Synthesis of 3-alkoxy/aryloxy - Lactams using diazoacetate esters as ketene precursors under photoirradiation

Article abstract of DOI:10.1055/s-0030-1259485

3-Alkoxy/aryloxy - lactams are synthesized in satisfactory to good yields from the reaction of imines and alkyl/aryl di-azoacetates under photoirradiation conditions. Typically, trans - lactams are obtained as the major products from linear imines using the current method. By contrast, the corresponding thermal reaction of imines and alkoxy/aryloxyacetyl chlorides, or their equivalents, in the presence of triethylamine affords cis - lactams as the major or exclusive products. The formation of trans - lactams from linear imines is attributed to isomerization of the imines from their trans-isomers into syn-isomers under UV irradiation. The reported method represents a metal-free and neutral approach for the synthesis of 3-alkoxy/aryloxy - lactams. Georg Thieme Verlag Stuttgart New York.

Full text of DOI:10.1055/s-0030-1259485

PAPER
723
Synthesis of 3-Alkoxy/Aryloxy-b-lactams Using Diazoacetate Esters as Ketene
Precursors Under Photoirradiation
S
ynthesis of 3-Alk
e
oxy/Arylox
n
y-
b
-lactamsgzhen Qi, Zhanhui Yang, Jiaxi Xu*
State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, Faculty of Science,
Beijing University of Chemical Technology, Beijing 100029, P. R. of China
Fax +86(10)64435565; E-mail: jxxu@mail.buct.edu.cn
Received 29 November 2010; revised 6 January 2011
of antibiotics such as penem derivatives.14 Additionally,
Abstract: 3-Alkoxy/aryloxy-b-lactams are synthesized in satisfac-
tory to good yields from the reaction of imines and alkyl/aryl di-
azoacetates under photoirradiation conditions. Typically, trans-b-
lactams are obtained as the major products from linear imines using
recent reports have described their anticancer activity.15
Although Brady and Dad,16 as well as Banik and Becker,17
have reported the synthesis of trans-3-alkoxy-b-lactams
the current method. By contrast, the corresponding thermal reaction from the cycloddition of imines and alkoxyacetic acids or
of imines and alkoxy/aryloxyacetyl chlorides, or their equivalents,
their chlorides, respectively, their methods were limited to
in the presence of triethylamine affords cis-b-lactams as the major
the preparation of trans-3-alkoxy-b-lactams possessing
or exclusive products. The formation of trans-b-lactams from linear
N-polycyclic aromatic substituents. It is thus desirable to
imines is attributed to isomerization of the imines from their trans-
develop an efficient and direct method to synthesize
isomers into syn-isomers under UV irradiation. The reported meth-
trans-alkoxy/aryloxy-b-lactams. It has been reported that
trans-3-alkyl/aryl-b-lactams were generated as the major
or sole products from reactions with a-diazo ketones as
the ketene precursors under photoirradiation.7 In our re-
cent investigation on the Staudinger reaction involving
monosubstituted ketenes with electron-acceptor substitu-
ents,18 we observed that ethoxycarbonylketene, generated
from ethyl 3-diazo-2-oxopropanate, can lose a molecule
of carbon monoxide to produce ethoxyketene, which fur-
ther reacts with imines under photoirradiation conditions
to give 3-alkoxy-b-lactams. This prompted us to attempt
to use alkyl and aryl diazoacetates directly as ketene pre-
cursors to prepare trans-alkoxy/aryloxy-b-lactams under
photoirradiation. Herein, we present the use of alkyl and
aryl diazoacetates for the synthesis of alkoxy/aryloxy-b-
lactams, in particular their trans-isomers.
od represents a metal-free and neutral approach for the synthesis of
3-alkoxy/aryloxy-b-lactams.
Key words: diazoacetate, imine, ketene, b-lactam, photoirradia-
tion, Staudinger reaction
Diazoacetate esters are important synthetic intermediates
in organic chemistry.1 They are used as carbene precur-
sors for the cyclopropanation of olefins1,2 and the aziridi-
nation of imines,3 and for insertion reactions with various
single bonds1,4 (C–H, N–H, O–H, S–H, C–S, etc.), and ac-
company the Wolff rearrangement to generate ketenes,
with subsequent nucleophilic addition to the ketenes in
some cases.1 They have also been utilized as ylide precur-
sors in nucleophilic additions1,5 and as 1,3-dipoles in
[2+3] cycloadditions.6 Although a-diazo ketones7 and
phenyl diazothioacetate8 have been applied as ketene pre-
cursors for the synthesis of b-lactams, diazoacetates have
seldom served as ketene precursors; examples include cy-
cloaddition with alkenes to afford 2-alkoxy/aryloxycy-
clobutanones,9 and one in which the cycloaddition of
ethyl diazoacetate with a cyclic imine gave a 3-ethoxy-b-
lactam derivative.10 3-Alkoxy/aryloxy-b-lactams have
been prepared previously from the reaction of imines and
alkoxy/aryloxyketenes, generated by elimination of the
corresponding alkoxy/aryloxyacetyl chlorides in the pres-
ence of a tertiary amine as a base, or from alkoxy/aryloxy-
acetic acid with activating agents.11 An alternative method
for the generation of alkoxy/aryloxyketenes is via photol-
ysis of chromium–alkoxy/aryloxycarbene complexes.12 In
the reported methods, cis-3-alkoxy/aryloxy-b-lactams
were generally obtained as the major or exclusive prod-
ucts. However, trans-acetoxy-b-lactams are very impor-
tant synthetic intermediates,13 especially for the synthesis
Alkyl and aryl diazoacetates can be prepared conveniently
from the corresponding glycine esters via diazotization
with nitrous acid, or from the corresponding chlorofor-
mates using diazomethane. Ethyl diazoacetate (1a) was
prepared from ethyl glycinate hydrochloride via diazoti-
zation with nitrous acid.19 Isopropyl, benzyl, and phenyl
diazoacetates 1b–d were synthesized from the corre-
sponding chloroformates and diazomethane20 (Scheme 1).
N2
EtO
NaNO2
H
EtO2CCH2NH2⋅HCl
NaOAc
RO
O
1a
N2
RO
Cl
CH2N2
H
O
O
1b–d
1b: R = i-Pr, 1c: R = Bn, 1d: R = Ph
SYNTHESIS 2011, No. 5, pp 0723–0730
Advanced online publication: 03.02.2011
x
x
.
x
x
.2
0
1
1
Scheme 1 Preparation of alkyl/aryl diazoacetates 1a–d
DOI: 10.1055/s-0030-1259485; Art ID: F21410SS
© Georg Thieme Verlag Stuttgart · New York

724
H. Qi et al.
PAPER
Table 1 Reaction of Diazoacetates 1a–d and Various Iminesa
Entry
1
Diazoacetate
Imine
b-Lactam
Yield (%)b
cis:transc
H
H
N
H
H
EtO
EtO
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Bn
+
1a
80
24:76
Ph
N
N
N
N
N
N
O
O
2a
( )
cis-3aa
( )
trans-3aa
H
H
H
H
N
i-PrO
i-PrO
Ph
Ph
Ph
+
2
3
4
5
1b
1c
1d
1d
45
75
99
78
22:78
30:70
33:67
67:33
Ph
N
O
O
Ph
2a
( )
cis-3ba
( )
trans-3ba
H
H
H
H
BnO
BnO
Ph
Ph
Ph
+
Ph
N
N
O
O
Ph
2a
( )
cis-3ca
( )
trans-3ca
H
H
H
H
PhO
PhO
Ph
Ph
Ph
+
+
Ph
N
N
O
O
Ph
2a
( )
cis-3da
( )
trans-3da
H
H
H
H
PhO
PhO
Ph
Bn
Ph
Ph
N
N
O
O
Bn
2b
( )
cis-3db
( )
trans-3db
H
H
N
O
EtO
O
6
7
8
1a
1b
1c
67
59
70
–
–
–
N
N
N
O
H
H
H
4a
4a
4a
( )
5aa
H
H
N
O
i-PrO
O
O
( )
5ba
H
H
N
O
BnO
O
O
( )
5ca
Synthesis 2011, No. 5, 723–730 © Thieme Stuttgart · New York

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Synthesis of 3-Alkoxy/Aryloxy-b-lactams
725
Table 1 Reaction of Diazoacetates 1a–d and Various Iminesa (continued)
Entry
Diazoacetate
Imine
b-Lactam
Yield (%)b
cis:transc
H
H
O
PhO
O
9
1d
76
–
N
N
O
H
4a
( )
5da
H
Me
O
PhO
O
10
11
1d
1d
62
52
–
–
N
N
O
Me
4b
( )
5db
Ph
H
Ph
PhO
Ph
S
S
N
N
O
O
Ph
( )
6
7
H
H
Ph
PhO
O
S
Ph
12
13
1d
1d
32
54
–
–
N
N
O
( )
8a
9a
Ph
N
PhO
Ph
S
N
O
( )
8b
9b
O
PhO
N
N
14
1d
78
–
N
H
10
( )
11
a Reaction conditions: diazoacetate (2 mmol), imine (1 mmol), CH2Cl2 (10 mL), UV irradiation, r.t., N2 atm, 6 h.
b Yield of isolated product (combined yield of cis and trans products).
c Ratio determined by 1H NMR spectral analysis of the reaction mixture.
We initially optimized the conditions for the preparation significant impact on the yield. Of the diazoacetates 1a–d,
of the alkoxy/aryloxy-b-lactams using the reaction of phe- phenyl diazoacetate (1d) produced the desired products in
nyl diazoacetate (1d) with benzylideneaniline (2a) as a the highest yields, but also with the lowest diastereoselec-
model reaction, in anhydrous solvents, under UV photoir- tivity (Table 1, entry 4), whereas isopropyl diazoacetate
radiation at room temperature (Scheme 2). The desired (1b) gave the lowest yield of b-lactam product, but with
products were obtained in good to excellent yields in the highest diastereoselectivity (Table 1, entry 2). The dif-
dichloromethane, chloroform, diethyl ether and THF, and ferent diazoacetates did not have any significant influence
in low yields in benzene, toluene and xylene. Dichlo- on the diastereoselectivity, the cis:trans ratios varied from
romethane was the best choice as solvent affording a 99% 33:67 (phenyl) to 22:78 (isopropyl). Phenyl diazoacetate
yield of b-lactam 3 (Table 1, entry 4). Different reaction (1d) also reacted with benzylidene benzylamine (2b) to
temperatures and modes of reagent addition (including in- afford cis- and trans-phenoxy-b-lactams 3db in a ratio of
termittent, stepwise, and one-pot addition) did not have a 67:33 (Table 1, entry 5). The trans-alkoxy/aryloxy-b-lac-
Synthesis 2011, No. 5, 723–730 © Thieme Stuttgart · New York

726
H. Qi et al.
PAPER
N2
H
H
N
H
H
N
hν
R1O
R1O
+
Ph
Ph
R1O
R2
CH2Cl2
H
H
N
+
N2
PhO
H
Ph
N
O
r.t., 6 h
+
PhO
2
O
O
R2
R2
O
H
O
( )
cis-3
2a: R2 = Ph
2b: R2 = Bn
( )
trans-3
Δ, 12 h
1
O
N
O
H
1d
4a
Scheme 2 Reaction of diazoacetates 1 and linear imines 2
( )-5da
in toluene trace
in xylene 24%
tams were obtained as the major products in the case of
linear imine 2a. The described procedure provides a direct
method for the preparation of trans-alkoxy/aryloxy-b-lac-
tams via the Staudinger reaction.
Scheme 4 Thermal reaction of diazoacetate 1d and imine 4a
Staudinger reaction is believed to be nucleophilic addition
of an imine to a ketene from the less hindered side. The
addition between alkoxyketenes and imines is also sup-
ported by the ‘torquoelectronic effect’, as put forward by
Hegedus to explain the stereochemical outcome of chro-
mium carbene–imine cycloadditions.22 That is, conrotato-
ry ring closure of iminium intermediates gives b-lactams
through favorable outward rotation of the alkoxy/aryloxy
groups. Under thermal conditions, cis-b-lactams were ob-
tained as the major or exclusive products with trans-
imines. However, in the current method (under photoirra-
diation conditions), both cis- and trans-b-lactams were
obtained from trans-imines, indicating that the linear
imine and/or the iminium moiety of the zwitterionic inter-
mediate (formed by addition of the imine to the ketene)
undergoes isomerization. On the basis of our previous in-
vestigation and proposal,7f alkoxy/aryloxy groups are
strong electron-donating groups and demonstrate very
fast ring closure rates in Staudinger reactions (more than
100 times faster than phthalimido, arylthio, aryl and alkyl
groups). Typically, isomerization of the alkoxyketene–
imine addition intermediates during formation of the 3-
alkoxy/aryloxy-b-lactams is not observed with alkoxy/
aryloxy ketenes generated from the corresponding acid
chlorides, or when chromium carbenes are used under
thermal conditions.11,12 Only the iminium intermediates
generated from imines with strong electron-withdrawing
N-substituents can partially isomerize in the alkoxy/aryl-
oxy ketene-participating Staudinger reaction.7f,g Thus, it is
believed that the iminium moiety of the zwitterionic inter-
mediates, generated from alkoxy/aryloxy ketenes, does
not isomerize in the current reactions. On the other hand,
it has been well documented that linear E-imines isomer-
ize preferentially to their syn-isomers under UV irradia-
tion conditions.23 Therefore, it can be concluded that in
the current method, cis-b-lactams are obtained from the
E-imines directly, while some E-imines isomerize to their
Z-isomers under UV irradiation, which gives rise to trans-
b-lactams (Scheme 5).
This method was extended to reactions with various cyclic
imines, 4a,b, 6, 8a,b and 10 (Scheme 3). Reactions of cy-
clic imine 4a with diazoacetates 1a–d yielded the desired
products, all with trans configuration, in yields ranging
from 59% to 76% (Table 1, entries 6–9). However, steri-
cally hindered cyclic imines gave rise to the desired prod-
ucts in relatively low yields (Table 1, compare entries 9
and 10–13). Spectral analyses indicated that the structure
of b-lactam product 7, generated from imine 6 and diaz-
oacetate 1d, was identical to the product obtained from the
reaction of imine 6 and phenoxyacetyl chloride in the
presence of triethylamine under thermal conditions.21 By
contrast, the reaction of cyclic imine 10 and diazoacetate
1d produced [2+2+2] cycloadduct 11 as a pair of enantio-
mers, with no other diastereomers present, as was evident
from the 1H and 13C NMR spectra (Table 1, entry 14). It is
likely that cycloadduct 11 was generated from one mole-
cule of phenoxyketene and two molecules of imine 10.
Similarly, the [2+2+2]-type cycloadducts were also ob-
served in the reactions of a-diazo ketones and imines.7a,e
These results indicate that most of the cyclic imines stud-
ied give rise to the desired b-lactam products using the
current method.
R2
H
N2
R1O
X
R2
X
R1O
hν, CH2Cl2
+
H
N
N
r.t., 6 h
O
n
O
n
( )
1
Scheme 3 Reaction of diazoacetates 1a–d and various cyclic imines
To compare the current method with the thermal Wolff re-
arrangement,7f,g we attempted the reaction of phenyl di-
azoacetate (1d) with cyclic imine 4a under thermal
conditions. Only a trace amount of the desired product
5da was obtained in toluene, whilst a yield of 24% of 5da
was achieved in xylene, both reactions occurring at reflux
temperature over 12 hours. Hence the use of UV irradia-
tion is beneficial for the Wolff rearrangement of diazo-
acetates (Scheme 4).
After successful application of alkyl and aryl diazoace-
tates as ketene precursors in the synthesis of 3-alkoxy/aryl-
oxy-b-lactams, we hoped to extend this method to
diazoacetamides in order to prepare 3-mono/dialkylami-
no-b-lactams. 2-Diazo-N-methyl-N-phenylacetamide (1e)
was prepared from N-methyl-3-oxo-N-phenylbutamide,
itself synthesized from 2,2,6-trimethyl-1,3-dioxin-4-one
and N-methylaniline in xylene at reflux temperature, via
Regarding the reaction mechanism, the alkyl/aryl diazo-
acetate 1 undergoes a photo-induced Wolff rearrangement
via an alkoxy/aryloxy group shift to generate the corre-
sponding alkoxy/aryloxyketene, which further reacts with
the imine to give the desired 3-alkoxy/aryloxy-b-lactam
by way of the Staudinger reaction. The first step in the
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PAPER
Synthesis of 3-Alkoxy/Aryloxy-b-lactams
727
O
O
N2
RO
H
– N2
O
O
RO
RO
TsN3
Et3N
PhNHMe
xylene
O
H
H
C
O
hν
Ph
N
O
O
Me
O
1
R2
H
H
R1O
R2
H
H
R1O
O
O
ring closure
exo attack
Ph
H
NaOMe
N
N
R2
H
Ph
O
N
–O
R3
cis-( )-β-lactam 3
N
MeOH
O
Me
1e
N2
R3
N2
Me
N
R3
(E)-Imine 2
R1O
H
Cl
O
CHN2
CH2N2
O2N
hν
isomerize
R2
C
O
O
O
O2N
H
O
Me
H
H
H
N
MeNH2
H
N
R2
R1O
R2
R3
N
H
R3
R1O
–O
N2
H
ring closure
(Z)-Imine 2
1f
Ph
N
exo attack
O
R3
Ph
O
trans-( )-β-lactam 3
N
O
N
Me
2a
N
Scheme 5 Proposed mechanism for the reaction of diazoacetates 1
and linear imines 2
Ph
H
hν, CH2Cl2
+
O
r.t., 6 h
Me
N2
1e
12
diazo transformation with tosyl azide and subsequent hy-
drolysis with sodium methoxide.24 2-Diazo-N-methylacet-
amide (1f) was prepared from methylamine aminolysis of
4-nitrophenyl diazoacetate,20 which was obtained from 4-
nitrophenyl chloroformate and diazomethane. However,
in the photo-induced reactions with imines 2a and 4a, di-
azoacetamide 1e produced, in both cases, 1-methylindo-
lin-2-one (12) as the product of intramolecular carbene
insertion, instead of the desired b-lactam products. Simi-
lar reactions of diazoacetamide 1f yielded decomposition
products. These results indicated that diazoacetamides
could not be used as mono/dialkylaminoketene precursors
for the preparation of 3-mono/dialkylamino-b-lactams
(Scheme 6).
N
yield 54% in reaction with 2a
yield 80% in reaction with 4a
H
4a
Ph
Ph
N
O
2a
Me
H
hν, CH2Cl2
r.t., 6 h
+
N
decomposition
products
O
H
N2
1f
N
H
4a
Scheme 6 Reaction of diazoacetamides 1e,f with linear imine 2a
and cyclic imine 4a
recorded on Varian Mercury 200 (200 MHz), Varian Mercury Plus
300 (300 MHz), or Bruker AMX 400 (400 MHz) spectrometers in
CDCl3 with TMS as the internal standard. HRMS data were
obtained on a Bruker APEX IV Fourier transform ion cyclotron
resonance mass spectrometer. Ethyl diazoacetate was prepared
from ethyl glycinate hydrochloride via diazotization with nitrous
acid.19 Isopropyl, benzyl and phenyl diazoacetates 1b–d, and 4-
nitrophenyl diazoacetate were synthesized from the corresponding
chloroformates and diazomethane.20 2-Diazo-N-methylacetamide
(1f) was prepared via aminolysis of 4-nitrophenyl diazoacetate
with methylamine.20 Column chromatography was carried out on
Haiyang brand silica gel (200–300 mesh). The analytical data of all
known diazoacetates and acetamides were identical to those
reported in the literature.19,20,24 CH2Cl2 was dried over CaH2 and
freshly distilled prior to use. CAUTION: Although no explosions
occurred in any of our experiments, diazomethane is toxic and
potentially explosive. Diazoacetates and diazoacetamides are also
potentially explosive. The operations must be carried out in a well-
ventilated hood with an adequate safety shield.
In summary, 3-alkoxy/aryloxy-b-lactams have been syn-
thesized conveniently in satisfactory to good yields by
way of the photo-induced Staudinger reaction of imines
and alkyl/aryl diazoacetates. Initially, the diazoacetates
generated alkoxy/aryloxyketenes, via the photo-induced
Wolff rearrangement, which underwent subsequent
Staudinger reactions with various imines to give the de-
sired b-lactam products. Compared with the correspond-
ing thermal Staudinger reaction, in which the ketenes
produced through base-mediated elimination of the corre-
sponding alkoxy/aryloxyacetyl chlorides, or their equiva-
lents, gave cis-b-lactams as the major or sole products, the
current method provides in most cases, trans-b-lactams
predominantly from linear imines. The formation of
trans-b-lactams from linear imines is attributed to isomer-
ization of the imines from their trans-isomers into their
syn-isomers under UV irradiation. The present method
represents a neutral approach to synthesize 3-alkoxy/aryl-
oxy-b-lactams via the Staudinger reaction.
2-Diazo-N-methyl-N-phenylacetamide (1e)
A soln of 2,2,6-trimethyl-1,3-dioxin-4-one (7.358 g, 50 mmol) and
N-methylaniline (4.822 g, 45 mmol) in xylene (50 mL) was heated
at reflux temperature for 2 h. After removal of the solvent, the resi-
due was subjected to silica gel column chromatography [EtOAc–PE
(30–60 °C), 1:4] to afford N-methyl-3-oxo-N-phenylbutanamide as
a red oil, yield: 7.29 g (85%).
Melting points were measured on a Yanaco MP-500 melting point
apparatus and are uncorrected. IR spectra were determined on a
1
Nicolet 5700 FT-IR spectrometer. H and 13C NMR spectra were
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H. Qi et al.
PAPER
TsN3 (7.89 g, 40 mmol) in CH2Cl2 (15 mL) was added to a soln of
N-methyl-3-oxo-N-phenylbutanamide (7.29 g, 38 mmol) and Et3N
(7.71 g, 76 mmol) in CH2Cl2 (30 mL). The soln was stirred for 2.5
h at r.t. and then washed with 35% aq KOH soln [KOH (18 g) in
H2O (500 mL)] (5 × 100 mL) and H2O (2 × 100 mL). The resulting
aqueous mixture was extracted with Et2O (2 × 100 mL), and the
combined organic phase was then dried over anhyd Na2SO4 and
concd under reduced pressure. The product was separated chro-
matographically on a silica gel column [EtOAc–PE (30–60 °C),
1:4] to give 2-diazo-N-methyl-3-oxo-N-phenylbutanamide as yel-
low oil, yield: 7.43 g (90%).
13C NMR (50 MHz, CDCl3): d = 21.1, 22.1, 62.5, 72.7, 81.9, 117.4,
124.2, 128.2, 128.3, 128.4, 129.0, 133.8, 137.2, 165.0.
HRMS (ESI): m/z [M + H]+ calcd for C18H20NO2: 282.1489; found:
282.1491.
( )-trans-3-Isopropoxy-1,4-diphenylazetidin-2-one (trans-3ba)
Colorless oil; yield: 98 mg (35%).
IR (KBr): 1760 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 1.18 (d, J = 6.0 Hz, 3 H, CH3),
1.25 (d, J = 6.3 Hz, 3 H, CH3), 3.85 (sept, J = 6.0 Hz, 1 H, CH),
4.49 (d, J = 1.8 Hz, 1 H, CH), 4.84 (d, J = 1.8 Hz, 1 H, CH), 7.00–
7.41 (m, 10 H, ArH).
13C NMR (50 MHz, CDCl3): d = 22.4, 22.6, 64.8, 73.6, 88.9, 117.4,
124.1, 126.0, 128.6, 128.9, 129.2, 136.3, 137.1, 165.0.
2-Diazo-N-methyl-3-oxo-N-phenylbutanamide (4.817 g, 22 mmol)
was dissolved in MeOH (25 mL) and the resulting soln treated with
an equimolar soln of NaOMe in MeOH (10 mL) at r.t. The mixture
was heated at reflux temperature for 3 h, cooled, and poured onto
H2O. The product was extracted with Et2O (3 × 50 mL) and the
combined organic layer dried over anhyd Na2SO4 and evaporated.
The residue was purified by flash column chromatography on a sil-
ica gel column [EtOAc–PE (60–90 °C), 1:4] to give 2-diazo-N-
methyl-N-phenylacetamide as a yellow oil, yield: 3.54 g (92%).
HRMS (ESI): m/z [M + H]+ calcd for C18H20NO2: 282.1489; found:
282.1483.
( )-cis-3-Benzyloxy-1,4-diphenylazetidin-2-one (cis-3ca)
Colorless crystals; yield: 74 mg (22%); mp 149–151 °C (Lit.25 148–
150 °C).
1H NMR (200 MHz, CDCl3): d = 4.27 (d, J = 11.2 Hz, 1 H of
CH2O), 4.38 (d, J = 11.2 Hz, 1 H of CH2O), 5.02 (d, J = 4.8 Hz, 1
H, CH), 5.23 (d, J = 4.8 Hz, 1 H, CH), 6.92–7.41 (m, 15 H, ArH).
1H NMR (300 MHz, CDCl3): d = 3.33 (s, 3 H, CH3), 4.53 (s, 1 H,
CH), 7.20–7.45 (m, 5 H, ArH).
Photoirradiation of Diazoacetic Acid Derivatives and Imines;
General Procedure
A soln of diazoacetate or diazoacetamide (2 mmol) and imine (1
mmol) in CH2Cl2 (10 mL) was irradiated using a medium pressure
Hg lamp at r.t. under an N2 atm for 6 h. After removal of the solvent,
the residue was separated chromatographically on a silica gel col-
umn [EtOAc–PE (60–90 °C), 1:20] to afford the product.
13C NMR (100 MHz, CDCl3): d = 62.0, 72.5, 82.7, 117.5, 124.4,
128.0, 128.1, 128.3, 128.7, 129.1, 133.5, 136.3, 137.1, 164.3.
( )-trans-3-Benzyloxy-1,4-diphenylazetidin-2-one (trans-3ca)
Colorless crystals; yield: 173 mg (53%); mp 148–150 °C (Lit.26
148–150 °C).
( )-cis-3-Ethoxy-1,4-diphenylazetidin-2-one (cis-3aa)
Colorless crystals; yield: 51 mg (19%); mp 154–155 °C.
IR (KBr): 1745 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 4.56 (d, J = 1.8 Hz, 1 H, CH), 4.65
(d, J = 11.7 Hz, 1 H of CH2O), 4.87 (d, J = 1.8 Hz, 1 H, CH), 4.90
(d, J = 11.7 Hz, 1 H of CH2O), 7.02–7.34 (m, 15 H, ArH).
13C NMR (100 MHz, CDCl3): d = 63.9, 73.2, 89.8, 117.6, 124.4,
126.1, 128.25, 128.30, 128.6, 128.7, 129.1, 129.2, 136.2, 136.9,
137.2, 164.4.
1H NMR (300 MHz, CDCl3): d = 0.87 (t, J = 6.9 Hz, 3 H, CH3), 3.16
(dq, J = 9.0, 6.9 Hz, 1 H of CH2O), 3.45 (dq, J = 9.0, 6.9 Hz, 1 H of
CH2O), 4.93 (d, J = 4.8 Hz, 1 H, CH), 5.20 (d, J = 4.5 Hz, 1 H, CH),
7.03–7.40 (m, 10 H, ArH).
( )-cis-3-Phenoxy-1,4-diphenylazetidin-2-one (cis-3da)
Colorless crystals; yield: 103 mg (33%); mp 194–195 °C (Lit.27
193–195 °C).
1H NMR (200 MHz, CDCl3): d = 5.41 (d, J = 5.0 Hz, 1 H, CH), 5.58
(d, J = 5.0 Hz, 1 H, CH), 6.59–7.47 (m, 15 H, ArH).
13C NMR (75.5 MHz, CDCl3): d = 15.5, 62.0, 66.4, 83.5, 117.4,
124.3, 128.0, 128.4, 128.5, 129.0, 133.4, 137.1, 164.4.
HRMS (ESI): m/z [M + H]+ calcd for C17H18NO2: 268.1332; found:
268.1329.
13C NMR (100 MHz, CDCl3): d = 62.1, 81.2, 115.8, 117.6, 122.2,
124.6, 128.1, 128.4, 128.8, 129.2, 129.3, 132.6, 137.0, 157.0, 163.1.
( )-trans-3-Ethoxy-1,4-diphenylazetidin-2-one (trans-3aa)
Colorless crystals; yield: 162 mg (61%); mp 113–114 °C.
IR (KBr): 1754 (C=O) cm–1.
( )-trans-3-Phenoxy-1,4-diphenylazetidin-2-one (trans-3da)
Colorless crystals; yield: 209 mg (66%); mp 112–113 °C (Lit.28
110–113 °C).
1H NMR (200 MHz, CDCl3): d = 5.02 (d, J = 1.6 Hz, 1 H, CH), 5.12
(d, J = 1.6 Hz, 1 H, CH), 6.85–7.50 (m, 15 H, ArH).
13C NMR (100 MHz, CDCl3): d = 64.0, 87.4, 115.5, 117.7, 122.4,
124.7, 126.5, 129.18, 129.24, 129.5, 129.7, 135.6, 137.0, 157.1,
162.7.
1H NMR (300 MHz, CDCl3): d = 1.28 (t, J = 7.0 Hz, 3 H, CH3), 3.71
(dq, J = 9.3, 7.0 Hz, 1 H of CH2O), 3.81 (dq, J = 9.3, 7.0 Hz, 1 H of
CH2O), 4.47 (d, J = 1.8 Hz, 1 H, CH), 4.91 (d, J = 1.8 Hz, 1 H, CH),
7.05–7.42 (m, 10 H, ArH).
13C NMR (75.5 MHz, CDCl3): d = 15.5, 63.8, 66.7, 90.1, 117.5,
124.3, 126.0, 128.7, 129.0, 129.2, 136.4, 137.1, 164.5.
HRMS (ESI): m/z [M + Na]+ calcd for C17H17NNaO2: 290.1151;
found: 290.1151.
( )-cis-1-Benzyl-3-phenoxy-4-phenylazetidin-2-one (cis-3db)
Colorless crystals; yield: 171 mg (52%); mp 117–118 °C (Lit.29
116–117 °C).
1H NMR (400 MHz, CDCl3): d = 3.87 (d, J = 14.8 Hz, 1 H of CH2),
4.75 (d, J = 4.4 Hz, 1 H, CH), 4.90 (d, J = 14.8 Hz, 1 H of CH2),
5.40 (d, J = 4.4 Hz, 1 H, CH), 6.69–7.33 (m, 15 H, ArH).
13C NMR (100 MHz, CDCl3): d = 44.2, 61.5, 82.2, 115.6, 122.0,
128.0, 128.3, 128.66, 128.68, 128.9, 129.2, 132.7, 134.8, 156.9,
165.6.
( )-cis-3-Isopropoxy-1,4-diphenylazetidin-2-one (cis-3ba)
Colorless crystals; yield: 28 mg (10%); mp 154–155 °C.
IR (KBr): 1738 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 0.64 (d, J = 6.0 Hz, 3 H, CH3),
1.09 (d, J = 6.0 Hz, 3 H, CH3), 3.40 (sept, J = 6.0 Hz, 1 H, CH),
5.02 (d, J = 4.5 Hz, 1 H, CH), 5.18 (d, J = 4.5 Hz, 1 H, CH), 7.03–
7.37 (m, 10 H, ArH).
Synthesis 2011, No. 5, 723–730 © Thieme Stuttgart · New York

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Synthesis of 3-Alkoxy/Aryloxy-b-lactams
729
( )-trans-1-Benzyl-3-phenoxy-4-phenylazetidin-2-one (trans-
3db)
Colorless crystals; yield: 85.5 mg (26%); mp 103–104 °C.
13C NMR (75 MHz, CDCl3): d = 60.6, 83.0, 116.4, 120.3, 121.6,
121.9, 122.9, 125.1, 125.4, 125.9, 128.6, 129.5, 129.8, 130.5, 144.2,
157.3, 158.6, 161.6.
IR (KBr): 1752 (C=O) cm–1.
HRMS (ESI): m/z [M + H]+ calcd for C21H16NO3: 330.1125; found:
330.1129.
1H NMR (400 MHz, CDCl3): d = 3.80 (d, J = 14.8 Hz, 1 H of CH2),
4.41 (d, J = 1.2 Hz, 1 H, CH), 4.91 (d, J = 14.8 Hz, 1 H of CH2),
5.02 (d, J = 1.2 Hz, 1 H, CH), 6.77–7.45 (m, 15 H, ArH).
13C NMR (100 MHz, CDCl3): d = 44.5, 63.1, 87.5, 115.4, 122.1,
127.0, 128.0, 128.6, 128.9, 129.2, 129.3, 129.6, 134.6, 135.3, 157.1,
165.3.
( )-trans-1,12b-Dihydro-12b-methyl-1-phenoxyazeto[1,2-
d]dibenzo[b,f][1,4]oxazepin-2-one (5db)
Colorless crystals; yield: 213 mg (62%); mp 43–44 °C.
IR (KBr): 1755 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 2.11 (s, 3 H, CH3), 5.65 (s, 1 H,
CH), 7.05–8.18 (m, 13 H, ArH).
13C NMR (50 MHz, CDCl3): d = 22.7, 67.8, 84.9, 116.7, 120.9,
121.5, 122.5, 122.8, 125.0, 125.2, 125.5, 128.7, 129.8, 130.1, 133.9,
143.6, 157.0, 157.7, 162.5.
HRMS (ESI): m/z [M + H]+ calcd for C22H20NO2: 330.1489; found:
330.1494.
( )-trans-1-Ethoxy-1,12b-dihydroazeto[1,2-d]diben-
zo[b,f][1,4]oxazepin-2-one (5aa)
Colorless oil; yield: 188 mg (67%).
IR (KBr): 1754 (C=O) cm–1.
HRMS (ESI): m/z [M + H]+ calcd for C22H18NO3: 344.1281; found:
344.1280.
1H NMR (300 MHz, CDCl3): d = 1.36 (t, J = 6.9 Hz, 3 H, CH3),
3.84 (dq, J = 9.0, 6.9 Hz, 1 H of CH2O), 3.97 (dq, J = 9.0, 6.9 Hz,
1 H of CH2O), 5.05 (d, J = 2.1 Hz, 1 H, CH), 5.61 (d, J = 1.8 Hz, 1
H, CH), 6.99–8.08 (m, 8 H, ArH).
13C NMR (75.5 MHz, CDCl3): d = 15.2, 60.5, 66.5, 84.5, 120.3,
121.6, 121.7, 124.8, 125.3, 126.0, 129.3, 129.7, 130.4, 144.1, 150.7,
158.6, 162.9.
rel-(2S,2aR,4R)-2,2a,3,4-Tetrahydro-2-phenoxy-2a,4-diphenyl-
azeto[1,2-d]benzo[b][1,4]thiazepin-1-one (7)
Colorless crystals; yield: 233.5 mg (52%); mp 190–191 °C (Lit.21
190–191 °C).
IR (KBr): 1765 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 3.23 (dd, J = 14.1, 11.1 Hz, 1 H
of CH2), 3.68 (d, J = 14.1 Hz, 1 H of CH2), 4.02 (d, J = 11.1 Hz, 1
H, CH), 5.40 (s, 1 H, CH), 6.68–8.03 (m, 19 H, ArH).
13C NMR (50 MHz, CDCl3): d = 44.9, 48.4, 71.0, 88.4, 115.5, 122.2,
126.8, 126.9, 128.1, 128.2, 128.4, 129.2, 129.3, 129.8, 132.5, 134.6,
137.6, 140.8, 152.9, 156.7, 164.0.
HRMS (ESI): m/z [M + Na]+ calcd for C17H15NNaO3: 304.0944;
found: 304.0937.
( )-trans-1,12b-Dihydro-1-isopropoxyazeto[1,2-d]diben-
zo[b,f][1,4]oxazepin-2-one (5ba)
Colorless oil; yield: 174 mg (59%).
IR (KBr): 1757 (C=O) cm–1.
HRMS (ESI): m/z [M + H]+ calcd for C29H24NO2S: 450.1522;
found: 450.1522.
1H NMR (300 MHz, CDCl3): d = 1.33 (d, J = 6.0 Hz, 3 H, CH3),
1.39 (d, J = 6.3 Hz, 3 H, CH3), 4.05 (sept, J = 6.0 Hz, 1 H, CH),
5.06 (d, J = 2.1 Hz, 1 H, CH), 5.56 (d, J = 1.8 Hz, 1 H, CH), 6.95–
8.08 (m, 8 H, ArH).
13C NMR (75.5 MHz, CDCl3): d = 22.4, 22.7, 61.5, 73.5, 83.1,
120.2, 121.5, 121.8, 124.7, 125.3, 125.8, 129.3, 129.7, 130.3, 144.1,
158.6, 163.3.
( )-trans-7-Phenoxy-6-phenyl-5-oxa-1-azabicyclo[4.2.0]octan-
8-one (9a)
Colorless crystals; yield: 94.5 mg (32%); mp 140–141 °C (Lit.30
139–140 °C).
IR (KBr): 1776 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 1.49 (m, 1 H of CH2), 2.03 (m, 1
H of CH2), 3.08 (m, 1 H of CH2N), 3.79 (m, 1 H of CH2N), 4.03 (m,
2 H, CH2O), 5.24 (s, 1 H, CH), 6.69–7.50 (m, 10 H, ArH).
13C NMR (50 MHz, CDCl3): d = 24.1, 36.5, 62.7, 89.1, 90.8, 115.2,
121.8, 127.7, 128.1, 128.7, 129.0, 132.7, 156.4, 164.5.
HRMS (ESI): m/z [M + H]+ calcd for C18H18NO3: 296.1281; found:
296.1277.
HRMS (ESI): m/z [M + H]+ calcd for C18H18NO3: 296.1281; found:
296.1280.
( )-trans-1-Benzyloxy-1,12b-dihydroazeto[1,2-d]diben-
zo[b,f][1,4]oxazepin-2-one (5ca)
Colorless oil; yield: 240 mg (70%).
IR (KBr): 1750 (C=O) cm–1.
( )-trans-7-Phenoxy-6-phenyl-5-thia-1-azabicyclo[4.2.0]octan-
1H NMR (300 MHz, CDCl3): d = 4.83 (d, J = 11.7 Hz, 1 H of
CH2O), 4.95 (d, J = 11.7 Hz, 1 H of CH2O), 5.07 (d, J = 2.1 Hz, 1
H, CH), 5.59 (d, J = 2.1 Hz, 1 H, CH), 6.94–8.07 (m, 13 H, ArH).
13C NMR (75 MHz, CDCl3): d = 60.5, 72.5, 83.4, 120.1, 121.5,
121.6, 124.7, 125.1, 125.2, 125.8, 127.9, 128.2, 128.5, 129.0, 129.5,
130.2, 136.5, 144.0, 158.4, 162.7.
8-one (9b)
Colorless crystals; yield: 168 mg (54%); mp 130–131 °C (Lit.26
130–131 °C).
1H NMR (400 MHz, CDCl3): d = 1.89 (m, 2 H), 2.73 (m, 2 H), 3.04
(m, 1 H), 4.15 (m, 1 H), 5.39 (s, 1 H), 6.62–7.60 (m, 10 H).
13C NMR (100 MHz, CDCl3): d = 23.8, 26.0, 37.6, 70.2, 91.0, 115.4,
122.2, 128.1, 128.5, 128.8, 129.2, 134.6, 156.5, 162.5.
HRMS (ESI): m/z [M + H]+ calcd for C22H18NO3: 344.1281; found:
344.1292.
4b,5,9,13b,15,16-Hexahydro-5-phenoxy-6H,8H-pyrimido[2,1-
a:4,3-a¢]diisoquinolin-6-one (11)
( )-trans-1,12b-Dihydro-1-phenoxyazeto[1,2-d]diben-
zo[b,f][1,4]oxazepin-2-one (5da)
Colorless crystals; yield: 174 mg (76%); mp 157–158 °C.
IR (KBr): 1755 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 5.62 (d, J = 2.2 Hz, 1 H, CH), 5.84
(d, J = 2.2 Hz, 1 H, CH), 7.00–8.08 (m, 13 H, ArH).
Colorless crystals; yield: 309 mg (78%); mp 183–184 °C.
IR (KBr): 1653 (C=O) cm–1.
1H NMR (300 MHz, CDCl3): d = 2.57 (m, 1 H of CH2), 2.79 (m, 2
H of CH2), 3.01 (m, 3 H of CH2), 3.36 (m, 1 H of CH2), 4.68 (d,
Synthesis 2011, No. 5, 723–730 © Thieme Stuttgart · New York

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H. Qi et al.
PAPER
Jiao, L.; Zhang, S. W.; Xu, J. X. J. Org. Chem. 2005, 70,
J = 4.8 Hz, 1 H, CHN), 4.80 (d, J = 5.1 Hz, 1 H, CHO), 4.97 (m, 1
H of CH2), 5.88 (s, 1 H, CHN2), 6.67–7.53 (m, 13 H, ArH).
334. (f) Jiao, L.; Liang, Y.; Xu, J. X. J. Am. Chem. Soc. 2006,
128, 6060. (g) Wang, Y. K.; Liang, Y.; Jiao, L.; Du, D. M.;
Xu, J. X. J. Org. Chem. 2006, 71, 6983.
13C NMR (50 MHz, CDCl3): d = 28.3, 28.5, 36.9, 38.3, 61.7, 74.9,
76.4, 117.5, 121.9, 125.4, 126.2, 126.9, 127.0, 127.4, 127.7, 128.6,
128.8, 132.4, 132.7, 135.7, 136.5, 160.3, 167.3.
HRMS (ESI): m/z [M + H]+ calcd for C26H25N2O2: 397.1911; found:
397.1921.
(8) (a) Lawlor, M. D.; Lee, T. W.; Danheiser, R. L. J. Org.
Chem. 2000, 65, 4375. (b) Danheiser, R. L.; Okamoto, I.;
Lawlor, M. D.; Lee, T. W. Org. Synth. 2003, 80, 160.
(c) Jiao, L.; Zhang, Q. F.; Liang, Y.; Zhang, Q. W.; Xu, J. X.
J. Org. Chem. 2006, 71, 815. (d) Jiao, L.; Liang, Y.; Zhang,
Q. F.; Zhang, S. W.; Xu, J. X. Synthesis 2006, 659.
(9) (a) Do Minh, T.; Strausz, O. P. J. Am. Chem. Soc. 1970, 92,
1766. (b) Sugimura, T.; Tei, T.; Mori, A.; Okuyama, T.; Tai,
A. J. Am. Chem. Soc. 2000, 122, 2128.
1-Methyl-2-indolinone (12)
Yellow crystals; yield: 118 mg (80%); mp 91–92 °C (Lit.31 88–89
°C).
1H NMR (300 MHz, CDCl3): d = 3.20 (s, 3 H, CH3), 3.50 (s, 2 H,
CH2), 6.80–7.31 (m, 4 H, ArH).
13C NMR (75.5 MHz, CDCl3): d = 26.0, 35.6, 107.9, 122.2, 124.2,
124.3, 127.7, 145.0, 174.9.
(10) Campbell, M. M.; Abbas, N.; Sainsbury, M. Tetrahedron
1985, 41, 5637.
(11) For recent reviews, see: (a) The Organic Chemistry of b-
Lactams; Georg, G. I., Ed.; Verlag Chemie: New York,
1993. (b) Palomo, C.; Oiarbide, M.; Aizpurua, J. M. In
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Stuttgart, 2006, 169–213. (c) Xu, J. X. ARKIVOC 2009, (ix),
21. For recent examples, see: (d) Liang, Y.; Jiao, L.; Zhang,
S. W.; Yu, Z. X.; Xu, J. X. J. Am. Chem. Soc. 2009, 131,
1542. (e) Li, B. N.; Wang, Y. K.; Du, D. M.; Xu, J. X. J. Org.
Chem. 2007, 72, 990. (f) Hu, L. B.; Wang, Y. K.; Li, B. N.;
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Acknowledgment
This project was supported partly by the National Natural Science
Foundation of China (Nos. 20972013 and 20772005), Beijing
Natural Science Foundation (No. 2092022), and by the specialized
Research Fund for the Doctoral Program of Higher Education,
Ministry of Education of China.
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