Photoinduced reactions of bicycloalkylidenes with isatin and isoquinolinetrione

Article abstract of DOI:10.1039/c2ob07158d

Photoinduced reactions of isatin and N-methyl-1,3,4-isoquinolinetrione with bicycloalkylidenes such as bicyclopropylidene, cyclopropylidenecyclobutane, cyclopropylidenecyclohexane and bicyclohexylidene were investigated. The reactions gave spirooxetanes as the major products derived from the [2 + 2] photocycloaddition pathway via 1,4-biradical recombination. Unusual products including the [4 + 2 + 2] cycloadducts, the oxoisochroman derivatives and other ring-rearranged products were derived from competitive pathways via 1,6-biradical recombination. The presence of oxygen in the reaction solution was found to be relevant to the distribution of different types of products. Mechanisms were proposed to rationalize the chemo- and regioselectivity in the photoreactions and the origin of the different types of products.

Full text of DOI:10.1039/c2ob07158d

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PAPER
Photoinduced reactions of bicycloalkylidenes with isatin and
isoquinolinetrione†
Dong-Dong Wu,a Ming-Tao He,a Qi-Di Liu,a Wei Wang,a Jie Zhou,a Lei Wang,a Hoong-Kun Fun,b
Jian-Hua Xua and Yan Zhang*a
Received 22nd December 2011, Accepted 9th March 2012
DOI: 10.1039/c2ob07158d
Photoinduced reactions of isatin and N-methyl-1,3,4-isoquinolinetrione with bicycloalkylidenes such as
bicyclopropylidene, cyclopropylidenecyclobutane, cyclopropylidenecyclohexane and bicyclohexylidene
were investigated. The reactions gave spirooxetanes as the major products derived from the [2 + 2]
photocycloaddition pathway via 1,4-biradical recombination. Unusual products including the [4 + 2 + 2]
cycloadducts, the oxoisochroman derivatives and other ring-rearranged products were derived from
competitive pathways via 1,6-biradical recombination. The presence of oxygen in the reaction solution
was found to be relevant to the distribution of different types of products. Mechanisms were proposed to
rationalize the chemo- and regioselectivity in the photoreactions and the origin of the different types of
products.
Introduction
Photocycloadditions of carbonyl compounds with CvC contain-
ing substrates, along with subsequent cascade reactions, have
provided an expeditious way to construct diversified organic fra-
meworks.1,2 Photoreactions of heterocyclic carbonyl compounds,
especially heterocyclic 1,2-dicarbonyl compounds such as isatin
and isoquinolinetrione, have been of continuous research interest
to us.3,4 The C3 carbonyl group of N-acetylisatin 1 was the
reactive site in Paterno–Büchi reactions with CvC or CuC
bonds3b,e–g and in hydrogen abstraction reactions.3c Photo-
cycloadditions involving the two adjacent carbonyl groups in
1–3 as a 1,4-dioxadiene have only been found in its photo-
reactions with specific oxazoles via a [4 + 4] cycloaddition
pathway.3a,d In photoreactions of isoquinolinetriones such as 4
with alkynes or oxazoles, the C4 carbonyl group on the isoqui-
noline ring was found to be the only reaction site.4
Bicycloalkylidenes such as bicyclopropylidene5 (5) cyclopropy-
lidenecyclobutane6 (6), cyclopropylidenecyclohexane7 (7) and
bicyclohexylidene8 (8), are unconventional alkene species with
unusual bonding properties. Theoretical and experimental
studies on these bicycloalkylidenes have indicated that the
central double bonds in 5 are substantially shorter than the
normal CvC bonds with a bond length of 1.304 Å.9,10 The
extra strain caused by the cyclopropyl rings led to many unusual
reactivities of 5 in thermal reactions, which have been systemati-
cally studied over the past decades.11,12 It is also known that 5
has a much higher HOMO energy than methylenecyclopro-
pane.13 The crystal structure of bicyclohexylidene 8 revealed that
the two cyclohexane rings were in the chair conformation and
the length of the central double bond was 1.332 Å.14
aSchool of Chemistry and Chemical Engineering, State Key Laboratory
of Analytical Chemistry for Life Science, Nanjing University, Nanjing,
210093, P.R. China. E-mail: njuzy@nju.edu.cn; Fax: +86-25-83685976
bX-ray Crystallography Unit, School of Physics, Universiti Sains
Malaysia, 11800 USM Penang, Malaysia
†Electronic supplementary information (ESI) available: Crystal structure
of compounds 12, 31 and 32; control experiments; 1H NMR and 13C
NMR spectra of all the new compounds. CCDC 838079–838081,
859787, 859788. For ESI and crystallographic data in CIF or other elec-
tronic format see DOI: 10.1039/c2ob07158d
Due to the unusual physical and bonding properties of these
bicycloalkylidenes, unusual reactivities and applications of
cyclopropylidene cycloalkanes6,7,15 as well as those of
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bicyclohexylidene16 have been reported. De Meijere et al. has
systematically investigated the thermal reactions and transform-
ations of bicyclopropylidene 5 in the past decades.11,12,17 On the
other hand, photoreactions involving the bicycloalkylidenes and
their synthetic application have rarely been explored except for a
few examples of photooxidation18 and photoinduced conversion
in hydroxylic media19 or rare-gas matrices.20 Recently we
reported the [4 + 2] photocycloaddition of bicycloalkylidenes
with 9,10-phenanthrenedione followed by photooxidation as a
facile and highly atom-economic method for the preparation of
biaryl containing bislactones.21
Here we report the photoinduced reactions of substituted isatin
(1–3) and N-methyl-1,3,4-isoquinolinetrione (4) with four
cycloalkylidenes (5–8). Comparison of the photoreactions of
isatin and isoquinolinetrione with the four bicycloalkylidenes
could provide detailed information on electronic and steric
effects on the photoreaction pathway partitioning. Besides, the
photoreactions could also serve as facile and atom-economic
approaches for the preparation of various spirocycloalkyl hetero-
cycles which are otherwise difficult to prepare.
Results and discussion
Photoreaction of isatin with 5
The photoreaction of 1 with 5 proceeded smoothly in benzene
and complete conversion of 1 could be achieved after 12 hours
of irradiation at wavelengths higher than 400 nm. As shown in
Scheme 1, four products 9–12 were obtained from the photolysis
during which inert gas was purged. The major product, 9, was
the spirooxetane fused with two spirocyclopropyl which was
derived from the common Paterno–Büchi reaction. Products 10
and 11 were a pair of diastereoisomeric [4 + 2 + 2] cycloadducts.
The relative configuration of the diastereoisomer 10 was deter-
mined by X-Ray crystallographic analysis (Fig. 1). Product 12
was an oxoisochroman derivative fused with two spirocyclopro-
pyl rings whose structure has also been confirmed by X-Ray
crystallographic analysis (ESI†). When the reaction mixture was
irradiated under an oxygen atmosphere, only 9 and 12 were
obtained with a total yield of 86% (Table 1).
The formation of the major [2 + 2] cycloadduct 9 was not sen-
sitive to the atmosphere during photolysis (Table 1). While the
formation of the [4 + 2 + 2] cycloadducts (10, 11) and the oxo-
isochroman 12 seemed to be competitive and the presence of
oxygen favored the formation of 12. Reaction pathways leading
to the formation of 9–12 are proposed in Scheme 2. The photo-
excited N-acetylisatin 1* reacted with 5 to give the biradical
intermediate DR1. The involvement of biradical intermediates in
Paterno–Büchi reactions is well established.3 In the reaction of 1
with 5, the involvement of biradical species was also confirmed
by a control experiment to trap the biradical which eliminated
the formation of 9–12 (ESI†).
Although cyclopropylcarbinyl radicals are usually prone to
undergo ring opening reactions and serve as radical clocks,22 the
radical center at the cyclopropyl carbon in DR1 did not induce
ring opening of the other cyclopropane before the radical recom-
bination. This is most likely because the cyclopropyl group at
the radical center can efficiently stabilize it, preventing the
α-cyclopropane ring from being opened. Recombination of the
1,4-biradical led to the major spirooxetane product 9, while 1,6-
biradical recombination gave the [4 + 2] cycloadduct 13 which
was highly reactive for further reaction with another 1* or with
O2. The thermal hetero-Diels–Alder reaction pathway23 which
could also lead to the formation of 13 has been excluded since
HPLC monitoring of a mixture of 5 with 1 in benzene either at
room temperature or under reflux did not show any change of
the starting material.
Scheme 1 Photoreaction of 1 with 5.
Reaction of the intermediate 13 with 1* was regioselective to
give two diastereoisomeric [4 + 2 + 2] cycloadducts 10 and 11.
Fig. 1 Crystal structure of compound 10.
Table 1 Results of photoreactions of 5 with isatin
Products and yieldsa (%)
Entry
Isatin
Atmosphere
Spirooxetanes
[4 + 2 + 2] cycloadducts
Oxoisochroman
1
2
3
4
1
inert
O2
O2
9 (63)
9 (62)
15 (84)
16 (35)
10 (4), 11 (6)
—
12 (6)
b
12 (24)
—
b
b
2
3
—
—
b
O2
17 (47)
a Isolated yields. b Undetectable.
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Scheme 2 Reaction pathway proposed for the photoreaction of 1 with 5.
Scheme 3 Photoreactions of 5 with isatin 2 and 3.
The same regioselectivity was observed in the [4 + 4 + 2] cyclo-
addition of 1 with oxazoles.3a,d Formation of the oxoisochroman
product 12 may result from photooxygenation of the primary
product 13. Since 13 was highly reactive and could not be
obtained, the pathway leading to 12 was still quite clear at this
stage. However, we have confirmed that 12 was not the second-
ary product of 9–11 by carrying out a control experiment using
9–11 as the substrate for photoirradiation or thermal decompo-
sition. Besides, the fact that photoreaction of 1 with 5 under an
oxygen atmosphere resulted in an increased yield of 12 at the
expense of 10 and 11 was in accord with the reaction pathway
proposed in Scheme 2.
Substitution groups on 1 also showed influence on the for-
mation of the oxoisochroman type product. As shown in
Scheme 3 and Table 1, photoreaction of 5 with 2 with a Cl atom
at C4 of the indole ring gave the spirooxetane product exclu-
sively upon photoirradiation under an oxygen atmosphere.
Thereby indicating that the ring-rearrangement following the
decarbonylation step involved the C–H at the C4 of the indole
ring. The substituent at the indole N was also relevant to the rela-
tive ratio of the spirooxetane product and the oxoisochroman
type product as shown in the reaction of 5 with 3.
Scheme 4 Products from reactions of 1 with 6 and 7.
photocycloadditions. Products and yields of the photoreactions
are shown in Scheme 4 and Table 2. The reaction of 1 with 6
under an inert atmosphere gave two regioisomeric spirooxetane
products (18 and 19) and two diastereoisomeric [4 + 2 + 2]
photocycloadducts (20 and 21). Formation of the oxoisochroman
type product 22 was observed only upon irradiation under an
oxygen atmosphere. The reaction pathways leading to these pro-
ducts are shown in Scheme 5.
The two spirooxetane products 18 and 19 were formed via
radical recombination of the biradical DR3 and DR4 respectively.
Chemo- and regioselectivity can be ascribed to the steric
hindrance for biradical recombination. The relative ratio of the
[4 + 2 + 2] cycloadducts to the [2 + 2] cycloadducts was around
1 : 3, which was higher than that found in the reaction of 1 with
5. It revealed that the 1,6-biradical recombination in DR4
happened more readily as compared with DR1 in Scheme 2. The
relative ratio of the two regioisomers 18 to 19 in the final pro-
ducts was over 4 : 1, which revealed that the steric hindrance for
the 1,4-biradical recombination in DR3 was less than that in
DR4. The relatively higher steric hindrance for 1,4-biradical
recombination in DR4 pushed the less sterically hindered 1,6-
biradical recombination to take place preferentially, leading to
the formation of 28 and the following [4 + 2 + 2] cycloadduct or
the oxoisochroman type product.
Photoreaction of 1 with 6 and 7
Photoreactions of 1 with the other bicycloalkylidenes including
6 and 7 were then investigated. The unsymmetric feature of 6
and 7 allowed us to explore the regioselectivity of the
The photoreaction of 1 with 7 proceeded with similar chemo-,
regio- and diastereoselectivity. As shown in Table 2, two
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Table 2 Results of photoreactions of 1 with 6 and 7
Products and yieldsa
Spirooxetane
Entry
Bicycloalkylidene
Atmosphere
[4 + 2 + 2] cycloadducts
Oxoisochroman
b
1
2
3
4
6
7
Inert
O2
Inert
O2
18 (48), 19 (11)
18 (54), 19 (14)
23 (25), 24 (11)
23 (31), 24 (16)
20 (3), 21 (17)
—
—
22 (12)
—
b
b
25 (9), 26 (31)
—
b
27 (28)
a Isolated yields. b Undetectable.
Products 32 and 33 were derived from hydrogen abstraction of
1* from the allylic carbon adjacent to the CvC in 8. The struc-
ture of product 32 was confirmed by X-Ray crystallographic
analysis (ESI†). The formation of hydrogen abstraction products
indicated that the two cyclohexyl groups impeded the cyclo-
addition pathway whilst providing an alternative pathway for
consuming the excited 1. Moreover, photoreaction under an
oxygen atmosphere also only gave the spirooxetane 29 and the
ring arrangement product 31.
Photoreaction of 4 with 5 and 6
Photoreactions of bicycloalkylidenes with the isoquinolinetrione
4 were then explored. The C4 carbonyl group in 4 has been
known as the reactive position for photoreactions with alkynes
or oxazoles.4 As shown in Scheme 8, photolysis of 4 and 5 in
acetonitrile under an inert atmosphere gave the spirooxetane 35
and three other minor products 36, 37 and 38. Compound 36
was confirmed to be the secondary product of the spirooxetane
35 because photolysis of 35 resulted in the formation of 36.
Product 37 was the [4 + 2] cycloadduct of 4 with 5. The for-
mation of the spirodioxolane 38 was unexpected since the C4
carbonyl group in 4 remained intact while the less reactive C3
carbonyl group was involved in the reaction. X-Ray crystallo-
graphic analysis of 38 confirmed its structure (Fig. 2). The same
reaction under an oxygen atmosphere gave 35 and 38
exclusively.
Scheme 5 Proposed pathway for reaction of 1 with 6.
regioisomeric spirooxetanes (23 and 24) and two diastereoiso-
meric [4 + 2 + 2] cycloadducts (25 and 26) were obtained from
the photoreaction under an inert atmosphere. Photoreaction
under an oxygen atmosphere also gave the corresponding oxo-
isochroman 27 together with the spirooxetanes 23 and 24.
Photolysis of 4 with 6 under an inert atmosphere yielded three
products including the spirooxetane 39, the dioxine 40 and the
spirodioxolane 41 (Scheme 8 and Table 3). It was noteworthy
that the regioselectivity was high both in the formation of the
spirooxetane and in the formation of the dioxine. No regio-
isomers of 39 or 40 were detected. Moreover, formation of the
secondary product of 39 was not observed. Compared with 37,
40 was more stable and could be purified for characterization.
Furthermore, a control experiment using 40 as the substrate for
photoirradiation under an oxygen atmosphere resulted in the for-
mation of product 41.
A mechanism for the photoreactions between 4 and the bicy-
cloalkylidenes is proposed in Scheme 9. The recombination of
the 1,4-biradical resulted in the formation of spirooxetanes (35
or 39). Further photolysis of 35 resulted in the homolysis of the
C–O to give a biradical intermediate with one radical center α to
the cyclopropyl ring. Ring cleavage and biradical recombination
give the secondary product 36. On the other hand, the recombi-
nation of the 1,6-biradical led to the formation of the dioxines
(37 or 40) which could be further photooxidized to give 38 or
Photoreaction of 1 with 8
The photoreaction of 1 with 8 proceeded smoothly to give five
products (Scheme 6). The spirooxetane product 29 was obtained
with a yield of 38%, which was significantly lower than the
yield of 1 in the reaction of 1 with 5. The two bulky cyclohexyl
groups might have impeded the [2 + 2] cycloaddition of 1 with 8
even more. The alternative [4 + 2] cycloaddition pathway
resulted in tiny amounts of the dioxine type product 30. Com-
pared to other [4 + 2] intermediates such as 13, compound 30
was less reactive because the two bulky cyclohexyl groups
caused extra steric hindrance for the further formation of
[4 + 2 + 2] cycloadduct. Therefore 30 has been isolated and
characterized, which provided direct evidence for the involve-
ment of the [4 + 2] cycloadducts in the reaction pathway.
Photoirradiation of 30 under an oxygen atmosphere could
convert it into 31. Structure of the ring-rearranged product 31
was confirmed by X-Ray crystallographic analysis (ESI†) and
the pathway leading to its formation is proposed in Scheme 7.
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Scheme 6 Photoreaction of 1 with 8.
Scheme 7 Proposed pathway for reaction of 1 with 8.
Fig. 2 Crystal structure of compound 38.
Scheme 8 Photoreaction products of 4 with 5 and 6.
reported. Except for the spirooxetane products derived from the
conventional Paterno–Büchi reactions of CvC with CvO, other
unusual products derived from the competitive pathways or sec-
ondary reaction of the primary products have been obtained.
Photolysis of isatin 1 with the bicycloalkylidenes 5–7 gave
[4 + 2 + 2] cycloadducts and oxoisochroman derivatives other
than the spirooxetane products. The presence of oxygen during
photolysis favored the formation of oxoisochroman derivatives at
41 respectively. The mechanism proposed could be well sup-
ported by the control experiments described above.
Conclusions
In summary, unusual photoinduced reactions of bicycloalkyli-
denes 5–8 with isatin 1–3 and isoquinolinetrione 4 have been
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Table 3 Results of photoreactions of 4 with 5 and 6
Products and yieldsa
Spirooxetane
Entry
Bicycloalkylidene
Atmosphere
Dioxine
Spirodioxolane
Other
1
2
3
4
5
6
Inert
O2
Inert
O2
35 (31)
35 (51)
39 (39)
39 (48)
37 (18)
—
38(19)
38 (39)
41 (18)
41 (39)
36 (14)
b
40 (25)
—
b
a Isolated yields. b Undetectable.
Scheme 9 Proposed pathway for reaction of 4 with bicycloalkylidenes.
Photolysis of 1 with 5 in anhydrous benzene
the expense of the [4 + 2 + 2] cycloadducts. Photoreactions of
isoquinolinetrione 4 with cyclopropylidenecyclanes also pro-
ceeded via the [2 + 2] and [4 + 2] pathway, leading to spirooxe-
tanes, [4 + 2] cycloadducts and their secondary products. A
mechanism leading to different type of products has been pro-
posed and supported by control experiments. These photo-
reactions not only provided important information on the
unusual reactivity of the strained alkenes at their excited states,
but also developed a useful approach for the preparation of
cyclopropyl annelated heterocyclic compounds which are other-
wise difficult to synthesize.
A solution of 1 (378 mg, 2 mmol) and 5 (320 mg, 4 mmol) in
anhydrous benzene (50 mL) was photolyzed with inert gas
(oxygen) bubbling for 12 h to reach a complete conversion of 1.
Flash column chromatography on 300–400 mesh silica gel with
petroleum ether–ethyl acetate as eluents afforded pure analytical
samples of 9–12 (9 and 12 for oxygen bubbling).
9, colorless crystal from acetone–petroleum ether; m.
1
p. 137–139 °C; H NMR (300 MHz, CDCl3) δ 8.14 (d, J = 8.3
Hz, 1H), 7.71 (dd, J = 7.3, 1.1 Hz, 1H), 7.35 (td, J = 7.7, 1.5
Hz, 1H), 7.27 (td, J = 7.4, 1.1 Hz, 1H), 2.64 (s, 3H), 1.16–1.07
(m, 1H), 1.02–0.93 (m, 1H), 0.73–0.41 (m, 6H); 13C NMR
(75 MHz, CDCl3) δ 175.4, 170.4, 140.6, 131.1, 126.0, 125.9,
125.7, 116.7, 85.2, 73.9, 33.4, 26.5, 8.8, 8.0, 7.0 (2C); IR (KBr)
cm−1: 2995, 1770, 1701, 1607, 1462, 1171, 1100, 768; MS m/z
(% base) 269 (M+, 9), 241 (6), 227 (47), 199 (40), 171 (100),
143 (26), 115 (21), 90 (9), 43 (68); EA found: C, 71.40; H,
5.79; N, 5.18. Calc. for C16H15NO3 C, 71.36; H, 5.61; N,
5.20%.
10, the representative diatereosiomer was crystalized from
acetone–petroleum ether; m.p. 239–242 °C; 1H NMR
(300 MHz, CDCl3) δ 8.30 (d, J = 8.2 Hz, 1H), 8.14 (d, J = 8.1
Hz, 1H), 7.37–7.31 (m, 1H), 7.25–7.19 (m, 1H), 6.93 (t, 1H, J =
7.6 Hz), 6.82–6.73 (m, 2H), 6.52 (d, J = 7.0 Hz, 1H), 2.73 (s,
3H), 2.43 (s, 3H), 1.75–1.66 (m, 1H), 1.46–1.37 (m, 1H),
0.93–0.80 (m, 2H), 0.63–0.37 (m, 4H); 13C NMR (75 MHz,
CDCl3) δ 171.3, 170.6, 169.8, 144.3, 139.6, 131.3, 131.2, 125.1,
125.0, 124.4, 124.2, 116.8, 116.4, 61.3, 60.3, 26.7, 24.3, 15.0,
Experimental
General procedures for the preparative photolysis of 1,2-
dicarbonyl compounds with bicycloalkylidenes
The bicycloalkylidenes were prepared according to reported
methods.5–8 The light source for the photolysis was a medium-
pressure mercury lamp (500 W) in a cooling water jacket that
was further surrounded by a layer of filter solution (1 cm thick,
20% aqueous sodium nitrite) to cut off light of wavelength
shorter than 400 nm. The solution of 1,2-dicarbonyl compounds
and an excess amount of bicycloalkylidenes in anhydrous
benzene or acetonitrile irradiated with continuous gas (inert gas
or oxygen) purging. The reaction course was monitored by TLC.
At the end of the reaction, the solvent was removed under
reduced pressure and the residue was separated by flash chrom-
atography on a silica gel column.
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12.1, 9.2, 9.0; IR (KBr) cm−1: 3021, 1765, 1718, 1686, 1462,
1227, 1172, 935, 761; MS m/z (% base) 269 (18), 146 (100), 79
(47), 43 (76); EA found: C, 67.98; H, 4.90; N, 6.22. Calc. for
C26H22N2O6 C, 68.11; H, 4.84; N, 6.11%.
16, colorless crystal from acetone–petroleum ether;
m.p. 131–133 °C; H NMR (300 MHz, CDCl3) δ 7.79 (d, J =
1
7.9 Hz, 1H), 7.67 (d, J = 8.0 Hz, 1H), 7.35–7.29 (m, 1H), 7.21
(t, J = 8.0 Hz, 1H), 1.58 (s, 9H), 1.14–1.04 (m, 1H), 0.98–0.88
(m, 1H), 0.65–0.30 (m, 6H); 13C NMR (75 MHz, CDCl3) δ
172.7, 149.1, 140.2, 130.9, 126.1, 125.6, 124.9, 115.1, 84.3,
1
11, white powder; m.p. 217–218 °C; H NMR (300 MHz,
CDCl3) δ 8.31 (d, J = 7.4 Hz, 1H), 8.22 (d, J = 8.1 Hz, 1H),
8.12 (d, J = 7.1 Hz, 1H), 7.45 (t, J = 7.8 Hz, 1H), 7.43–7.32 (m,
2 H), 7.05 (d, J = 7.3 Hz, 1H), 6.97 (d, J = 7.2 Hz, 1H), 2.40 (s,
3 H), 2.20 (s, 3 H), 1.67–1.60 (m, 1 H), 1.38–1.28 (m, 1 H),
1.00–0.93 (m, 1 H), 0.91–0.82 (m, 1 H), 0.69–0.56 (m, 2 H),
0.48 (dt, J = 10.9, 6.8 Hz, 1 H), 0.38 (dt, J = 10.4, 6.5 Hz, 1 H);
13C NMR (75 MHz, CDCl3) δ 172.5, 170.2, 169.5, 146.1,
140.8, 131.8, 131.5, 128.2, 125.1, 124.4, 122.3, 116.9, 116.6,
106.1, 93.5, 60.4, 60.3, 26.2, 24.0, 14.3, 12.5, 8.8, 8.5; MS
(ESI) m/z (%) 459 [M + H]+; EA found: C, 68.05; H, 4.88; N,
6.08. Calc. for C26H22N2O6 C, 68.11; H, 4.84; N, 6.11%.
73.7, 33.0, 29.7, 28.1 (3C), 8.7, 7.9, 7.0, 6.8; IR (KBr) cm−1
:
2972, 1799, 1467, 1308, 1146, 750; MS m/z (% base) 227 (20),
199 (12), 171 (67), 143 (17), 57 (100); EA found: C, 69.85;
H, 6.53; N, 4.14. Calc. for C19H21NO4 C, 69.71; H, 6.47;
N, 4.28%.
17, white powder; m.p. 91–94 °C; 1H NMR (300 MHz,
CDCl3) δ 10.6 (br, 1H), 8.34 (dd, J = 8.4, 1.0 Hz, 1H), 7.46 (t, J
= 8.0 Hz, 1H), 6.53 (dd, J = 7.7, 1.2 Hz, 1H), 1.53 (s, 9H),
1.12–1.07 (m, 2H), 1.06–1.00 (m, 2H), 0.95–0.90 (m, 2H),
0.65–0.60 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 168.5, 153.1,
145.3, 143.6, 135.2, 117.4, 114.4, 111.4, 80.9, 65.8, 28.5, 22.2,
13.0, 9.9; IR (KBr) cm−1: 3266, 1716, 1683, 1584, 1532, 1272,
1245, 1156, 809; MS m/z (% base) 215 (9), 187 (21), 173 (100),
159 (41), 130 (84), 41 (45); EA found: C, 68.58; H, 6.59; N,
4.36. Calc. for C18H21NO4 C, 68.55; H, 6.71; N, 4.44%.
12, colorless crystal from acetone–petroleum ether; m.
1
p. 110–112 °C; H NMR (300 MHz, CDCl3) δ 11.35 (br, 1H),
8.58 (dd, J = 8.5, 0.7 Hz, 1H), 7.48 (t, J = 8.2 Hz, 1H), 6.61
(dd, J = 7.7, 0.6 Hz, 1H), 2.24 (s, 3H), 1.12–1.07 (m, 2H),
1.05–1.00 (m, 2H), 0.96–0.91 (m, 2H), 0.65–0.60 (m, 2H); 13C
NMR (75 MHz, CDCl3) δ 169.5, 168.7, 145.3, 142.7, 135.5,
118.8, 115.7, 111.8, 66.0, 25.8, 22.1, 13.0 (2C), 9.9 (2C); IR
(KBr) cm−1: 3456, 2927, 1782, 1754, 1718, 1697, 1464, 1373,
1278, 1167, 766; MS m/z (% base) 257 (M+, 18), 229 (21), 215
(37), 188 (28), 159 (100), 130 (27), 77 (13); EA found: C,
70.09; H, 5.80; N, 5.66. Calc. for C15H15NO3 C, 70.02; H, 5.88;
N, 5.44%.
Photolysis of 1 with 6 in anhydrous benzene
A solution of 1 (378 mg, 2 mmol) and 6 (376 mg, 4 mmol) in
anhydrous benzene (50 mL) was photolyzed with inert gas
(oxygen) bubbling for 4 h (12 h) to reach a complete conversion
of 1. Flash column chromatography on 300–400 mesh silica gel
with petroleum ether–ethyl acetate as eluents afforded pure
analytical samples of 18–21 (18, 19 and 22 for oxygen
bubbling).
Photolysis of 2 with 5 in anhydrous benzene under oxygen
atmosphere
18, colorless crystal from acetone–petroleum ether;
m.p. 158–160 °C; 1H NMR (300 MHz, CDCl3) δ 8.17–8.13 (m,
1H), 7.57–7.53 (m, 1H), 7.37 (td, J = 7.6, 1.6 Hz, 1H), 7.28 (td,
J = 7.5, 1.0 Hz, 1H), 2.67 (s, 3H), 2.65–2.43 (m, 3H), 2.36–2.29
(m, 1H), 1.79–1.66 (m, 1H), 1.13–1.02 (m, 1H), 0.99–0.80 (m,
2H), 0.57–0.50 (m, 1H), 0.39–0.32 (m, 1H); 13C NMR
(75 MHz, CDCl3) δ 176.3, 170.7, 140.6, 131.2, 126.2, 126.0,
125.8, 116.9, 89.9, 37.1, 35.2, 34.9, 26.7, 11.7, 7.8, 7.6; IR
(KBr) cm−1: 2972, 1774, 1705, 1466, 1374, 1305, 1170, 756;
MS m/z (% base) 283 (M+, 1.7), 241 (58.8), 213 (41), 185 (76),
171 (61), 146 (66), 43 (100); EA found: C, 72.01; H, 6.01; N,
4.93. Calc. for C17H17NO3 C, 72.07; H, 6.05; N, 4.94%.
19, white powder; m.p. 84–87 °C; 1H NMR (300 MHz,
CDCl3) δ 8.23 (d, J = 8.2 Hz, 1H), 7.45–7.38 (m, 2H),
7.28–7.22 (m, 1H), 2.66 (s, 3H), 2.62–2.50 (m, 2H), 2.35–2.24
(m, 2H), 1.89–1.76 (m, 1H), 1.41–1.31 (m, 1H), 1.15–1.05 (m,
3H), 0.96–0.91 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 173.4,
170.6, 141.1, 132.1, 126.0, 125.8, 124.9, 117.2, 84.8, 77.4, 70.7,
34.1, 33.1, 26.7, 13.1, 9.0, 6.9; IR (KBr) cm−1: 2925, 1775,
1717, 1464, 1270, 1118, 763; MS m/z (% base) 201 (4.8), 213
(41.1), 146 (100), 82 (15), 54 (28), 43 (35); EA found: C, 72.13;
H, 6.08; N, 4.90. Calc. for C17H17NO3 C, 72.07; H, 6.05; N,
4.94%.
A solution of 2 (446 mg, 2 mmol) and 5 (320 mg, 4 mmol) in
anhydrous benzene (50 mL) was photolyzed with oxygen bub-
bling for 12 h to reach a complete conversion of 2. Flash column
chromatography on 300–400 mesh silica gel with petroleum
ether–ethyl acetate as eluents afforded pure analytical samples of
15.
15, colorless crystal from acetone–petroleum ether; m.
1
p. 187–189 °C; H NMR (300 MHz, CDCl3) δ 8.12 (d, J = 7.9
Hz, 1H), 7.31 (t, J = 8.0 Hz, 1H), 7.23 (d, J = 8.2 Hz, 1H), 2.67
(s, 3H), 1.12–1.04 (m, 2H), 0.70–0.50 (m, 6H); 13C NMR
(75 MHz, CDCl3) δ 174.8, 170.5, 142.1, 133.3, 132.3, 127.1,
122.5, 115.2, 74.5, 31.4, 26.8, 8.8, 8.7, 7.8, 7.6; IR (KBr) cm−1
:
1770, 1713, 1597, 1443, 1372, 1140, 792; MS m/z (% base) 303
(M+, 0.04), 261 (9), 233 (38), 205 (100), 43 (83); EA found: C,
63.33; H, 4.70; Cl, 11.65; N, 4.66. Calc. for C16H14ClNO3 C,
63.24; H, 4.65; Cl, 11.67%.
Photolysis of 3 with 5 in anhydrous benzene under oxygen
atmosphere
A solution of 3 (494 mg, 2 mmol) and 5 (320 mg, 4 mmol) in
anhydrous benzene (50 mL) was photolyzed with oxygen bub-
bling for 12 h to reach a complete conversion of 3. Flash column
chromatography on 300–400 mesh silica gel with petroleum
ether–ethyl acetate as eluents afforded pure analytical samples of
16 and 17.
20, colorless crystal from acetone–petroleum ether;
1
m.p. 143–146 °C; H NMR (300 MHz, CDCl3) δ 8.27 (d, J =
8.2 Hz, 1H), 8.11 (d, J = 8.0 Hz, 1H), 7.34–7.28 (m, 1H),
7.22–7.16 (m, 1H), 6.89 (td, J = 7.5, 0.8 Hz, 1H), 6.77 (td, J =
7.6, 0.9 Hz, 1H), 6.69 (d, J = 7.5, 0.8 Hz, 1H), 6.51 (dd, J = 7.6,
3632 | Org. Biomol. Chem., 2012, 10, 3626–3635
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0.8 Hz, 1H), 3.28–3.18 (m, 1H), 3.10–3.00 (m, 1H), 2.71 (s,
3H), 2.56 (s, 3H), 2.27–2.17 (m, 1H), 2.01–1.91 (m, 1H),
1.65–1.52 (m, 2H), 0.98–0.92 (m, 2H), 0.50–0.42 (m, 1H),
0.30–0.22 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 171.2, 170.5,
170.0, 144.5, 139.5, 131.3, 131.1, 125.0, 124.9, 124.8, 124.5,
124.0, 123.6, 116.8, 116.2, 107.3, 87.4, 80.4, 60.3, 35.3, 31.5,
26.7, 24.5, 13.3, 8.6, 8.4; IR (KBr) cm−1: 2955, 1778, 1709,
1683, 1462, 1388, 1275, 1241, 1170, 766; MS m/z (% base) 283
(1.6), 146 (75), 79 (59), 43 (100); EA found: C, 68.67; H, 5.20;
N, 5.87. Calc. for C27H24N2O6 C, 68.63; H, 5.12; N, 5.93%.
21, colorless crystal from acetone–petroleum ether;
(15), 85 (27), 43 (84); EA found: C, 73.47; H, 7.06; N, 4.30.
Calc. for C19H21NO3 C, 73.29; H, 6.80; N, 4.50%.
25, colorless crystal from acetone–petroleum ether;
1
m.p. 160–162 °C; H NMR (300 MHz, CDCl3) δ 8.30 (d, J =
8.2 Hz, 1H), 8.11 (d, J = 8.3 Hz, 1H), 7.36–7.30 (m, 1H),
7.23–7.17 (m, 1H), 6.90 (td, J = 7.5, 0.8 Hz, 1H), 6.78 (td, J =
7.6, 0.9 Hz, 1H), 6.67 (dd, J = 7.5, 0.7 Hz, 1H), 6.45 (dd, J =
7.6, 0.7 Hz, 1H), 2.72 (s, 3H), 2.60 (s, 3H), 1.93–1.57 (m, 6H),
1.44–1.13 (m, 3H), 0.90–0.69 (m, 2H) , 0.62–0.48 (m, 2H) ,
0.27–0.20 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 171.6, 170.5,
170.2, 144.6, 139.5, 131.4, 131.2, 124.9, 124.8, 124.7, 124.6,
124.5, 123.6, 116.9, 116.2, 78.7, 62.6, 33.2, 32.9, 26.7, 25.6,
24.5, 21.5, 10.5, 9.4; IR (KBr) cm−1: 2932, 1777, 1720, 1684,
1463, 1384, 1269, 1236, 754; MS m/z (% base) 311 (5), 162
(42), 146 (100), 90 (23), 79(17), 43 (40); EA found: C, 69.74;
H, 5.49; N, 5.61. Calc. for C29H28N2O6 C, 69.59; H, 5.64;
N, 5.60%.
1
m.p. 123–126 °C; H NMR (300 MHz, CDCl3) δ 8.28 (d, J =
8.3 Hz, 1H), 8.18 (d, J = 7.9 Hz, 1H), 7.91 (d, J = 7.3 Hz, 1H),
7.45 (t, J = 7.5 Hz, 1H), 7.38–7.28 (m, 2H), 7.01 (t, J = 7.3 Hz,
1H), 6.94 (d, J = 6.9 Hz, 1H), 3.06–3.01 (m, 2H), 2.54 (s, 3H),
2.15–2.11 (m, 5H), 1.77–1.62 (m, 2H), 1.00–0.85 (m, 2H),
0.52–0.40 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 172.8, 170.0,
169.7, 146.1, 140.5, 131.7, 131.4, 127.9, 125.0, 124.2, 123.8,
122.1, 122.0, 116.9, 116.5, 106.7, 98.4, 87.0, 76.8, 60.7, 34.7,
31.1, 26.0, 24.1, 13.5, 9.0, 8.4; IR (KBr) cm−1: 2954, 1768,
1718, 1689, 1462, 1375, 1288, 1240, 1171, 754; MS (ESI) m/z
473 [M + H]+; EA found: C, 68.77; H, 5.08; N, 5.91. Calc. for
C27H24N2O6 C, 68.63; H, 5.12; N, 5.93%.
26, colorless crystal from acetone–petroleum ether;
1
m.p. 150–153 °C; H NMR (300 MHz, CDCl3) δ 8.31 (d, J =
8.4 Hz, 1H), 8.21 (d, J = 8.1 Hz, 1H), 8.02 (d, J = 7.7 Hz, 1H),
7.48–7.29 (m, 3H), 7.06–6.95 (m, 2H), 2.57 (s, 3H), 2.17 (s,
3H), 1.92–1.11 (m, 9H), 0.91–0.37 (m, 5H); 13C NMR
(75 MHz, CDCl3) δ 172.8, 170.1, 169.8, 146.0, 140.7, 131.7,
131.4, 128.2, 125.1, 124.2, 124.0, 122.7, 122.2, 117.0, 116.6,
77.3, 62.5, 34.6, 32.8, 26.1, 25.4, 24.2, 21.5, 21.2, 11.2, 9.5; IR
(KBr) cm−1: 2938, 1768, 1718, 1687, 1462, 1375, 1290, 1235,
756; MS m/z (% base) 191 (45), 146 (99), 132 (48), 71 (100), 43
(58); EA found: C, 69.59; H, 5.64; N, 5.60. Calc. for
C29H28N2O6 C, 69.59; H, 5.64; N, 5.60%.
1
22, white powder; H NMR (300 MHz, CDCl3) δ 11.27 (br.,
1 H), 8.63 (dd, J = 8.6, 0.9 Hz, 1H), 7.61 (t, J = 8.0 Hz, 1H),
7.24 (dd, J = 7.7, 1.0 Hz, 1H), 2.32–2.22 (m, 5 H), 2.17–1.95
(m, 4 H), 1.09–1.04 (m, 2 H), 0.94–0.89 (m, 2 H); 13C NMR
(75 MHz, CDCl3) δ 169.5, 168.5, 148.1, 142.6, 135.6, 119.3,
117.6, 109.3, 67.3, 43.0, 29.9, 28.6, 25.7, 15.1, 8.6 (2C); MS
(ESI) m/z (%) 272 [M + H]+; EA found: C, 70.88; H, 6.23;
N, 5.00. Calc. for C16H17NO3 C, 70.83; H, 6.32; N, 5.16%.
27, colorless liquid; 1H NMR (300 MHz, CDCl3) δ 11.22 (br,
1 H), 8.60 (dd, J = 8.5, 1.0 Hz, 1H), 7.53 (t, J = 8.1 Hz, 1H),
7.29 (dd, J = 7.9, 0.9 Hz, 1H), 2.23 (s, 3H), 1.88–0.87 (m, 14
H); 13C NMR (75 MHz, CDCl3) δ 169.5, 168.6, 150.0, 142.3,
134.6, 119.8, 119.3, 110.6, 70.1, 38.5, 30.4, 29.9, 25.7, 25.5,
22.8, 9.0; MS (ESI) m/z 300 [M + H]+.
Photolysis of 1 with 7 in anhydrous benzene
A solution of 1 (378 mg, 2 mmol) and 7 (488 mg, 4 mmol) in
anhydrous benzene (50 mL) was photolyzed with inert gas
(oxygen) bubbling for 12 h to reach a complete conversion of 1.
Flash column chromatography on 300–400 mesh silica gel with
petroleum ether–ethyl acetate as eluents afforded pure analytical
samples of 23–26 (23, 24 and 27 for oxygen bubbling).
Photolysis of 1 with 8 in anhydrous benzene
A solution of 1 (378 mg, 2 mmol) and 8 (656 mg, 4 mmol) in
anhydrous benzene (50 mL) was photolyzed with inert gas
(oxygen) bubbling for 12 h to reach a complete conversion of 1.
Flash column chromatography on 300–400 mesh silica gel with
petroleum ether–ethyl acetate as eluents afforded pure analytical
samples of 29–33 (29 and 31 for oxygen bubbling).
23, colorless liquid; 1H NMR (300 MHz, CDCl3) δ 8.24 (d, J
= 8.2 Hz, 1H), 7.70 (dd, J = 7.5, 1.3 Hz, 1H), 7.40 (td, J = 8.0,
1.5 Hz, 1H), 7.27 (td, J = 7.5, 1.0 Hz, 1H), 2.69 (s, 3H),
2.47–2.42 (m, 1H), 2.10–2.05 (m, 1H), 1.49–0.69 (m, 12H); 13C
NMR (75 MHz, CDCl3) δ 176.4, 170.5, 139.8, 130.6, 126.1,
125.1, 117.0, 116.6, 87.8, 76.5, 50.4, 31.4, 30.4, 26.6, 25.1,
23.8, 22.5, 7.4, 7.0; IR (KBr) cm−1: 2931, 2856, 1774, 1712,
1464, 1371, 1338, 1274, 1169, 1108, 757; MS m/z (% base) 311
(0.18), 255 (94), 213 (100), 146 (60), 43 (41); EA found: C,
73.38; H, 6.67; N, 4.45. Calc. for C19H21NO3 C, 73.29; H, 6.80;
N, 4.50%.
29, colorless crystal from acetone–petroleum ether;
1
m.p. 241–243 °C; H NMR (300 MHz, CDCl3) δ 8.19 (d, J =
8.1 Hz, 1H), 7.61 (d, J = 6.9 Hz, 1H), 7.36 (td, J = 7.9, 1.3 Hz,
1H), 7.24 (t, J = 7.6 Hz, 1H), 2.66 (br, 4H), 2.45–2.38 (m, 1H),
2.26–2.09 (m, 2H), 1.73–1.42 (m, 10H), 1.30–1.00 (m, 4H),
0.90–0.77 (m, 2H), 0.30–0.21 (m, 1H); 13C NMR (75 MHz,
CDCl3) δ 177.8, 170.5, 139.7, 130.3, 127.3, 125.9, 125.0, 116.4,
88.1, 52.0, 33.9, 33.2, 29.0, 28.2, 26.6, 25.7, 25.2, 24.2, 22.8,
22.4; IR (KBr) cm−1: 2924, 1766, 1712, 1463, 1371, 1274,
1167, 765; MS m/z (% base) 353 (M+, 13), 191 (56), 163 (75),
149 (53), 81 (100), 67 (86); EA found: C, 74.69; H, 7.58; N,
4.11. Calc. for C22H27NO3 C, 74.76; H, 7.70; N, 3.96%.
24, colorless liquid; 1H NMR (300 MHz, CDCl3) δ 8.24 (d, J
= 8.0 Hz, 1H), 7.47–7.38 (m, 2H), 7.25 (t, J = 7.5 Hz, 1H), 2.65
(s, 3H) , 2.21 (d, J = 13.6 Hz, 1H), 2.07 (d, J = 12.8 Hz, 1H),
1.75–1.60 (m, 5H), 1.42–0.87 (m, 6H), 0.72–0.65 (m, 1H); 13C
NMR (75 MHz, CDCl3) δ 173.7, 170.6, 141.1, 131.8, 125.9,
125.4, 124.9, 117.1, 100.9, 83.1, 70.8, 36.2, 33.7, 26.6, 25.6,
22.7, 22.3, 8.9, 6.0; IR (KBr) cm−1: 2933, 2860, 1779, 1715,
1466, 1371, 1335, 1268, 1170, 1121, 754; MS m/z (% base) 310
1
30, white powder; H NMR (300 MHz, CDCl3) δ 8.44 (dd, J
= 7.3, 1.3 Hz, 1H), 7.39 (dd, J = 6.9, 1.5 Hz, 1H), 7.26–7.15 (m,
2H), 2.68 (s, 3H), 1.99–1.16 (m, 20H); 13C NMR (75 MHz,
This journal is © The Royal Society of Chemistry 2012
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CDCl3) δ 168.7, 131.9, 128.8, 123.9, 122.8, 122.5, 117.5, 116.6,
114.9, 84.7, 79.4, 25.9, 25.8, 25.6, 21.7, 21.4; MS m/z (% base)
353 (M+, 19), 191 (57), 163 (91), 149 (100), 81 (96), 67 (85).
31, colorless crystal from acetone–petroleum ether;
8.0, 1.3 Hz, 1 H), 7.69 (td, J = 7.9, 1.4 Hz, 1 H), 7.47 (td, J =
7.6, 1.0 Hz, 1 H), 7.40 (d, J = 7.8 Hz, 1 H), 3.36 (s, 3 H), 3.20
(dt, J = 18.3, 10.2 Hz, 1 H), 2.92–2.82 (m, 1 H), 2.68 (qd, J =
9.7, 2.4 Hz, 1 H), 2.51 (dt, J = 13.3, 10.0 Hz, 1 H), 1.42–1.34
(m, 1 H), 1.23–1.26 (m, 1 H), 0.61–0.53 (m, 1 H), 0.49–0.42
(m, 1 H); 13C NMR (75 MHz, CDCl3) δ 216.1, 776.8, 164.3,
140.6, 134.0, 129.1, 128.2 (2C), 125.4, 53.5, 40.9, 37.1, 36.2,
27.2, 21.0, 16.2; MS m/z (% base) 241 (100), 213 (36), 128
(13.6); EA found: C, 71.44; H, 5.69; N, 5.10. Calc. for
C16H15NO3 C, 71.36; H, 5.61; N, 5.20%.
1
m.p. 141–144 °C; H NMR (300 MHz, CD3COCD3) δ 7.44 (t,
J = 7.4 Hz, 1H), 7.29 (t, J = 7.1 Hz, 1H), 7.23 (d, J = 8.2 Hz,
1H), 7.14 (d, J = 8.1 Hz, 1H), 2.34–2.21 (m, 2H), 2.19 (s, 3H),
1.86–1.23 (m, 18H); 13C NMR (75 MHz, CD3COCD3) δ 145.5,
130.4, 126.6, 125.1, 124.3 78.9, 31.7 31.6, 31.2, 29.2, 25.1,
24.9, 21.5, 21.2, 20.7, 20.6; IR (KBr) cm−1: 3437, 2925, 1772,
1693, 1463, 1379, 1176, 764; MS m/z (% base) 370 (M − 1+,
0.03), 190 (6), 164 (100), 162 (88), 146 (56), 117 (78) , 81 (72);
EA found: C, 71.65; H, 7.30; N, 3.74. Calc. for C22H27NO4 C,
71.52; H, 7.37; N, 3.79%.
38, colorless crystal from acetone–petroleum ether;
1
m.p. 100–102 °C; H NMR (300 MHz, CDCl3) δ 8.25 (d, J =
7.7 Hz, 1 H), 8.04 (dd, J = 7.8, 1.0 Hz, 1 H), 7.77 (td, J = 7.6,
1.4 Hz, 1 H), 7.68 (td, J = 7.5, 1.1 Hz, 1 H), 3.24 (s, 3 H),
1.18–1.02 (m, 4 H), 0.63–0.46(m, 4 H); 13C NMR (75 MHz,
CDCl3) δ 186.1, 162.5, 135.3, 133.1, 131.4, 129.4, 128.9, 126.6,
106.8, 67.1 (2C), 27.5, 8.3 (2C), 7.3 (2C); MS m/z (% base) 285
(12.1), 187 37.6), 104 (38.5), 68 (100); EA found: C, 67.33; H,
5.37; N, 4.74. Calc. for C16H15NO4 C, 7.36; H, 5.30; N, 4.91%.
32, colorless crystal from acetone–petroleum ether;
1
m.p. 101–102 °C; H NMR (300 MHz, CDCl3) δ 8.21 (d, J =
8.1 Hz, 1H), 7.40–7.33 (m, 2H), 7.24 (t, J = 7.2 Hz, 1H), 3.34
(br, 2H), 2.72–2.66 (m, 4H), 2.37–2.14 (m, 5H), 1.82–1.18 (m,
12H); 13C NMR (75 MHz, CDCl3) δ 180.6, 170.7, 141.0,
140.4, 130.5, 130.0, 125.7, 123.8, 116.4, 78.1, 46.1, 31.6, 31.1,
29.0, 28.9, 27.1, 27.0, 26.7, 25.8, 25.7, 22.5; IR (KBr) cm−1
:
Photolysis of 4 with 6 in anhydrous acetonitrile
3481, 2929, 1748, 1721, 1461, 1368, 1270, 1168, 760; MS m/z
(% base) 353 (M+, 1), 335 (18), 292 (27), 162 (55), 146 (78),
119 (96) , 91 (100); EA found: C, 74.69; H, 7.57; N, 4.08. Calc.
for C22H27NO3 C, 74.76; H, 7.70; N, 3.96%.
A solution of 4 (378 mg, 2 mmol) and 6 (376 mg, 4 mmol) in
anhydrous acetonitrile (50 mL) was photolyzed with inert gas
(oxygen) bubbling for 12 h to reach a complete conversion of 4.
Flash column chromatography with chloroform as eluent
afforded pure analytical samples of 39–41. (39 and 41 for
oxygen bubbling).
33, colorless crystal from acetone–petroleum ether;
1
m.p. 151–153 °C; H NMR (300 MHz, CDCl3) δ 8.14 (d, J =
8.1 Hz, 1H), 7.38–7.28 (m, 2H), 7.16 (t, J = 7.6 Hz, 1H), 3.04
(br, 1H), 2.54 (s, 3H), 2.32–2.28 (m, 1H), 2.04–1.07 (m, 18H);
13C NMR (75 MHz, CDCl3) δ 179.9, 170.1, 140.1, 129.8,
129.1, 127.8, 125.6, 124.6, 116.3, 81.2, 51.1, 27.0, 26.4, 26.3,
26.0, 25.8, 23.4, 22.0; IR (KBr) cm−1: 3457, 2925, 1748, 1712,
1463, 1370, 1267, 1172, 763; MS m/z (% base) 353 (M+, 1),
335 (18), 292 (27), 163 (100), 146 (29), 95 (76), 81 (71); EA
found: C, 74.85; H, 7.63; N, 4.00. Calc. for C22H27NO3 C,
74.76; H, 7.70; N, 3.96%.
39, colorless crystal from acetone–petroleum ether;
1
m.p. 135–137 °C; H NMR (300 MHz, CDCl3) δ 8.07 (d, J =
8.0 Hz, 1H), 7.85 (d, J = 7.7 Hz, 1H), 7.71 (t, J = 7.4 Hz, 1H),
7.48 (t, J = 7.5 Hz, 1H), 3.32 (s, 3H), 2.74 (dd, J = 22.3, 10.2
Hz, 1H), 2.57 (dd, J = 21.9, 10.4 Hz, 1H), 2.50–2.42 (m, 1H),
2.29–2.23 (m, 1H), 1.79–1.67 (m, 1H), 1.09–0.93 (m, 1H),
0.81–0.73 (m, 1H), 0.66–0.58 (m, 1H), 0.51–0.43 (m, 1H),
−0.02–0.10 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 173.1,
164.0, 138.6, 134.5, 129.1, 128.4, 126.5, 124.3, 89.4, 83.5,
42.8, 35.4, 34.7, 27.2, 11.9, 8.2, 7.7; MS m/z (% base) 282 (6.1),
227 (100), 213 (41.5), 170 (30.0), 128 (91.7); EA found: C,
72.13; H, 5.97; N, 4.98. Calc. for C17H17NO3 C, 72.07; H, 6.05;
N, 4.94%.
Photolysis of 4 with 5 in anhydrous acetonitrile
A solution of 4 (378 mg, 2 mmol) and 5 (320 mg, 4 mmol) in
anhydrous acetonitrile (50 mL) was photolyzed with inert gas
(oxygen) bubbling for 12 h to reach a complete conversion of 4.
Flash column chromatography on 300–400 mesh silica gel with
petroleum ether–ethyl acetate as eluents afforded pure analytical
samples of 35, 36 and 38. An impure sample of 37 was obtained.
(35 and 38 for oxygen bubbling).
40, straw yellow powder; 1H NMR (300 MHz, CDCl3) δ 8.35
(d, J = 7.7 Hz, 1H), 7.58 (d, J = 3.9 Hz, 2H), 7.34–7.28 (m,
1H), 3.58 (s, 3H), 2.43–2.32 (m, 2H), 2.20–2.11 (m, 2H),
2.08–1.94 (m, 1H), 1.78–1.62 (m, 1H), 1.14–1.09 (m, 2H),
0.97–0.92 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 160.2, 132.2,
131.6, 128.2, 124.4, 120.8, 118.7, 81.5, 60.8, 31.6 (2C), 31.1,
28.1, 12.9, 9.1 (2C); MS m/z (% base) 283 (13.9), 215 (100),
190 (10.8), 104 (11.0), 79 (67.0); EA found: C, 71.88; H, 6.03;
N, 5.00. Calc. for C17H17NO3 C, 72.07; H, 6.05; N, 4.94%.
41, white powder; m.p. 89–90 °C; 1H NMR (300 MHz,
CDCl3) δ 8.25 (dd, J = 7.6, 0.8 Hz, 1H), 8.01 (dd, J = 7.6, 1.1
Hz, 1H), 7.77 (td, J = 7.6, 1.4 Hz, 1H), 7.67 (td, J = 7.5, 1.1 Hz,
1H), 3.15 (s, 3H), 2.67–2.51 (m, 2H), 2.33–2.20 (m, 2H),
1.84–1.71 (m, 1H), 1.33–1.18 (m, 1H), 1.06–0.97 (m, 3H),
0.90–0.84 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 186.9, 162.5,
135.3, 133.0, 131.56, 129.5, 128.9, 126.6, 107.1, 84.6, 70.7,
33.9, 33.6, 27.3, 12.8, 9.3, 7.2; MS m/z (% base) 190 (0.7), 161
(59.7), 104 (100), 76 (61.6).
35, colorless crystal from acetone–petroleum ether;
1
m.p. 145–146 °C; H NMR (300 MHz, CDCl3) δ 8.12 (dd, J =
7.9, 0.5 Hz, 1 H), 8.07 (d, J = 7.8 Hz, 1 H), 7.77 (td, J = 7.8, 1.2
Hz, 1 H), 7.52 (td, J = 8.0, 1.1 Hz, 1 H), 3.37 (s, 3 H),
1.33–1.23 (m, 1 H), 1.13–1.03 (m, 1 H), 0.67–0.30 (m, 5 H),
0.05–0.03 (m, 1 H); 13C NMR (75 MHz, CDCl3) δ 172.4,
164.0, 138.3, 134.6, 129.3, 128.5, 126.8, 124.4, 73.3, 39.3,
27.3, 8.8, 7.8, 7.7, 7.3; MS m/z (% base) 269 (0.3), 241 (7.2),
146 (25.2), 104 (68), 76 (71.8); EA found: C, 71.37; H, 5.55; N,
5.25. Calc. for C16H15NO3 C, 71.36; H, 5.61; N, 5.20%.
36, colorless crystal from acetone–petroleum ether;
1
m.p. 163–164 °C; H NMR (300 MHz, CDCl3) δ 8.23 (dd, J =
3634 | Org. Biomol. Chem., 2012, 10, 3626–3635
This journal is © The Royal Society of Chemistry 2012

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Acknowledgements
The authors would like to acknowledge financial support
from the National Basic Research Program of China (No.
2011CB935800), National Natural Science Foundation of China
(20972067, 90813035), the Program for New Century Excellent
Talents in University (NCET-08–0271) and the Austria–China
Cooperation project (2007DFA41590, WTZ-Project No. CN 08/
2010).
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