Selective trifluoromethylation and alkynylation of tetrahydroisoquinolines using visible light irradiation by Rose Bengal

Article abstract of DOI:10.1016/j.jfluchem.2012.05.009

A convenient and efficient method for oxidative coupling of tetrahydroisoquinoline derivatives with trimethyl(trifluoromethyl)silane and terminal alkynes to 1-trifluoromethylated or 1-alkynylated tetrahydroisoquinolines via CH activation was developed usi

Full text of DOI:10.1016/j.jfluchem.2012.05.009

Journal of Fluorine Chemistry 140 (2012) 88–94
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Selective trifluoromethylation and alkynylation of tetrahydroisoquinolines using
visible light irradiation by Rose Bengal
a
b
a
Weijun Fu a, , Wenbo Guo , Guanglong Zou , Chen Xu
*
a College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022, PR China
b School of Chemistry and Environmental Science, Guizhou University for Nationalities, Guiyang 550025, PR China
A R T I C L E I N F O
A B S T R A C T
Article history:
A convenient and efficient method for oxidative coupling of tetrahydroisoquinoline derivatives with
trimethyl(trifluoromethyl)silane and terminal alkynes to 1-trifluoromethylated or 1-alkynylated
tetrahydroisoquinolines via C–H activation was developed using visible light irradiation. The protocol
uses Rose Bengal as the catalyst, air as terminal oxidant, and the trifluoromethylation or alkynylation was
Received 23 January 2012
Received in revised form 8 May 2012
Accepted 10 May 2012
Available online 17 May 2012
selectively performed at the
a
-position of nitrogen under extremely mild conditions.
ß 2012 Elsevier B.V. All rights reserved.
Keywords:
Photooxidation
Visible light
Trifluoromethylation
Alkynylation
Trimethyl(trifluoromethyl)silane
Tetrahydroisoquinoline
1. Introduction
copper-catalyzed trifluoromethylation of N-aryl-tetrahydroiso-
quinolines with TMSCF3 via oxidative sp3 C–H activation at the
Considering the importance of amines containing trifluor-
omethyl group at the C– atom and alkaloids in industry as
a-position of nitrogen using DDQ as terminal oxidant [35]. Qing
a
and co-workers reported that benzoyl peroxide (BPO)-promoted
oxidative trifluoromethylation of tertiary amines proceeded
successfully under transition-metal-free reaction conditions
[36]. Despite this extensive progress, the search for an efficient
and practical catalytic system for trifluoromethylation of
tertiary amines remains a challenge.
With the emergence of the concept of ‘‘green chemistry’’,
photoredox catalyzed organic transformations have been attracting
much attention in recent years, not only because these transforma-
tions exhibit some particular or unexpected reactivities in some
cases but also because they are significantly useful for green
chemistry [37–40]. Over the past 5 years, a variety of metal-based
and organic dyes-based photosensitizers, as photoredox catalysts
for organic transformations under visible light irradiation have been
developed [41–54]. Among these transformations, the oxidative
cross-dehydrogenative coupling (CDC) reaction is an attractive
strategy. In this case, generation of iminium ion intermediates by
using visible-light photoredox catalysis followed by reactions with
pharmaceutical and agrochemical drugs [1–3], straightforward
and eco-friendly preparation of these compounds still repre-
sents a challenging task for chemists. The traditional methods
for synthesizing such compounds include nucleophilic addition
and 1,3-proton shift reactions involving imines of trifluoroacetic
aldehyde [4–6], as well as addition reactions of trifluoromethyl
carbanion at the C55N bond of azomethine substrates and
iminium cations [7–11]. Recently, transition metal-catalyzed
C–H bond activation directly to form C–C bond has attracted
great attention and a number of excellent results have been
obtained because it avoids the preparation of functional groups
and makes synthetic schemes shorter and more efficient
[12–17]. Among these reactions, oxidation of an sp3 C–H bond
adjacent to a nitrogen atom in a tertiary amine, followed by
attack of a carbon nucleophile, is a powerful strategy for C–C
bond formation [18–20]. This method resides in the generation
of an iminium ion intermediate in the presence of metal
catalysts such as CuI, VIV, FeIII, FeII, or RuII and oxidants such as
hydrogen peroxide, oxygen, and tert-butylhydroperoxide
[21–34]. For example, Li and co-workers developed an efficient
carbon pronucleophiles would give
a-substituted products [55–60].
a
-Trifluoromethylation of tetrahydroisoquinolines is a power-
ful transformation in organic synthesis because 1-trifluoromethyl-
tetrahydroisoquinoline derivatives are highly important bioactive
compounds [61,62]. Combining all the above principles and as a
continuation of our interest in the design and discovery of new
reactions for the synthesis of fluorinated heterocycles [63,64],
* Corresponding author. Fax: +86 379 69810261.
E-mail address: wjfu@lynu.edu.cn (W. Fu).
0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jfluchem.2012.05.009

W. Fu et al. / Journal of Fluorine Chemistry 140 (2012) 88–94
89
RB (5mol%)
Green LEDs
TMSCF3/KF
RB (5mol%)
N
N
N
Ar
Ar
R
Ar
CuI (10 mol%)
H
CF3
R
Scheme 1.
a-Trifluoromethylation and alkynylation of tetrahydroisoquinolines.
herein, we report a visible-light-induced oxidative
a
-trifluoro-
this transformation. No reaction was observed in the absence of
any of these components (Table 1, entries 11–13).
methylation and -alkynylation of tetrahydroisoquinolines using
a
Rose Bengal as visible light photocatalyst under transition-metal-
free reaction conditions (Scheme 1).
After having established the optimized conditions for the
present reaction, various tetrahydroisoquinoline derivatives 1a–
n were subjected to the above conditions, and the results are
summarized in Table 2. As indicated, the oxidative trifluoro-
methylation of all the substrates proceeded smoothly to provide
the corresponding products 2a–n in 52–74% yields. The reaction
could tolerate various substituents on the aromatic groups.
Generally, electron-withdrawing aryl groups including fluoro,
chloro, bromo and trifluoromethyl (Table 2, entries 2–5) allowed
the reaction to be completed in a longer time. On the other hand,
electron-donating substitutent on the benzene ring such as
methyl (Table 2, entry 6) and methoxy (Table 2, entries 7 and 8)
proceeded well. In addition, N-naphthyl, N-allyl and N-benzyl
tetrahydroisoquinolines also underwent facile CDC reactions with
TMSCF3 to afford the desired coupled products 2i–k in 65, 58, 60%
yields, respectively (Table 2, entries 9–11). However, N-alkyl-
substituted tetrahydroisoquinoline proved less reactive and gave
1-trifluoromethylated tetrahydroisoquinoline in 52% yield (Table
2, entry 12). Interestingly, the substrates incorporation of a bromo
group at the C7-position in the dihydroisoquinoline or two
methoxy substituents at the C6- and C7-positions also reacted
smoothly with TMSCF3 to give the products 2k or 2l in 65% and 60%
yield, respectively (Table 2, entries 13 and 14). When N-H and
N-Boc tetrahydroisoquinolines were used, the CDC reactions did
not occur at all under visible light irradiation (Table 2, entries
15 and 16).
2. Results and discussion
Our initial investigation focused on the oxidative trifluoro-
methylation of 2-phenyl-1,2,3,4-tetrahydroisoquinoline 1a as an
example for the optimization of the reaction conditions. We found
that treatment 1a with Rose Bengal (RB, 5 mol%), TMSCF3
(3.0 equiv.) and KF (3.0 equiv.) in CH3CN under irradiation by
visible light afforded
a-trifluoromethylation product 2a in 45%
yield after 48 h (Table 1, entry 1). With this encouraging result, we
first examined the influence of organic dyes on the reaction.
Amongst the dyes tested, Rose Bengal showed the best reactivity.
Other dyes such as Rhodamine B or Eosin Y provided 2a in 30% and
41% yield, respectively, while tetraphenylporphyrin (TPP) was less
efficient (Table 1, entries 2–4). Switching the light source to green
LEDs and increasing the amount of TMCF3 from 3 equiv. to 5 equiv.,
the yield of the desired product 2a was increased to 67% (Table 1,
entries 5 and 6). On using other solvent such as DMF or toluene, the
product 2a could be isolated in lower yield (Table 1, entries 7 and
8). With respect to the catalyst loading, 5 mol% of RB was found to
be optimal. When a lower loading of RB (2 mol%), the reaction also
proceeded but sluggishly (Table 1, entry 9). However, no significant
improvement was observed with 10 mol% of RB (Table 1, entry 10).
Importantly, photocatalyst, visible light and air were all critical for
Table 1
Optimization of the reaction conditions.a
.
organic dye
N
N
Ph
Ph
LEDs,TMSCF3/KF
H
1a
CF3
2a
Entry
Organic dye
Solvent
TMSCF3 (equiv.)
LED color
Time (h)
Yield (%)b
1
2
RB (5 mol%)
Rhodamine B (5 mol%)
TPP (5 mol%)
Eosin Y (5 mol%)
RB (5 mol%)
RB (5 mol%)
RB (5 mol%)
RB (5 mol%)
RB (2 mol%)
RB (10 mol%)
RB (5 mol%)
RB (5 mol%)
–
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
DMF
3
3
3
3
3
5
5
5
5
5
5
5
5
White light
White light
White light
White light
Green
48
48
48
48
36
36
48
48
48
36
48
48
48
45
30
3
Trace
41
56
67
43
37
43
68
0
4
5
6
Green
7
Green
8
Toluene
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
Green
9
Green
10
11c
12d
13e
Green
–
Green
Trace
0
Green
a
Reaction conditions: 1a (0.3 mmol), TMSCF3/KF and solvent (3.0 mL).
Isolated yield.
b
c
Reaction was carried out in the dark.
d
e
Reaction was carried out under an N2 atmosphere.
Reaction was carried out without catalyst.

90
W. Fu et al. / Journal of Fluorine Chemistry 140 (2012) 88–94
Table 2
Visible-light-induced
a
-trifluoromethylation of tetrahydroisoquinolines.a
Entry
1
Substrate
Product
Time (h)
36
Yield (%)b
2a, 67
N
N
N
CF3
N
F
2
3
4
5
6
7
48
48
48
72
30
30
2b, 69
2c, 73
2d, 71
2e, 56
2f, 74
2g, 69
F
CF3
N
Cl
N
N
N
Cl
CF3
N
Br
Br
CF3
N
CF3
CH3
CF3
CF3
N
N
CH3
CF3
N
OCH3
N
OCH3
CF3
H3CO
8
N
30
2h, 63
N
H3CO
CF3
N
9
10
11
40
48
48
2i, 65
2j, 58
2k, 60
N
CF3
CF3
N
N
CF3
N
Ph
N
Ph
N
CH3
12
13
14
72
48
48
2l, 52
N
CH3
CF3
N
Ph
2m, 65
2n, 60
Br
N
Ph
Ph
Br
CF3
H3CO
H3CO
H3CO
H3CO
N
Ph
N
CF3

W. Fu et al. / Journal of Fluorine Chemistry 140 (2012) 88–94
91
Table 2 (Continued )
Entry
Substrate
Product
Time (h)
72
Yield (%)b
15
0
NH
16
72
0
N
BOC
a
Reaction conditions: 1a (0.3 mmol), TMSCF3 (1.5 mmol), KF (1.5 mmol), RB (5 mol%) in CH3CN (3.0 mL).
b
Isolated yield.
Table 3
Visible-light-induced
a
-alkynylation of tetrahydroisoquinolines.a
.
visible light
N
Ar
RB (5 mol%)
+
N
Ar
CuI (10 mol%)
R
1
3
Entry
Ar
R
Time (h)
Yield (%)b
1
2
Ph
Ph
36
48
48
40
40
48
30
30
40
48
3a, 73
3b, 69
3c, 65
3d, 82
3e, 80
3f, 53
3g, 69
3h, 63
3i, 65
3j, 75
Ph
4-CH3C6H4
3
Ph
4-CH3OC6H4
4
Ph
4-F C6H4
5
Ph
4-Br C6H4
6
Ph
Bu
Ph
Ph
Ph
Ph
7
4-CH3C6H4
4-CH3OC6H4
4-ClC6H4
2-Naphthy
8
9
10
a
Reaction conditions: 1a (0.3 mmol), alkynes (0.45 mmol), CuI (10 mol%), RB (5 mol%) in CH3CN (3.0 mL).
b
Isolated yield.
After successful oxidative trifluoromethylation of tetrahydroi-
reaction conditions and the desired alkynylation products were
obtained in good isolated yields.
soquinolines, we turned our attention to apply this methodology
for the alkynylation of N-aryl tetrahydroisoquinolines and the
results are summarized in Table 3. In general, aromatic alkynes
electron-donating substituents on the benzene ring gave slightly
lower yields of desired products, whereas the electron-inductive
substituent afforded the best yields among all results for being apt
to form an alkynylcopper intermediate. We also investigated the
influence of the substituents attached to the isoquinoline. A variety
of different N-arylated isoquinolines were subjected to the general
Based on the above results and related literature [59,60], a
plausible reaction mechanism is depicted in Scheme 2. The
reductive quenching of RB*, the excited state of RB, generated
under visible light irradiation, by N-aryl tetrahydroisoquinolines 1
would form radical cation A and RB radical anion. Subsequent
electron transfer from RB radical anion to molecular oxygen
regenerates RB and at the same time generates dioxygen radical
anion, which could then abstract a hydrogen atom from the
HO2
R
Cu
N
N
N
N
Ar
Ar
Ar
Ar
B
1
H
*
A
RB
RB
TMSCF3/KF
R
[O2]
3
Visible Light
RB
N
O2
Ar
CF3
2
Scheme 2. Proposed mechanism for the trifluoromethylation and alkynylation of tetrahydroisoquinolines.

92
W. Fu et al. / Journal of Fluorine Chemistry 140 (2012) 88–94
a
-position of the radical cation A to give an iminium intermediate B
128.5, 126.4, 126.0 (q, J = 285.5 Hz), 123.9, 115.7 (d, J = 0.7 Hz),
61.3 (q, J = 29.8 Hz), 43.8, 27.4 (d, J = 1.3 Hz); MS (EI) m/z 311 (M+);
Anal. Calcd. for C16H13F3NCl: (%) C, 61.65; H, 4.20; N, 4.49. Found: C,
61.81; H, 4.12; N, 4.63.
and release HO2À. The iminium intermediate B undergoes addition
with TMSCF3/KF and alkynylcopper to afford the final product 2 or 3.
3. Conclusion
4.2.4. 2-(4-Bromophenyl)-1-(trifluoromethyl)-1,2,3,4-
In conclusion, we have developed a simple and effective aerobic,
tetrahydroisoquinoline (2d)
metal-free catalytic reaction for the direct oxidative
a-trifluor-
1H NMR (400 MHz, CDCl3):
d
7.36–7.21 (m, 6H), 6.85 (d,
J = 9.2 Hz, 2H), 5.08 (q, J = 8.4 Hz, 1H), 3.78–3.71 (m, 1H), 3.49–3.41
(m, 1H), 3.00–3.10 (m, 2H); 13C NMR (100 MHz, CDCl3):
148.4,
136.7,132.1, 128.9 (q, J = 1.8 Hz), 128.5, 126.5 (q, J = 285.0 Hz),
116.1, 111.2, 61.3 (q, J = 30.1 Hz), 43.7, 27.4; MS (EI) m/z 355 (M+);
Anal. Calcd. for C16H13BrF3N: (%) C, 53.95; H, 3.68; N, 3.93. Found:
C, 54.13; H, 3.79; N, 3.80.
omethylation and -alkynylation of N-aryl tetrahydroisoquinolines
a
by means of visible-light irradiation. The process showed consider-
able synthetic advantages in terms of product diversity and the
operational simplicity, practicability as well as the mild reaction
conditions using visible light as the energy source.
d
4. Experimental
4.2.5. 1-(Trifluoromethyl)-2-(4-(trifluoromethyl)phenyl)-1,2,3,4-
4.1. General
tetrahydroisoquinoline (2e)
1H NMR (400 MHz, CDCl3):
d 7.55 (d, J = 8.8 Hz, 2H), 7.36–7.25
Chemicals used were obtained from commercial suppliers and
used without further purifications. 1H NMR spectra and 13C NMR
spectra were measured in CDCl3 and recorded on Bruker Avance-
400 spectrometer (400 MHz for 1H NMR, 100 MHz for 13C NMR)
with TMS as an internal standard. EIMS were determined with a
HP5989B mass spectrometer. Elemental analyses were performed
on an EA-1110 instrument.
(m, 4H), 7.01 (d, J = 8.8 Hz, 2H), 5.23 (q, J = 8.0 Hz, 1H), 3.86–3.79
(m, 1H), 3.54–3.48 (m, 1H), 3.00–3.19 (m, 2H); 13C NMR (100 MHz,
CDCl3):
d 151.4 (d, J = 0.8 Hz), 136.4,129.1, 128.8 (dd, J = 1.6 Hz,
J = 2.8 Hz), 128.5, 128.4 (q, J = 235.6 Hz), 127.21 (d, J = 286.0 Hz),
126.7, 126.6 (q, J = 4.0 Hz), 113.2 (d, J = 1.2 Hz), 60.7 (q, J = 30.6 Hz),
43.6, 27.3 (q, J = 2.1 Hz); MS (EI) m/z 345 (M+); Anal. Calcd. for
C17H13F6N: (%) C, 59.13; H, 3.79; N, 4.06. Found: C, 59.28; H, 3.97;
N, 3.98.
4.2. Typical procedure for trifluoromethylation of
tetrahydroisoquinolines
4.2.6. 1-(Trifluoromethyl)-1,2,3,4-tetrahydro-2-p-tolylisoquinoline
(2f)
RB (0.015 mmol, 5 mol%) was added to a mixture of 2-phenyl-
1,2,3,4-tetrahydroisoquinoline 1a (0.3 mmol), potassium fluoride
(1.5 mmol) and trifluoromethyltrimethylsilane (1.5 mmol) in
CH3CN (3 mL). The resulting mixture was stirred at room
temperature under green LEDs irradiation. After 1a was completely
consumed (monitored by TLC), the solvent was removed in vacuo.
The crude product was directly purified by SiO2 gel column
chromatography to give the corresponding product 2a.
1H NMR (400 MHz, CDCl3):
d 7.31–7.27 (m, 2H), 7.24–7.19 (m,
2H), 7.09 (d, J = 8.4 Hz, 2H), 6.88 (d, J = 8.0 Hz, 2H), 5.11 (q,
J = 8.0 Hz, 1H), 3.78–3.72 (m, 1H), 3.49–3.43 (m, 1H), 3.00–3.06 (br
s, 2H), 2.27 (s, 3H); 13C NMR (100 MHz, CDCl3):
d 147.4, 137.1,
129.9, 129.0, 128.9 (d, J = 1.3 Hz), 128.7, 128.6, 126.4, 126.2 (q,
J = 284.9 Hz), 115.0, 61.4 (q, J = 29.6 Hz), 43.9, 27.4, 20.4; MS (EI) m/
z 291 (M+); Anal. Calcd. for C17H16F3N: (%) C, 70.09; H, 5.54; N, 4.81.
Found: C, 70.21; H, 5.30; N, 4.93.
4.2.1. 1-(Trifluoromethyl)-1,2,3,4-tetrahydro-2-phenylisoquinoline
4.2.7. 1-(Trifluoromethyl)-1,2,3,4-tetrahydro-2-(4-
(2a)
methoxyphenyl)isoquinoline (2g)
1H NMR (400 MHz, CDCl3):
d
7.30–7.22(m, 6H), 6.99 (d, J = 8.0 Hz,
2H), 6.86 (t, J = 7.6 Hz, 1H), 5.17 (q, J = 7.6 Hz, 1H), 3.82–3.77 (m, 1H),
3.54–3.48 (m, 1H), 3.02–3.07 (m, 2H); 13C NMR (100 MHz, CDCl3):
149.4, 137.1, 129.4, 129.0 (d, J = 2.0 Hz), 128.9, 128.6, 126.5, 126.2 (q,
J = 285.0 Hz), 119.2, 114.6, 114.5, 61.2 (q, J = 29.6 Hz), 43.6, 27.5; MS
(EI) m/z 277 (M+); Anal. Calcd. for C16H14F3N: (%) C, 69.30; H, 5.09; N,
5.05. Found: C, 69.42; H, 5.24; N, 4.98.
1H NMR (400 MHz, CDCl3):
d 7.33–7.21 (m, 4H), 6.94 (d,
J = 8.8 Hz, 2H), 6.85 (d, J = 8.8 Hz, 2H), 5.01 (q, J = 8.0 Hz, 1H), 3.77
(s, 3H), 3.75–3.72 (m, 1H), 3.46–3.40 (m, 1H), 2.96–3.00 (m, 2H);
13C NMR (100 MHz, CDCl3):
d 153.6, 144.2, 137.1, 129.0, 128.8,
128.7, 126.4, 126.0 (q, J = 284.7 Hz), 117.6, 114.7, 62.0 (q,
J = 29.5 Hz), 55.8, 44.8, 27.3; MS (EI) m/z 307 (M+); Anal. Calcd.
for C17H16F3NO: (%) C, 66.44; H, 5.25; N, 4.56. Found: C, 66.18; H,
5.09; N, 4.70.
d
4.2.2. 1-(Trifluoromethyl)-2-(4-fluorophenyl)-1,2,3,4-
tetrahydroisoquinoline (2b)
4.2.8. 1-(Trifluoromethyl)-1,2,3,4-tetrahydro-2-(2-
1H NMR (400 MHz, CDCl3):
d
7.35–7.20 (m, 4H), 7.03–6.90 (m,
4H), 5.07 (q, J = 8.4 Hz, 1H), 3.77–3.69 (m, 1H), 3.48–3.39 (m, 1H),
2.94–3.07 (m, 2H); 13C NMR (100 MHz, CDCl3):
156.9 (d,
methoxyphenyl)isoquinoline (2h)
1H NMR (400 MHz, CDCl3):
d 7.35–7.20 (m, 4H), 6.99 (t,
d
J = 8.0 Hz, 2H), 6.86 (d, J = 8.0 Hz, 2H), 5.15 (q, J = 8.4 Hz, 1H), 3.80
J = 238.0 Hz), 146.2 (d, J = 2.5 Hz), 136.8, 128.9 (q, J = 1.5 Hz), 128.8
(q, J = 1.5 Hz), 128.7, 128.6 (q, J = 0.8 Hz), 126.5, 126.1 (q,
J = 285.2 Hz), 116.7 (d, J = 1.0 Hz), 116.5 (d, J = 0.8 Hz), 115.8,
115.7, 61.6 (q, J = 29.5 Hz), 44.5 (d, J = 1.0 Hz), 27.3 (d, J = 1.2 Hz);
MS (EI) m/z 295 (M+); Anal. Calcd. for C16H13F4N: (%) C, 65.08; H,
4.44; N, 4.74. Found: C, 65.23; H, 4.19; N, 4.55.
(s, 3H), 3.74–3.69 (m, 1H), 3.52–3.45 (m, 1H), 2.90–3.05 (m, 2H);
13C NMR (100 MHz, CDCl3):
d 153.2, 139.9, 136.7, 129.3, 128.9,
128.7, 128.1, 126.4 (q, J = 287.3 Hz), 125.9, 124.2, 123.9, 121.2,
121.1, 60.6 (q, J = 27.0 Hz), 55.6, 45.3, 28.1; MS (EI) m/z 307 (M+);
Anal. Calcd. for C17H16F3NO: (%) C, 66.44; H, 5.25; N, 4.56. Found: C,
66.31; H, 5.41; N, 4.63.
4.2.3. 2-(4-Chlorophenyl)-1-(trifluoromethyl)-1,2,3,4-
4.2.9. 1-(Trifluoromethyl)-1,2,3,4-tetrahydro-2-(naphthalen-1-
tetrahydroisoquinoline (2c)
yl)isoquinoline (2i)
1H NMR (400 MHz, CDCl3):
d
7.37–7.21 (m, 6H), 6.89 (d,
J = 9.2 Hz, 2H), 5.09 (q, J = 8.0 Hz, 1H), 3.78–3.70 (m, 1H), 3.48–3.40
(m, 1H), 2.96–3.10 (m, 2H); 13C NMR (100 MHz, CDCl3):
147.9,
136.7, 129.3, 129.1, 128.9, 128.8 (q, J = 1.6 Hz), 128.6 (d, J = 1.2 Hz),
1H NMR (400 MHz, CDCl3):
d 8.34–8.30 (m, 1H), 7.90–7.86 (m,
1H), 7.63 (d, J = 8.2 Hz, 1H), 7.55–7.46 (m, 3H), 7.41–7.24 (m, 4H),
7.01 (br, 1H), 5.01 (q, J = 8.4 Hz, 1H), 3.87–3.76 (m, 1H), 3.43–3.38
(m, 1H), 3.00–2.83 (m, 2H); 13C NMR (100 MHz, CDCl3):
d
d 148.4,

W. Fu et al. / Journal of Fluorine Chemistry 140 (2012) 88–94
93
137.3, 134.9, 129.2, 128.8 (q, J = 2.3 Hz), 128.5, 126.2, 126.1, 126.0,
125.8, 125.1, 123.8, 119.9, 113.1, 62.3 (q, J = 28.9 Hz), 47.2, 26.4;
MS (EI) m/z 327 (M+); Anal. Calcd. for C20H16F3N: (%) C, 73.38; H,
4.93; N, 4.28. Found: C, 73.30; H, 4.92; N, 4.40.
directly purified by SiO2 gel column chromatography to give the
corresponding product 3a.
4.3.1. 1,2,3,4-Tetrahydro-2-phenyl-1-(2-phenylethynyl)isoquinoline
(3a)
4.2.10. 2-Allyl-1,2,3,4-tetrahydroisoquinoline (2j)
1H NMR (400 MHz, CDCl3):
d 7.43–7.30 (m, 5H), 7.26–7.20 (m,
1H NMR (400 MHz, CDCl3):
d
7.44–7.32 (m, 4H), 6.11–6.01 (m,
6H), 7.15 (d, J = 7.9 Hz, 2H), 6.93 (t, J = 7.2 Hz, 1H), 5.68 (s, 1H), 3.81–
1H), 5.35–5.28 (m, 2H), 4.34 (q, J = 8.4 Hz, 1H), 3.55 (d, J = 7.2 Hz,
2H), 3.46–3.40 (m, 1H), 2.98–2.87 (m, 3H); 13C NMR (100 MHz,
3.74 (m, 1H), 3.72–3.65 (m, 1H), 3.27–3.12 (m, 1H), 2.99 (dt,
J = 16.2 Hz, J = 4.0 Hz, 1); 13C NMR (100 MHz, CDCl3):
d 149.5, 135.2,
CDCl3):
d
137.5, 134.9, 129.5 (dd, J = 1.8 Hz, J = 3.2 Hz), 128.5, 128.3
134.3, 131.7, 129.2, 128.9, 128.1, 128.0, 127.5, 127.3, 126.2, 122.9,
(dd, J = 1.0 Hz, J = 1.2 Hz), 128.0, 127.2 (q, J = 284.0 Hz), 126.0,
118.3, 61.3 (q, J = 28.2 Hz), 59.0, 46.1, 28.9; MS (EI) m/z 241 (M+);
Anal. Calcd. for C13H14F3N: (%) C, 64.72; H, 5.85; N, 5.81. Found: C,
64.60; H, 5.68; N, 5.92.
119.8, 116.7, 88.5, 84.7, 52.3, 43.4, 28.7; MS (EI) m/z 309 (M+).
4.3.2. 1,2,3,4-Tetrahydro-2-phenyl-1-(2-p-tolylethynyl)isoquinoline
(3b)
1H NMR (400 MHz, CDCl3):
d 7.41–7.30 (m, 3H), 7.25–7.13 (m,
4.2.11. 2-Benzyl-1-(trifluoromethyl)-1,2,3,4-tetrahydroisoquinoline
7H), 7.01 (d, J = 8.0 Hz, 2H), 6.90 (t, J = 7.2 Hz, 1H), 5.65 (s, 1H), 3.80–
3.65 (m, 2H), 3.25–3.12 (m, 1H), 3.01 (dt, J = 16.0 Hz, J = 3.6 Hz, 1H),
2.29 (s, 3H); 13C NMR (100 MHz, CDCl3):
d149.5, 138.1, 135.4, 134.3,
(2k)
1H NMR (400 MHz, CDCl3):
d
7.35–7.10 (m, 9H), 4.20 (q,
J = 8.0 Hz, 1H), 3.89 (dd, J = 13.6 Hz, J = 40.8 Hz, 2H), 3.25–3.140 (m,
1H), 2.73–2.65 (m, 2H), 2.61–2.54 (m, 1H); 13C NMR (100 MHz,
131.5, 129.2, 128.8, 128.7, 127.5, 127.1, 126.1, 119.7, 119.6, 116.8,
87.6, 84.9, 52.3, 43.5, 28.8, 21.3; MS (EI) m/z 323 (M+).
CDCl3):
d 137.6, 136.3, 128.6 (d, J = 1.7 Hz), 127.6, 127.5, 127.4,
127.1, 126.3, 125.1 (d, J = 283.1 Hz), 61.5 (q, J = 27.5 Hz), 59.6, 44.3,
26.4; MS (EI) m/z 291 (M+); Anal. Calcd. for C17H16F3N: (%) C, 70.09;
H, 5.54; N, 4.81. Found: C, 70.22; H, 5.76; N, 4.70.
4.3.3. 1,2,3,4-Tetrahydro-1-(2-(4-methoxyphenyl)ethynyl)-2-
phenylisoquinoline (3c)
1H NMR (400 MHz, CDCl3):
d 7.35–7.32 (m, 1H), 7.31–7.26 (m,
2H), 7.21–7.15 (m, 4H), 7.15–7.10 (m, 1H), 7.08 (d, J = 8.0 Hz, 2H),
6.84 (dd, J = 7.6, 7.6 Hz, 1H), 6.69 (dt, J = 8.8, 2.4 Hz, 2H), 5.59 (s,
1H), 3.75–3.61 (m, 2H), 3.66 (s, 3H), 3.10 (ddd, J = 16.0, 9.6, 6.2 Hz,
4.2.12. 1-(Trifluoromethyl)-1,2,3,4-tetrahydro-2-methylisoquinoline
(2l)
1H NMR (400 MHz, CDCl3):
d
7.23–7.10 (m, 4H), 3.99 (q,
J = 8.0 Hz, 1H), 3.21–3.14 (m, 1H), 2.87–2.80 (m, 1H), 2.76–2.69 (m,
1H), 2.61 (s, 3H), 2.57–2.53 (m, 1H); 13C NMR (100 MHz, CDCl3):
1H), 2.92 (dt, J = 16.0, 3.6 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d
159.1, 149.3, 135.4, 134.2, 132.9, 128.9, 128.7, 127.3, 126.9, 126.0,
119.3, 116.4, 114.9, 113.5, 87.0, 84.5, 55.2, 52.2, 43.4, 28.9; MS (EI)
m/z 339 (M+).
d
137.6, 129.4 (q, J = 1.8 Hz), 128.3, 128.2 (q, J = 1.5 Hz), 128.1, 126.1
(q, J = 282.1 Hz), 126.1, 64.9 (q, J = 29.7 Hz), 49.9, 45.5 (t, J = 1.6 Hz),
28.1; MS (EI) m/z 215 (M+); Anal. Calcd. for C11H12F3N: (%) C, 61.39;
H, 5.62; N, 6.51. Found: C, 61.54; H, 5.50; N, 6.63.
4.3.4. 1-(2-(4-Fluorophenyl)ethynyl)-1,2,3,4-tetrahydro-2-
phenylisoquinoline (3d)
1H NMR (400 MHz, CDCl3):
d 7.41–7.18 (m, 8H), 7.12 (d,
4.2.13. 7-bromo-1-(trifluoromethyl)-1,2,3,4-tetrahydro-2-
J = 8.0 Hz, 2H), 6.94–6.85 (m, 3H), 5.62 (s, 1H), 3.82–3.71 (m, 1H),
3.70–3.60 (m, 1H), 3.15 (ddd, J = 16.0, 10.4, 6.0 Hz, 1H), 2.98 (ddd,
J = 16.0, 3.8, 3.8 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d 163.6 (d,
phenylisoquinoline (2m)
1H NMR (400 MHz, CDCl3):
d
7.45 (s, 1H), 7.40 (d, J = 8.4 Hz, 1H),
7.30–7.21 (m, 2H), 7.06 (d, J = 8.0 Hz, 1H), 6.92 (d, J = 8.0 Hz, 2H),
6.87 (t, J = 7.6 Hz, 1H), 5.12 (q, J = 8.0 Hz, 1H), 3.77–3.70 (m, 1H),
3.57–3.18 (m, 1H), 2.97–2.93 (m, 2H); 13C NMR (100 MHz, CDCl3):
J = 247.3 Hz), 149.4, 135.1, 134.0, 133.4 (d, J = 8.5 Hz), 129.0, 128.9,
127.1, 127.0, 126.1, 119.6, 118.9 (d, J = 3.2 Hz), 116.5, 115.2 (d,
J = 22.3 Hz), 88.4, 83.5, 52.4, 43.5, 29.1; MS (EI) m/z 327 (M+).
d
149.2, 135.8, 131.8, 131.5 (q, J = 2.1 Hz), 130.8 (q, J = 1.6 Hz),
130.2, 129.5, 125.9 (q, J = 286.0 Hz), 119.7, 119.6, 114.9 (d,
J = 1.2 Hz), 60.7 (d, J = 29.9 Hz), 43.2 (d, J = 0.8 Hz), 26.7 (d,
J = 1.6 Hz); MS (EI) m/z 355 (M+); Anal. Calcd. for C16H13BrF3N:
(%) C, 53.95; H, 3.68; N, 3.93. Found: C, 53.87; H, 3.79; N, 3.80.
4.3.5. 1-(2-(4-Bromophenyl)ethynyl)-1,2,3,4-tetrahydro-2-
phenylisoquinoline (3e)
1H NMR (400 MHz, CDCl3):
d 7.36–7.28 (m, 4H), 7.25–7.15 (m,
4H), 7.13–7.05 (m, 4H), 6.89 (dt, J = 7.6, 1.2 Hz, 1H), 5.61 (s, 1H),
3.77–3.58 (m, 2H), 3.13 (ddd, J = 15.6, 9.6, 5.6 Hz, 1H), 2.95 (dt,
J = 16.0, 4.4 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d 149.4, 134.9,
4.2.14. 1-(Trifluoromethyl)-1,2,3,4-tetrahydro-6,7-dimethoxy-2-
phenylisoquinoline (2n)
134.3, 133.0, 131.2, 129.0, 128.8, 127.3, 127.2, 126.3, 122.1, 121.8,
119.6, 116.5, 89.7, 83.6, 52.3, 43.5, 28.9; MS (EI) m/z 387 (M+).
1H NMR (400 MHz, CDCl3):
d
7.31 (t, J = 8.4 Hz, 2H), 7.00 (d,
J = 8.0 Hz, 2H), 6.91–6.86 (m, 2H), 6.73 (s, 1H), 5.13 (q, J = 7.6 Hz,
1H), 3.90 (s, 6H), 3.82–3.75 (m, 1H), 3.61–3.53 (m, 1H), 2.97–2.91
4.3.6. 1-(Hex-1-ynyl)-1,2,3,4-tetrahydro-2-phenylisoquinoline (3f)
(m, 2H); 13C NMR (100 MHz, CDCl3):
d
149.5, 129.2, 147.4, 129.3,
1H NMR (400 MHz, CDCl3):
d 7.26–7.19 (m, 3H), 7.15–7.06 (m,
126.2 (q, J = 285.7 Hz), 120.4, 120.3, 119.2, 114.8, 111.5 (q,
J = 2.2 Hz), 111.2, 60.8 (q, J = 29.6 Hz), 56.0, 55.9, 43.4, 26.7 (q,
J = 1.2 Hz); MS (EI) m/z 337 (M+); Anal. Calcd. for C18H18F3NO2: (%)
C, 64.09; H, 5.38; N, 4.15. Found: C, 64.24; H, 5.57; N, 4.02.
3H), 6.98 (d, J = 8.2 Hz, 2H), 6.81 (t, J = 7.2 Hz, 1H), 5.36 (s, 1H), 3.62
(m, 1H), 3.52 (ddd, J = 12.4 Hz, J = 10.4 Hz, J = 4.4 Hz, 1H), 3.04 (ddd,
J = 16.2 Hz, J = 10.2 Hz, J = 6.0 Hz, 1H), 2.86 (dt, J = 16.0 Hz,
J = 3.6 Hz, 1H), 2.02 (m, 2H), 1.32–1.23 (m, 2H), 1.22–1.11 (m,
2H), 0.75 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3):
d 136.2,
4.3. Typical procedure for alkynylation of tetrahydroisoquinolines
134.1, 129.2, 128.9, 127.3, 127.1, 126.1, 119.6, 116.8, 52.0, 43.4,
30.8, 28.8, 21.7, 18.5, 13.4; MS (EI) m/z 289 (M+).
RB (5 mol%) was added to a mixture of 2-phenyl-1,2,3,4-
tetrahydroisoquinoline 1a (0.3 mmol), CuI (10 mol%) and alkyne
(0.45 mmol, 1.5 equiv.) in CH3CN (3 mL). The resulting mixture
was stirred at room temperature under green LEDs irradiation for
the time indicated. After 1a was completely consumed (monitored
by TLC), the solvent was removed in vacuo. The crude product was
4.3.7. 1,2,3,4-Tetrahydro-1-(2-phenylethynyl)-2-p-tolylisoquinoline
(3g)
1H NMR (400 MHz, CDCl3):
d 7.41–7.35 (m, 1H), 7.35–7.27 (m,
1H), 7.25–7.16 (m, 2H), 7.13 (d, J = 8.4 Hz, 1H), 7.04 (d, J = 8.4 Hz,
1H), 5.61 (s, 1H), 3.71–3.60 (m, 1H), 3.18 (ddd, J = 16.6 Hz,

94
W. Fu et al. / Journal of Fluorine Chemistry 140 (2012) 88–94
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J = 9.4 Hz, J = 7.4 Hz, 1H), 2.96 (dt, J = 16.0 Hz, J = 3.5 Hz, 1H), 2.31
(s, 1H); 13C NMR (100 MHz, CDCl3):
134.2, 131.7, 129.7, 128.9,
128.2, 128.1, 127.4, 127.3, 126.2, 117.5, 53.1, 43.9, 28.8, 20.6; MS
(EI) m/z 323 (M+).
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d
4.3.8. 1,2,3,4-Tetrahydro-2-(4-methoxyphenyl)-1-(2-
phenylethynyl)isoquinoline (3h)
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1H NMR (400 MHz, CDCl3):
d 7.35 (s, 1H), 7.26–7.06 (m, 10H),
6.89 (d, J = 8.0 Hz, 2H), 5.52 (s, 1H), 3.81 (s, 3H), 3.71–3.46 (m, 2H),
3.15 (ddd, J = 16.0, 10.8, 6.8 Hz, 1H), 2.95 (d, J = 16.4 Hz, 1H); 13C
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NMR (100 MHz, CDCl3):
d 154.4, 144.3, 135.8, 134.2, 131.9, 129.4,
128.2, 128.1, 127.6, 127.3, 126.4, 123.3, 120.3, 114.8, 89.1, 85.8,
55.9, 54.7, 44.9, 29.6. MS (EI) m/z 339 (M+).
4.3.9. 2-(4-Chlorophenyl)-1,2,3,4-tetrahydro-1-(2-
phenylethynyl)isoquinoline (3i)
1H NMR (400 MHz, CDCl3):
d 7.46–7.35 (m, 1H), 7.34–7.20 (m,
10H), 7.06 (d, J = 8.8 Hz, 2H), 5.65 (s, 1H), 3.76–3.70 (m, 2H), 3.20
(ddd, J = 16.0 Hz, J = 9.6 Hz, J = 7.2 Hz, 1H), 3.05 (dt, J = 16.0 Hz,
J = 4.0 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d 148.4, 135.2, 134.0,
131.9, 129.1, 128.9, 128.3, 128.2, 127.5, 127.3, 126.4, 124.5, 122.8,
117.9, 88.3, 85.2, 52.3, 43.6, 28.8; MS (EI) m/z 343 (M+).
4.3.10. 1,2,3,4-Tetrahydro-2-(naphthalen-3-yl)-1-(2-
phenylethynyl)isoquinoline (3j)
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1H NMR (400 MHz, CDCl3):
d 7.82–7.71 (m, 3H), 7.44–7.39 (m,
4H), 7.35–7.20 (m, 9H), 5.81 (s, 1H), 3.91 (m, 1H), 3.58 (ddd,
J = 12.4 Hz, J = 10.4 Hz, J = 4.4 Hz, 1H), 3.12 (ddd, J = 16.0 Hz,
J = 10.4 Hz, J = 6.2 Hz, 1H), 2.94 (dt, J = 16.0 Hz, J = 4.0 Hz, 1H),
2.34–2.27 (m, 1H); 13C NMR (100 MHz, CDCl3):
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d 147.3, 135.4,
134.7, 134.3, 131.7, 129.1, 128.9, 128.5, 128.1, 127.6, 127.5, 127.4,
126.9, 126.3, 126.2, 123.5, 122.9, 119.3, 111.5, 88.3, 85.1, 52.5, 43.6,
28.9; MS (EI) m/z 359 (M+).
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Acknowledgments
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We are grateful to the National Natural Science Foundation of
China (Project Nos. 20902042 and 20902043) and Foundation of
He’nan Educational Committee (No. 2010B150020).
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