Organoselenium-Catalyzed Oxidative Ring Expansion of Methylenecyclopropanes with Hydrogen Peroxide

Article abstract of DOI:10.1002/cctc.201501309

Catalyst screening and optimization of reaction conditions allowed control of the organoselenium-catalyzed oxidative ring expansion of highly active methylenecyclopropanes to give substituted cyclobutanones selectively. This protocol employs H₂O₂ as a clean oxidant and generates no waste and, therefore, provides green access to useful, but not readily available, substituted cyclobutanones under mild conditions.

Full text of DOI:10.1002/cctc.201501309

DOI: 10.1002/cctc.201501309
Communications
Organoselenium-Catalyzed Oxidative Ring Expansion of
Methylenecyclopropanes with Hydrogen Peroxide
Lei Yu,* Fenglin Chen, and Yuanhua Ding[a]
Catalyst screening and optimization of reaction conditions al-
lowed control of the organoselenium-catalyzed oxidative ring
expansion of highly active methylenecyclopropanes to give
substituted cyclobutanones selectively. This protocol employs
H2O2 as a clean oxidant and generates no waste and, therefore,
provides green access to useful, but not readily available,
substituted cyclobutanones under mild conditions.
green synthetic methodologies, we performed a series of orga-
noselenium-catalyzed transformations by using H2O2 as a clean
oxidant.[11] On this basis, we envisioned that the oxidative ring
expansion of MCPs to cyclobutanones might be achieved by
an organoselenium-catalyzed method by using H2O2 as the oxi-
dant. The organoselenium-catalyzed oxidation of simple al-
kenes by H2O2 has already been reported,[10j,11g,h] but its appli-
cation to the ring expansion of MCPs is still unknown. Given
that MCPs are highly active molecules with multiple reaction
sites and that the produced cyclobutanones may also undergo
further Baeyer–Villiger oxidation,[11d,f] selective oxidation by
using the strong oxidant H2O2 faces tremendous challenges
(Scheme 1). Recently, after careful catalyst screening and opti-
mization of the reaction conditions, we achieved the organose-
lenium-catalyzed selective oxidative ring expansion of MCPs by
using H2O2 as the oxidant. Herein, we wish to report our
findings.
Methylenecyclopropanes (MCPs) are highly strained but readily
available building blocks that have been widely employed to
synthesize a variety of useful compounds.[1,2] Ring-expansion
reactions of MCPs[1d,3,4] are significant, because they provide
more opportunities to construct difficult-to-access four-mem-
bered-ring structures that widely exist in bioactive intermedi-
ates in drug discovery.[5] Among the reported works, the oxida-
tive ring expansion of MCPs to useful substituted cyclobuta-
nones has attracted much attention during the past decade.[4]
In 2004, Shi et al. reported the Lewis acid mediated ring expan-
sion of MCPs with the use of either diisopropyl azodicarboxy-
late or diethyl azodicarboxylate.[4a] Later, Huang et al. found
that MCPs could be oxidized by CeIV to produce cyclobuta-
nones in moderate yields through a single-electron-transfer
mechanism.[4b] The reaction could be improved with the assis-
tance of O2.[4c] These pioneering methods provide convenient
access to substituted cyclobutanones. However, they require
the use of an excess amount of a chemical oxidant, which in-
evitably results in the generation of waste; furthermore, the
substrates are limited to disubstituted MCPs. As such, there is
still sufficient room for further improvement.
Scheme 1. Challenges for the selective oxidation of MCPs.
The oxidation of 1,1’-(cyclopropylidenemethylene)dibenzene
(1a) with H2O2 was chosen as the model reaction to optimize
the reaction conditions. A blank reaction without any catalyst
was initially performed, but it led to a mixture of products, in
which desired product 2a was isolated in only 18% yield and
benzophenone, the decomposition product of 1a, was
obtained in 31% yield [Eq. (1)].
On the other hand, the chemistry of organoselenium com-
pounds has been developing rapidly in recent years.[6,7] The
ecofriendly aspects of this field have attracted much atten-
tion.[8–11] Besides, because of its clean procedures and transi-
tion-metal-free conditions in addition to the fact that the cata-
lyst element can be metabolized and is safe to the environ-
ment,[12] organoselenium catalysis has been noted as a poten-
tial alternative for transition-metal-catalyzed reactions in the
synthesis of medicines.[9–11] During our continuous studies on
[a] Dr. L. Yu, F. Chen, Prof. Y. Ding
Jiangsu Co-innovation Centre for Prevention and Control
of Important Animal Infectious Diseases and Zoonoses
Jiangsu Key Laboratory of Zoonosis
School of Chemistry and Chemical Engineering
Yangzhou University
Then, the reaction with various organoselenium catalysts
was investigated. Heating 1a and H2O2 in MeCN with (PhSe)2
(5 mol%) as the catalyst at 408C afforded desired product 2a
in 55% yield (Table 1, entry 1). The yield was enhanced to 60%
at 508C but began to decrease at elevated temperatures
(Table 1, entry 2 vs. entries 3–5). A series of organoselenium
Yangzhou, Jiangsu 225002 (P.R. China)
E-mail: yulei@yzu.edu.cn
Supporting Information and ORCID(s) from the author(s) for this article
are available on the WWW under http://dx.doi.org/10.1002/
cctc.201501309.
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on the aryl ring resulted in improved reactivity of MCP 1b rela-
tive to that of unsubstituted 1a, and the reaction of 1b under
the standard conditions led to 2b in a decreased yield of 56%,
whereas a series of unidentified complexes were observed by
thin-layer chromatography (TLC). Fortunately, the reaction pro-
ceeded smoothly at 258C to give 2b in a good yield of 80%
[Eq. (2)].
Table 1. Optimization of the reaction conditions.[a]
Entry
Se catalyst[b]
[(mol%)]
T
H2O2
[equiv.][c]
Yield[d]
[%]
[8C]
1
2
3
4
5
6
7
8
(PhSe)2 (5)
(PhSe)2 (5)
(PhSe)2 (5)
(PhSe)2 (5)
40
50
60
70
80
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
1.2–3.0
6.0
5.0
5.0
55[e]
60[e]
45[e]
41[e]
38[e]
47[e]
37[e]
63
(PhSe)2 (5)
(4-MeOC6H4Se)2 (5)
(4-Me2NC6H4Se)2 (5)
(4-FC6H4Se)2 (5)
(3-FC6H4Se)2 (5)
(2-FC6H4Se)2 (5)
[3,5-(CF3)2C6H3Se]2 (5)
(1-C10H7Se)2 (5)
(BnSe)2 (5)
9
65
71
48
Bearing two EDGs, MCP 1c was even more reactive than 1a
and 1b. Thus, ice-bath cooling was necessary to slow down
the reaction to decrease the amount of overoxidation. The
reaction at 08C afforded 2c in 51% yield, but at À108C, 2c
was obtained in only 26% yield, and a large amount of sub-
strate 1c was observed by TLC [Eq. (3)].
10
11
12
13
14
15
16
17
18
19
20
21
43[e]
24[e]
26[e]
8–23[e]
22–28[e]
17[e]
39–52[e]
60
(CySe)2 (5)
R1SeR2 (5)[f]
(PhS)2 or (PhTe)2 (5)
SeO2 (5)
(2-FC6H4Se)2 (5)
(2-FC6H4Se)2 (5)
(2-FC6H4Se)2 (10)
(2-FC6H4Se)2 (0.1–2)
59
24–62[e]
[a] Compound 1a (0.3 mmol) and MeCN (1 mL) were employed. [b] Cata-
lyst loading based on 1a. [c] H2O2 molar dosage based on 1a. [d] Yield of
isolated 2a based on 1a. [e] Reaction was incomplete. [f] PhSePh, EtSePh,
iPrSePh, and CySePh were employed.[13]
In contrast, bearing EWGs, electron-deficient MCPs 1d–f
were much more stable than 1a–c, and they afforded products
2d–f in very poor yields under the standard conditions, where-
as most of the starting material remained unreacted [Eq. (3)].
However, at an elevated reaction temperature (808C), the sub-
strates were oxidized smoothly to give corresponding cyclo-
butanones 2d–f in moderate yields [Eq. (4)].
Dialkyl MCP 1g was also a favorable substrate for the reac-
tion, and it gave 2g in moderate yield [Eq. (5)]. Notably, 2g is
a useful but inaccessible intermediate in drug discovery.[14]
The oxidative ring expansion of monosubstituted MCPs 1h–
l was tested. Unfortunately, similar to that already reported,[4]
reaction of these monosubstituted MCPs under the standard
conditions led to a series of unidentified complexes, possibly
compounds were then employed as catalysts for screening.
Electron-enriched diselenides gave the products in very poor
yields (Table 1, entries 6 and 7), whereas electron-deficient dis-
elenides clearly improved the reaction yield (Table 1, entries 8–
10). Among the studied candidates, (2-FC6H4Se)2 was screened
to be the best catalyst, and it gave 2a in 71% yield (Table 1,
entry 10 vs. entries 8 and 9). Bearing two electron-withdrawing
groups (EWGs), electron-deficient [3,5-(CF3)2C6H3Se]2 led to 2a
in a very low yield and a series of unidentified byproducts
were generated simultaneously (Table 1, entry 11). Bulky bis(1-
naphthyl) diselenide (1-C10H7Se)2 and the alkyl diselenides di-
benzyl diselenide [(BnSe)2] and dicyclohexyl diselenide [(CySe)2]
were not efficient catalysts for this reaction (Table 1, en-
tries 12–14). Reactions with selenides as catalysts afforded 2a
in low yields (Table 1, entry 15). (PhS)2, (PhTe)2, and SeO2 also
showed poor catalytic activity for the reaction (Table 1, en-
tries 16 and 17).[13] The reaction required an excess amount of
H2O2, but more than 5.0 equivalents of H2O2 resulted in a de-
creased yield of 2a as a result of overoxidation (Table 1,
entry 10 vs. entries 18 and 19).[13] The catalyst loading was also
examined, and fortunately, 5 mol% of the catalyst, as we ini-
tially employed, was the best dosage (Table 1, entry 10 vs.
entries 20 and 21).[13]
The scope of the reaction was next investigated. Substitu-
ents on the substrate largely affected the reaction. Introduc-
tion of a methyl group as an electron-donating group (EDG)
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because of the fact that the substrates were too active and de-
composed under the oxidative conditions [Eq. (6)]. Efforts to
optimize the reaction conditions for the selective oxidative
ring expansion of monosubstituted MCP 1h (R=Ph) failed.[13]
cyclobutyl cation 5, which affords 6 through intramolecular re-
arrangement.[3e,h,o,p,15] Decomposition of 6 affords final product
2 and organoseleninic acid 7, which regenerates catalytic spe-
cies 3 after oxidation by H2O2 (Scheme 2).[11f] Although this
mechanism remains to be fully clarified and alternative pro-
cesses may also exist, Scheme 2 should be the most likely
mechanism on the basis of the above experimental findings
and related literature.
In conclusion, we developed a novel method for the synthe-
sis of useful substituted cyclobutanones through the organose-
lenium-catalyzed ring-expansion reaction of methylenecyclo-
propanes by using H2O2 as a green oxidant. The oxidation level
and selectivity of the reaction were controlled through modifi-
cation of the reaction conditions. It seems that the reaction is
very sensitive to substituents in the substrate, that is, different
substrates might require quite different conditions. Further
studies on the organoselenium-catalyzed ring-expansion reac-
tion are ongoing in our laboratory.
Cyclopropyl-ring-substituted MCPs 1m–p were also em-
ployed as substrates [Eq. (7)]. A methyl group as an EDG on
the cyclopropyl ring largely enhanced the electron density of
the substrate and, thus, made the substrate even more reac-
tive than the simple MCP. In the oxidation of MCPs 1m–p, (4-
FC6H4Se)2 instead of previously employed (2-FC6H4Se)2 was the
preferred catalyst. The oxidation of MCP 1m at 258C led to iso-
mers 2m and 2m’ in 53% yield, with a molar ratio of 2m/
2m’=4:1. The oxidation of electron-rich MCP 1n was per-
formed at a low temperature to afford isomers 2n and 2n’ in
a 1:2 molar ratio in 38% yield. Electron-deficient MCP 1o was
more stable and an elevated reaction temperature was re-
quired. At 808C, 1o was smoothly oxidized to 2o and 2o’ in
60% yield with a 4:1 molar ratio. Interestingly, the oxidation of
MCP 1p led to 2p as the sole product in moderate yield
[Eq. (7)].
Experimental Section
General methods
MCPs 1a–l were prepared according to the literature through
Wittig reaction of cyclopropylidene ylide 8 with ketones or alde-
hydes [Eq. (8)].[1l,16] MCPs 1m–p were synthesized by a similar reac-
tion by using commercially available 1,3-dibromobutane as the
starting material to produce ylide 9 [Eq. (9)].
Organoselenium catalysts were commercially available or were pre-
pared through known methods.[11g] Solvents were analytically pure
(AR) and were directly used without any special treatment. All reac-
tions were monitored by TLC. IR spectra were measured with
a Bruker Tensor 27 infrared spectrometer. 1H NMR and 13C NMR
spectra were recorded with a Bruker Avance 600/400 instrument
On the basis of our previous work as well as literature prece-
dent, a plausible mechanism is proposed (Scheme 2). As con-
firmed by 77Se NMR spectroscopy, the oxidation of the disele-
nide by H2O2 leads to seleninoperoxoic acid 3.[11f] Electrophilic
addition of 3 to MCP 1 leads to intermediate 4.[3o,11b] As the
cyclopropylmethylium cation bears a selenium group at the
a position, ring expansion of 4 occurs to give intermediate
1
(600/400 MHz for H and 150/100 MHz for 13C NMR) by using CDCl3
as the solvent. Chemical shifts for 1H NMR and 13C NMR were re-
ferred to internal Me4Si (d=0 ppm). Mass spectra were measured
with a Shimadzu GCMS-QP2010 Ultra spectrometer (EI). Elemental
analysis was measured with a Vario EL cube elemental analysis in-
strument.
Typical procedure for the synthesis of 2
A reaction tube was charged with MCP 1 (0.3 mmol) and the orga-
noselenium catalyst (5 mol%, 0.015 mmol). A solution of 30 w/w
aq H2O2 (1.5 mmol) in MeCN (1 mL) was then injected by syringe.
The mixture was stirred at the temperatures mentioned above. The
reaction was monitored by TLC (petroleum ether/EtOAc=15:1).
Upon completion of the reaction, the solvent was evaporated
under reduced pressure, and the residue was isolated by prepara-
tive TLC (petroleum ether/EtOAc=15:1) to afford product 2.
Scheme 2. Possible mechanism.
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Communications
J=8.4 Hz, 2H), 1.89–1.83 (m, 4H), 1.69–1.75 (m, 2H), 1.55–
1.47 ppm (m, 2H); 13C NMR (100 MHz, CDCl3): d=216.1, 146.6,
128.3, 126.7, 126.1, 65.5, 43.1, 41.7, 31.4, 29.5, 23.6 ppm; MS (EI,
70 eV): m/z (%): 214 (5) [M+], 103 (100); known compound.[14]
Characterization data
2,2-Diphenylcyclobutanone (2a): Yield: 47.3 mg, 71%; oil; IR (film):
n˜ =3022, 1777, 1657, 1596, 1490, 1445, 1177, 1074, 695 cmÀ1
;
1H NMR (600 MHz, CDCl3, Me4Si): d=7.37 (d, J=7.8 Hz, 4H), 7.29 (t,
J=7.8 Hz, 4H), 7.19 (t, J=7.5 Hz, 2H), 3.13 (t, J=8.7 Hz, 2H),
2.81 ppm (t, J=8.7 Hz, 2H); 13C NMR (150 MHz, CDCl3): d=208.7,
142.1, 128.7, 126.9, 126.4, 76.2, 43.4, 25.6 ppm; MS (EI, 70 eV): m/z
(%): 222 (2) [M+], 180 (100), 179 (47), 165 (72); known com-
pound.[4c]
4-Methyl-2,2-diphenylcyclobutan-1-one (2m) and 3-methyl-2,2-di-
phenylcyclobutan-1-one (2m’): Yield: 37.6 mg, 53%; oil; IR (2m
and 2m’, film): n˜ =1774, 1658, 1598, 1492, 1446, 1083, 762, 638,
537 cmÀ1 1H NMR (2m, 400 MHz, CDCl3, Me4Si): d=7.35–7.03 (m,
;
10H), 3.37–3.15 (m, 1H), 3.05–2.99 (m, 1H), 2.32–2.27 (m, 1H),
1.14–1.12 ppm (d, J=7.2 Hz, 3H); 1H NMR (2m’, 400 MHz, CDCl3,
Me4Si): d=7.35–7.03 (m, 10H), 3.37–3.15 (m, 2H), 2.67–2.61 (m,
1H), 0.97–0.96 ppm (d, J=7.2 Hz, 3H); 13C NMR (2m and 2m’,
100 MHz, CDCl3): d=211.5, 209.2, 142.6, 142.2, 128.9, 128.5, 127.7,
127.0, 126.7, 126.5, 77.9, 73.9, 51.1, 50.6, 34.2, 29.8, 18.6, 13.8 ppm;
MS (2m and 2m’, EI, 70 eV): m/z (%): 236 (26) [M+], 180 (100); ele-
mental analysis calcd (%) for C17H16O (2m and 2m’, 236.31): C
86.40, H 6.82; found: C 86.56, H 6.61.
2-(4-Methylphenyl)-2-phenylcyclobutan-1-one (2b): Yield: 56.7 mg,
80%; oil; IR (film): n˜ =2921, 1779, 1656, 1598, 1445, 812, 698 cmÀ1
;
1H NMR (600 MHz, CDCl3, Me4Si): d=7.36–7.35 (m, 2H), 7.30–7.28
(m, 2H), 7.25 (d, J=8.4 Hz, 2H), 7.20–7.18 (m, 1H), 7.11 (d, J=
7.8 Hz, 2H), 3.16–3.13 (m, 2H), 2.80 (t, J=8.7 Hz, 2H), 2.29 ppm (s,
3H); 13C NMR (150 MHz, CDCl3): d=208.9, 142.3, 139.2, 136.6,
129.4, 128.7, 126.8, 126.4, 126.3, 76.0, 43.4, 25.7, 21.0 ppm; MS (EI,
70 eV): m/z (%): 236 (2) [M+], 194 (100), 179 (72), 178 (46); known
compound.[4c]
4-Methyl-2,2-bis(4-methylphenyl)cyclobutan-1-one (2n) and 3-
methyl-2,2-bis(4-methylphenyl)cyclobutan-1-one
(2n’):
Yield:
2-(3,4-Dimethylphenyl)-2-phenylcyclobutanone (2c): Yield: 38.3 mg,
51%; oil; IR (film): n˜ =2921, 1779, 1655, 1605, 1495, 1447,
30.1 mg, 38%; oil; IR (2n and 2n’, film): n˜ =1737, 1654, 1608, 1510,
1
1455, 1277, 926, 819, 749, 468 cmÀ1; H NMR (2n, 400 MHz, CDCl3,
699 cmÀ1 1H NMR (600 MHz, CDCl3, Me4Si): d=7.37 (d, J=7.8 Hz,
;
Me4Si): d=7.23–6.91 (m, 8H), 2.66–2.60 (m, 1H), 2.29 (d, J=2.4 Hz,
1H), 2.26 (d, J=2.4 Hz, 1H), 2.20 (s, 6H), 0.98–0.96 ppm (d, J=
2H), 7.29 (t, J=7.8 Hz, 2H), 7.20 (t, J=7.2 Hz, 1H), 7.13 (s, 1H),
7.10–7.06 (m, 2H), 3.16–3.12 (m, 2H), 2.82–2.79 (m, 2H), 2.22 (s,
3H), 2.20 ppm (s, 3H); 13C NMR (150 MHz, CDCl3): d=209.1, 142.4,
139.6, 137.0, 135.3, 129.9, 128.7, 127.6, 126.8, 126.4, 123.8, 76.0,
43.3, 25.7, 19.9, 19.3 ppm; MS (EI, 70 eV): m/z (%): 250 (1) [M+], 207
(100), 192 (66), 177 (34); elemental analysis calcd (%) for C18H18O
(250.33): C 86.36, H 7.25; found: C 86.19, H 7.12.
1
6.8 Hz, 3H); H NMR (2n’, 400 MHz, CDCl3, Me4Si): d=7.23–6.91 (m,
8H), 3.37–3.15 (m, 2H), 3.01–2.96 (m, 1H), 2.21 (s, 6H), 1.14 ppm
(d, J=7.2 Hz, 3H); 13C NMR (2n and 2n’, 100 MHz, CDCl3): d=
212.0, 209.8, 139.9, 139.4, 136.6, 136.2, 129.5, 129.2, 127.5, 126.4,
77.3, 73.3, 51.1, 50.5, 34.2, 26.9, 21.0, 21.0, 18.6, 13.9 ppm; MS (2n
and 2n’, EI, 70 eV): m/z (%): 264 (23) [M+], 208 (100), 193 (90); ele-
mental analysis calcd (%) for C19H20O (2n and 2n’, 264.36): C 86.32,
H 7.63; found: C 86.18, H 7.50.
2-(2-Chlorophenyl)-2-phenylcyclobutanone (2d): Yield: 47.7 mg,
62%; oil; IR (film): n˜ =1779, 1652, 1471, 1445, 755, 695 cmÀ1
;
1H NMR (400 MHz, CDCl3, Me4Si): d=7.77–7.74 (m, 1H), 7.36–7.18
(m, 8H), 3.27–3.22 (m, 1H), 3.18–3.12 (m, 2H), 2.75–2.68 ppm (m,
1H); 13C NMR (100 MHz, CDCl3): d=207.6, 139.4, 137.9, 133.3,
131.2, 128.5, 128.4, 128.2, 126.9, 126.8, 126.5, 75.2, 43.0, 24.4 ppm;
MS (EI, 70 eV): m/z (%): 221 (1) [M+ÀCl], 179 (100); known com-
pound.[4a]
2,2-Bis(4-fluorophenyl)-4-methylcyclobutan-1-one (2o) and 2,2-
bis(4-fluorophenyl)-3-methylcyclobutan-1-one (2o’):Yield: 49.0 mg,
60%; oil; IR (2o and 2o’, film): n˜ =1775, 1601, 1507, 1455, 1410,
1
1229, 913, 834, 768, 731, 588, 577, 540 cmÀ1; H NMR (2o, 400 MHz,
CDCl3, Me4Si): d=7.75–6.87 (m, 8H), 3.42–3.32 (m, 1H), 3.02–2.96
(m, 1H), 2.28–2.23 (m, 1H), 1.16–1.14 ppm (d, J=7.6 Hz, 3H);
1H NMR (2o’, 400 MHz, CDCl3, Me4Si): d=7.75–6.87 (m, 8H), 3.24–
3.19 (m, 2H), 2.70–2.62 (m, 1H), 0.97 ppm (d, J=6.8 Hz, 3H);
13C NMR (2o and 2o’, 100 MHz, CDCl3): d=211.1, 208.7, 162.9 (d,
2-(4-Chlorophenyl)-2-phenylcyclobutanone (2e): Yield: 46.2 mg,
60%; oil; IR (film): n˜ =1782, 1660, 1596, 1490, 1077, 698 cmÀ1
;
1H NMR (400 MHz, CDCl3, Me4Si): d=7.78–7.14 (m, 1H), 7.50–7.44
(m, 1H), 7.35–7.21 (m, 7H), 3.24–3.09 (m, 2H), 2.87–2.73 ppm (m,
2H); 13C NMR (100 MHz, CDCl3): d=208.2, 141.6, 140.5, 132.8,
128.8, 128.8, 127.7, 127.1, 126.2, 75.5, 43.4, 25.5 ppm; MS (EI,
70 eV): m/z (%): 221 (1) [M+ÀCl], 104 (100); known compound.[4b]
J
CÀF =17.6 Hz), 160.5 (d, JCÀF =17.0 Hz), 138.2 (d, JCÀF =3.2 Hz),
137.7 (d, JCÀF =3.2 Hz), 129.2(d, JCÀF =7.9 Hz), 128.6 (d, JCÀF
=
7.9 Hz), 128.1–128.0(m), 115.9–115.3(m), 76.5, 72.4, 51.2, 50.7, 34.4,
29.9, 18.5, 13.8 ppm; MS (2o and 2o’, EI, 70 eV): m/z (%): 272 (2)
[M+], 216 (100); elemental analysis calcd (%) for C17H14 F2O (2o
and 2o’, 272.29): C 74.99 H 5.18; found: C 74.82, H 5.23.
2,2-Bis(4-chlorophenyl)cyclobutanone (2 f): Yield: 56.8 mg, 65%; oil;
IR (film): n˜ =1653, 1587, 1459, 850, 753 cmÀ1 1H NMR (600 MHz,
;
2,2-Bis(4-chlorophenyl)-4-methylcyclobutan-1-one
46.7 mg, 51%; oil; IR (film): n˜ =1776, 1652, 1490, 1399, 1285, 1089,
1012, 830, 753, 668 cmÀ1 1H NMR (400 MHz, CDCl3, Me4Si): d=
(2p):
Yield:
CDCl3, Me4Si): d=7.27 (s, 8H), 3.17 (t, J=8.7 Hz, 2H), 2.78 ppm (t,
J=8.7 Hz, 2H); 13C NMR (150 MHz, CDCl3): d=207.8, 140.1, 133.1,
129.0, 127.7, 74.9, 43.6, 25.6 ppm; MS (EI, 70 eV): m/z (%): 255 (1)
[M+ÀCl], 251 (8), 249 (12), 140 (38), 138 (100); known com-
pound.[4c]
;
7.66–7.64 (d, J=8.0 Hz, 4H), 7.41–7.39 (d, J=8.0 Hz, 4H), 3.40–3.34
(m, 1H), 3.02–2.96 (m, 1H), 2.29–2.24 (m, 1H), 1.16–1.15 ppm (d,
J=7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=193.4, 140.2, 139.2,
135.5, 133.2, 131.3, 129.1, 128.8, 127.8, 72.6, 50.9, 34.1, 13.9 ppm;
MS (EI, 70 eV): m/z (%): 304 (2) [M+], 248 (100), 178 (95); elemental
analysis calcd (%) for C17H14Cl2O (305.20): C 66.90, H 4.62; found: C
66.74, H 4.45.
7-Phenylspiro[3.5]nonan-1-one (2g): Yield: 33.4 mg, 52%. cis-2g:
oil; IR (film): n˜ =1759, 1658, 1631, 1600, 1493, 1444, 760, 700 cmÀ1
;
1H NMR (400 MHz, CDCl3, Me4Si): d=7.30–7.26 (m, 2H), 7.24–7.15
(m, 3H), 2.97 (t, J=8.4 Hz, 2H), 2.43–2.49 (m, 1H), 2.15 (d, J=
13.6 Hz, 2H), 1.86–1.97 (m, 2H), 1.77–1.81 (m, 4H), 1.56–1.64 ppm
(m, 2H); 13C NMR (100 MHz, CDCl3): d=215.3, 146.8, 128.3, 126.9,
125.9, 64.1, 43.6, 40.8, 33.6, 30.9, 24.7 ppm; MS (EI, 70 eV): m/z (%):
214 (12) [M+], 104 (100); trans-2g: oil; IR (film): 1774, 750,
698 cmÀ1
;
1H NMR (400 MHz, CDCl3, Me4Si): d=7.32–7.28 (m, 2H),
7.21–7.19 (m, 3H), 3.04 (t, J=8.4 Hz, 2H), 2.45–2.53 (m, 1H), 1.95 (t,
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Communications
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Acknowledgements
This work was supported by the National Natural Science Foun-
dation of China (NNSFC) (21202141, 21173182), Priority Academic
Program Development (PAPD) of Jiangsu Higher Education Insti-
tutions, Yangzhou Nature Science Foundation (YZ2014040), the
Opening Foundation of the Key Laboratory of Environmental Ma-
terials and Engineering of Jiangsu Province (K14010), and the
Open Project Program of Jiangsu Key Laboratory of Zoonosis
(R1509). We thank Prof. Qing Xu for suggestions and the analysis
centre of Yangzhou University for assistance.
Keywords: green chemistry
selectivity control · selenium · small ring systems
·
methylenecyclopropanes
·
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Received: November 26, 2015
Published online on January 20, 2016
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