B(C6F5)3: an efficient catalyst for reductive alkylation of alkoxy benzenes and for synthesis of triarylmethanes using aldehydes

Article abstract of DOI:10.1016/j.tetlet.2009.09.085

Tris(pentafluorophenyl)borane [B(C₆F₅)₃] has been used as an efficient catalyst for reductive alkylation of alkoxy benzenes using aldehydes as an alkylating agent in the presence of polymethylhydrosiloxane (PMHS). Various alkylated trimethoxybenzene derivatives have been prepared in good to high yields. In addition, B(C₆F₅)₃ was also used as a catalyst for the reaction of electron-rich arenes with aldehydes to obtain triarylmethanes. The use of reductive alkylation protocol for the synthesis of an isochroman and tetrahydroisoquinoline derivatives has also been demonstrated.

Full text of DOI:10.1016/j.tetlet.2009.09.085

Tetrahedron Letters 50 (2009) 6693–6697
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Tetrahedron Letters
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B(C6F5)3: an efficient catalyst for reductive alkylation of alkoxy benzenes
and for synthesis of triarylmethanes using aldehydes
*
S. Chandrasekhar , Sanjida Khatun, G. Rajesh, Ch. Raji Reddy
Organic Division-I, Indian Institute of Chemical Technology, Hyderabad 500 007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 28 April 2009
Revised 11 September 2009
Accepted 16 September 2009
Available online 19 September 2009
Tris(pentafluorophenyl)borane [B(C6F5)3] has been used as an efficient catalyst for reductive alkylation of
alkoxy benzenes using aldehydes as an alkylating agent in the presence of polymethylhydrosiloxane
(PMHS). Various alkylated trimethoxybenzene derivatives have been prepared in good to high yields.
In addition, B(C6F5)3 was also used as a catalyst for the reaction of electron-rich arenes with aldehydes
to obtain triarylmethanes. The use of reductive alkylation protocol for the synthesis of an isochroman
and tetrahydroisoquinoline derivatives has also been demonstrated.
Keywords:
Ó 2009 Elsevier Ltd. All rights reserved.
Tris(pentafluorophenyl)borane
Polymethylhydrosiloxane
Reductive alkylation
Electron-rich arenes
Aldehyde
Friedel–Crafts alkylation of aromatic compounds is one of the
important reactions, which has found significant applications in
the synthesis of various biologically active compounds.1 Common
synthetic methods for the alkylation include the reaction of aro-
matic compounds with alkyl halides in the presence of Lewis acid
activators.2 The alternative methods used to obtain the alkylated
aromatics are; acylation followed by reduction,3 alkylation with
alcohol or its derivatives,4,5 and alkenylation with organometallic
reagents.6 Further, reductive alkylation of aromatic compounds
can be achieved by using carbonyl compounds as alkylating agents,7
which are very limited. Hence, there has been a considerable interest
in the development of a mild and efficient method for reductive
alkylation of aromatics.
The efficiency of tris(pentafluorophenyl)borane [B(C6F5)3] cata-
lyst has been revealed in combination with silanes for the various
reduction procedures by us8 and others.9 In our continued interest
in the development of new reduction procedures,8,10 we envi-
sioned that the reductive alkylation of electron-rich aromatics (1)
with aldehydes (2) in the presence of PMHS–B(C6F5)3 would pro-
ceed smoothly to give the alkylated products (3).
representative aromatic compound. As can be seen from Table 1,
varieties of aldehydes were used as alkylating agents to give the
corresponding alkylated trimethoxybenzene in good yields. Ali-
phatic aldehydes 2a, 2b, and 2c, successfully participated in the
reductive alkylation of trimethoxybenzene under the present reac-
tion conditions to provide the corresponding alkylated products 3a
to 3c (Table 1, entries 1–3) without rearrangement. Further, substi-
tuted aromatic aldehydes such as 2-nitro, 4-fluoro, 3-hydroxy, and
2,5-dimethoxy benzaldehydes, 2e, 2f, 2g, and 2h, were well reacted
with trimethoxybenzene under PMHS–B(C6F5)3 reagent system to
give the corresponding benzylated trimethoxybenzenes, 3e to 3h
(Table 1, entries 5–8). To our delight, furanose aldehyde 2j obtained
from glucose di-acetonide, was also used as an alkylating agent to
obtain trimethoxybenzyl furanose 3j in 89% yield (Table 1, entry
10) which can be mimicked as C-aryl sugar. However, the reaction
of trimethoxybenzene with acetophenone (2k) was unsuccessful
even under reflux temperature and/or for longer reaction time (Ta-
ble 1, entry 11).
The encouraging results described above for the reductive alkyl-
ation of 1,3,5-trimethoxybenzene spurred us to test the reactivity
With this idea, we first attempted the reaction of trimethoxyben-
zene (1a) with benzaldehyde (2d) in CH2Cl2 using polymethylhy-
drosiloxane in the presence of 5 mol % of B(C6F5)3 and the reaction
was completed in 1 h to give the benzyl trimethoxybenzene (3d)
in 90% yield (Scheme 1 and Table 1, entry 4). Further, the generality
of this reaction was examined by using trimethoxybenzene (1a) as a
R
MeO
OMe
+ Ph-CHO
PMHS
MeO
OMe
B(C6F5)3-5 mol%
CH2Cl2, rt, 1h
OMe
2d
3d
OMe
1a
R = alkyl, aryl
Scheme 1. Reductive alkylation.
* Corresponding author. Tel.: +91 40 27193210; fax: +91 40 27160512.
E-mail address: srivaric@iict.res.in (S. Chandrasekhar).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.09.085

6694
S. Chandrasekhar et al. / Tetrahedron Letters 50 (2009) 6693–6697
Table 1
Reductive alkylation of trimethoxybenzene (1) with aldehydes using PMHS–5 mol % of B(C6F5)3
Entry
1
Aldehyde (2)
Time (h)
Product (3)
OMe
Yielda (%)
92
1
2a
3a
3b
3c
3d
3e
3f
CHO
MeO
MeO
MeO
MeO
MeO
MeO
OMe
OMe
OMe
OMe
OMe
OMe
OMe
2
3
1.5
1.5
1
91
91
90
88
88
87
94
91
89
—
2b
2c
CHO
CHO
3
4
OMe
4
PHCHO 2d
Ph
OMe
NO2
NO2
CHO
5
1
2e
OMe
OMe
CHO
2f
6
1.5
2.5
2
F
F
OMe
OMe
HO
CHO
2g
OH
7
3g
OMe
OMe
MeO
MeO
OMe
OMe
CHO
8
3h
2h
OMe
CHO
OMe
O
OMe
OMe
OMe
OMe
9
2
O
3i
2i
MeO
MeO
OMe
O
O
O
O
OHC
BnO
O
10
1.5
12
O
BnO
OMe
2j
3j
O
11b
No reaction
2k
a
Isolated yield.
Reaction was also carried at reflux temperature.
b
of other electron-rich arenes. Thus, the reaction of 3,5-dimethoxy-
benzyl alcohol (1b) and 3,5-dibenzyloxybenzyl alcohol (1c) with
benzaldehyde (2d) in the presence of PMHS and 5 mol % of
B(C6F5)3 was tested, which gave the corresponding alkylated prod-
ucts 3k and 3l in good yields (Table 2, entries 1 and 2). On the other
hand, the treatment of indole (1d) and 2-methylfuran (1e) with
benzaldehyde under the described reductive alkylation conditions
[PMHS–B(C6F5)3] did not provide the expected reductive alkylative
product, instead the triarylmethanes 4a and 4b were obtained
(Table 2, entries 3 and 4). The formation of these products was ob-
served within 15 min. This may be due to the more nucleophilic
nature of indole and 2-methylfuran compared to the PMHS in
the presence of B(C6F5)3.11 To obtain the triarylmethane product
from 1,3,5-trimethoxybenzne (1a), the reaction of 1a was carried
out with benzaldehyde and 5 mol % of B(C6F5)3 in the absence of
PMHS and as expected the triarylmethane 4c was obtained in

S. Chandrasekhar et al. / Tetrahedron Letters 50 (2009) 6693–6697
6695
Table 2
Reaction of electron-rich arenes with benzaldehyde (2d) using PMHS–5 mol % of B(C6F5)3
Entry
Arene
Time (h)
Product
Yielda (%)
OH
OH
1b
3k
1
2
78
73
MeO
OMe
MeO
OMe
Ph
OH
OH
1c
3l
2
2.5
BnO
OBn
BnO
OBn
Ph
Ph
3
4
0.25
0.25
94
92
N
N
H
1d
N
H
4a
H
Ph
O
1e
O
O
4b
MeO
Ph
MeO
OMe
MeO
5b
3
85
OMe
MeO
OMe
OMe
OMe
1a
4c
a
b
c
Isolated yield.
Reaction was also carried out in the absence of PMHS.
Yield calculated based on indole.
Table 3
B(C6F5)3-catalyzed reaction of electron-rich arenes with aldehydes
Entry
Arene
Aldehyde
Time (h)
Product
Yielda (%)
F
F
F
F
F
F
4c
1
1a
3
82
2l
CHO
[2,4,6-(OMe)3] [2,4,6-(OMe)3]
Br
B2
OH
2
1a
2.5
78
OH
CHO
4d
2m
[2,4,6-(OMe)3] [2,4,6-(OMe)3]
F
F
F
3
1d
1e
2l
0.5
0.5
93
92
N
N
H
4e
H
Br
OH
4
2m
4f
O
O
a
Isolated yield.

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S. Chandrasekhar et al. / Tetrahedron Letters 50 (2009) 6693–6697
3. (a) Roth, B.; Aig, E.; Rauckman, B. S.; Strelitz, J. Z.; Phillips, A. P. J. Med. Chem.
X
X
PMHS
B(C6F5)3-5 mol%
1981, 24, 933; (b) Matsumoto, T.; Singh, I. P.; Etoh, H.; Tanaka, H. Chem. Lett.
2001, 210; (c) Katritzky, A. R.; Tao, H.; Jiang, R.; Suzuki, K.; Kirichenko, K. J. Org.
Chem. 2007, 72, 407.
CHO
OMe
CH2Cl2, rt, 2 h
4. (a) Nay, B.; Collet, M.; Lebon, M.; Cheze, C.; Vercauteren, J. Tetrahedron Lett.
2002, 43, 2675; (b) Cottineau, B.; Chenault, J.; Guillaumet, G. Tetrahedron Lett.
2006, 47, 817.
5. (a) Butsugan, Y.; Nagai, K.; Nagaya, F.; Tabuchi, H.; Yamada, K.; Araki, S. Bull.
Chem. Soc. Jpn. 1988, 61, 1707; (b) Bergh, A.; Leffler, H.; Sundin, A.; Nilsson, U. J.;
Kann, N. Tetrahedron 2006, 62, 8309; (c) Li, C.; Wang, J. J. Org. Chem. 2007, 72,
7431.
MeO
MeO
OMe
X= O, 5a
X= NBoc, 5b
X= O, 64%, 6a
X= NBoc, 46%, 6b
Scheme 2. Intramolecular reductive alkylation.
6. (a) Shi, Z.; He, C. J. Org. Chem. 2004, 69, 3669; (b) Roelens, F.; Huvaere, K.;
Dhooge, W.; Cleemput, M. V.; Comhaire, F.; Keukeleire, D. D. Eur. J. Med. Chem.
2005, 40, 1042; (c) Roelens, F.; Heldring, N.; Dhooge, W.; Bengtsson, M.;
Comhaire, F.; Gustafsson, J. A.; Treuter, E.; Keukeleire, D. D. J. Med. Chem. 2006,
49, 7357.
7. (a) Miyai, T.; Onishi, Y.; Baba, A. Tetrahedron Lett. 1998, 39, 6291; (b) Dube, D.;
Scholte, A. A. Tetrahedron Lett. 1999, 40, 2295; (c) Miyai, T.; Onishi, Y.; Baba, A.
Tetrahedron 1999, 55, 1017; (d) Augustine, J. K.; Naik, Y. A.; Mandal, A. B.;
Alagarsamy, P.; Akabote, V. Synlett 2008, 2429.
85% yield (Table 2, entry 5). This observation of triarylmethane for-
mation12–14 in the presence of B(C6F5)3 prompted us to examine
the diversity in the aldehyde part. Table 3 describes the reaction
of electron-rich arenes 1a, 1d, and 1e with different aldehydes to
obtain the corresponding alkylated products 4c to 4f in good yields
(Table 3, entries 1–5).
8. (a) Chandrasekhar, S.; Chandrasekhar, G.; Vijeender, K.; Reddy, M. S.
Tetrahedron Lett. 2006, 47, 3475; (b) Chandrasekhar, S.; Chandrashekar, G.;
Reddy, M. S.; Srihari, P. Org. Biomol. Chem. 2006, 4, 1650; (c) Chandrasekhar, S.;
Chandrashekar, G.; Babu, B. N.; Vijeender, K.; Reddy, K. V. Tetrahedron Lett.
2004, 45, 5497; (d) Chandrasekhar, S.; Reddy, C. R.; Babu, B. N. J. Org. Chem.
2002, 67, 9080. and references cited therein.
9. (a) Gevorgyan, V.; Rubin, M.; Benson, S.; Liu, J.-X.; Yamamoto, Y. J. Org. Chem.
2000, 65, 6179; (b) Parks, D. J.; Piers, W. E. J. Am. Chem. Soc. 1996, 118, 9440; (c)
Gevorgyan, V.; Rubin, M.; Liu, J.-X.; Yamamoto, Y. J. Org. Chem. 2001, 66, 1672;
(d) Parks, D. J.; Blackwell, J. M.; Piers, W. E. J. Org. Chem. 2000, 65, 3090; (e)
Dierker, G.; Ugolotti, J.; Kehr, G.; Froehlich, R.; Erker, G. Adv. Synth. Cat. 2009,
351, 1080; (f) Chojnowski, J.; Rubinsztajn, S.; Cella, J. A.; Fortuniak, W.; Cypryk,
M.; Kurjata, J.; Kazmierski, K. Organometallics 2005, 24, 6077.
10. (a) Reddy, C. R.; Vijeender, K.; Parida, B. B.; Madhavi, P. P.; Chandrasekhar, S.
Tetrahedron Lett. 2007, 48, 2765; (b) Chandrasekhar, S.; Debjit, B.; Reddy, C. R.
Synthesis 2007, 1509.
11. These results indicate that the electron-rich arene will first undergo Friedel–
Crafts alkylation with aldehyde followed by nucleophilic addition of hydride or
with arene based on their reactivity.
Next, we set out to expand this method to application for the
intramolecular reductive alkylation (Scheme 2). Consequently,
treatment of 5a and 5b with PMHS–B(C6F5)3 reagent system
afforded the corresponding intramolecular alkylated products,
isochroman derivative 6a (64%) and tetrahydroisoquinoline deriva-
tive 6b (46%) without effecting the Boc protection. All the products
obtained were fully characterized by 1H, 13C NMR, mass, and IR
spectra.15
In summary, an efficient B(C6F5)3-catalyzed reductive alkylation
of alkoxybenzenes using aldehyde as alkylating agents is success-
fully established in the presence of PMHS. Further, B(C6F5)3-cata-
lyzed reaction of electron-rich arenes with aldehydes to obtain
triarylmethanes has also been demonstrated. The reaction de-
scribed here is mild, efficient, general, and gives good yield of the
product. The utility of the present method was successfully dem-
onstrated for the synthesis of isochroman and tetrahydroisoquino-
line derivatives.
12. The importance of triarylmethanes, see: (a) Mibu, N.; Sumoto, K. Chem. Pharm.
Bull. 2000, 48, 1810; (b) Nair, V.; Thomas, S.; Mathew, S. C.; Abhilash, K. G.
Tetrahedron 2006, 62, 6731.
13. Earlier methods for the preparation of triarylmethanes, see: (a) Roomi, M.;
MacDonald, S. Can. J. Chem 1970, 48, 139; (b) Banerji, J.; Chatterjee, A.; Manna,
S.; Pascard, C.; Prange, T.; Shoolery, J. Heterocycles 1981, 15, 325; (c) Chen, D.;
Yu, L.; Wang, P. G. Tetrahedron Lett. 1996, 37, 4467; (d) Babu, G.; Sridhar, N.;
Perumal, P. T. Synth. Commun. 2000, 30, 1609; (e) Yadav, J. S.; Reddy, B. V. S.;
Murthy, C. V. S. R.; Kumar, G. M.; Madan, C. Synthesis 2001, 783; (f) Yadav, J. S.;
Reddy, B. V. S.; Satheesh, G. Tetrahedron Lett. 2004, 45, 3673; (g) Sharma, G. V.
M.; Reddy, J. J.; Lakshmi, P. S.; Krishna, P. R. Tetrahedron Lett. 2004, 45, 7729.
and references cited therein.
14. Recent methods for the preparation of triarylmethanes, see: (a) Nair, V.;
Abhilash, K. G.; Vidya, N. Org. Lett. 2005, 7, 5857; (b) Nair, V.; Abhilash, K. G.;
Vidya, N. Synthesis 2006, 3647; (c) Roy, S.; Roy, U. K.; Choudhury, J.; Poddar, S. J.
Org. Chem. 2007, 72, 3100; (d) Kodomari, M.; Nagamatsu, M.; Akaike, M.;
Aoyama, T. Tetrahedron Lett. 2008, 49, 2537.
Representative experimental procedure for reductive alkylation:
To
a stirred solution of trimethoxybenzene (1a, 1 mmol) in
dichloromethane, benzaldehyde (2d, 1 mmol) was added. To this
stirred solution, polymethylhydrosiloxane (3 mmol) and 5 mol %
of B(C6F5)3 were added at room temperature and the reaction
progress was monitored by TLC analysis. After the completion of
the reaction (1 h), the solvent was evaporated under vacuum and
the residue was purified by column chromatography on silica gel
using ethyl acetate and hexanes (10:90) as eluent to give the ben-
zyl trimethoxybenzene 3d in 90% yield.
15. Spectral data of new compounds: (3e): mp 95.7–96.5 °C; 1H NMR (CDCl3,
300 MHz): d 7.78 (dd, J = 1.32, 8.12 Hz, 1H), 7.35 (dt, J = 1.3, 7.5 Hz, 1H), 7.25–
7.13 (m, 2H), 6.13 (s, 2H), 4.22 (s, 2H), 3.81 (s, 3H), 3.73 (s, 6H); 13C NMR
(CDCl3, 75 MHz): d 160.2 (2C), 158.8, 149.9, 136.7, 132.2, 130.6, 126.0, 123.7,
108.1, 90.3 (2C), 55.5 (2C), 55.3, 24.2; HRMS (ESI) calcd for C16H17NO5Na:
326.1015 M+Na+, found: 326.1004 M+Na+; IR (KBr): mmax 2924, 2853, 1606,
1520, 1462, 1352, 1211, 1150 cmꢀ1; (3f): mp 162.4–163.6 °C; 1H NMR (CDCl3,
300 MHz): d 6.99 (q, J = 5.6, 8.3 Hz, 1H), 6.82 (t, J = 8.7 Hz, 1H), 6.17 (s, 1H), 6.1
(s, 3H), 3.78 (s, 4H), 3.51 (s, 7H); 13C NMR (CDCl3, 75 MHz): d 161.9, 159.6,
159.1, 158.8, 141.1, 129.0, 128.9, 113.9, 113.6, 113.3, 91.7 (2C), 56.0 (2C), 55.0,
36.4; HRMS (ESI) calcd for C16H16O3F: 275.1095 MꢀHꢀ, found: 275.1083
MꢀHꢀ; IR (neat): mmax 2935, 2838, 1596, 1460, 1223, 1120 cmꢀ1; (3g): mp
121.8–122.9 °C; 1H NMR (CDCl3, 300 MHz): d 7.07 (t, J = 7.8 Hz, 1H), 6.81 (d,
J = 7.5 Hz, 1H), 6.66 (s, 1H), 6.58 (dd, J = 2.4, 8.1 Hz, 1H), 6.14 (s, 2H), 3.88 (s,
2H), 3.8 (s, 3H), 3.7 (s, 6H); 13C NMR (CDCl3, 75 MHz): d 159.6 (2C), 158.8,
155.2, 144.1, 128.9, 120.9, 115.3, 112.1, 109.8, 90.6 (2C), 55.7 (2C), 55.3, 28.1;
HRMS (ESI) calcd for C16H19O4: 275.1296 M+H+, found: 275.1283 M+H+; IR
(neat): mmax 3392, 2928, 2841, 1605, 1458, 1201, 1117 cmꢀ1; (3h): mp 126.8–
127.8 °C; 1H NMR (CDCl3, 300 MHz): d 6.66 (d, J = 8.7 Hz, 1H), 6.51 (dd, J = 3.1,
8.7 Hz, 1H), 6.15 (d, J = 3.0 Hz, 1H), 6.09 (s, 2H), 3.83 (s, 3H), 3.80 (s, 3H), 3.78 (s,
2H), 3.73 (s, 6H), 3.60 (s, 3H); 13C NMR (CDCl3, 75 MHz): d 159.8 (2C), 159.3,
153.4, 151.8, 131.6, 115.1, 110.6, 109.3, 108.2, 90.58 (2C), 56.1 (2C), 55.7, 55.4,
55.2, 22.2; HRMS (ESI) calcd for C18H22O5Na: 341.1375 M+Na+, found:
Representative experimental procedure for the synthesis of triar-
ylmethanes: To a stirred solution of indole (1d, 1 mmol) in dichloro-
methane, trifluoromethyl benzaldehyde (2l, 0.5 mmol) and 5 mol %
of B(C6F5)3 were added at room temperature and the reaction pro-
gress was monitored by TLC analysis. After the completion of the
reaction (0.5 h), the solvent was evaporated under vacuum and
the residue was purified by column chromatography on silica gel
using ethyl acetate and hexanes (15:85) as eluent to give the triar-
ylmethane 4e in 93% yield.
Acknowledgments
S.K. thanks CSIR, New Delhi and G.R. thanks UGC, New Delhi, for
the award of research fellowships. The authors thank the referees
for their valuable suggestions.
References and notes
341.1364 M+Na+; IR (neat): mmax 2925, 2834, 1603, 1461, 1202, 1118 cmꢀ1
;
1. (a) Nat. Prod. Chem; Nakanishi, K., Goto, T., Ito, S., Natori, S., Nozoe, S., Eds.;
Kodansha Scientific: Tokyo, 1975; p 131; (b) Olah, G. A.; Krishnamurti, R.;
Prakash, G. K. S.. In Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon
Press: Oxford, 1991; Vol. 3, p 293; (c) Roberts, R. M.; Khalaf, A. A.. Friedel–Crafts
Alkylation Chemistry. In A Century of Discovery; Dekker: New York, 1984.
2. (a) Ackermann, W.; Heesing, A. Chem. Ber. 1977, 110, 3126; (b) Inoue, M.;
Umaki, N.; Sugita, T.; Ichikawa, K. Nippon Kagaku Kaishi 1978, 775.
(3i): mp 95.7–96.7 °C; 1H NMR (CDCl3, 300 MHz): d 7.11–6.76 (m, 8H), 6.16 (s,
2H), 3.98 (s, 2H), 3.82 (s, 3H), 3.79 (s, 3H), 3.71 (s, 6H); 13C NMR (CDCl3,
75 MHz): d 159.7 (2C), 159.2, 155.3, 155.0, 151.7, 132.9, 129.0, 126.3, 122.9,
119.2 (2C), 118.1, 114.5 (2C), 108.7, 90.5 (2C), 55.6 (2C), 55.3 (2C), 22.1; HRMS
(ESI) calcd for C23H25O5: 381.1715 M+H+, found: 381.1701 M+H+; IR (KBr): mmax
2925, 2837, 1602, 1502, 1452, 1211, 1118 cmꢀ1; (3j): ½a D27
ꢀ29.6 (c 0.8, CHCl3);
ꢁ

S. Chandrasekhar et al. / Tetrahedron Letters 50 (2009) 6693–6697
6697
1H NMR (CDCl3, 300 MHz): d 7.44–7.27 (m, 5H), 6.12 (s, 2H), 5.92 (d, J = 3.9 Hz,
1H), 4.64 (s, 1H), 4.56 (d, J = 3.9 Hz, 1H), 4.54–4.42 (m, 2H), 3.8 (s, 3H), 3.72 (s,
7H), 3.17–3.02 (m, 2H), 1.44 (s, 3H), 1.29 (s, 3H); 13C NMR (CDCl3, 75 MHz): d
159.6 (2C), 159.2, 138.1, 128.2 (2C), 127.5 (2C), 127.3, 111.1, 107.3, 104.6, 90.6
(2C), 82.4, 82.3, 79.8, 71.7,55.5 (2C), 55.2, 26.7, 26.3, 21.3; HRMS (ESI) calcd for
C24H30O7Na: 453.1879 M+Na+, found: 453.1889 M+Na+; IR (neat): mmax 2932,
2841, 1603, 1458, 1207, 1134, 1076 cmꢀ1; (3k): mp 184.2–186.3 0C; 1H NMR
(CDCl3, 300 MHz): d 7.41–7.24 (m, 5H), 6.56–6.50 (m, 2H), 4.55 (s, 2H), 4.51 (s,
2H), 3.81–3.67 (m, 6H); 13C NMR (75 MHz, CDCl3): d 160.8 (2C), 140.7, 138.1,
128.3, 128.2, 127.8, 127.6, 126.8, 105.4, 100.3, 99.6, 72.0, 55.3 (2C), 29.6; HRMS
(ESI) calcd for C16H19O3: 259.1329 [M+H]+, found: 259.1327 [M+H]+; IR (neat):
6.08 (m, 5H), 3.79 (s, 6H), 3.55 (s, 12H); 13C NMR (75 MHz, CDCl3): d 159.5,
152.0, 151.8, 148.7, 148.6, 142.5, 112.1, 111.5, 111.2, 91.4, 55.8, 55.1, 36.4;
HRMS (ESI) calcd for C25H26F3O6: 479.1676 [M+H]+, found: 479.1675 [M+H]+;
IR (KBr): mmax 2934, 2838, 1593, 1225, 1124 cmꢀ1; (4d): mp 188–189 °C; 1H
NMR (300 MHz, CDCl3): d 7.15–7.05 (m, 2H), 6.65 (d, J = 8.8 Hz, 1H), 6.33 (s,
1H), 6.13 (s, 1H), 6.10 (s, 4H), 3.77 (s, 6H), 3.57 (s, 12H); 13C NMR (75 MHz,
CDCl3): d 159.6, 159.3, 154.7, 132.8, 129.1, 117.3, 111.4, 91.7, 56.0, 55.1, 34.0;
HRMS (ESI): calcd for C25H27BrO7: 519.3817; found: 521.098 [M+2]; IR (KBr):
mmax 2925, 2843, 1596, 1461, 1117 cmꢀ1; (4e): 1H NMR (300 MHz, CDCl3): d
7.97 (s, 2H), 7.44–7.29 (m, J = 4H), 7.28–7.13 (m, J = 2H), 7.11–6.88 (m, J = 4H),
6.67 (s, 2H), 5.82 (s, 1H); 13C NMR (75 MHz, CDCl3): d 136.6, 126.5, 123.5,
122.2, 119.5, 119.52, 118.1, 112.6, 112.3, 111.2, 39.5; MS (ESI): m/z 376.3; IR
(KBr): mmax 3415, 1627, 1523, 1342, 1093, 750 cmꢀ1; (4f): 1H NMR (300 MHz,
m
max 3449, 2924, 2851, 1601, 1460, 1355, 1202, 1153, 1061, 753 cmꢀ1; (3l): mp
208.9–210.3 °C; 1H NMR (CDCl3, 300 MHz): d 7.45–7.24 (m, 15H), 6.65–6.60
(m, 2H), 5.04 (s, 4H), 4.53 (s, 2H), 4.50 (s, 2H); 13C NMR (75 MHz, CDCl3): d
160.8 (2C), 140.7 (2C), 138.1 (2C), 128.3 (3C), 128.2 (2C), 127.8 (4C),127.6 (2C),
126.8, 100.3, 99.6 (2C), 72.0 (2C), 55.3, 29.6; MA (APCI): m/z 411 [M+H]+; IR
CDCl3):
d 7.24 (dd, J = 2.4, 8.4 Hz, 1H), 7.19 (d, J = 8.4 Hz, 1H), 6.69 (d,
J = 8.4 Hz,1H), 5.93 (dd, J = 3.0, 14.5 Hz, 4H), 5.57 (br s, 1H), 5.52 (s, 1H), 2.25 (s,
6H); 13C NMR (75 MHz, CDCl3): d 152.7, 152.0, 150.6, 132.4, 131.2, 128.0, 118.2,
112.8, 108.7, 106.2, 77.4, 76.9, 76.5, 39.8, 13.6; MS (ESI): m/z 347.4; IR (KBr):
(neat): mmax 3450, 2922, 2853, 1600, 1453, 1376, 1217, 1155, 1056, 770 cmꢀ1
;
(4c): mp 170–172 °C; 1H NMR (300 MHz, CDCl3): d 6.72–6.59 (m, 2H), 6.12–
mmax 3503, 2921, 2853, 1487, 1216, 782 cmꢀ1
.