Unusual photocyclization of perfluoro cis-1,2-dimethyl-1,3-butadienyl benzenes as a means to synthesize partially fluorinated naphthalenes

Article abstract of DOI:10.1016/j.jfluchem.2015.09.016

Photoirradiation of the titled compounds perfluoro-cis-1,2-dimethyl-butadienyl benzenes (1), which were prepared in several steps from perfluorovinyl bromide, results in the formation of the corresponding novel naphthalene derivatives and 1,4-dihydronaphthalenes. Isolated 1,1,2-trifluoro-3,4-bis(trifluoromethyl)-1,4-dihydronaphthalene (3a) could be converted into 1,2-bistrifluoromethyl-3,4-difluoronaphthalene (2a) by base treatment (DABCO); however, 3a did not lead to 2a by photoreaction, suggesting 3a was not a possible photochemical precursor. Competitive photoreaction studies suggest that varying the substituent on benzene ring (e.g. methyl or trifluoromethyl) does not significantly affect the reaction rate. Presently, this reaction mechanism is not yet clearly understood.

Full text of DOI:10.1016/j.jfluchem.2015.09.016

Accepted Manuscript
Title: Unusual Photocyclization of Perfluoro
cis-1,2-Dimethyl-1,3-Butadienyl Benzenes as a means to
Synthesize Partially Fluorinated Naphthalenes
Author: Michiharu Yamamoto Dale C. Swenson Donald J.
Burton
PII:
S0022-1139(15)00292-4
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2015.09.016
FLUOR 8668
To appear in:
FLUOR
Received date:
Revised date:
Accepted date:
27-7-2015
21-9-2015
22-9-2015
Please cite this article as: M. Yamamoto, D.C. Swenson, D.J. Burton, Unusual
Photocyclization of Perfluoro cis-1,2-Dimethyl-1,3-Butadienyl Benzenes as a means to
Synthesize Partially Fluorinated Naphthalenes, Journal of Fluorine Chemistry (2015),
http://dx.doi.org/10.1016/j.jfluchem.2015.09.016
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

*Graphical Abstract - Pictogram
Graphical Abstract
Page 1 of 27

*Graphical Abstract - Synopsis
Graphical Abstract Synopsis
The preparation of perfluoro cis-1,2-dimethyl butadienyl copper reagent and
subsequent coupling with aryl iodides is described. Photocyclization of the
corresponding butadienyl benzenes give novel naphthalene derivatives and 1,4-
dihydronaphthalenes. Additionally, naphthalene derivatives are prepared by
treatment of 1,4-dihydronaphthalenes with DABCO.
Page 2 of 27

*Highlights (for review)
Research Highlights
1. The preparation of perfluoro cis-1,2-dimethyl butadienyl copper reagent.
2. Preparation of perfluoro cis-1,2-dimethyl butadienyl benzenes from copper
reagent and aryl iodides.
3. Photocyclization to give novel naphthalene derivatives and 1,4-
dihydronaphthalenes.
4. Naphthalene derivative prepared by treatment of 1,4-dihydronaphthalene
with DABCO.
Page 3 of 27

*Manuscript
Unusual Photocyclization of Perfluoro cis-1,2-Dimethyl-1,3-
Butadienyl Benzenes as a means to Synthesize Partially
Fluorinated Naphthalenes.
Michiharu Yamamoto, Dale C. Swenson, and Donald J. Burton*
Department of Chemistry, The University of Iowa, Iowa City, IA 52242, USA
------------------------------------------------------------------------------------------------------------
Abstract:
Photoirradiation of the titled compounds perfluoro-cis-1,2-dimethyl-butadienyl
benzenes (1), which were prepared in several steps from perfluorovinyl bromide,
results in the formation of the corresponding novel naphthalene derivatives and 1,4-
dihydronaphthalenes. Isolated 1,1,2-trifluoro-3,4-bis(trifluoromethyl)-1,4-
dihydronaphthalene (3a) could be converted into 1,2-bistrifluoromethyl-3,4-
difluoronaphthalene (2a) by base treatment (DABCO); however, 3a did not lead to
2a by photoreaction, suggesting 3a was not a possible photochemical precursor.
Competitive photoreaction studies suggest that varying the substituent on benzene
ring (e.g. methyl or trifluoromethyl) does not significantly affect the reaction rate.
Presently, this reaction mechanism is not yet clearly understood.
Keyword: Photocyclization, perfluoro-cis-1,2-dimethyl-butadienylbenzene,
1,2-difluoro-3,4-bis(trifluoromethyl)naphthalene, photoelimination of HF,
and 1,1,2-trifluoro-3,4-bis(trifluoromethyl)-1,4-dihydronaphthalene.
*Corresponding author. Tel.: +1 319 335 1363. Fax: +1 319 335 1270.
E-mail address: mburton105@gmail.com (D.J. Burton).
----------------------------------------------------------------------------------------------------------
1. Introduction
We have reported that trifluoromethylcopper [1], F-vinyl copper [2,3], and F-
acetylenic copper [4] reagents could be readily obtained via copper(I) halide
metathesis reaction of the corresponding cadmium or zinc reagent (Eq. 1). These
1
Page 4 of 27

reagents have found extensive utility in preparative organofluorine chemistry [5].
Terminal F-vinyl copper reagents added to perfluoroalkynes can give extended
dienyl copper reagents, which could be functionalized via coupling reactions (Eq. 2)
[6, 7]. The reaction of F-dienyl copper reagents with aryl halides generates coupled
products (Eq. 3) [6, 7, 8, 9]. We focused on perfluoro cis-1,2-dimethyl butadienyl
benzenes (1) which could be readily prepared from perfluoro-1,3-butadienyl copper
(6) reagents (Scheme 1).
Scheme 1. Synthesis of perfluoro cis-1,2-dimethyl butadienyl benzenes (1)
2. Results and Discussion
Preparation of 1 was carried out by the method [6] shown in Table 1. These
transformations were carried out by the one-pot reaction under N2 atmosphere.
Conversion of 5 to 6 was done at room temperature and the yield was calculated by
19F-NMR spectroscopy using an internal trifluoromethyl benzene standard. In the
conversion of 6 to 1, a variety of functionalized aryl iodides were added (mole ratio
2
Page 5 of 27

0.70 equivalent) to the copper reagent 6 and reaction mixtures were heated at 80-
90 °C overnight. After reaction, compounds of general structure 1 were isolated by
silica gel chromatography. The resultant benzenes 1 in hexane were photolyzed
using a Rayonet reactor at 254nm in a quartz tube at 30-40 °C under degassed
conditions (Scheme 2).
Table 1. Preparation of perfluoro-cis-1,2-dimethyl-butadienyl benzenes 1
Entry
1a
Aryl Iodide
1
Yielda
76%
1b
1c
1d
1e
83%
87%
86%
91%
3
Page 6 of 27

1f
52%
aIsolated yields based on aryl-iodide
Scheme 2. Synthesis of 1,1,2-trifluoro-3,4-bis(trifluoromethyl)-1,4-
dihydronaphthalene (3) and 1,2-bistrifluoromethyl-3,4-difluoronaphthalene (2)
In the case of p-substituted perfluoro cis-1,2-dimethyl butadienyl benzenes
1a-d, photolysis of 1 leads to the unusual intramolecular cyclization and two
principal products are obtained (Table 2). In these reactions, the 1,4-
dihydronaphthalene derivatives 3a-d were the minor photocyclization products.
The predominant naphthalene derivatives 2a-d were obtained after
photocyclization accompanied by photoelimination of HF.
Table 2. Photoreaction of p-substituted perfluoro-cis-1,2-dimethyl-butadienyl
benzenes 1a-d.
Entry
Yielda (%)
1
2a-d
3a-d
unknown
4
Page 7 of 27

a
46 (65)
53 (64)
50 (59)
59 (67)
19 (29)
26 (29)
24(25)
14 (27)
(6)
(7)
b
c
(16)
(6)
d
aIsolated yields (GC yields)
The formation of naphthalene derivatives 2a-d and 1,4-dihydronaphthalenes
3a-d were confirmed via GC-MS and NMR spectra analysis of isolated compounds
(Table 3 and 4).
Table 3. Selected NMR data of isolated p-naphthalene compounds 2a-d.
Entry
19F-NMR
2a
ppm
Hz
Jbc
34
34
32
32
Z
H
CF3
OCH3
Cl
Fa (3F)
-51.4(q)
-51.4(q)
-51.3(q)
-51.5(q)
Fb (3F)
Fc (1F)
Fd (1F)
Jab
17
16
16
16
Jcd
17
17
16
18
-54.1(qd)
-54.4(qd)
-53.7(qd)
-54.2(qd)
-138.7(qd)
-139.6(qd)
-142.2(qd)
-140.1(qd)
-142.6(d)
-136.4(d)
-140.3(d)
-138.2(d)
2b
2c
2d
ppm
Hz
J1,2
1H-NMR
Z
H1
H2
H3
H4
5
Page 8 of 27

2a
2b
2c
2d
H
CF3
OCH3
Cl
7.7-8.2 (4H)
8.5 (1H, d)
8.0 (1H, d)
8.5 (1H, d)
-
7.9 (1H, d)
7.1 (1H, d)
8.2 (1H, d)
-
-
-
8.5 (1H, s)
7.1 (1H, s)
8.0 (1H, s)
8
8
9
ppm
Hz
2J3,F
14
14
14
14
13C-NMR
2a
Z
H
CF3
OCH3
Cl
C1
C3
C4
2J1,F
1J3,F
258
263
257
261
1J4,F
2J4,F
14
14
14
14
123.7(q)
126.6(q)
123.3(q)
124.1(q)
144.3(dd)
148.8(dd)
144.3(dd)
147.3(dd)
148.8(dd)
144.7(dd)
147.1(dd)
144.6(dd)
34
39
36
32
255
262
256
259
2b
2c
2d
Table 4. Selected NMR data of isolated 1,4-dihydronaphthalene compounds 3a-d.
Entry
19F-NMR
3a
ppm
Fc (1F)
Hz
Z
H
CF3
OCH3
Cl
Fa (3F)
-60.7(d)
-60.8(d)
-60.7(d)
-60.8(d)
Fb (3F)
-69.6(s)
-69.3(s)
-69.9(s)
-69.6(s)
Fd (1F)
Fe (1F)
Ja,H5
7
7
6
6
Jcd
-114.9(m)
-114.2(m)
-115.6(m)
-114.7(m)
ppm
-85.3(dd)
-85.5(dd)
-85.4(dd)
-85.5(dd)
-101.3(dd)
-101.3(dd)
-101.3(dd)
-101.3(dd)
304
306
304
304
3b
3c
3d
Hz
1H-NMR
3a
Z
H
CF3
OCH3
Cl
H1
H2
H3
H4
H5
J1,2
-
8
9
8
J1,Fa
7
7
6
6
7.9-7.5(4H)
7.9(1H, d)
7.4 (1H, d)
7.6 (1H, d)
ppm
4.6(1H, q)
4.6(1H, q)
4.5(1H, q)
4.5(1H, q)
3b
3c
3d
7.7 (1H, d)
7.1 (1H, d)
7.4 (1H, d)
-
-
-
8.1 (1H, s)
7.3 (1H, s)
7.8 (1H, s)
Hz
13C-NMR
3a
Z
H
CF3
C1
C2
C3
C4
C5
2J1,F
31
31
31
31
1J3,F
294
294
294
294
1J4,F
236
235
239
239
43.7(q) 111.1(m) 156.7(dt) 109.9(td)
43.8(q) 111.1(m) 156.4(dt) 109.3(td)
OCH3 43.2(q) 111.1(m) 156.7(dt) 109.7(td)
Cl 43.7(q) 111.1(m) 156.7(dt) 109.4(td)
131.0(t)
132.1(t)
132.2(t)
133.4(t)
3b
3c
3d
The 19F-NMR spectrum of the naphthalene derivatives showed the resonance
of the two fluorines and two trifluoromethyl groups instead of the three vinyl
fluorines and two trifluoromethyl groups which were observed in the staring
compounds 1a-d. The coupling patterns of the two aryl fluorines (doublet, J = 16-18
Hz and quartet-doublet, J = 32-34, 16-18 Hz) and the two trifluoromethyl groups
6
Page 9 of 27

(quartet, J = 16-17 Hz, and doublet-quartet, J = 32-34, 16-17 Hz) supported these
naphthalene structures (Table 3).
In contrast, 19F-NMR spectra of 1,4-dihydronaphthalene derivatives 3a-d
exhibited a fluorine, difluoromethylene, and two trifluoromethyl groups (Table 4).
Splitting of methylene H5 into a quartet (3JH5,F = 6-7 Hz) in the 1H-NMR spectrum
and splitting of C1 (2JC1,F = 31 Hz) in the 13C-NMR spectrum supports the assigned
structures. The existence of three (3b-d) or four (3a) aromatic protons, excluding
H5 (since no structures could be written without breaking aromaticity), provides
further support.
To our knowledge, only two examples of photocyclizations which are
accompanied by HF photoelimination have been reported. Although the reaction
mechanism are not clearly understood, Fokin and coworkers [10] found that N-
methyl-2,3,4,5-tetrafluoro diphenyl amine was converted to 2,3,4-trifluoro-9-methyl
carbazole with HF photoelimination. Mallory [11] also found that 1-
fluoro[5]helicenes proceed through HF photoelimination in their conversion to
benzo[ghi]perylene. An NMR study of this compound was independently carried out
by Gorsane [12].
The treatment of isolated 3a with 1,4-diazabicyclo[2.2.2]octane base (DABCO),
resulted in the naphthalene derivative 2a (Scheme 3). Photolysis of 3a, however,
does not afford 2a, implicating an intermediate other than 3a as the photochemical
precursor to 2a.
Scheme 3. HF elimination of 3a to 2a with use of DABCO
7
Page 10 of 27

The photolysis of 1,4-bis(perfluoro cis-1,2-dimethyl-1,3-butadienyl) benzene 1f
leads to multiple products. Among them, two major products, anthracene (7) and
phenanthrene (8) could be isolated (Scheme 4). In this reaction, phenanthrene 8 is
the favored product, although for reasons unclear. In conjunction with various
analytical data (e.g. NMR), X-ray crystal analysis data (Fig. 1) also assisted in the
assignment of chemical structures. From X-ray analysis, phenanthrene derivative 8
has a twisted structure (twisted angle of 8 is 27° between ring A and C), while
anthracene derivative 7 has a planar structure [13].
Scheme 4. Photolysis of 1f to lead 7 and 8.
Figure 1. Crystal Sturture of a) 7 and b) 8.
8
Page 11 of 27

Photolysis of m-methyl substituted benzene 1e was carried out under similar
conditions and generates four major products (Scheme 5). The obtained products
could not be completely separated due to extremely close boiling points and similar
TLC behavior. However, the naphthalene derivatives and 1,4-dihydronaphthalene
derivatives could be separated as mixtures of 2e/2e’ and 3e/3e’.
Scheme 5. Photoreaction of m-CH3 substituted 1e.
From the NMR spectrum and GC yields, the mixture of naphthalene
derivatives 2e/2e’ consisted of 40% 2e and 60% 2e’. Having similar 19F-NMR
spectra (Table 5), compounds 2e and 2e’ were differentiated on the basis of the
respective H4 coupling patterns in the 1H-NMR. For the methyl H4 protons,
compound 2e’ exhibited a singlet, while the 2e methyl 4H protons were split into a
doublet by the adjacent Fd ( JH4-Fd = 8 Hz).
9
Page 12 of 27

Table 5. NMR data of m-naphthalene mixtures 2e and 2e’.
Entry
19F-NMR
2e
ppm
Hz
Fa (3F)
-51.4(m)
-51.4(m)
Fb (3F)
-54.2(m)
-54.0(m)
Fc (1F)
Fd (1F)
-129.7(bs)
-139.2(d)
Jbc
34
34
Jcd
14
18
-143.0(qd)
-144.1(qd)
2e’
ppm
Hz
J4,Fd
8
0
1H-NMR
2e
H1-3
7.4-7.9 (3H, m)
7.4-7.9 (3H, m)
H4
2.8 (d)
2.8 (d)
2e’
Lack of diagnostic difference in the NMR spectra prevented the direct
assignment of either 3e or 3e’ as the major component in the observed 3/7 ratio.
However, a mixture of the 3e/3e’ was converted to a 3/7 mixture of the 2e/2e’ by
treatment with diazabicycloundecene (DBU) in CDCl3 (Scheme 6). The 19F-NMR
spectrum of the reaction mixture was consistent with the structures 2e and 2e’.
Thus, the conversion of 1,4-dihydronaphthalene derivatives to the naphthalene
derivatives provided the structural confirmation and facilitated determination of
the 3e/3e’ ratio (Table 6).
Table 6. NMR data of 1,4-dihydronaphthalene mixtures 3e and 3e’.
Entry
19F-NMR
ppm
Hz
Jce
Fa (3F) or Fb (3F)
Fc (1F)
Fd (1F) or Fe (1F)
Jcd
Jde
10
Page 13 of 27

3e
3e’
-60.9(m) -69.9(s)
-60.9(m) -69.6(s)
-115.4(m)
-115.1(m)
-93.8(dd)
-84.9(dd)
-95.8(dd)
-101.1(dd)
22
23
14
13
309
303
ppm
Hz
1H-NMR
3e
H1-3
7.3-7.7(3H, m)
7.3-7.7(3H, m)
H4
H5
2.6 (1H, m)
2.4 (1H, s)
4.5 (1H, m)
4.4 (1H, m)
3e’
Scheme 6. Conversion of the mixture 3e/3e’ into 2e/2e’.
To probe the photoreaction mechanism, we initially hypothesized the
involvement of electrophilic attack on the benzene ring and that this step might be
slowest and rate determining. As a consequence, we expect that reaction rates
would be sensitive to the nature of the substituent on the benzene ring. That is,
electron-donating groups should enhance reaction rate through stabilization of the
intermediate cation while electron-withdrawing groups slow the reaction rate
through destabilization. Competitive photoreaction studies were carried out
between several perfluoro cis-1,2-dimethyl butadienyl benzenes 1. Direct
competition between non-substituted benzene 1a and m-methyl-substituted
benzene 1e, however resulted in little difference in reaction rate, suggesting that the
methyl inductive effect contributed insignificantly to the reaction rate. Similarly,
competition between p-trifluoromethyl-substituted benzene 1b and non-
substituted 1a resulted in no significant decrease in reaction rate. The failure of
both p-trifluoromethyl 1b and m-methyl 1e to significantly influence reaction rate
was inconsistent with a mechanism in which electrophilic attack was rate
11
Page 14 of 27

determining. Additional detailed studies are required to elucidate other mechanistic
pathways (i.e. radical).
Figure 2. Competitive photolysis of 1a (dash, ---) and 1e (m-CH3, solid, -).
Formation of 1,4-
dihydronaphthalenes 3a & 3e/3e’
Consumption of 1a & 1e
Formation of Naphthalenes 3a &
Figure 3. Competitive photolysis of 1a (dash, ---) and 1b (p-CF3, solid, -).
Formation of 1,4-
dihydronaphthalenes 3a & 3b
Formation of Naphthalenes 3a & 3b
Consumption of 1a & 1b
3. Experimental
3.1
General experimental procedures
Routine 19F-NMR spectra were recorded on a JEOL FX90Q Spectrometer
(83.81 MHz) and high-resolution data was obtained on a Bruker AC-300
Spectrometer (282.41 MHz). Chemical shifts have been reported in ppm relative to
internal CFCl3. Spectra of reaction mixtures were obtained in the 7Li external lock
12
Page 15 of 27

mode. Quantitative determinations were carried out by integration relative to
internal benzotrifluoride. Routine 1H-NMR (300.17 MHz) spectra and high-
resolution data were generally obtained on a Bruker AC-300 Spectrometer. Unless
noted otherwise, CDCl3 was used as the NMR lock solvent. Chemical shifts have been
reported in ppm relative to internal TMS. High resolution {1H} 13C NMR spectra
were recorded on a Bruker AC-300 Spectrometer (75.48 MHz). Chemical shifts have
been reported in ppm relative to internal TMS. High-resolution mass spectra were
obtained by the University of Iowa High Resolution Mass Spectrometry Facility.
Photolysis experiments were preformed in a Rayonet Reactor with 254nm bulbs.
Analytical GLPC were performed on a Hewlett–Packard Model 5890 equipped with a
thermal conductivity detector and 3393A integrator. The column was packed with
5% OV-101 on chromo- sorb P. UV measurements (hexane) were made with a
Hewlett-Packard 8452A diode array spectrophotometer. All boiling points were
determined during fractional distillation using a partial immersion thermometer
and are uncorrected. 4 Å molecular sieves (Fisher) were activated by heating under
vacuum (300 °C at 0.5 mm Hg) overnight. DMF was dried overnight over CaH2 and
then distilled at reduced pressure. Silica gel was purchased from EM Science (Silica
Gel 60, particle sized 0.063-0.200 μm, 70-230 Mesh, ASTM). CuBr was purified by
the method reported by Morken [14]. Hexafluorobutyne can be prepared by the zinc
dehalogenation of CF3CCl2CCl2CF3 or purchased from PCR Specialty Chemicals.
Bromotrifluoroethylene (Halocarbon), DBU, DABCO, and substituted aryl iodides
were obtained from commercial sources and used without further purification.
13
Page 16 of 27

3.2
Activation of Zinc Powder
Zinc powder (70 g) was suspended in 200 mL of water and 3 mL of conc. HCl
was added dropwise. After stirring for 15 min, the precipitate was washed with
water (3 x 500 mL). The zinc powder was then dried under vacuum for 3 h.
3.3
Preparation of CF2=CFCu (5),
An oven-dried one-liter 3-necked flask, equipped with a dry ice/IPA
condenser, N2 inlet, septum port, and magnetic stirring bar, was charged with
activated Zn powder (19 g, 290 mmol) and dry DMF (300 mL). Then
trifluorobromoethylene (16 g, 100 mmol) was then slowly added into this solution.
The resultant mixture was gently heated with a heat gun until an exothermic
reaction (50-60 °C) occurred. Additional trifluorobromoethylene (32 g, 200 mmol)
was then condensed into the solution, maintaining the internal temperature for an
additional 3 h, and then unreacted olefin was removed by vacuum. The NMR yield
of CF2=CFZnBr was 62%. A 1000 mL two-necked flask, equipped with dry ice-IPA
condenser, N2 inlet, and septum port was charged with CuBr (29.4 g, 192 mmol). To
this flask, the CF2=CFZnBr/DMF solution (0.62 M, 300 mL, 186 mmol) was
transferred by syringe. The reaction mixture was stirred for 20 min at room
temperature and then check by 19F NMR to verify formation of the copper reagent
[15]. CF2=CFZnBr: 19F NMR (83.9 MHz, JEOL FX-90Q, DMF) -94.7 ppm (dd, 1F, cis-
CF=CF2, Fa), -128.9 ppm (dd, 1F, trans-CF=CF2, Fb), -193.3 ppm (dd, 1F, CF=CF2, Fc),
(Jab = 93 Hz, Jac = 34 Hz, Jbc = 105 Hz). CF2=CFCu: 19F NMR (83.9 MHz, JEOL FX-90Q,
DMF) -96.1 ppm (dd, 1F, cis-CF=CF2, Fa), -131.3 ppm (dd, 1F, trans-CF=CF2, Fb), -
182.8 ppm (dd, 1F, CF=CF2, Fc), (Jab = 100 Hz, Jac = 32 Hz, Jbc = 100 Hz).
14
Page 17 of 27

3.4
Preparation of CF2=CF-C(CF3)=C(CCF3)Cu (6),
F-2-butyne (33.0 g, 206 mmol) was slowly condensed into the above copper
DMF solution of 5 at 0 °C. The reaction mixture was stirred for 3 h at room
temperature. The NMR yield (based on CF2=CFZnBr) was quantitative. 19F NMR
(83.9 MHz, JEOL FX-90Q, DMF) -53.5 ppm (bs, 3F, CF3, Fa), -58.2 ppm (q, 3F, CF3,
Fb), -102.5 ppm (dd, 1F, cis-CF=CF2, Fc), -115.8 ppm (dd, 1F, trans-CF=CF2, Fd), -
158.5 ppm (dd, 1F, CF=CF2, Fe), (Jcd = 73 Hz, Jce = 28 Hz, Jde = 117 Hz).
3.5
Preparation of Z-1,1,2,5,5,5-hexafluoro-4-aryl-3-trifluoromethyl-1,3-
pentadiene derivatives (1a-f).
A 250 mL two-necked flask, equipped with magnetic stirrer and septum port
was charged with copper compound 6 (42 mL, 26 mmol). Then aryl iodine (18
mmol) was added at once and the solution was heated with an oil bath to 70-80°C
and stirred for 16 h under N2. The cooled reaction mixture was poured into water
(50 mL) and ether (100 mL). The ether layer was washed with water (2 x 50 mL)
and dried over anhydrous MgSO4. After filtration, a rotary evaporator removed the
solvent. The crude mixture was purified via silica gel (70-230 mesh)
chromatography (hexane). Yields are also shown in Table 1.
1a: Yield 5.8 g (76%); GLPC purity 97%; 19F NMR (CDCl3) -59.6 ppm (q, 3F, -CF3, Fa),
-60.3 ppm (q, 3F, -CF3, Fb), -99.1 ppm (dd, 1F, cis-CF=CF2, Fc), -111.9 ppm (dd, 1F,
trans-CF=CF2, Fd), -165.4 ppm (dd, 1F, -CF=CF2, Fe), (Jab = 13 Hz, Jcd = 61 Hz, Jce = 32
Hz, Jde = 117 Hz); 1H NMR (CDCl3) 7.2-7.4 ppm (m, 5H); 13C {1H} NMR (CDCl3) 153.2
ppm (ddd, -CF=CF2, 1JCF = 294 Hz, 280 Hz, 2JCF = 46 Hz), 148.3 ppm (q, ϕ-C(CF3)=C,
2JCF = 32 Hz), 131.9 ppm (s), 130.8 ppm (s), 129.1 ppm (s), 128.1 ppm (s), 126.2 ppm
(m, -C(CF3)=C(CF3)-CF), 122.4 ppm (ddd, -CF=CF2, 1JCF = 236 Hz, 2JCF = 54 Hz, 24 Hz),
121.1 ppm (q, -CF3, 1JCF = 275 Hz), 120.9 ppm (q, -CF3, 1JCF = 275 Hz); GC-MS 320 (M+,
15
Page 18 of 27

13), 300 (M+-HF, 17), 281 (13), 251 (100), 231 (42), 201 (83), 182 (74), 151 (37);
HRMS (C12H5F9, calculated: 320.0248, observed: 320.0244); UV (cyclohexane) c =
3.29x10-4, λmax = 206 nm (A = 1.910, ε = 5800), λ = 230 nm (A = 1.360, ε = 4100),
257 nm (A = 1.550, ε = 4700), 280 nm (A = 1.650, ε = 5000); FT-IR (cm-1, CCl4) 3080
(w, C-H), 1795 (s, -CF=CF2), 1630 (m), 1446 (s), 1321 (s), 1291 (s), 1238 (s), 1214
(s), 1195 (s) 1182 (s), 1172 (s), 1132 (s), 871 (m), 843 (m), 710 (m).
1b: Yield 83%; GLPC purity 97%; 19F NMR (CDCl3) -59.7 ppm (q, 3F, -CF3, Fa), -60.1
ppm (q, 3F, -CF3, Fb), -63.7 ppm (s, 3F, ϕ-CF3, Fc), -97.0 ppm (dd, 1F, cis-CF=CF2, Fd),
-111.0 ppm (dd, 1F, trans-CF=CF2, Fe), -165.9 ppm (dd, 1F, -CF=CF2, Ff), (Jab = 13 Hz,
Jde = 59 Hz, Jdf = 32 Hz, Jef = 118 Hz); 1H NMR (CDCl3) 7.7 ppm (d, 2H, 3JHH = 8 Hz) 7.4
ppm (d, 2H, 3JHH = 8 Hz); 13C {1H} NMR (CDCl3) 152.7 ppm (ddd, -CF=CF2, 1JCF = 294
Hz, 280 Hz, 2JCF = 45 Hz), 146.1 ppm (m, ϕ-C(CF3)=C), 138.1 ppm (s), 134.8 ppm (s),
132.7 ppm (q, -C(CF3), 2JCF = 33 Hz), 127.4 ppm (q, -CF3, 1JCF = 266 Hz), 125.9 ppm
(s), 123.5 ppm (q, -CF3, 1JCF = 272 Hz), 121.5 ppm (m, -CF=CF2), 120.7 ppm (q, -CF3,
1JCF = 266 Hz); GC-MS 388 (M+, 5), 369 (M+-F, 16), 319 (70), 299 (34), 269 (77), 250
(100), 219 (59), 200 (71) HRMS (C13H4F12, calculated: 388.0121, observed:
388.0121); UV (cyclohexane) c = 1.93x10-4, λmax = 212 nm (A = 1.244, ε = 6400), λ =
244 nm (A = 0.607, ε = 3100), 268 nm (A = 0.560, ε = 2900); FT-IR (cm-1, CCl4) 1795
(s, -CF=CF2), 1730 (m, C=C), 1500 (w), 1440 (w), 1324 (s) 1292 (s), 1241 (s), 1214
(s), 1194 (s), 1178 (s), 1144 (s), 1078 (m), 723 (m).
1c: Yield 87%; GLPC purity 96%; 19F NMR (CDCl3) -59.5 ppm (q, 3F, -CF3, Fa), -60.4
ppm (q, 3F, -CF3, Fb), -99.5 ppm (dd, 1F, cis-CF=CF2, Fc), -112.3 ppm (dd, 1F, trans-
CF=CF2, Fd), -164.9 ppm (dd, 1F, -CF=CF2, Fe), (Jab = 12 Hz, Jcd = 61 Hz, Jce = 32 Hz, Jde
= 117 Hz); 1H NMR (CDCl3) 7.2 ppm (d, 2H), 6.9 ppm (d, 2H), 3.8 ppm (s, 3H); 13C
{1H} NMR (CDCl3) 161.8 (s), 153.2 ppm (ddd, -CF=CF2, 1JCF = 294 Hz, 280 Hz, 2JCF = 46
Hz), 148.8 ppm (q, ϕ-C(CF3)=C, 2JCF = 34 Hz), 129.9 ppm (s), 125.2 ppm (m, -
C(CF3)=C(CF3)-CF), 124.0 ppm (s), 123.0 ppm (ddd, -CF=CF2, 1JCF = 236 Hz, 2JCF = 55
Hz, 26 Hz), 121.2 ppm (q, -CF3, 1JCF = 274 Hz), 121.0 ppm (q, -CF3, 1JCF = 275 Hz),
114.5 ppm (s), 55.3 ppm (s); GC-MS 351 (M++1, 17), 332 (M+-F, 9), 282 (100), 231
(30), 212 (19), 169 (24); HRMS (C13H7F9O, calculated: 350.0353, observed:
350.0346); UV (cyclohexane) c = 3.86x10-4, λmax = 226 nm (A = 2.267, ε = 5000), λ =
310 nm (A = 1.143, ε = 3000); FT-IR (cm-1, CCl4) 3010 (m), 2962 (m), 2938 (m),
2912(m), 2842 (m), 1787 (s, -CF=CF2), 1609 (s, C=C), 1513 (s), 1464 (m), 1443 (s),
1419 (s), 1351 (s), 1320 (s), 1290 (s), 1256 (s), 1239 (s), 1214 (s), 1194 (s), 1173
(s), 1132 (s), 874 (s), 828 (s).
1d: Yield 86%; GLPC purity 98%; 19F NMR (CDCl3) -59.6 ppm (q, 3F, -CF3, Fa), -60.3
ppm (q, 3F, -CF3, Fb), -98.1 ppm (dd, 1F, cis-CF=CF2, Fc), -111.5 ppm (dd, 1F, trans-
CF=CF2, Fd), -165.6 ppm (dd, 1F, -CF=CF2, Fe), (Jab = 13 Hz, Jcd = 61 Hz, Jce = 32 Hz, Jde
= 118 Hz); 1H NMR (CDCl3) 7.4 ppm (d, 2H, 3JHH = 8 Hz), 7.2 ppm (d, 2H, 3JHH = 8 Hz);
13C {1H} NMR (CDCl3) 153.1 ppm (ddd, -CF=CF2, 1JCF = 295 Hz, 280 Hz, 2JCF = 46 Hz),
147.2 ppm (q, ϕ-C(CF3)=C, 2JCF = 34 Hz), 137.5 ppm (s), 130.2 ppm (s), 129.8 ppm
(s), 129.6 ppm (s), 126.3 ppm (m, -C(CF3)=C(CF3)-CF), 122.2 ppm (ddd, -CF=CF2, 1JCF
= 238 Hz, 2JCF = 53 Hz, 26 Hz), 120.8 ppm (q, -CF3, 1JCF = 275 Hz), 120.8 ppm (two
16
Page 19 of 27

peak overlapping, q, -CF3, 1JCF = 275 Hz); GC-MS 356 (M++2, 6), 354 (M+, 16), 319
(M+-Cl, 97), 287 (23), 285 (78), 269 (78), 250 (100), 235 (41), 200 (50); HRMS
(C12H4F9Cl , calculated: 353.9858, observed: 353.9854); UV (cyclohexane) c =
4.24x10-4, λmax = 220 nm (A = 1.526, ε = 3600), λ = 258 nm (A = 0.587, ε = 1380), λ
= 284 nm (A = 0.568, ε = 1340); FT-IR (cm-1, CCl4) 1780 (s, -CF=CF2), 1620 (w), 1595
(m), 1492 (m), 1351 (s), 1320 (s), 1291 (s), 1285 (s), 1266 (s), 1241 (s), 1233 (s),
1222 (s), 1212 (s), 1192 (s), 1182 (s), 1176 (s), 1163 (s), 1152 (s), 1134 (s), 1095
(s), 1019 (m), 872 (m), 820 (m).
1e: Yield 91%; GLPC purity 96%; 19F NMR (CDCl3) -59.6 ppm (q, 3F, -CF3, Fa), -60.4
ppm (q, 3F, -CF3, Fb), -99.4 ppm (dd, 1F, cis-CF=CF2, Fc), -112.1 ppm (dd, 1F, trans-
CF=CF2, Fd), -165.1 ppm (dd, 1F, -CF=CF2, Fe), (Jab = 13 Hz, Jcd = 62 Hz, Jce = 32 Hz, Jde
= 117 Hz); 1H NMR (CDCl3) 7.1-7.3 ppm (m, 4H), 2.4 ppm (s, 3H); 13C {1H} NMR
(CDCl3) 153.5 ppm (ddd, -CF=CF2, 1JCF = 294 Hz, 280 Hz, 2JCF = 48 Hz), 148.7 ppm (q,
ϕ-C(CF3)=C, 2JCF = 34 Hz), 139.3 ppm (s), 132.0 ppm (s), 131.6 ppm (s), 129.0 ppm
(s), 128.7 ppm (s), 126.7 ppm (m, -C(CF3)=C(CF3)-CF), 125.3 ppm (s), 122.5 ppm
(ddd, -CF=CF2, 1JCF = 240 Hz, 2JCF = 55 Hz, 26 Hz), 121.2 ppm (q, -CF3, 1JCF = 276 Hz),
121.0 ppm (q, -CF3, 1JCF = 276 Hz), 21.4 ppm (s); GC-MS 334 (M+, 21), 295 (9), 265
(100), 245 (26), 215 (72), 196 (46), 146 (26); HRMS (C13H7F9, calculated: 334.0404,
observed: 334.0396); UV (cyclohexane) c = 2.54x10-4, λmax = 206 nm (A = 0.587, ε =
2310), λ = 268 nm (A = 0.026, ε = 100); FT-IR (cm-1, CCl4) 3042 (w), 3031 (w), 2960
(w, C-H), 2928 (w, C-H), 1789 (s, -CF=CF2), 1606 (w), 1487 (m), 1353 (m), 1319 (s),
1294 (s), 1289 (s), 1251 (s), 1244 (s), 1230 (s), 1225 (s), 1219 (s), 1213 (s), 1210
(s), 1201 (s), 1190 (s), 1181 (s), 1172 (s), 1166 (s), 1162 (s), 1132 (s), 848 (m), 723
(m), 621 (m).
1f: Yield 52%; mp 141-142 °C; 19F NMR (376 MHz, JEOL GX-400, CDCl3) -60.2 ppm
(qm, 3F, -CF3, Fa), -60.5 ppm (qm, 3F, -CF3, Fb), -98.6 ppm (ddm, 1F, cis-CF=CF2, Fc),
-111.6 ppm (dd, 1F, trans-CF=CF2, Fd), -166.6 ppm (ddm, 1F, -CF=CF2, Fe), (Jab = 13
Hz, Jcd = 59 Hz, Jce = 33 Hz, Jde = 117 Hz); 1H NMR (400 MHz, JEOL GX-400, CDCl3) 7.4
ppm (s, 4H); 13C {1H} NMR (100 MHz, JEOL GX-400, CDCl3) 152.6 ppm (ddd, -CF=CF2,
1JCF = 297 Hz, 281 Hz, 2JCF = 46 Hz), 146.2 ppm (qm, ϕ-C(CF3)=C, 2JCF = 34 Hz), 133.5
ppm (s), 128.3 ppm (s), 126.3 ppm (m, -C(CF3)=C(CF3)-CF), 121.7 ppm (ddd, -
CF=CF2, 1JCF = 236 Hz, 2JCF = 54 Hz, 24 Hz), 120.3 ppm (q, -CF3, 1JCF = 269 Hz), 120.1
ppm (q, -CF3, 1JCF = 269 Hz);GC-MS 562 (M+, 3), 493 (26), 423 (20), 355 (40), 305
(42), 250 (42), 69 (CF3, 100); HRMS (C18H4F18, calculated: 562.0026, observed:
562.0027); UV (cyclohexane) c = 1.78x10-4, λmax = 216 nm (A = 1.784, ε = 10000), λ
= 254 nm (A = 1.554, ε = 8700), λ = 272 nm (A = 1.526, ε = 8600); FT-IR (cm-1, CCl4)
1790 (m, -CF=CF2), 1324 (s), 1292 (s), 1267 (s), 1239 (s), 1217 (s), 1194 (s), 1177
(s), 1134 (s), 867 (w), 721 (w), 715 (w).
17
Page 20 of 27

3.6
Preparation of 1,2-difluoro-3,4-bis(trifluoromethyl)naphthalene (2a-e), 1,1,2-
trifluoro-3,4-bis(trifluoromethyl)-1,4-dihydronaphthalene (3a-e), anthracene (7) and
phenanthrene (8) via photocyclization.
Compound 1 (1.0g) was dissolved in hexane (10 mL) in a Rotaflo quartz tube.
After freezing this solution in liq. N2, the tube was degassed by a vacuum pump.
Then the solution was thawed and placed in the photoreactor (254 nm). After
reaction the solvent was evaporated and the obtained residue was purified via silica
gel (70-230 mesh) chromatography (hexane) to yield 2 and 3. Yields are shown in
Table 2.
2a: Yield 430 mg (46%); mp 141-142 °C; 19F NMR (CDCl3) -50.6 ppm (q, 3F, -
C(CF3)=C(CF3)-CF=, Fa), -53.3 ppm (dq, 3F, -C(CF3)=C(CF3)-CF=, Fb), -138.5 ppm (d,
1F, -C(CF3)-CF=CF-, Fc), -143.5 ppm (dq, 1F, -C(CF3)-CF=CF-, Fd), (Jab = 17 Hz, Jbd =
33 Hz , Jcd = 18 Hz); 1H NMR (CDCl3) 8.3-7.7 ppm (m, 4H); 13C {1H} NMR (acetone-d6)
148.9 ppm (dd, -CF=CF-, 1JCF = 258 Hz, 2JCF = 14 Hz), 144.4 ppm (dd, -CF=CF-, 1JCF =
255 Hz, 2JCF = 14 Hz), 131.2 ppm (s), 130.3 ppm (s), 128.1 ppm (bs), 126.6 ppm (m),
125.5 ppm (m), 124.0 ppm (q, -CF3, 1JCF = 276 Hz), 123.7 ppm (qm, -C(CF3), 2JCF = 34
Hz), 123.1 ppm (q, -CF3, 1JCF = 277 Hz), 121.1 ppm (bs); GC-MS 301 (M++1, 12), 300
(M+, 100), 423 (28), 250 (100), 231 (40), 211 (12); HRMS (C12H4F8, calculated:
300.0185, observed: 300.0193); UV (cyclohexane) c = 6.83x10-5, λmax = 228 nm (A
= 2.966, ε = 43400), λ = 281 nm (A = 0.4177, ε = 6100), λ = 334 nm (A = 0.2945, ε =
4300); FT-IR (cm-1, CCl4) 1650 (m), 1616 (m), 1467 (m), 1402 (s), 1379 (s), 1315
(s), 1237 (s), 1211 (s), 1176 (s), 1141 (s), 952 (w).
2b: Yield 53%; GLPC purity 97%; 19F NMR (CDCl3) -51.4 ppm (q, 3F, -C(CF3)=C(CF3)-
CF=, Fa), -54.4 ppm (dq, 3F, -C(CF3)=C(CF3)-CF=, Fb), -64.2 ppm (s, 3F, -CF3, Fc) -
136.4 ppm (d, 1F, -C(CF3)-CF=CF-, Fd), -139.6 ppm (dq, 1F, -C(CF3)-CF=CF-, Fe), (Jab
= 16 Hz, Jbe = 32 Hz , Jde = 17 Hz); 1H NMR (CDCl3) 8.5 ppm (s, 1H), 8.4 ppm (d, 1H,
3JHH = 8 Hz), 7.9 ppm (d, 1H, 3JHH = 8 Hz); 13C {1H} NMR (CDCl3) 148.9 ppm (dd, -
CF=CF-, 1JCF = 263 Hz, 2JCF = 14 Hz), 144.7 ppm (dd, -CF=CF-, 1JCF = 262 Hz, 2JCF = 14
Hz), 132.1 ppm (q, -C(CF3), 2JCF = 34 Hz), 128.8 ppm (s), 127.9 ppm (m), 126.6 ppm
(qm, -C(CF3)=C(CF3)-CF=, 2JCF = 39 Hz), 125.5 ppm (d, -CF=CF-C-, 2JCF = 14 Hz), 124.7
ppm (s), 123.5 ppm (q, -CF3, 1JCF = 273 Hz), 122.8 ppm (q, -CF3, 1JCF = 274 Hz), 121.6
ppm (q, -CF3, 1JCF = 277 Hz), 118.6 ppm (q, -C(CF3)=C(CF3)-C-, 3JCF = 5 Hz); GC-MS
368 (M+, 92), 349 (M+-F, 44), 318 (38), 299 (100), 249 (33), 229 (21), 211 (25);
HRMS (C13H3F11, calculated: 368.0059, observed: 368.0059); UV (cyclohexane) c =
2.98x10-5, λmax = 224 nm (A = 2.091, ε = 70200), λ = 276 nm (A = 0.1920, ε = 6400),
λ = 336 nm (A = 0.1374, ε = 4600); FT-IR (cm-1, CCl4) 3100 (w), 1680 (m), 1648 (s),
18
Page 21 of 27

1631 (s), 1434 (s), 1393 (s), 1327 (s), 1291 (s), 1232 (s), 1208 (s), 1177 (s), 1145
(s), 1125 (s), 1074 (s), 1027 (s), 902 (s), 861 (s), 855 (m), 697 (m).
2c: Yield 50%; GLPC purity 98%; 19F NMR (CDCl3) -51.3 ppm (q, 3F, -C(CF3)=C(CF3)-
CF=, Fa), -53.7 ppm (dq, 3F, -C(CF3)=C(CF3)-CF=, Fb), -140.3 ppm (d, 1F, -C(CF3)-
CF=CF-, Fc), -142.2 ppm (dq, 1F, -C(CF3)-CF=CF-, Fd), (Jab = 16 Hz, Jbd = 32 Hz , Jcd =
16 Hz); 1H NMR (CDCl3) 8.0 ppm (d, 1H), 7.1 ppm (m, 2H), 3.9 ppm (s, 3H); 13C {1H}
NMR (CDCl3) 160.6 ppm (s),147.1 ppm (dd, -CF=CF-, 1JCF = 257 Hz, 2JCF = 14 Hz),
144.3 ppm (dd, -CF=CF-, 1JCF = 256 Hz, 2JCF = 14 Hz), 128.1 ppm (m), 127.9 ppm (s),
124.0 ppm (q, -CF3, 1JCF = 276 Hz), 123.3 ppm (q, C-C(CF3)=C(CF3)-, 2JCF = 36 Hz),
123.0 ppm (q, -CF3, 1JCF = 276 Hz), 122.9 ppm (s), 122.3 ppm (s), 117.1 ppm (m),
97.6 ppm (q, 4JCF = 6 Hz), 55.8 ppm (s); GC-MS 331 (M++1, 11), 330 (M+, 100), 311
(M+-F, 21), 287 (30), 268 (10), 237 (13), 218 (30); HRMS (C13H6F8O , calculated:
330.0291, observed: 330.0280); UV (cyclohexane) c = 4.48x10-5, λmax = 245 nm (A
= 2.426, ε = 54000), λ = 304 nm (A = 0.3141, ε = 7000); FT-IR (cm-1, CCl4) 2970 (w),
2940 (w), 1720 (w), 1620 (m), 1485 (m), 1312 (s), 1300 (s), 1279 (s), 1258 (s),
1245 (s), 1231 (s), 1222 (s), 1205 (s), 1171 (s), 1141 (m), 879 (m).
2d: Yield 59%; GLPC purity >99%; 19F NMR (CDCl3) -51.4 ppm (q, 3F, -
C(CF3)=C(CF3)-CF=, Fa), -54.2 ppm (dq, 3F, -C(CF3)=C(CF3)-CF=, Fb), -138.2 ppm (d,
1F, -C(CF3)-CF=CF-, Fc), -140.1 ppm (dq, 1F, -C(CF3)-CF=CF-, Fd), (Jab = 16 Hz, Jbd =
32 Hz , Jcd = 18 Hz); 1H NMR (CDCl3) 8.2 ppm (dm, 1H, 3JHH = 9 Hz), 8.0 ppm (s, 1H),
7.5 ppm (dm, 1H, 3JHH = 9 Hz); 13C {1H} NMR (CDCl3) 147.3 ppm (dd, -CF=CF-, 1JCF =
261 Hz, 2JCF = 14 Hz), 144.6 ppm (dd, -CF=CF-, 1JCF = 259 Hz, 2JCF = 14 Hz), 137.1 ppm
(s), 130.0 ppm (s), 128.0 ppm (s), 126.1 ppm (d, C-CF=CF-, 2JCF = 12 Hz), 125.7 ppm
(s), 124.1 ppm (m), 122.3 ppm (q, -CF3, 1JCF = 277Hz), 121.9 ppm (q, -CF3, 1JCF = 277
Hz), 120.6 ppm (m), 119.4 ppm (m); GC-MS 336 (M++2, 43), 334 (M+, 100), 315 (M+-
35
F, 22), 299 (23), 284 (20), 265 (31); HRMS (C12H3F8 Cl, calculated: 333.9796,
observed: 333.9797); UV (cyclohexane) c = 3.29x10-5, λmax = 236 nm (A = 1.427, ε =
43400), λ = 290 nm (A = 0.1561, ε = 4700), λ = 336 nm (A = 0.0566, ε = 1700); FT-IR
(cm-1, CCl4) 2990 (w), 2880 (w), 1790 (w), 1641 (m), 1615 (m), 1609 (w), 1495 (m),
1463 (m), 1455 (m), 1433 (m), 1386 (m), 1322 (m), 1297 (s), 1269 (s), 1205 (s),
1193 (s), 1178 (s), 1143 (s), 1027 (m), 858 (m), 821 (m).
2e: GLPC Yield 25%; 19F NMR (CDCl3) -51.4 ppm (m, 3F, -C(CF3)=C(CF3)-CF=, Fa), -
54.2 ppm (m, 3F, -C(CF3)=C(CF3)-CF=, Fb), -129.7 ppm (m, 1F, -C(CF3)-CF=CF-, Fd), -
143.0 ppm (dq, 1F, -C(CF3)-CF=CF-, Fc), (Jbc = 34 Hz , Jcd = 14 Hz); 1H NMR (CDCl3)
7.9-7.4 ppm (m, 3H), 2.8 ppm (d, 3H, 5JHF = 8 Hz); GC-MS 315 (M++1, 13), 314 (M+,
100), 295 (27), 263 (12), 245 (99), 224 (28), 175 (27).
2e’: GLPC Yield 36%;
19F NMR (CDCl3) -51.4 ppm (m, 3F, -C(CF3)=C(CF3)-CF=, Fa), -54.0 ppm (m, 3F, -
C(CF3)=C(CF3)-CF=, Fb), -139.2 ppm (d, 1F, -C(CF3)-CF=CF-, Fc), -144.1 ppm (dq, 1F,
-C(CF3)-CF=CF-, Fd), (Jbd = 34 Hz , Jcd = 18 Hz); 1H NMR (CDCl3) 7.9-7.4 ppm (m, 3H),
19
Page 22 of 27

2.5 ppm (s, 3H); GC-MS 315 (M++1, 13), 314 (M+, 100), 295 (M+-F, 27), 263 (13), 245
(98), 224 (32), 175 (18).
3a: Yield 190 mg (19%); GLPC purity 99%; 19F NMR (CDCl3) -60.7 ppm (m, 3F, -
CH(CF3)-C(CF3)=, Fa), -69.6 ppm (s, 3F, -CH(CF3)-C(CF3)=CF-, Fb), -85.3 ppm (dd, 1F,
=CF-F2-, Fc), -101.3 ppm (dd, 1F, =CF-F2-, Fd), -114.9 ppm (m, 1F, =CF-CF2-, Fe),
(Jcd = 304 Hz, Jce = 30 Hz , Jde = 13 Hz); 1H NMR (CDCl3) 7.9-7.5 ppm (m, 4H), 4.6 ppm
(qm, 1H, -CH(CF3)-, 3JHF = 7 Hz); 13C {1H} NMR (CDCl3) 156.7 ppm (dt, =CF-CF2-, 1JCF =
294 Hz, 2JCF = 29 Hz), 131.6 ppm (s) 131.0 ppm (t, C-CF2-CF=, 2JCF = 24 Hz), 130.3
ppm (s), 129.6 ppm (s), 127.4 ppm (s), 126.2 ppm (s), 124.1 ppm (q, -CF3, 1JCF = 277
Hz), 121.8 ppm (q, -CF3, 1JCF = 272 Hz), 111.1 ppm (q, -CH(CF3)-C(CF3)=CF-, 2JCF = 30
Hz), 109.9 ppm (ddd, =CF-CF2-, 1JCF = 239 Hz, 236 Hz, 2JCF = 23 Hz), 43.7 ppm (q, –
CH(CF3)-, 2JCF = 31 Hz); GC-MS 320 (M+, 13), 301 (8), 251 (100), 232 (24), 201 (63),
182 (63); HRMS (C12H5F9, calculated: 320.0248, observed: 320.0249); UV
(cyclohexane) c = 3.28x10-4, λmax = 216 nm (A = 1.565, ε = 4800), λ = 272 nm (A =
0.2328, ε = 710); FT-IR (cm-1, CCl4) 2828 (w, C-H), 2853 (w), 1721 (m), 1461 (w),
1392 (m), 1315 (s), 1303 (s), 1260 (s), 1244 (s), 1184 (s), 1162 (s), 1138 (s), 1118
(s), 1059 (m), 992 (m), 658 (m).
3b: Yield 26%; GLPC purity 95%; 19F NMR (CDCl3) -60.7 ppm (m, 3F, -CH(CF3)-
C(CF3)=, Fa), -63.7 ppm (s, 3F, -CH(CF3)-C(CF3)=CF-, Fb), -69.2 ppm (s, 3F, -CF3, Fc), -
85.4 ppm (dd, 1F, =CF-F2-, Fd), -101.6 ppm (dd, 1F, =CF-F2-, Fe), -114.1 ppm (m, 1F,
=CF-CF2-, Ff), (JaH = 7 Hz, Jde = 306 Hz , Jdf = 13 Hz, Jef = 21 Hz); 1H NMR (CDCl3) 8.1
ppm (s, 1H), 7.9 ppm (d, 1H, 3JHH = 7 Hz), 7.7 ppm (d 1H, 3JHH = 7 Hz), 4.6 ppm (q, 1H,
-CH(CF3)-, 3JHF = 7 Hz); 13C {1H} NMR (CDCl3) 156.4 ppm (dt, =CF-CF2-, 1JCF = 294 Hz,
2JCF = 27 Hz), 133.3 ppm (q, -C(CF3), 2JCF = 34 Hz), 132.1 ppm (t, C-CF2-CF=, 2JCF = 21
Hz), 131.1 ppm (s), 130.5 ppm (s), 128.4 ppm (s), 123.8 ppm (q, -CF3, 1JCF = 272 Hz),
123.6 ppm (q, -CF3, 1JCF = 277 Hz), 123.6 ppm (s), 121.3 ppm (q, -CF3, 1JCF = 284 Hz),
111.1 ppm (m, -CH(CF3)-C(CF3)=CF-), 109.3 ppm (ddd, =CF-CF2-, 1JCF = 238 Hz, 235
Hz, 2JCF = 23 Hz), 43.8 ppm (q, –CH(CF3)-, 2JCF = 31 Hz); GC-MS 388 (M+, 8), 369 (M+-F,
14), 319 (100), 300 (20), 269 (61), 265 (61), 200 (26); HRMS (C13H4F12, calculated:
388.0121, observed: 388.0118); UV (cyclohexane) c = 2.58x10-4, λmax = 226 nm (A
= 0.893, ε = 3500), λ = 338 nm (A = 0.075, ε = 290); FT-IR (cm-1, CCl4) 1720 (w),
1443 (w), 1388 (w), 1343 (w), 1316 (m), 1282 (m), 1246 (s), 1232 (s), 1198 (s),
1186 (s), 1165 (s), 1146 (s), 1124 (m), 1095 (m), 1067 (w), 911 (w).
3c: Yield 24%; GLPC purity 95%; 19F NMR (CDCl3) -60.7 ppm (m, 3F, -CH(CF3)-
C(CF3)=, Fa), -69.9 ppm (s, 3F, -CH(CF3)-C(CF3)=CF-, Fb), -85.4 ppm (dd, 1F, =CF-F2-,
Fc), -101.4 ppm (dd, 1F, =CF-F2-, Fd), -115.5 ppm (m, 1F, =CF-CF2-, Fe), (Jcd = 304 Hz,
Jce = 23 Hz , Jde = 14 Hz); 1H NMR (CDCl3) 7.4 ppm (d, 1H, 3JHH = 9 Hz), 7.3 ppm (s), 7.1
ppm (d, 1H, 3JHH = 9 Hz) 4.5 ppm (qm, 1H, -CH(CF3)-, 3JHF = 7 Hz), 3.9 ppm (s, 3H); 13C
{1H} NMR (CDCl3) 161.2 ppm (s),156.8 ppm (dt, =CF-CF2-, 1JCF = 293 Hz, 2JCF = 29=8
Hz), 132.2 ppm (t, C-CF2-CF=, 2JCF = 24 Hz), 131.0 ppm (s), 124.0 ppm (q, -CF3, 1JCF =
282 Hz), 121.3 ppm (q, -CF3, 1JCF = 275 Hz), 119.3 ppm (bs), 118.9 ppm (s), 109.7
ppm (m), 110.2 ppm (m), 109.7 ppm (ddd, =CF-CF2-, 1JCF = 239 Hz, 236 Hz, 2JCF = 24
Hz), 55.8 ppm (s), 43.3 ppm (q, –CH(CF3)-, 2JCF = 31 Hz); GC-MS 350 (M+, 22), 331
20
Page 23 of 27

(M+-F, 9), 281 (100), 231 (23), 212 (40), 169 (32); HRMS (C13H7F9O, calculated:
350.0353, observed: 350.0358); UV (cyclohexane) c = 3.14x10-4, λmax = 212 nm (A
= 1.038, ε = 3300), λ = 242 nm (A = 0.625, ε = 2000), λ = 334 nm (A = 0.468, ε =
1500); FT-IR (cm-1, CCl4) 2959 (w), 2930 (w), 1723 (m), 1682 (m), 1656 (m), 1649
(m), 1636 (m), 1624 (m), 1594 (m), 1550 (m), 1449 (m), 1410 (s), 1340 (m), 1306
(m), 1274 (m), 1264 (m), 1231 (m), 1210 (s), 1202 (s), 1192 (s), 1168 (s), 1148 (s),
1003 (w), 908 (m).
3d: Yield 14%; GLPC purity 95%; 19F NMR (CDCl3) -60.8 ppm (m, 3F, -CH(CF3)-
C(CF3)=, Fa), -69.5 ppm (s, 3F, -CH(CF3)-C(CF3)=CF-, Fb), -85.5 ppm (dd, 1F, =CF-F2-,
Fc), -101.5 ppm (dd, 1F, =CF-F2-, Fd), -114.7 ppm (m, 1F, =CF-CF2-, Fe), (JFH = 6 Hz,
Jcd = 305 Hz, Jce = 23 Hz , Jde = 14 Hz); 1H NMR (CDCl3) 7.8 ppm (m, 1H), 7.6 ppm (dm,
1H, 3JHH = 8 Hz), 7.4 ppm (d, 1H, 3JHH = 8 Hz), 4.5 ppm (q, 1H, -CH(CF3)-, 3JHF = 6 Hz);
13C {1H} NMR (CDCl3) 156.7 ppm (dt, =CF-CF2-, 1JCF = 294 Hz, 2JCF = 28 Hz), 137.3
ppm (s), 133.4 ppm (t, C-CF2-CF=, 2JCF = 28 Hz), 132.2 ppm (s), 131.2 ppm (s), 126.8
ppm (m), 126.0 ppm (s), 124.0 ppm (q, -CF3, 1JCF = 274 Hz), 121.3 ppm (q, -CF3, 1JCF =
274 Hz), 111.1 ppm (m), 109.4 ppm (ddd, =CF-CF2-, 1JCF = 240 Hz, 239 Hz, 2JCF = 24
Hz), 43.7 ppm (q, –CH(CF3)-, 2JCF = 31 Hz); GC-MS 354 (M+, 15), 335 (M+-F, 7), 287
35
(41), 285 (100), 250 (22), 235 (44), 216 (54); HRMS (C12H4F9 Cl, calculated:
353.9858, observed: 353.9844); UV (cyclohexane) c = 3.53x10-4, λmax = 220 nm (A
= 2.013, ε = 5700), λ = 272 nm (A = 0.172, ε = 500), λ = 282 nm (A = 0.163, ε = 460);
FT-IR (cm-1, CCl4) 1710 (m), 1492 (w), 1430 (w), 1382 (m), 1316 (m), 1299 (m),
1278 (m), 1244 (s), 1232 (s), 1204 (s), 1196 (s), 1186 (s), 1165 (s), 1142 (s), 1122
(s), 1110 (s), 1065 (s), 855 (m).
3e: GLPC Yield 7%; 19F NMR (CDCl3) -60.9 ppm (m, 3F, -CF3, Fa), -69.9 ppm (s, 3F, -
CF3, Fb), -93.8 ppm (dd, 1F, =CF-F2-, Fc), -95.8 ppm (dd, 1F, =CF-F2-, Fd), -115.4 ppm
(m, 1F, =CF-CF2-, Fe), (Jcd = 309 Hz, Jce = 22 Hz , Jde = 14 Hz); 1H NMR (CDCl3) 7.7-7.3
ppm (m, 3H), 4.5 ppm (m, 1H) 2.6 ppm (m, 3H); GC-MS 334 (M+, 58), 315 (M+-F, 18),
283 (60), 265 (100), 245 (26), 215 (27), 196 (81).
3e’: GLPC Yield 18%; 19F NMR (CDCl3) -60.9 ppm (m, 3F, -CF3, Fa), -69.6 ppm (s, 3F,
-CF3, Fb), -84.9 ppm (dd, 1F, =CF-F2-, Fc), -101.1 ppm (dd, 1F, =CF-F2-, Fd), -115.1
ppm (m, 1F, =CF-CF2-, Fe), (Jae = 13 Hz, Jcd = 303 Hz, Jce = 23 Hz); 1H NMR (CDCl3) 7.7-
7.3 ppm (m, 3H), 4.5 ppm (m, 1H), 2.4 ppm (m, 3H); GC-MS 334 (M+, 24), 265 (100),
246 (14), 215 (48), 196 (29), 146 (15).
7: Yield 7%; mp 155-156 °C; 19F NMR (acetone-d6) -51.7 ppm (q, 6F, -C(CF3)=C(CF3)-
CF=, Fa), -54.6 ppm (dq, 6F, -C(CF3)=C(CF3)-CF=, Fb), -136.1 ppm (d, 2F, =C(CF3)-
CF=CF-, Fc), -140.3 ppm (qd, 2F, =C(CF3)-CF=CF-, Fd), (Jab = 16 Hz, Jbd = 32 Hz, , Jcd =
15 Hz); 1H NMR (acetone-d6) 9.3 ppm (s, 2H); 13C {1H} NMR (acetone-d6) 149.0 ppm
(dd, -CF=CF-, 1JCF = 262 Hz, 2JCF = 14 Hz), 144.1 ppm (dd, -CF=CF-, 1JCF = 257 Hz, 2JCF =
14 Hz), 126.2 ppm (s), 125.3 ppm (d, C-CF=CF-, 2JCF = 13 Hz), 124.8 ppm (m), 123.7
ppm (q, -CF3, 1JCF = 271 Hz), 122.4 ppm (q, -CF3, 1JCF = 276 Hz), 120.6 ppm (s); GC-MS
523 (M++1, 17), 522 (M+, 100), 503 (M+-F, 33), 472 (25), 453 (42), 315 (25); HRMS
(C18H2F16, calculated: 521.9901, observed: 521.9924); UV (cyclohexane) c = 5.42x10-
21
Page 24 of 27

5, λmax = 260 nm (A = 2.80, ε = 51700), λ = 205 nm (A = 1.48, ε = 27300), λ = 400 nm
(A = 0.190, ε = 3500), λ = 430 nm (A = 0.230, ε = 4250); FT-IR (cm-1, CCl4) 1631 (m),
1549 (w), 1455 (m), 1441 (w), 1430 (w), 1385 (m), 1372 (m), 1360 (m), 1329 (s),
1294 (s), 1261 (s), 1232 (s), 1182 (s), 1146 (s), 1058 (w), 934 (w).
8: Yield 28%; mp 129-130 °C; 19F NMR (CDCl3) -50.0 ppm (q, 6F, -C(CF3)=C(CF3)-
CF=, Fa), -54.5 ppm (dq, 6F, -C(CF3)=C(CF3)-CF=, Fb), -115.7 ppm (bs, 2F, -C(CF3)-
CF=CF-, Fc), -134.2 ppm (qm, 2F, -C(CF3)-CF=CF-, Fd), (Jab = 16 Hz, Jbd = 34 Hz); 1H
NMR (CDCl3) 8.2 ppm (s, 2H); 13C {1H} NMR (CDCl3) 150.1 ppm (dd, -CF=CF-, 1JCF =
267 Hz, 2JCF = 15 Hz), 147.6 ppm (dm, -CF=CF-, 1JCF = 265 Hz), 128.2 ppm (s), 125.7
ppm (m), 124.5 ppm (dm, C-CF=CF-, 2JCF = 31 Hz), 123.8 ppm (m), 122.7 ppm (q, -
CF3, 1JCF = 276 Hz), 122.6 ppm (m, 2JCF = 33 Hz), 121.5 ppm (q, -CF3, 1JCF = 275 Hz),
118.4 ppm (bs); GC-MS 523 (M++1, 18), 522 (M+, 100), 503 (M+-F, 30), 472 (27), 453
(33), 315 (13); HRMS (C18H2F16, calculated: 521.9901, observed: 521.9879); UV
(cyclohexane) c = 5.43x10-5, λmax = 260 nm (A = 2.17, ε = 40000), λ = 205 nm (A =
1.68, ε = 310), λ = 300 nm (A = 0.415, ε = 7650), λ = 310 nm (A = 0.415, ε = 7650);
FT-IR (cm-1, CCl4) 1600 (w), 1493 (w), 1454 (w), 1434 (m), 1416 (m), 1352 (m),
1334 (m), 1292 (m), 1274 (m), 1250 (w), 1221 (s), 1200 (s), 1178 (s), 1145 (s),
1080 (w), 1010 (w), 902 (w), 871 (w).
3.7
Conversion of 3a into 2a (NMR tube scale).
The isolated 3a (60 mg, 0.20 mmol) was dissolved with CDCl3 (1.0 mL) and
DABCO (30 mg, 0.27 mmol) was added. After 30 min at room temperature, the
reaction mixture was checked by 19F-NMR. Spectral data matched well with that
obtained for the previously isolated 2a. The conversion was quantitative.
Additionally, the isolated 3a (100 mg) was dissolved in hexane (1.0 mL) and this
solution was put into the photoreactor using the same method as in 3.6. After 2 days,
no photoconversion to 2a was observed.
3.8
Conversion of 3e/3e’ into 2e/2e’ (NMR tube scale).
The mixture of 3e/3e’ (80 mg, 0.20 mmol) was dissolved with CDCl3 (1.0 mL)
and DBU (35 mg, 0.23 mmol) was added. After 30 min at room temperature, the
22
Page 25 of 27

reaction mixture was checked by 19F-NMR. This spectrum coincided with a
previously isolated mixture of 2e/2e’.
4. Conclusion
In conclusion, readily prepared perfluoro cis-1,2-dimethyl butadienyl
benzenes (1) underwent photocyclization to yield novel naphthalene and 1,4-
dihydronaphthalene derivatives. The isolated 1,4-dihydronaphthalene could be
converted to their respective naphthalenes by base treatment but not
photochemically. Competitive photochemical reactions indicate that varying the
benzene substituent did not significantly affect reaction rate, suggesting that the
mechanism does not involve electrophilic attack on the benzene as the rate-
determining step.
5. Acknowledgement
We wish to thank the National Science Foundation and the Air Force Office of
Scientific Research for support of this work. M. Y. wishes to thank Nitto Denko Co.,
Ltd. (Japan) for the release time to pursue this research. D. J. wishes to thank
Michael Sinnwell for help with manuscript preparation.
6. References
[1] D.M. Wiemers, D.J. Burton, J. Am. Chem. Soc., 108 (1986) 832-834; D.J Burton,
Actualite Chimique, (1987) 142-146.
[2] D.J. Burton, in: J.F. Liebman, A. Greenberg, W.R Dolbier Jr. (Eds.), Fluorine
containing molecules: structure, reactivity, synthesis, and Applications; Wiley-VCH
Verlag GmbH, New York, 1988
23
Page 26 of 27

[3] D.J. Burton, S.W Hansen, J. Am. Chem. Soc., 108 (1986) 4229-4230.
[4] T.D. Spawn, Ph.D. Thesis, University of Iowa, 1987
[5] D.J. Burton, C.R. Davis, in: Z. Rappoport, I. Marek (Eds), The Chemistry of
organocopper compounds, Wiley, England, 2009, pp. 991-1032
[6] S.W. Hansen, Ph.D. Thesis, University of Iowa (1984).
[7] K.J. MacNeil, D.J. Burton. J. Org. Chem., 58 (1993) 4411-4417
[8] D.J. Burton, S.W. Hansen. J. Fluorine Chem., 130 (2009) 775-779
[9] R.D. Guneratne, D.J. Burton. J. Fluorine Chem., 98 (1999) 11-17
[10] E.P. Fokin, T.N. Gerasimova, T.V Fomenko, and N.V. Semikolenova, Zh. Org.
Khim., 14 (1978) 834-841
[11] F.B. Mallory, C.W. Mallory, J. Org. Chem., 48 (1983) 526-532
[12] M. Gorsane, N. Defay, R.H. Martin, Bull. Soc. Chim. Belg., 94 (1985) 425-30
[13] D.C. Swenson, M. Yamamoto, D.J. Burton, Acta Cryst. C54 (1998) 846-849
[14] P.A. Morken, P.C. Bachand, D.C. Swenson, D.J. Burton, J. Am. Chem. Soc. 1993,
115, 5430-5439.
[15] S.W. Hansen, T.D. Spawn, D.J. Burton. J. Fluorine Chem., 35 (1987) 415-420
24
Page 27 of 27