A one-pot procedure for methylenating carbonyl compounds using the Nysted reagent and titanocene dichloride

Article abstract of DOI:10.1016/j.tetlet.2011.04.017

The combination of the Nysted reagent and titanocene dichloride methylenates aldehydes and ketones to give alkenes, and in a microwave-assisted process, esters and lactones give enol ethers. The methylenating agent in this one-pot procedure is presumed to be titanocene methylidene, which is the same reactive intermediate as that generated from Tebbe, Petasis and Grubbs reagents, each of which have to be prepared before use.

Full text of DOI:10.1016/j.tetlet.2011.04.017

Tetrahedron Letters 52 (2011) 3020–3022
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A one-pot procedure for methylenating carbonyl compounds using
the Nysted reagent and titanocene dichloride
Adam Haahr a, Zoran Rankovic b, Richard C. Hartley a,
⇑
a WestChem, Department of Chemistry, The Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK
b MSD, Newhouse ML1 5SH, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The combination of the Nysted reagent and titanocene dichloride methylenates aldehydes and ketones to
give alkenes, and in a microwave-assisted process, esters and lactones give enol ethers. The methylenat-
ing agent in this one-pot procedure is presumed to be titanocene methylidene, which is the same reactive
intermediate as that generated from Tebbe, Petasis and Grubbs reagents, each of which have to be pre-
pared before use.
Received 20 January 2011
Revised 16 March 2011
Accepted 1 April 2011
Available online 9 April 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Titanium
Schrock carbene
Carbenoid
Zinc
Microwave-assisted reactions
The Tebbe reagent1 1 and Petasis reagent2 2 are widely used for
the methylenation of carbonyl compounds 5 to give alkenes 6
(Scheme 1).3 They are non-basic reagents that can be used for
the methylenation of aldehydes and ketones when a Wittig reagent
would promote epimerisation of chiral centres or retro-Michael
reactions, or would fail to react due to steric hindrance. Most
importantly, they will convert carboxylic acid derivatives directly
into hetero-substituted alkenes,3,4 rather than inducing the nucle-
ophilic substitution observed with Wittig reagents. Although, it is
too reactive to be isolated, titanocene methylidene 4 is believed
to be the reactive intermediate and the formation of Grubbs
reagent 3 from the Tebbe reagent and 2-methylpropene,5 and ther-
mal regeneration of the titanocene methylidene 4 supports this, as
does the isolation of related Schrock carbenes.6 Both the Tebbe
reagent 1 and the Petasis reagent 2 are prepared from titanocene
dichloride,7–9 and though both are available commercially as
solutions in toluene, they are extremely expensive, and the Tebbe
reagent in particular can be unsatisfactory when not freshly pre-
pared. It would be more satisfactory if titanocene methylidene 4
(or an equivalent titanium-containing 1,1-bimetallic3) could be
generated in situ in a one-pot procedure from titanocene dichlo-
ride without the use of reactive methyllithium or methylmagne-
sium halide.
, Lewis base
Me
Me
Ti
Al
Ti
Cl
Tebbe reagent 1
Grubbs reagent 3
Lewis
base
Δ
Δ
Me
Ti
Ti CH2
Me
α-elimination
– CH4
Petasis
Reagent 2
Titanocene methylidene 4
O
R
G
5
+ Cp2Ti=O
R
G
6
G = H, alkyl, aryl, OR', OSi
SR', SiR'3, NR'2
The reagent 8 patented by Nysted in 1975 is believed to have
the structure shown,10 and is commercially available as a suspen-
Scheme 1.
⇑
Corresponding author. Tel.: +44 141 330 4398; fax: +44 141 330 4888.
E-mail addresses: Richard.Hartley@glasgow.ac.uk, Richard.Hartley@chem.gla.
sion in THF. We reasoned that the combination of titanocene
dichloride (7) and the Nysted reagent 8 would give titanocene
ac.uk (R.C. Hartley).
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.04.017

A. Haahr et al. / Tetrahedron Letters 52 (2011) 3020–3022
2 eq.
3021
2 eq.
1 eq.
X
Zn
O
OMe
OMe
X
Ti CH2
Cl
Cl
BrZn
ZnBr
+
Ti
MeO
OMe
4
a 63% (RT, 2 h)
b 77% (RT, 5 h)
+ ZnCl2 + 2ZnClBr
7
Nysted reagent 8
X
O
O
Scheme 2.
X
O2N
NO2
methylidene 4 directly (Scheme 2). The Nysted reagent 8 has been
used with titanium tetrachloride, trichloride or dichloride to meth-
ylenate aldehydes and ketones,11–13 a reaction that also works with
Lewis acids such as boron trifluoride,12,14 but has never been used
in combination with titanocene dichloride, or to achieve methyle-
nation of carboxylic acid derivatives. Our approach could be
viewed as a simplified access to the reagent system, derived from
CH2(ZnI)2 and titanocene dichloride, used by Eisch and Piotrowski
to methylenate two ketones.15
Our methylenation was optimized by varying the ratio of
Nysted reagent 8 to titanocene dichloride (7), the number of equiv-
alents of the new reagent relative to the carbonyl compound, its
mode of preparation, and the reaction temperature. The expected
1:2 ratio of Nysted reagent 8 to titanocene dichloride (7) proved
most effective and heating was required to generate the reagent.
Although, 1 mol of Nysted reagent 8 should give rise to 2 mol of
titanium carbenoid 4 in this way (Scheme 2), it proved best to
use equimolar quantities of the carbonyl compound and the
Nysted reagent 8. Similarly, 2 equiv of Petasis reagent 2 are often
used in methylenation reactions because the reagent reacts with
the titanocene oxide side product.9
c 76% (–78 °C, 20 min)
d 59% (–78 °C, 20 min)
X
X
Ph
Ph
OMe
e 86% (RT, 3 h)
f 75% (RT, 19 h)
X
H
Ph
H
g 51% (RT, 1 h)
H
H
h 49% (RT, 4 h)
X
9 X = O
10 X = CH2
H
Figure 1. Aldehydes and ketones 9a–h methylenated with isolated yields of
product alkenes 10a–h and conditions in parentheses.
X
X
MeO
Ph
Cl
OBn
OnC8H17
i 60%a
A range of carbonyl compounds 9a–n were methylenated using
the new reagent (Scheme 3, Figs. 1 and 2). When methylenating
aldehydes and ketones, the reagent was generated by heating the
Nysted reagent 8 and titanocene dichloride (7) together in THF un-
til a red solution was formed and then reactions were carried out at
a lower temperature.16,17 The electron-rich benzaldehyde and ace-
tophenone derivatives 9a,b reacted smoothly at room temperature.
In accordance with the nucleophilic nature of the reagent, the elec-
tron-poor derivatives 9c,d reacted much more rapidly and required
low temperature to avoid over-reaction, beginning at ꢀ78 °C and
j 39%b
X
O
X
OnC8H17
Ph
l 52%a,c
Ph
k 38%b
X
O
OBn
OBn
H
X
O
allowing to warm for the short time shown. The
a,b-unsaturated
BnO
aldehyde 9e and benzophenone 9f presented no problem and the
branched aldehyde 9g and cyclic ketone 9h were successfully
methylenated, though the yields were modest.
OBn
m 30%a,c (56%)
9 X = O
10 X = CH2
n 50%a,c
Reactions with carboxylic acid derivatives required higher tem-
perature and so pre-generation of the reagent was not necessary:
all components were simply mixed and heated together.18,19 Meth-
ylenations were best achieved using microwave irradiation
(100 W), which gave complete conversion in 22 min at 75 °C; con-
ventional heating required longer reaction times and led to decom-
position. Similar advantages to microwave heating have been
observed with the Petasis reagent.20 Alkanoate ester 9i worked
well, isolated yields were lower for enol ether 10j,k derived benzo-
ate derivatives and more equivalents of the reagent were required.
Methylenation of lactones 9l–n was successful with 1 equiv of the
reagent, but ethyl pivalate had to be included as a sacrificial steri-
cally-hindered ester9,21 to avoid products resulting from the reac-
Figure 2. Esters 9i–k and lactones 9l–n methylenated and yields of enol ethers
10i–n produced using (a) a 1:1:2 mol ratio of ester/lactone, Nysted reagent and
titanocene dichloride; (b) a 1:2:4 mol ratio of ester/lactone, Nysted reagent and
titanocene dichloride; (c) with 1 equiv of ethyl pivalate. All reactions were carried
out at 75 °C in a microwave (100 W) for 22 min.
tion between the product enol ether and the titanocene
methylidene (the same type of reaction that is exploited to form
the Grubbs reagent 35). All the enol ethers were acid-sensitive, so
purification on neutral alumina was necessary; indeed the enol
ether 10m derived from (+)-sclareolide was so sensitive that
hydrolysis was carried out with HCl in THF–water and the yield
for the corresponding ketone is reported in parentheses.
In summary, we have introduced a new one-pot procedure for
the methylenation of carbonyl compounds by in situ generation
of titanocene methylidene or a related 1,1-bimetallic complex from
the commercially available Nysted reagent 8. Methylenation of es-
ters and lactones involves simply mixing the reagents and heating
them under microwave irradiation for less than half an hour. The
for aldehydes and ketones:
1 eq. Nysted-Cp2TiCl2 (1:2)
THF, RT or –78 °C
O
R1
R2
R1
R2
for esters and lactones:
1 eq. Nysted, 2 eq. Cp2TiCl2
THF, μW, 75 °C (100 W)
9a-n
10a-n
Scheme 3.

3022
A. Haahr et al. / Tetrahedron Letters 52 (2011) 3020–3022
as an oil: Rf [SiO2, Et2O–Pet. ether (1:1)] 0.66. dH (400 MHz, CDCl3) 0.86 (3H, t,
J = 6.8 Hz, CH3), 1.16–1.44 (8H, m, 4 ꢁ CH2), 2.22–2.32 (1H, m, 20-H), 2.60 (1H,
dd, J = 13.4, 7.6 Hz, 10-CHAHB), 2.65 (1H, dd, J = 13.5, 6.7 Hz, 10-CHAHB), 4.85 (1H,
ddd, J = 17.0, 2.0, 0.8 Hz, @CHCHD), 4.92 (1H, ddd, J = 10.3, 2.0, 0.3 Hz, @CHCHD),
5.53–5.59 (1H, m, @CH), 7.11–7.19 (3H, m, ArH), 7.23–7.30 (2H, m, ArH); dC
(100 MHz, CDCl3) 14.1 (CH3), 22.6 (CH2), 23.8 (CH2), 31.9 (CH2), 34.1 (CH2), 41.8
(CH2), 45.7 (CH), 114.4 (CH2), 125.7 (CH), 128.0 (CH), 129.3 (CH), 140.7 (C),
142.6 (CH); IR (cmꢀ1) 3150 (Ar-H), 2926 (C–H), 1641 (C@C); LRMS (EI+): 202
[M+Å, 36%], 104 (30), 91 (100), 69 (62); HRMS: 202.1720, C15H22 requires M+Å
202.1722.
brevity, simplicity and relatively low temperature of this one-pot
procedure should mean that it competes effectively with the pop-
ular Petasis and Tebbe reagents 1 and 2, which must be preformed
prior to use.
Acknowledgements
The University of Glasgow and MSD are thanked for financial
support.
18. Typical procedure: lactone 9l–n (0.5 mmol) was dissolved in dry THF (1.5 mL)
and titanocene dichloride (1 mmol), the Nysted reagent (0.5 mmol, 20 wt % in
THF) and ethyl pivalate (0.5 mmol) were added. The reaction mixture was
irradiated in a DiscoverÒ CEM focussed microwave synthesis system (100 W,
75 °C, 22 min). This gave a black solution which was quenched and worked-up
as before.16 Flash column chromatography (neutral alumina, Brockmann V, Pet.
ether–Et2O) gave the enol ether 10l–n.
References and notes
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3613.
2. Petasis, N. A.; Bzowej, E. I. J. Am. Chem. Soc. 1990, 112, 6392–6394.
3. For reviews, see: (a) Hartley, R. C.; Li, J.; Main, C. A.; McKiernan, G. J. Tetrahedron
2007, 63, 4825–4864; (b) Hartley, R. C.; McKiernan, G. J. J. Chem. Soc., Perkin
Trans. 1 2002, 2763–2793.
4. Recent examples include: (a) Hans, S. K.; Camara, F.; Altiti, A.; Martín-
Montalvo, A.; Brautigan, D. L.; Heimark, D.; Larner, J.; Grindrod, S.; Brown, M. L.;
Mootoo, D. R. Bioorg. Med. Chem. 2010, 18, 1103–1110; (b) Gómez, A. M.; Barrio,
A.; Pedregosa, A.; Uriel, C.; Valverde, S.; López, J. C. Eur. J. Org. Chem. 2010,
2910–2920; (c) Woodward, H.; Smith, N.; Gallagher, T. Synlett 2010, 869–872;
(d) Brand, C.; Rauch, G.; Zanoni, M.; Dittrich, B.; Werz, D. B. J. Org. Chem. 2009,
74, 8779–8786; (e) Imagawa, H.; Saijo, H.; Kurisaki, T.; Yamamoto, H.; Kubo,
M.; Fukuyama, Y.; Nishizawa, M. Org. Lett. 2009, 11, 1253–1255; (f) Liang, G.;
Bateman, L. J.; Totah, N. I. Chem. Commun. 2009, 6457–6459; (g) Mak, S. Y. F.;
Chiang, G. C. H.; Davidson, J. E. P.; Davies, J. E.; Ayscough, A.; Pain, G.; Burton, J.
W.; Holmes, A. B. Tetrahedron: Asymmetry 2009, 20, 921–944; (h) Mehta, G.;
Bhat, B. A. Tetrahedron Lett. 2009, 50, 2474–2477; (i) Smith, A. B., III; Bosanac,
T.; Basu, K. J. Am. Chem. Soc. 2009, 131, 2348–2358.
5. Brown-Wensley, K. A.; Buchwald, S. L.; Cannizzo, L.; Clawson, L.; Ho, S.;
Meinhardt, D.; Stille, J. R.; Straus, D.; Grubbs, R. H. Pure Appl. Chem. 1983, 55,
1733–1744.
6. For reviews see: (a) Schrock, R. R. Chem. Rev. 2002, 102, 145–179; (b) Dörwald,
F. Z. Metal Carbenes in Organic Synthesis; Wiley-VCH: Weinheim, 1999.
7. Pine, S. H.; Kim, G.; Lee, V. Org. Synth. 1990, 69, 72–79.
8. Payack, J. F.; Hughes, D. L.; Cai, D.; Cottrell, I. F.; Verhoeven, T. R. Org. Synth.
2002, 79, 19–26.
9. For the large-scale preparation of Petasis reagent 2 see: Payack, J. F.; Huffman,
M. A.; Cai, D. W.; Hughes, D. L.; Collins, P. C.; Johnson, B. K.; Cottrell, I. F.; Tuma,
L. D. Org. Process Res. Dev. 2004, 8, 256–259.
19. The analytical data for enol ether 10n are in agreement with the literature.28
Data for enol ethers 10i–m are as follows. Compound 10i oil; Rf [Al2O3, Et2O–
Pet. ether (1:9)] 0.77; dH (400 MHz, CDCl3) 2.48 (2H, t, J = 7.2 Hz, CH2), 2.86 (2H,
t, J = 7.2 Hz, CH2), 3.93 (1H, d, J = 2.1 Hz, @CHAHB), 3.97 (1H, d, J = 2.1 Hz,
@CHAHB), 4.36 (2H, s, OCH2), 7.10–7.41 (10H, m, ArH); dC (100 MHz, CDCl3)
33.7 (CH2), 36.9 (CH2), 69.2 (CH2), 82.1 (CH2), 125.8 (CH), 125.8 (CH), 127.4
(CH), 127.7 (CH), 128.3 (CH), 128.4 (CH), 137.3 (C), 161.7 (C), 162.4 (C); IR
(cmꢀ1) 3027 (Ar-H), 2924 (C–H), 1654 (C@C), 1495 (Ar); LRMS (CI+): 239
[(M+H)+, 37%], 113 (44), 107 (90); HRMS: 239.1434, C17H19O requires (M+H)+
239.1346. Compound 10j oil; Rf [Al2O3, Et2O–Pet. ether (1:9)] 0.87; dH
(400 MHz, CDCl3) 0.89 (3H, t, J = 7.0 Hz, CH3), 1.20–1.38 (8H, m, 4 ꢁ CH2),
1.50–1.52 (2H, m, CH2), 1.79 (2H, quint., J = 6.5 Hz, OCH2CH2), 3.82 (3H, s,
OMe), 3.84 (2H, t, J = 6.4 Hz, OCH2), 4.18 (1H, d, J = 2.5 Hz, @CHAHB), 4.62 (1H, d,
J = 2.5 Hz, @CHAHB), 6.85 (1H, dt, J = 7.0, 2.4 Hz, 4-H or 6-H), 7.17–7.33 (3H, m,
ArH); dC (100 MHz, CDCl3) 14.1 (CH3), 22.3 (CH2), 26.3 (CH2), 29.1 (CH2), 29.3
(CH2), 29.4 (CH2), 31.8 (CH2), 55.2 (CH3), 67.8 (CH2), 82.3 (CH2), 111.1 (CH),
113.8 (CH), 118.0 (CH), 129.1 (CH), 138.2 (C), 159.4 (C), 159.8 (C); IR (cmꢀ1
)
2928 (Ar-H), 1599 (C@C); LRMS (CI+) 263 [(M+H)+, 100%], 151 (53); HRMS:
263.2018, C17H27O2 requires (M+H)+ 263.2011. Compound 10k oil; Rf [Al2O3,
Et2O–Pet. ether (1:9)] 0.83. dH (400 MHz, CDCl3) 0.89 (3H, t, J = 6.7 Hz, CH3),
1.19–1.42 (8H, m, 4 ꢁ CH2), 1.43–1.52 (2H, m, CH2), 1.79 (2H, quint., J = 6.6 Hz,
OCH2CH2), 3.84 (2H, t, J = 6.5 Hz, OCH2), 4.22 (1H, d, J = 2.8 Hz, @CHAHB), 4.63
(1H, d, J = 2.8 Hz, @CHAHB), 7.24–7.29 (2H, m, ArH), 7.50 (1H, dt, J = 6.8, 1.8 Hz,
4-H or 6-H), 7.60 (1H, d, J = 2.0 Hz, 2-H); dC (100 MHz, CDCl3) 14.1 (CH3), 22.7
(CH2), 26.3 (CH2), 29.0 (CH2), 29.3 (CH2), 29.7 (CH2), 31.8 (CH2), 68.0 (CH2), 83.0
(CH2), 123.5 (CH), 126.3 (CH), 129.3 (CH), 129.4 (CH), 134.1 (C), 138.6 (C), 157.7
(C); IR (cmꢀ1) 2925 (Ar-H) 1564 (C@C), 786 (C–Cl); LRMS (EI+): 268 [M+Å
40%], 266 [M+Å 35Cl), 81], 188 (27), 157 (17) 155 (45), 136 (14) 134 (47), 91
(100); HRMS: 266.1465 and 268.1455, C16H23O35Cl requires M+Å 266.1437 and
16H23O37Cl requires M+Å 268.1413. Compound 10l oil; Rf [Al2O3, Et2O–Pet.
(
37Cl),
(
10. Nysted, L. N. U.S. Patent 3865848, 1975; Nysted, L. N. Chem. Abstr. 1975, 83,
10406q.
C
ether (1:9)] 0.53; dH (400 MHz, CDCl3) 2.78 (2H, t, J = 6.3 Hz, 4-CH2), 3.64 (1H,
d, J = 1.8 Hz, @CHAHB), 4.00 (2H, t, J = 6.3 Hz, OCH2), 4.55 (1H, d, J = 1.8 Hz,
@CHAHB), 7.25–7.32 (10H, m, ArH); dC (100 MHz, CDCl3) 40.0 (CH2), 58.9 (C),
67.2 (CH2), 84.7 (CH2), 126.7 (CH), 128.2 (CH), 128.5 (CH), 143.6 (C), 167.4 (C);
IR (cmꢀ1) 3058 (Ar-H), 1666 (Ar), 1491 (C@C); LRMS (FAB+): 237 [(M+H)+, 20%],
221 (20), 207 (20), 147 (20), 84 (100); HRMS: 237.1264, C17H17O requires
(M+H)+ 237.1279. Compound 10m amorphous solid; Rf [Al2O3, Et2O–Pet. ether
(1:19)] 0.67; dH (400 MHz, CDCl3) 0.83 (3H, s, 60-Me), 0.86 (3H, s, 60-Me), 0.88
11. (a) Matsubara, S.; Mizuno, T.; Otake, Y.; Kobata, M.; Utimoto, K.; Takai, K.
Synlett 1998, 1369–1371; (b) Watson, A. T.; Park, K.; Wiemer, D. F.; Scott, W. J. J.
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Wolff, C.; Peters, E.-M.; Peters, K.; von Schnering, H. G. Tetrahedron 1995, 51,
1623–1630; (d) Collins, P. W.; Shone, R. L.; Perkins, W. E.; Gasiecki, A. F.; Kalish,
V. J.; Kramer, S. W.; Bianchi, R. G. J. Med. Chem. 1992, 35, 694–704.
12. Matsubara, S.; Sugihara, M.; Utimoto, K. Synlett 1998, 313–315.
13. Recent examples with TiCl4 include: (a) Cren, S.; Schar, P.; Renaud, P.; Schenk,
K. J. Org. Chem. 2009, 74, 2942–2946; (b) Huang, H.; Greenberg, M. M. J. Org.
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(3H, s, 9a0-Me), 1.00 (1H, dd, 5a0-H, J = 12.5, 2.7 Hz), 1.05 (1H, dd, 70-Hax
,
J = 13.3, 2.5 Hz), 1.10–1.48 (5H, m, 40-CHAHB, 50-CHAHB, 70-Heq, 80-CHAHB, 90-
CHAHB), 1.19 (3H, s, 3b0-Me), 1.52-1.73 (3H, m, 50-CHAHB, 80-CHAHB, 90-CHAHB),
1.81 (1H, dq, 40-CHAHB, J = 13.9, 3.8 Hz), 2.00 (1H, dt, 9b-H, J = 11.7, 3.3 Hz),
2.28–2.43 (2H, m, 1-H), 3.89 (1H, s, @CH2), 4.22 (1H, s, @CH2); dC (100 MHz,
CDCl3) 15.2 (CH3), 18.3 (CH2), 20.8 (CH2), 21.0 (CH3), 21.5 (CH3), 27.5 (CH2),
33.0 (CH), 33.4 (C), 36.2 (C), 39.1 (CH2), 39.7 (CH2), 42.3 (CH2), 55.9 (CH3), 59.8
(CH), 81.3 (CH2), 84.4 (C), 161.9 (C); IR (cmꢀ1) 2927 (C–H), 1706 (C@C), 1671
(C@C); LRMS (EI+) 248 [(M)+ 21%], 196 (32), 177 (30), 84 (100);
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16. Typical procedure: titanocene dichloride (2 mmol) was suspended in dry THF
(5 mL) under argon and the Nysted reagent added (1 mmol, 20 wt % in THF).
This was heated to 40 °C for 30 min until a very dark red solution formed and
was then cooled to the appropriate temperature for reaction (rt or ꢀ78 °C). A
solution of the aldehyde or ketone 9a–h (2 mmol) in dry THF (3 mL) was then
added. The mixture was stirred until no starting material remained (see Fig. 1
for reaction time) and then quenched by pouring into satd aq NaHCO3 (50 mL),
and extracted with Et2O (3 ꢁ 50 mL). The organic extracts were combined then
washed with brine (100 mL), dried (Na2SO4) and concentrated under reduced
pressure. Flash column chromatography (SiO2, Pet. ether–Et2O) afforded the
alkene 10a–h.
HRMS: 248.2138, C17H28O requires, 248.2140; ½a D25
ꢂ
+32.1 (c 0.8, CHCl3); mp
72–74 °C.
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28. Yang, W.; Yang, Y.; Gu, Y.; Wang, S.; Chang, C.; Lin, C. J. Org. Chem. 2002, 67,
3773–3782.
17. The analytical data are in agreement with the literature for alkenes 10a,22 b,23
d,24 e,25 f,26 and h.27 Alkene 10c was isolated as yellow needles: Rf [SiO2, Et2O–
Pet. ether (1:1)] 0.48. dH (400 MHz, CDCl3) 5.45 (1H, d, J = 10.9 Hz, @CHAHB),
5.65 (1H, d, J = 17.2 Hz, @CHAHB), 6.15 (2H, s, CH2O2), 7.02 (1H, s, 4-H), 7.23
(1H, dd, J = 17.2, 10.9 Hz, ArCH@), 7.52 (1H, s, 7-H); dC (100 MHz, CDCl3) 102.6
(CH2), 104.9 (CH), 106.8 (CH), 117.5 (CH2), 130.4 (C), 132.8 (CH), 141.5 (C),
147.1 (C), 151.5 (C); IR (cmꢀ1) 3090 (Ar-H), 2925 (Ar-H), 1602 (C@C), 1499
(NO2), 1329 (NO2); LRMS (CI+) 194 [(M+H)+, 100%], 164 (17); HRMS: 194.0457,
C9H8NO4 requires (M+H)+ 194.0453; mp 59–63 °C. Compound 10g was isolated