compound 11 (12 mg, 8%) as a brown oil
2
and exo,exoꢀ8 (87 mg, 57%) as a brown solid.
1
1
Exo,exo-dimethyl 3,3a,3a ,4-tetrahydro-3,12b:4,6a-diepoxyperylene-3a,3a -dicarboxylate (8). mp
1
1
73ꢀ175 ºC; H NMR (400 MHz, CDCl ) δ 7.95 (dd, J = 8.3, 0.9 Hz, 2H), 7.78 (dd, J = 7.1, 1.1 Hz,
3
2
H), 7.56 (dd, J = 8.1, 7.2 Hz, 2H), 7.04 (d, J = 5.5 Hz, 2H), 6.86 (dd, J = 5.5, 1.7 Hz, 2H), 5.26 (d, J =
1
3
1.7 Hz, 2H), 3.70 (s, 3H), 3.34 (s, 3H) ppm; C NMR (100 MHz, CDCl ) δ 170.4 (C), 170.1 (C), 141.4
3
(2CH), 139.9 (2CH), 133.6 (C), 130.2 (2CH), 129.3 (C), 128.4 (2C), 128.1 (2CH), 125.8 (2CH), 90.2
(2C), 84.7 (2CH), 74.3 (C), 69.7 (C), 52.2 (CH ), 52.0 (CH ) ppm; LRMS (CI) m/z (%): 403 (M++1,
3
3
4
0), 399 (19), 371 (100); HRMS (CI) calcd. for C H O : 403.1182, found: 403.1174.
24 19 6
1
Dimethyl 3-(8-(furan-2-yl)naphthalen-1-yl)-6-hydroxyphthalate (11). H NMR (400 MHz, CDCl )
3
δ 10.79 (s, 1H), 7.94 (dd, J = 5.9, 2.7 Hz, 1H), 7.90 (dd, J = 8.2, 1.3 Hz, 1H), 7.50ꢀ7.45 (m, 3H), 7.33
(dd, J = 7.1, 1.3 Hz, 1H), 7.09 (dd, J = 1.8, 0.8 Hz, 1H), 7.05 (d, J = 8.6 Hz, 1H) 6.72 (d, J = 8.6 Hz,
1
H), 6.13 (dd, J = 3.2, 0.8 Hz, 1H), 6.03 (dd, J = 3.2, 1.8 Hz, 1H), 3.90 (s, 3H), 3.40 (s, 3H) ppm; 13C
NMR (100 MHz, CDCl ) δ 169.6 (C), 168.7 (C), 160.1 (2C), 153.0 (C), 141.2 (CH), 136.8 (CH),
3
1
35.8 (C), 134.8 (C), 133.3 (C), 132.1 (C), 131.2 (CH), 130.8 (CH), 130.6 (C), 130.0 (CH), 129.2
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(
CH), 124.9 (CH), 124.8 (CH), 117.7 (CH), 110.8 (CH), 109.8 (CH), 108.5 (C), 52.8 (CH ), 51.7 (CH )
3 3
ppm; LRMS (CI) m/z (%): 402 (M+, 35), 371 (100); HRMS (EI) calcd. for C H O : 402.1103,
2
4
18
6
found: 402.1106.
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General procedure for the tandem [4+2]/[4+2] cycloadditions of oligofuran derivatives 1 and
arynes
Finely powdered anhydrous CsF (1.5 mmol) was added to a solution of aryne precursor (0.5 mmol) and
1
,8ꢀdifurylnaphthalene (1a, 0.5 mmol) in MeCN (10 mL), and the mixture was stirred at r.t. for 24 h.
Then, CH Cl (10 mL) was added and the mixture was concentrated under reduced pressure. The
2
2
residue was purified by column chromatography (SiO ; 9:1 to 1:1 hexane/EtOAc), affording exo,exo
2
adducts.
1
Exo,exo-3b ,6,6a,7-tetrahydro-3b,6:7,11b-diepoxybenzo[a]perylene (15a). 194 mg, 99% yield,
1
yellowish solid, mp 177ꢀ179  C; H NMR (400 MHz, CDCl ) δ 8.03ꢀ7.98 (m, 2H), 7.94 (dd, J = 7.1,
3
0
.9 Hz, 1H), 7.82 (dd, J = 7.0, 1.0 Hz, 1H), 7.64ꢀ7.57 (m, 2H), 7.35 (m, 1H), 7.27ꢀ 7.19 (m, 3H), 6.77
(d, J = 5.6 Hz, 1H), 6.72 (dd, J = 5.6, 1.7 Hz, 1H), 5.45 (s, 1H), 5.23 (d, J = 1.6 Hz, 1H), 2.36 (d, J =
13
6.1 Hz, 1H), 2.34 (d, J = 6.1 Hz, 1H) ppm; C NMR (100 MHz, CDCl ) δ 148.5 (C), 147.7 (C), 140.3
3
(
CH), 139.9 (CH), 134.0 (C), 130.6 (C), 130.2 (CH), 130.1 (CH), 129.6 (C), 128.6 (CH), 128.2 (CH),
127.9 (C), 126.6 (2CH), 125.9 (CH), 125.8 (CH), 119.8 (CH), 119.7 (CH), 85.9 (C), 85.8 (C), 82.1
CH), 80.7 (CH), 53.5 (CH), 51.0 (CH) ppm; MS (EI), m/z (%): 336 (36), 307 (95), 289 (100); HRMS
calcd. for C H O ,: 336.1150, found: 336.1152.
(
2
4
16
2
Exo,exo-6,7-di-p-tolyl-3b1,6,6a,7-tetrahydro-3b,6:7,11b-diepoxybenzo[a]perylene (15b). 210 mg,
1
8
3% yield, yellowish solid, mp 188ꢀ190 ºC; H NMR (400 MHz, CDCl ) δ 8.09ꢀ8.02 (m, 3H), 7.88
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(dd, J = 7.0, 0.8 Hz, 1H), 7.68 (dd, J = 7.9, 7.4 Hz, 1H), 7.62 (dd, J =7.3, 7.2 Hz, 1H), 7.28ꢀ7.25 (m,
3
4
5
6
7
8
9
1
1
1
1
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1
1
H), 7.19 (t, J = 7.3 Hz, 1H), 7.12 (dt, J = 7.40, 0.7 Hz, 1H), 7.23ꢀ7.08 (m, 5H), 6.90 (d, J = 5.5 Hz,
H), 6.85 (d, J = 5.5 Hz, 1H), 6.73 (d, J = 8.0 Hz, 2H), 6.69 (d, J = 7.6 Hz, 2H), 3.09 (d, J = 6.0 Hz,
1
3
H), 2.86 (d, J = 6.0 Hz, 1H), 2.20 (s, 3H), 2.18 (s, 3H) ppm; C NMR (100 MHz, CDCl  δ 151.4 (C),
3
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2
3
4
5
6
7
8
9
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2
3
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9
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48.8 (C), 143.9 (CH), 141.0 (CH), 135.8 (C), 135.3 (C), 134.1 (C), 133.6 (C), 132.5 (C), 130.7 (C),
130.2 (CH), 130.1 (CH), 129.8 (C), 129.1 (CH), 128.7 (CH), 128.1 (2CH), 128.0 (2CH), 128.0 (C),
26.57 (CH), 126.55 (CH), 126.0 (2CH), 125.95 (CH), 125.89 (CH), 125.8 (2CH), 119.8 (CH), 119.4
CH), 93.0 (C), 90.3 (C), 85.6 (C), 84.8 (C), 57.9 (CH), 57.0 (CH), 21.0 (CH ), 20.9 (CH ) ppm;
1
(
3
3
+
LRMS (EI) m/z (%): 516 (10, M ), 397 (70), 276 (20), 119 (100); HRMS (EI) calcd. for C H O :
3
8
28
2
5
16.2089, found: 516.2091.
1
Exo,exo-6,7-dimesityl-3b ,6,6a,7-tetrahydro-3b,6:7,11b-diepoxybenzo[a]perylene (15c). 34 mg,
1
1
5% yield, white solid, mp 266 ºC (d); H NMR (400 MHz, CDCl )

δ δ 8.07ꢀ8.02 (m, 2H), 7.92 (dd, J
3
=
7.1, 1.1 Hz, 1H), 7.83 (dd, J = 7.00, 1.2 Hz, 1H), 7.69 (dd, J = 8.2, 7.2 Hz 1H), 7.63 (dd, J = 8.2, 7.1
Hz 1H), 7.33 (d, J = 5.6 Hz, 1H), 7.27ꢀ7.24 (m, 1H), 7.20 (dt, J = 7.2, 1.4 Hz, 1H), 7.11 (dd, J = 7.2,
1.0 Hz, 1H), 7.09ꢀ7.06 (m 1H), 6.92 (d, J = 5.6 Hz, 1H), 6.68 (s, 1H), 6.51 (s, 1H), 6.26 (s, 1H), 6.16
(
(
(
(
s, 1H), 3.71 (d, J = 6.0 Hz, 1H), 2.81 (d, J = 6.0 Hz, 1H), 2.57 (s, 3H), 2.39 (s, 3H), 2.27 (s, 3H), 2.11
1
3
s, 3H), 2.10 (s, 3 H), 2.09 (s, 3H) ppm; C NMR (75 MHz, CDCl ) δ 150.8 (C), 149.3 (C), 144.6
3
CH), 141.5 (CH), 139.3 (C), 137.7 (C), 135.3 (C), 135.1 (C), 134.6 (C), 133.7 (C), 132.5 (C), 131.4
CH), 130.8 (C), 130.7 (CH), 130.59 (C), 130.57 (C), 130.2 (C), 129.64 (CH), 129.62 (CH), 129.5
(CH), 129.2 (C), 128.7 (CH), 128.3 (CH), 128.1 (CH), 126.3 (CH), 125.9 (CH), 125.8 (2CH), 121.7
(CH), 119.6 (CH), 96.5 (C), 93.7 (C), 84.1 (C), 83.7 (C), 59.8 (CH), 55.1 (CH), 26.6 (CH ), 25.7
3
+
(CH ), 24.6 (CH ), 23.8 (CH ), 20.5 (CH ), 20.4 (CH ) ppm; LRMS (EI) m/z (%):572 (76, M ), 496
3
3
3
3
3
(27), 147 (100); HRMS (EI) calcd. for C H O : 572.2715, found: 572.2715.
4
2
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Exo,exo-9,10-difluoro-3b ,6,6a,7-tetrahydro-3b,6:7,11b-diepoxybenzo[y]perylene (34a). 396 mg,
1
53% yield, yellowish solid, mp 215ꢀ7 ºC (d); H NMR (500 MHz, CDCl ) δ 8.04 (d, J = 7.7 Hz, 1H),
3
8
.01 (d, J = 8.3 Hz, 1H), 7.88 (dd, J = 7.3, 1.2 Hz, 1H), 7.82 (dd, J = 7.1, 1.2 Hz, 1H), 7.64 (d, J = 8.6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
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4
5
6
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8
9
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8
9
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3
4
5
6
7
8
9
0
Hz, 1H), 7.61 (d, J = 8.5 Hz, 1H), 7.18 (dd, JH-F = 8.9, 6.8 Hz, 1H), 7.08 (dd, JH-F = 9.0, 6.7 Hz, 1H),
6.78 (d, J = 5.6 Hz, 1H), 6.74 (dd, J = 5.6, 1.7 Hz, 1H), 5.42 (s, 1H), 5.22 (d, J = 1.6 Hz, 1H), 2.41 (d,
13
J = 6.1 Hz, 1H), 2.39 (d, J = 6.2 Hz, 1H) ppm; C NMR (125 MHz, CDCl

δ 150.0 (d, JC-F = 12.9 Hz,
3
C), 148.03 (d, JC-F = 12.7 Hz, C), 144.2 (C), 143.8 (C), 140.3 (CH), 139.9 (C), 134.0 (CH), 130.5 (CH),
30.3 (C), 130.2 (CH), 129.3 (C), 128.4 (CH), 128.3 (CH), 127.0 (C), 126.0 (CH), 125.8 (CH), 109.9
1
(
d, JC-F = 20.2 Hz, CH), 109.7 (d, JC-F = 19.8 Hz, CH), 86.0 (C), 85.8 (C), 81.9 (CH), 80.2 (CH), 53.4
+
(CH), 51.0 (CH) ppm; LRMS (EI) m/z (%): 372 (M , 41), 354 (100), 325 (63), 288 (29); HRMS (EI)
calcd. for C H F O : 372.0962, found: 372.0953.
2
4
14
2
2
1
Exo,exo-9,10-difluoro-6,7-di-p-tolyl-3b ,6,6a,7-tetrahydro-3b,6:7,11b-diepoxybenzo[a]perylene
1
(
34b). 234 mg, 56% yield, yellowish solid, mp 224 ºC (d); H NMR (400 MHz, CDCl ) δ 8.09 (d, J =
3
8.3 Hz, 1H), 8.05 (d, J = 8.3 Hz, 1H), 7.98 (d, J = 7.0 Hz, 1H), 7.88 (d, J = 7.0 Hz, 1H), 7.69 (dd, J =
7
.9, 7.4 Hz, 1H), 7.63 (dd, J = 8.0, 7.3 Hz, 1H), 7.08 (dd, JH-F = 8.8 Hz, 6.9 Hz, 1H), 6.99ꢀ6.93 (m,
H), 6.91 (d, J = 5.5 Hz, 1H), 6.87 (d, J = 5.5 Hz, 1H), 6.83 (dd, JH-F = 9.0 Hz, 6.9 Hz, 1H), 6.75 (d, J
4
=
8.0 Hz, 2H), 6.68 (d, J = 7.6 Hz, 2H), 3.07 (d, J = 6.0 Hz, 1H), 2.84 (d, J = 6.0 Hz, 1H), 2.21 (s,
13
3
H), 2.17 (s, 3H) ppm; C NMR (100 MHz, CDCl  δ 149.2 (d, JC-F = 250 Hz, C), 149.0 (d, JC-F = 250
3
Hz, C), 147.5 (C), 144.02 (CH), 143.9 (C), 141.0 (CH), 136.02 (C), 135.80 (C), 134.1 (C), 133.2 (C),
31.7 (C), 130.6 (CH), 130.5 (C), 130.2 (CH), 129.5 (C), 128.9 (CH), 128.8 (CH), 128.3 (2CH), 128.1
1
(
2CH), 127.2 (C), 126.1 (CH), 126.0 (CH), 125.8 (4CH), 110.0 (d, JCꢀF = 18.3 Hz, CH), 109.4 (d, JCꢀF
=
1
9.5 Hz CH), 93.0 (C), 90.0 (C), 85.5 (C), 84.8 (C), 57.81 (CH), 56.94 (CH), 21.0 (CH ), 20.9 (CH )
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ppm; LRMS (EI) m/z (%): 552 (9, M ), 433 (36), 416 (12), 119 (100); HRMS (EI) calcd. for
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
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4
4
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5
5
5
5
5
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5
6
C H F O : 552. 1901, found: 552.1881.
38
26
2
2
1
Exo,exo-6,6a,7,9,10,11-hexahydro-3b H-3b,6:7,12b-diepoxyindeno[5,6-a]perylene (35). 107 mg,
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
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3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
8
2% yield, yellowish solid, mp 200 ºC (d); H NMR (300 MHz, CDCl ) δ 8.05ꢀ7.94 (m, 3H), 7.82 (d, J
3
= 7.0 Hz, 1H), 7.65ꢀ7.57 (m, J = Hz, 2H), 7.21 (s, 1H), 7.10 (s, 1H), 6.76 (d, J = 5.6 Hz,1H), 6.73 (dd,
J = 5.6, 1.6 Hz, 1H), 5.39 (s, 1H), 5.22 (d, J = 1.5 Hz, 1H), 2.97ꢀ2.80 (m, 4H), 2.42 (d, J = 6.1 Hz,
1
3
1H), 2.40 (d, J = 6.2 Hz, 1H), 2.18ꢀ2.06 (m, 2H) ppm; C NMR (75 MHz, CDCl  δ 147.1 (C), 146.3
3
(C), 142.53 (C), 142.51 (C), 140.2 (CH), 139.8 (CH), 134.0 (C), 130.6 (C), 130.02 (CH), 129.97 (CH),
1
29.7 (C), 128.6 (CH), 128.2 (C), 128.1 (CH), 125.8 (CH), 125.7 (CH), 116.2 (CH), 116.0 (CH), 85.85
(C), 85.6 (C), 82.0 (CH), 80.6 (CH), 53.8 (CH), 51.3 (CH), 32.71 (CH ), 32.62 (CH ), 25.70 (CH )
2
2
2
+
ppm; LRMS (EI) m/z (%): 376 (M , 22), 358 (100), 347 (62), 330 (37); HRMS (EI) calcd. for
C H O : 376.1463, found: 376.1462.
27 20
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Exo,exo-3b ,6,6a,7-tetrahydro-3b,6:7,12b-diepoxydibenzo[6,7:11,12]tetrafeno[2,3-d][1,3]dioxol
1
(36). 20 mg, 88% yield, yellowish solid, mp 160 ºC; H NMR (300 MHz, CDCl ) δ 8.02 (dd, J = 6.3,
3
1.4 Hz, 1H), 8.00 (dd, J = 6.3, 1.4 Hz, 1H), 7.93 (dd, J = 7.1, 1.2 Hz, 1H), 7.81 (dd, J = 7.0, 1.2 Hz,
1H), 7.64ꢀ7.58 (m, 2H), 6.87 (s, 1H), 6.77 (d, J = 5.7 Hz, 2H), 6.76 (s, 1H), 6.72 (dd, J = 5.6, 1.7 Hz,
1H), 6.01 (d, J = 1.4 Hz, 1H), 5.95 (d, J = 1.4 Hz, 1H), 5.35 (s, 1H), 5.19 (d, J = 1.7 Hz, 1H), 2.39 (d,
1
3
J = 6.1 Hz, 1H), 2.37 (d, J = 6.2 Hz, 1H) ppm; C NMR (75 MHz, CDCl  δ 146.2 (2C), 142.3 (C),
3
141.6 (C), 140.3 (CH), 139.9 (CH), 134.0 (C), 130.5 (C), 130.2 (CH), 130.1 (CH), 129.6 (C), 128.5
(CH), 128.2 (CH), 127.9 (C), 125.81 (CH), 125.79 (CH), 102.3 (CH), 102.0 (CH), 101.3 (CH ), 85.9
2
+
(C), 85.8 (C), 81.9 (CH), 80.6 (CH), 53.9 (CH), 51.3 (CH) ppm; LRMS (CI) m/z (%): 381 (M +1, 100),
3
63 (37), 347 (10); HRMS (CI) calcd. for C H O : 381.1127, found: 381.1127.
25 16 4
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Exo,exo-11-methoxy-3b ,6,6a,7-tetrahydro-3b,6:7,11b-diepoxybenzo[a]perylene (37). 21 mg, 5%
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yield, yellowish solid, mp 180 ºC (d); H NMR (300 MHz, CDCl

δ 7.99 (dd, J = 8.2, 1.2 Hz, 1H),
3
7
.98 (dd, J = 8.2, 1.2 Hz, 1H), 7.84 (dd, J = 7.2, 1.2 Hz, 1H), 7.79 (dd, J = 7.0, 1.2 Hz, 1H), 7.59 (dd, J
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0
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0
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0
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8
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0
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=
8.2, 7.2, Hz, 1H), 7.57 (dd, J = 8.2, 7.0, Hz, 1H), 7.23 (dd, J = 8.3, 7.2 Hz, 1H), 6.99 (d, J = 7.1 Hz,
1H), 6.790 (d, J = 8.2 Hz, 1H), 6.786 (d, J = 5.6 Hz, 1H), 6.70 (dd, J = 5.6, 1.7 Hz, 1H), 5.41 (s, 1H),
13
5
.20 (d, J = 1.7 Hz, 1H), 3.64 (s, 3H), 2.49 (d, J = 6.1 Hz, 1H), 2.40 (d, J = 6.1 Hz, 1H) ppm; C
NMR (75 MHz, CDCl  δ 152.8 (C), 150.8 (C), 140.03 (CH), 140.00 (CH), 133.7 (C), 133.6 (C), 130.5
3
(
CH), 130.1 (CH), 130.0 (C), 129.6 (CH), 129.5 (C), 128.9 (CH), 127.8 (CH), 127.7 (C), 125.5 (CH),
1
25.3 (CH), 112.5 (CH), 110.9 (CH), 86.3 (C), 86.1 (C), 81.9 (CH), 80.7 (CH), 55.2 (CH ), 53.8 (CH),
3
+
50.8 (CH) ppm; LRMS (EI) m/z (%):366 (M , 19), 348 (100), 305 (15); HRMS (EI) calcd. for
C H O : 366.1256, found: 366.1257.
25
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Exo,exo-3b ,6,6a,7-tetrahydro-3b,6:7,13c-diepoxynaphto[1,2-a]perylene (38a). 123 mg, 55% yield,
1
yellowish solid, mp 211 ºC (d); H NMR (500 MHz, CDCl

δ 8.04ꢀ7.99 (m, 3H), 7.91 (d, J = 8.3 Hz,
3
1H), 7.90 (d, J = 8.3 Hz, 1H), 7.82 (dd, J = 8.2, 1.2 Hz, 1H), 7.76 (d, J = 8.1 Hz, 1H), 7.64 (dd, J =
.1, 7.2 Hz, 1H), 7.61 (dd, J = 8.2, 7.6 Hz, 1H), 7.54 (dd, J = 6.9, 1.2 Hz, 1H), 7.47 (dd, J = 7.0, 1.1
Hz, 1H), 7.45 (d, J = 8.0 Hz, 1H), 6.76 (d, J = 3.9 Hz, 1H), 6.72 (dd, J = 5.6, 1.8 Hz, 1H), 5.97 (s, 1H),
8
13
5
.30 (d, J = 1.8 Hz, 1H), 2.44 (s, 2H) ppm; C NMR (125 MHz, CDCl ) δ 145.6 (C), 145.5 (C), 140.4
3
(
CH), 140.1 (CH), 134.1 (C), 132.8 (C), 130.6 (C), 130.2 (CH), 130.1 (CH), 129.7 (C), 128.9 (CH),
128.8 (CH), 128.3 (CH), 128.1 (C), 127.4 (CH), 126.7 (C), 126.6 (CH), 125.9 (CH), 125.8 (CH), 125.6
(
CH), 123.3 (CH), 118.5 (CH), 86.8 (C), 86.0 (C), 82.1 (CH), 79.3 (CH), 53.28 (CH), 52.4 (CH) ppm;
+
LRMS (EI) m/z (%): 386 (M , 33), 368 (100), 339 (51), 302 (20); HRMS (EI) calcd. for C H O :
28 18
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86.1307, found: 386.1307.
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Exo,exo-3b ,6,6a,7-tetrahydro-3b,6:7,13b-diepoxynaphtho[2,1-a]perylene (39a). 62 mg, 34% yield,
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yellowish solid, mp 189ꢀ191 ºC (d); H NMR (500 MHz, CDCl

δ 8.05 (d, J = 8.1 Hz, 1H), 8.04 (d, J
3
=
8.2 Hz, 1H), 7.88 (d, J = 8.0 Hz, 1H), 7.9 (d, J = 6.9 Hz, 1H), 7.83 (d, J = 6.9 Hz, 1H), 7.78 (d, J =
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.1 Hz, 1H), 7.64ꢀ7.56 (m, 2H), 7.54 (d, J = 8.1 Hz, 1H), 7.44 (d, J = 8.4 Hz, 1H), 7.36 (t, J = 7.4 Hz,
1H), 7.20 (t, J = 7.62 Hz, 1H), 6.80 (d, J = 5.6 Hz, 1H), 6.71 (d, J = 5.5 Hz, 1H), 5.57 (s, 1H), 5.21 (s,
13
1
H), 2.46 (d, J = 6.0 Hz, 1H), 2.41 (d, J = 6.0 Hz, 1H) ppm; C NMR (75 MHz, CDCl ) δ 146.9 (C),
3
143.4 (C), 126.7 (C), 140.4 (CH), 139.9 (CH), 134.0 (C), 133.5 (C), 130.5 (CH), 130.2 (2CH), 130.1
C), 129.7 (C), 129.0 (CH), 128.5 (C), 128.2 (CH), 128.1 (CH), 125.8 (CH), 125.7 (CH), 125.7 (CH),
(
1
25.0 (CH), 123.6 (CH), 118.3 (CH), 87.1 (C), 85.9 (C), 81.9 (CH), 80.8 (CH), 55.3 (CH), 50.9 (CH)
+
ppm; LRMS (EI) m/z (%): 386 (M , 69), 368 (158), 357 (100), 339 (87); HRMS (EI) calcd. for
C H O : 386.1307, found: 386.1316.
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Exo,exo-6,7-di-p-tolyl-3b ,6,6a,7-tetrahydro-3b,6:7,13c-diepoxynaphtho[1,2-a]perylene
(38b).
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3
5% yield (calculated by NMR), white solid; H NMR (500 MHz, CDCl
 8.12 (dd, J = 7.3, 1.1 Hz,
3
1H), 8.09 (dd, J = 7.3, 1.2 Hz, 1H), 7.99 (dd, J = 7.1, 1.1 Hz, 1H), 7.91 (dd, J = 7.0, 1.2 Hz, 1H), 7.86
d, J = 8.3 Hz, 1H), 7.71ꢀ7.62 (m, 3H), 7.48 (d, J = 8.4 Hz, 1H), 7.37 (ddd, J = 8.2, 6.8, 1.2 Hz, 1H),
.27ꢀ7.19 (m, 1H), 7.22 (d, J = 8.2 Hz, 1H), 7.07 (d, J = 7.7 Hz, 2H), 6.99 (d, J = 8.3 Hz, 2H), 6.94 (d,
(
7
J = 5.5 Hz, 1H), 6.86 (d, J = 5.5 Hz, 1H), 6.77 (d, J = 7.8 Hz, 2H), 6.69 (d, J = 7.8 Hz, 2H), 3.07 (d, J
13
=
6.0 Hz, 1H), 2.93 (d, J = 6.0 Hz, 1H), 2.23 (s, 3H), 2.19 (s, 3H) ppm; C NMR (100 MHz, CDCl ) δ
3
149.5 (C), 144.1 (CH), 143.6 (C), 141.1 (CH), 135.9 (C), 135.4 (C), 134.2 (C), 133.5 (C), 133.4 (C),
1
1
32.4 (C), 131.0 (CH), 130.3 (C), 130.22 (CH), 130.18 (CH), 129.8 (C), 129.0(CH), 128.60 (C),
28.57 (CH), 128.1 (3CH), 128.04 (2CH), 127.97 (CH), 126.5 (C), 126.3 (2CH), 125.8 (4CH), 125.1
(CH), 123.9 (CH), 118.2 (CH), 93.0 (C), 90.4 (C), 86.0 (C), 85.7 (C), 59.6 (CH), 57.0 (CH), 21.03
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