Magnetically Bistable Nitrenes: Matrix Isolation of Furoylnitrenes in Both Singlet and Triplet States and Triplet 3-Furylnitrene

Article abstract of DOI:10.1021/jacs.7b08957

Two simple acylnitrenes, 2-furoylnitrene (2) and 3-furoylnitrene (6), were generated through 266 nm laser photolysis of the corresponding azides. Both are magnetically bistable in cryogenic matrices, as evidenced by the direct observation of the closed-shell singlet state with IR spectroscopy in solid Ne, Ar, Kr, Xe, and N₂ matrices (3-40 K) and the triplet state in toluene (10 K) with EPR spectroscopy (³2: |D/hc| = 1.48 cm^-1 and |E/hc| = 0.029 cm^-136: |D/hc| = 1.39 cm^-1 and |E/hc|c = 0.039 cm^-1). Subsequent visible-light and UV laser irradiations led to the formation of furyl isocyanates (3 and 7) and ring-opening product 3-cyanoacrolein (9-E and 9-Z), respectively, in which the elusive 3-furylnitrene (³8) was also identified by IR and EPR spectroscopy (|D/hc| = 1.12 cm^-1 and |E/hc| = 0.005 cm^-1).

Full text of DOI:10.1021/jacs.7b08957

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Communication
Magnetically Bistable Nitrenes: Matrix-Isolation of Furoylnitrenes
in Both Singlet and Triplet States and Triplet 3-Furylnitrene
Ruijuan Feng, Yan Lu, Guohai Deng, Jian Xu, Zhuang Wu, Hongmin
Li, Qian Liu, Norito Kadowaki, Manabu Abe, and Xiaoqing Zeng
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b08957 • Publication Date (Web): 14 Dec 2017
Downloaded from http://pubs.acs.org on December 15, 2017
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Magnetically Bistable Nitrenes: Matrix-Isolation of Furoylnit-
renes in Both Singlet and Triplet States and Triplet 3-
Furylnitrene
7
8
9
1
1
1
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9
0
†
†
†
†
†
†
†
Ruijuan Feng, Yan Lu, Guohai Deng, Jian Xu, Zhuang Wu, Hongmin Li, Qian Liu, Norito Kaꢀ
‡
‡
,†
dowaki, Manabu Abe and Xiaoqing Zeng*
†
College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China.
‡
Department of Chemistry, Graduate School of Science, Hiroshima University, 1ꢀ3ꢀ1 Kagamiyama, HigashiꢀHiroshima Hiroꢀ
shima 739ꢀ8526, Japan.
Supporting Information Placeholder
9
alkoxynitrenes (ROꢀC(O)N) and carbamoylnitrenes (R Nꢀ
ABSTRACT: Two simple acylnitrenes, 2ꢀfuroylnitrene (2) and
ꢀfuroylnitrene (6), were generated through 266 nm laser
2
10
–1
C(O)N) adopt triplet multiplicity (ꢁEST > 0 kcal mol ).
3
photolysis of the corresponding azides. Both are magnetically
bistable in cryogenic matrices, as evidenced by the direct
observation of the closedꢀshell singlet state with IR spectroscopy
O
C
I
O
C
II
O
C
N
in solid Ne, Ar, Kr, Xe, and N matrices (3–40 K) and the triplet
2
R
N
R
N
R
3
state in toluene (10 K) with EPR spectroscopy ( 2: |D/hc| = 1.48
III
–1
–1
3
–1
cm and |E/hc| = 0.029 cm ; 6: |D/hc| = 1.39 cm and |E/hc|c =
–1
0
.039 cm ). Subsequent visibleꢀlight and UV laser irradiations led
Scheme 1. Structures of acylnitrenes
Therefore, fundamentally important simple acylnitrenes with alꢀ
most degenerate singlet and triplet states (ꢁEST ≈ 0 kcal mol )
should be viable candidates for isolation and characterization.
Very recently, arylcarbenes with small magnitude of ꢁEST have
been observed in their both singlet and triplet states in cryogenic
matrices. It was concluded that the magnetic bistability of carꢀ
benes should be a general phenomenon that solely depends on the
singletꢀtriplet gap ꢁE . Continuing our interest in the structure
and reactivity of αꢀoxo nitrenes, herein, we report the photoꢀ
chemistry of two furoylazides (1 and 5), in which furoylnitrenes
(2 and 6), featuring as rare magnetically bistable nitrenes, and the
elusive 3ꢀfurylnitrene (8) have been isolated and characterized in
cryogenic matrices.
to the formation of furyl isocyanates (3 and 7) and ringꢀopening
product 3ꢀcyanoacrolein (9ꢀE and 9ꢀZ), respectively, in which the
–
1
3
elusive 3ꢀfurylnitrene ( 8) was also identified by IR and EPR
–
1
–1
spectroscopy (|D/hc| = 1.12 cm and |E/hc| = 0.005 cm ).
11
Nitrenes are versatile reactive intermediates in chemical transforꢀ1
mations such as aziridination and CꢀH amidation reactions.
ST
1
2
Meanwhile, nitrenes have been broadly used in the functionalizaꢀ
2
tion of carbonꢀnanomaterials and photoaffinity labeling of bioꢀ
3
logical systems. As the most fundamental property of nitrenes,
electronic spin state determines the structure and reactivity. Genꢀ
erally, nitrenes prefer triplet ground state in which the two unꢀ
paired electrons have parallel spins, singly occupying pure p and
x
pz orbitals. Whereas, singlet state with antiparallel spin is less
O hv1
−N2
O
O
CN
hv
hv
CO
3
O
favorable due to much stronger Coulombic electronꢀelectron reꢀ
2
4
−
9-Z
pulsion. The singletꢀtriplet energy gaps (ꢁE ) in nitrenes depend
ST
O
C
C
NCO
strongly on the substituents. For instance, delocalization of unꢀ
N
4
hv
3
CN
O
N3
O
N
5
6
hv5
1
2
3
paired electron by conjugation in vinylnitrenes and arylnitrenes
hv4
can stabilize the singlet state relative to the triplet ground state
with reduced ꢁEST.
O
O
O
O
hv1
−N
hv2
hv3
Stabilization of the singlet state has also been proposed for
O
9-E
4
2
−CO
acylnitrenes (RC(O)N), which is due to bonding interaction beꢀ
C
C
NCO
N
tween the carbonyl oxygen (C=O) and the electronꢀdeficient
nitrene center (II, III, Scheme 1). This intramolecular interaction
results in closedꢀshell singlet state with a cyclic oxazirineꢀlike
structure (III). Experimentally, ultrafast spectroscopy, matrixꢀ
isolation spectroscopy, and electron paramagnetic resonance specꢀ
O
N3
O
N
5
6
7
8
Scheme 2. Photochemistry of furoylazides.
Prior to the experimental study, the ꢁE values for furoylnitrenes
together with HC(O)N and PhC(O)N were calculated (Table
). Although the B3LYP/6ꢀ311++G(3df,3pd) method is adequate
for the prediction of IR spectra, it tends to underestimate the staꢀ
bility of the singlet relative to the triplet for πꢀconjugated systems
troscopy (EPR) have confirmed singlet ground state (ꢁE < 0
ST
7,8
ST
13
–1
7
kcal mol ) for aroylnitrenes such as benzoylnitrene (PhC(O)N)
8
1
and naphthoylnitrene (2ꢀNpC(O)N), the higherꢀenergy triplet
state (I, Scheme 1) could only be detected as transient species by
ultrafast spectroscopy. Meanwhile, many acylnitrenes such as
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due to overemphasis of delocalization. In consistent with previꢀ
ous studies,
IR spectra (unscaled harmonic frequencies) of antiꢀ 2 and synꢀ 2,
respectively.
7,8,13
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
the CCSD(T)/augꢀccꢀpVTZ and CBSꢀQB3 methꢀ
ods conclusively predict the preference of triplet and singlet state
for the last two nitrenes, respectively. However, for both furoylnitꢀ
renes the sign of the calculated small ꢁEST values varies with the
computational methods, indicating that the two spin states are
almost equal in energy. For all four acylnitrenes, singleꢀpoint
energy calculations using the completeꢀactiveꢀspace secondꢀorder
perturbation theory (CASPT2) predicted preference of the triplet
state, and the openꢀshell singlet are significantly higher by more
–1
Several new IR bands appeared at around 1760 cm , and the corꢀ
responding carrier can be completely depleted by blue light irradiꢀ
ation (440±20 nm, 40 min), as a result 3 and traces of the azide
precursor 1 were formed (Figure 1B). To aid the assignment, IR
frequency calculations (B3LYP/6ꢀ311++G(3df,3pd)) of the most
likely candidate 2ꢀfuroylnitrene (2) were performed. The band
centered at 1752.3 cm coincides with the calculation of 1818
cm for the singlet nitrene (Figure 1C) in a more favorable anti
conformation (syn conformer: 1807 cm , Table S3). The frequenꢀ
cy is very close to the most characteristic C=N stretching vibraꢀ
tions found in other oxazirineꢀlike singlet aroylnitrenes such as
and 2ꢀNpC(O)N (1737 cm
in CCl ). The assignment is supported by the observation of an
isotopic shift of 8.5 cm upon Nꢀlabeling (Figure S2). Interestꢀ
ingly, there are several weaker bands in the range of 1800–1730
cm , all of which exhibit same photobehavior and also same
isotopic shift. These bands appear with minor shifts (< 10 cm )
and slightly changed intensities in independent experiments where
N was used as the matrix gas at 15 K (Figure S3). Hence, they
also belong to the nitrene 2, and the splittings might be caused by
weak interaction with the surrounding molecules in same matrix
–1
–1
–1
than 25 kcal mol (Table S1).
–1
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
–
1
Table 1. Calculated ꢀEST (kcal mol ) for acylnitrenes
–1
7aꢀb
–1
PhC(O)N (1760 cm in CD CN)
3
[
a]
[b]
8
species
B3LYP
8.3
CCSD(T)
2.2
CBSꢀQB3 CASPT2
4
–1
15
[
d]
HC(O)N
0.7
4.9
1.1
2.6
2.2
[
e]
PhC(O)N 4.6
–0.4
1.2
–4.7
–1.2
–1.1
–1
15
N
[c]
[f]
[f]
–1
2
6
6.5
5.8
[
c]
0.8
2
1
[a] At the 6ꢀ311++G(3df,3pd) basis set. [b] CCSD(T)/augꢀccꢀ
pVTZ//B3LYP/6ꢀ311++G(3df,3pd). [c] For the more stable conꢀ
1
5
cages (matrix site effect).
formers
pVTZ//CASSCF(6,5)/ccꢀpVTZ.
pVTZ//CASSCF(12,11)/ccꢀpVTZ.
of
the
two
states.
[e]
[f]
[d]
CASPT2(4,3)/ccꢀ
CASPT2(12,11)/ccꢀ
CASPT2(12,10)/ccꢀ
1
The selective depletion of 2 allows unambiguous identification of
15
the remaining IR bands and N isotopic shifts (Table S3). No
distinguishable IR band could be found for triplet 2ꢀfuroylnitrene,
especially for the most characteristic C=O stretching vibrations
which were predicted at 1603 (anti) and 1611 cm (syn) with
large IR intensities (anti: 127 km mol ; syn: 201 km mol ). Typꢀ
pVTZ//CASSCF(12,10)/ccꢀpVTZ. Positive values refer to the
triplet being more stable.
–1
–1
–1
The generation of 2ꢀfuroylnitrene (2) was performed by 266 nm
laser photolysis (10 mW, 30 s) of 2ꢀfuroylazide (1) in solid Ne
matrix (3 K). The IR difference spectrum (Figure 1A) shows the
depletion of the azide (ca. 80%) and the concomitant formation of
N2 (IR inactive) and the Curtiusꢀrearrangement product 2ꢀ
furylisocyanate (3, Table S2), the latter exhibits intense IR band
for the characteristic NCO asymmetric stretching vibration at
ically, matrixꢀisolated triplet acylnitrenes like CH OC(O)N (syn:
3
–1
–1 9b
–1 10
1
645.8 cm ; anti: 1602.8 cm ) and H NC(O)N (1644.4 cm )
2
display intense bands for this IR fundamental.1
The generation of singlet 3ꢀfuroylnitrene ( 6) through 266 nm
laser photolysis of 3ꢀfuroylazide (5) was also observed (Figure
2
A).
–1
–1
15
2
278.6 cm with a shift of 12.5 cm upon N labeling. Referꢀ
0.7
ence IR spectrum of 3 can be readily obtained since flash pyrolyꢀ
D)
C)
triplet syn-6
singlet anti-6
0
.6
sis of 1 at 500 K exclusively furnishes 3 and N (Figure S1).
7
2
0.5
7
7
7
7
7
7
6
0
0
0
A
0
.4
.3
.2
.1
7
7
7
7
6
7
5
7
0.7
D)
C)
triplet syn-2
singlet anti-2
B)
A)
6
5
6
5
6
0
.6
.5
5
6
6
6
3
7
6
6
3
6
0
ꢀ
3
0.4
3
3
3
6
6
3
3
3
2
3
*
3
3
1
1
2
3 3
2
1
1
3
2
0.0
-0.1
-0.2
0.3
0.2
0.1
0.0
B)
A)
2
2
*
2
3
2
2
2
2
ꢀA
3
2
3
3
2400 2200 2000 1800 1600 1400 1200 1000 800 600
−1
3 3
3
ν
/ cm
Figure 2. A) IR difference spectrum showing the decomposition
of 5 (bands pointing downward) in Ne matrix (3 K) upon a 266
nm laser irradiation; B) IR difference spectrum (5 times expanded
along the ꢁA axis) showing rearrangement of 6 to 7 upon subseꢀ
quent UV light irradiation (365 nm); CꢀD) B3LYP/6ꢀ
311++G(3df,3pd) calculated IR spectra (unscaled harmonic freꢀ
-
0.1
0.2
-
2
400 2200 2000 1800 1600 1400 1200 1000 800 600
−1
ν
/ cm
Figure 1. A) IR difference spectrum showing the decomposition
of 1 (bands pointing downward) in Ne matrix (3 K) upon a 266
nm laser irradiation; B) IR difference spectrum (5 times expanded
along the ꢁA axis) showing rearrangement of 2 to 3 upon subseꢀ
quent visible light irradiation (440±20 nm), bands of impurity
1
3
quencies) of antiꢀ 6 and synꢀ 6, respectively.
1
As can be seen in Figure 2B, 6 exhibits IR bands at 1786.0 and
764.2 cm for the C=N stretching vibration (1781.3 and 1762.3
cm in N ꢀmatrix, Figure S4), and the corresponding N isotopic
shifts are 10.1 and 8.2 cm (Figure S5), respectively. The remainꢀ
–1
1
H O (*) are marked; CꢀD) B3LYP/6ꢀ311++G(3df,3pd) calculated
2
–1
15
2
–1
2
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–
1
ing bands (> 600 cm ) show good agreement with the calculaꢀ
tions for the nitrene in the singlet state (Figure 2C). Subsequent
UV light (365 nm) irradiation leads to the expected rearrangement
to isocyanate 7. In order to convert the singlet furoylnitrenes to the
triplet state, attempts were made by warming the matrices (N2ꢀ
matrix to 25 K and Krꢀmatrix to 40 K, Figures S6ꢀS7), doping the
matrix with 1% water (Figures S8ꢀS9) or carbon monoxide (Figꢀ
ures S10), or irradiating with longerꢀwavelength light sources
(570 and 830 nm), however, only the rearrangement occurred in
the case of irradiations.
servation is consistent with the theoretical prediction that the opꢀ
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
timization of 4 in the initially generated singlet state led directly to
20
the ringꢀopened cyanoacrolein (9, Figure S12).
3
To verify the formation of 8, a Neꢀmatrix mainly containing 7
was irradiated with an ArF excimer laser (193 nm). The resulting
IR difference spectrum (Figure 4A) reflects the formation of CO
and new species with several weak IR bands, which can be distinꢀ
guished by subsequent purple light irradiation (400±20 nm), under
3
which 9 forms at the expense of 8 (Figure 4B). The assignment
was affirmed by comparing with the calculated spectrum of 8
15
Given the possibility that the absence of distinguishable IR bands
for triplet furoylnitrenes might be due to low abundances in cryoꢀ
genic matrices, the photochemistry (266 nm) of 2ꢀfuroylazide in
solid Ar (10 K) was followed by EPR spectroscopy. No EPR sigꢀ
nals for triplet species were observed. However, when the photolꢀ
ysis was performed in polar solvent toluene (10 K), typical EPR
signals for triplet nitrenes appeared after 2 min of irradiation (Figꢀ
ure 3). These signals are persistent at 10 K in the dark at least for
(Figure 4C) and also the Nꢀlabeling experiment (Figure S13). In
line with the observation with EPR spectroscopy, only 9 was obꢀ
served by IR spectroscopy when 3 was subjected to the UV laser
irradiation. Furthermore, the visible light (400±20 nm) induced
Z→E conformational conversion in 9 was observed (Figure S14).
The ringꢀopening of furylnitrenes (Figure S12) resembles the reꢀ
cently disclosed photochemistry of the putative isoelectronic fuꢀ
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
21
rylcarbenes, which were proposed as the intermediates in the
photolysis of furyldiazomethanes.
1
1 hours but disappear when warming the matrix to 50 K (Figure
S11), however, subsequent recooling the matrix to 10 K could not
recover the signals. Two sets of zeroꢀfield splitting (zfs) parameꢀ
0
.4
–1
–1
D)
C)
singlet 8
triplet 8
ters |D/hc| = 1.48 cm and |E/hc| = 0.029 cm and |D/hc| = 1.39
–1
–1
cm and |E/hc| = 0.039 cm are close to those of acylnitrenes like
CH OC(O)N (|D/hc| = 1.66 cm and |E/hc| = 0.020 cm ) and
H NC(O)N (|D/hc| = 1.59 cm and |E/hc| = 0.018 cm ), demonꢀ
7
9-Z
–
1
–1 9b
0.3
0.2
9-E
3
CO
9-E
–
1
–1 16
2
9
-Z
strating the presence of triplet furoylnitrene nitrenes. The obꢀ
7
7
3
–1
7
7
served D values agree with the predictions (synꢀ 2: 1.40 cm , synꢀ
3
–1
6
: 1.40 cm ) by the empirical linear correlation (D = 1.96673ρ –
.0557 cm ) with the calculated natural spin densities ρ (synꢀ 2:
B)
A)
8
7
–1
3
8
8
8
8
0
.1
2
1
8
8 8
3
1a,17
CO
8
5
.756, synꢀ 6: 1.755, B3LYP/EPRIII).
ꢀA
8
8
8
0
.0
3
5
7
7
5
7
7
75
5
5
-0.1
2
5
5
7
7
2
400 2200 2000 1800 1600 1400 1200 1000 800 600
1
0
1
2
A)
2
2
−1
ν
/ cm
Figure 4. A) IR difference spectrum showing the decomposition
of 5 and 7 in Ne matrix (3 K) upon 193 nm laser irradiation; B) IR
difference spectrum (20 times expanded along the ꢁA axis) showꢀ
6
3
-
-
8
ing the rearrangement of 8 to 9 in Z and E conformations upon
8
6
subsequent purple light irradiation (400±20 nm); CꢀD) B3LYP/6ꢀ
311++G(3df,3pd) calculated IR spectra (unscaled harmonic freꢀ
quencies) of triplet and singlet 8, respectively.
B)
-3
5
000
6000
7000
8000
9000
10000
In conclusion, two novel furoylnitrenes (2 and 6) have been genꢀ
erated from 266 nm laser photolysis of the corresponding azide
precursors. In consistent with the theoretically predicted small
Magnetic Field (G)
Figure 3. A) EPR spectrum (ν0 = 9.3963 GHz) showing generaꢀ
–1
3
–1
singletꢀtriplet energy gaps (ꢁEST ≈ 0 kcal mol ), subsequent charꢀ
tion of 2 (zfs parameters: |D/hc| = 1.48 cm and |E/hc| = 0.029
–1
acterization by IR and EPR spectroscopy demonstrates that both
nitrenes exist as persistent species in the closedꢀshell singlet and
triplet states in cryogenic matrices. Upon nearꢀvisible light irradiaꢀ
tions, furoylnitrenes rearrange to furylisocyanates, which further
dissociate into CO and 3ꢀcyanoacrolein via the intermediacy of
intriguing furylnitrenes. No evidence for the thermally initiated
switch of spin state in furoylnitrenes was obtained. The reason
cm ) during the photolysis (266 nm, 10 min) of 1 in solid toluene
at 10 K; B) EPR spectrum (ν0 = 9.3989 GHz) showing the generaꢀ
3
–1
–1
3
tion of 6 (|D/hc| = 1.39 cm and |E/hc| = 0.039 cm ) and 8
(
(
–1
–1
|D/hc| = 1.12 cm and |E/hc| = 0.005 cm ) during the photolysis
266 nm, 5 min) of 5 in solid toluene at 10 K.
–1
Additionally, a second triplet nitrene signal appeared during the
might be due to intrinsic barriers (9–10 kcal mol , B3LYP/6ꢀ
311++G(3df,3pd)) associated with the structural changes (Figures
S15ꢀS24) in the course of intersystem crossing (ISC), which could
hardly be reached by warming the matrix in the available temperaꢀ
ture range (up to 40 K). More importantly, these barriers are close
–
1
photolysis of 5. The parameters |D/hc| = 1.12 cm and |E/hc| =
–1
0
.005 cm imply the presence of an arylnitrene, for which usually
small zfs parameters were observed, such as phenylnitrene (|D/hc|
–1
–1 18
=
0.9896 cm and |E/hc| = 0.00 cm ) and 2ꢀpyrimidinylnitrene
–1
–1 19
–1
(|D/hc| = 1.217 cm and |E/hc| = 0.0052 cm ). Considering the
frequently observed COꢀelimination in covalent isocyanates,
this signal is very likely to be associated with 3ꢀfurylnitrene ( 8),
formed from COꢀelimination in 7. Instead, 2ꢀfurylnitrene (4) was
not observed in the laser photolysis of 2ꢀfuroylazide (1). The obꢀ
to those (10–11 kcal mol ) for the rearrangement of the singlet
9
b,10
furoylnitrenes to the isocyanates, which is thermodynamically
much more favorable due to the concomitant release of large
3
–1
amount of energy (>70 kcal mol ). Work in our group is ongoing
to replace the furyl group with other aryl substituents, in the hope
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of discovering heteroaroylnitrenes with thermally and/or photolytꢀ
ically switchable spin states in cryogenic matrices.
Hadad, C. M. Karney, W. L.; Kemnitz, C. R.; Platz, M. S. Acc. Chem. Res.
000, 33, 765–771. (c) Nues, C. M.; Knezz, S. N.; Reva, I.; Fausto, R.;
McMahon, R. J. J. Am. Chem. Soc. 2016, 138, 15287–15290. (d) Rau, N.
J.; Welles, E. A.; Wenthold, P. G. J. Am. Chem. Soc. 2013, 135, 683–690.
(7) (a) Pritchina, E. A.; Gritsan, N. P.; Maltsev, A.; Bally, T.; Autrey, T.;
Liu, Y. L.; Wang, Y. H.; Toscano, J. P. Phys. Chem. Chem. Phys. 2003, 5,
2
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ASSOCIATED CONTENT
Supporting Information
1
010–1018. (b) Desikan, V.; Liu, Y. L.; Toscano, J. P.; Jenks, W. S. J.
Org. Chem. 2007, 72, 6848–6859. (c) Wentrup, C.; Bornemann, H. Eur. J.
Org. Chem. 2005, 4521–4524. (d) Wasserman, E.; Smolinsky, G.; Yager,
W. A. J. Am. Chem. Soc. 1964, 86, 3166–3167.
Experimental details, theoretical methods, observed and calculated
IR spectra, and calculated energies and atomic coordinates. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(8) (a) Kubicki, J.; Zhang, Y.; Vyas, S.; Burdzinski, G.; Luk, H. L.; Wang,
J.; Xue, J.; Peng, H. ꢀL.; Pritchina, E. A.; Sliwa, M.; Buntinx, G.; Gritsan,
N. P.; Hadad, C. M.; Platz, M. S. J. Am. Chem. Soc. 2011, 133, 9751–
9761. (b) Kubicki, J.; Zhang, Y.; Wang, J.; Luk, H. L.; Peng, H. ꢀL.; Vyas,
S.; Platz, M. S. J. Am. Chem. Soc. 2009, 131, 4212–4213. (c) Kubicki, J.;
Zhang, Y.; Xue, J.; Luk, H. L.; Platz, M. S. Phys. Chem. Chem. Phys.
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AUTHOR INFORMATION
Corresponding Author
2
012, 14, 10377–10390.
(9) (a) Chavez, T. A.; Liu, Y.; Toscano, J. P. J. Org. Chem. 2016, 81,
320–6328. (b) Li, H. M.; Wu, Z.; Li, D. Q.; Wan, H. B.; Xu, J.; Abe, M.;
Zeng, X. Q. Chem. Commun. 2017, 53, 4783–4786.
10) Li, H. M.; Wan, H. B.; Wu, Z.; Li, D. Q.; Bégué, D.; Wentrup, C.;
*xqzeng@suda.edu.cn
6
Notes
(
The authors declare no competing financial interests.
Zeng, X. Q. Chem. ꢀEur. J. 2016, 22, 7856–7862, and references therein.
(11) (a) Tsegaw, Y. A.; Kadam, P. E.; Tötsch, N.; SanchezꢀGarcia, E.;
Sander, W. J. Am. Chem. Soc. 2017, 139, 12310–12316. (b) Costa, P.;
Lohmiller, T.; Trosien, I.; Savitsky, A.; Lubitz, W.; FernandezꢀOliva, M.;
SanchezꢀGarcia, E.; Sander, W. J. Am. Chem. Soc. 2016, 138, 1622–1629.
(c) Henkel, S.; Costa, P.; Klute, L.; Sokkar, P.; FernandezꢀOliva, M.;
Thiel, W.; SanchezꢀGarcia, E.; Sander, W. J. Am. Chem. Soc. 2016, 138,
ACKNOWLEDGMENT
This research was supported by the National Natural Science
Foundation of China (21422304, 21673147), and the Priority Acꢀ
ademic Program Development of Jiangsu Higher Education Instiꢀ
tutions (PAPD). M.A. acknowledges financial support by a Grantꢀ
inꢀAid for Science Research on Innovative Areas “Stimuliꢀ
responsive Chemical Species (No.2408)” (JSPS KAKENHI Grant
Number JP24109008).
1
689–1697.
(12) Wu, Z.; Li, D. Q.; Li, H. M.; Zhu, B. F.; Sun, H. L.; Francisco, J. S.;
Zeng, X. Q. Angew. Chem., Int. Ed. 2016, 55, 1507–1510. (b) Deng, G. H.;
Wu, Z.; Li, D. Q.; Linguerri, R.; Francisco, J. S.; Zeng, X. Q. J. Am.
Chem. Soc. 2016, 138, 11509–11512.
(13) (a) Mebel, A. M.; Luna, A.; Lin, M. C.; Morokuma, K. J. Chem. Phys.
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10746–10749.
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Chem. 2013, 66, 286–296.
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25, 480–482.
(19) Torker, S.; Kvaskoff, D.; Wentrup, C. J. Org. Chem. 2014, 79, 1758–
1770.
(20) Wenthold, P. G. J. Org. Chem. 2012, 77, 208–214.
(21) Pharr, C. R.; Kopff, L. A.; Bennett, B.; Reid, S.; McMahon, R. J. J.
Am. Chem. Soc. 2012, 134, 6443–6454.
(1) For very recent reviews, see: (a) Wentrup, C. Chem. Rev. 2017, 117,
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2) Park, J. Yan, M. Acc. Chem. Res. 2013, 46, 181–189, and references
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M. N.; Tarnovsky, A. N.; Wilson, R. M. J. Am. Chem. Soc. 2013, 135,
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3844–3867.
4) For examples, see: (a) Falvey, D. E.; Gudmundsdottir, A. D. Nitrenes
(
1
(
and Nitrenium Ions; Wiley: New York, 2013. (b) Gritsan, N. P.; Platz, M.
S.; Borden, W. T. The Study of Nitrenes by Theoretical Methods in Theoꢀ
retical Methods in Photochemistry; Kutateladze, A., Ed.; Taylor and Franꢀ
cis: Boca Raton, FL, 2005. (c) Reactive Intermediate Chemistry; Moss, R.
A., Platz, M. S., Jones, M. J., Jr., Eds.; John Wiley & Sons: Hoboken, NJ,
2
004. (d) BarbieuxꢀFlammang, M.; Vandevoorde, S.; Flammang, R.;
Wong, M. W.; Bibas, H.; Kennard, C. H. L.; Wentrup, C. J. Chem. Soc.,
Perkin Trans. 2, 2000, 473–478.
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mundsdottir, A. D. J. Am. Chem. Soc. 2016, 138, 14905–14914. (b)
Sarkar, S. K.; Sawai, A.; Kanahara, K.; Wentrup, C.; Abe, M.; Gudꢀ
mundsdottir, A. D. J. Am. Chem. Soc. 2015, 137, 4207–4214.
(6) (a) Kvaskoff, D.; Lüerssen, H.; Bednarek, P.; Wentrup, C. J. Am.
Chem. Soc. 2014, 136, 15203–15214. (b) Borden, W. T.; Gritsan, N. P.;
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Figure 1. A) IR difference spectrum showing the decomposition of 1 (bands pointing downward) in Ne matrix
(3 K) upon a 266 nm laser irradiation; B) IR difference spectrum (5 times expanded along the ∆A axis)
showing rearrangement of 2 to 3 upon subsequent visible light irradiation (440±20 nm), bands of impurity
H2O (*) are marked; CꢀD) B3LYP/6ꢀ311++G(3df,3pd) calculated IR spectra (unscaled harmonic
frequencies) of antiꢀ12 and synꢀ32, respectively.
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Figure 2. A) IR difference spectrum showing the decomposition of 5 (bands pointing downward) in Ne matrix
(
3 K) upon a 266 nm laser irradiation; B) IR difference spectrum (5 times expanded along the ∆A axis)
showing rearrangement of 6 to 7 upon subsequent UV light irradiation (365 nm); CꢀD) B3LYP/6ꢀ
3
11++G(3df,3pd) calculated IR spectra (unscaled harmonic frequencies) of antiꢀ16 and synꢀ36,
respectively.
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Figure 3. A) EPR spectrum (v0 = 9.3963 GHz) showing generation of 32 (zfs parameters: |D/hc| = 1.48 cm–
1
and |E/hc| = 0.029 cm–1) during the photolysis (266 nm, 10 min) of 1 in solid toluene at 10 K; B) EPR
spectrum (v0 = 9.3989 GHz) showing the generation of 36 (|D/hc| = 1.39 cm–1 and |E/hc| = 0.039 cm–1)
and 38 (|D/hc| = 1.12 cm–1 and |E/hc| = 0.005 cm–1) during the photolysis (266 nm, 5 min) of 5 in solid
toluene at 10 K.
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Figure 4. A) IR difference spectrum showing the decomposition of 5 and 7 in Ne matrix (3 K) upon 193 nm
laser irradiation; B) IR difference spectrum (20 times expanded along the ∆A axis) showing the
rearrangement of 38 to 9 in Z and E conformations upon subsequent purple light irradiation (400±20 nm);
CꢀD) B3LYP/6ꢀ311++G(3df,3pd) calculated IR spectra (unscaled harmonic frequencies) of triplet and singlet
8
, respectively.
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Scheme 1. Structures of acylnitrenes
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Scheme 2. Photochemistry of furoylazides.
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Graphical abstract
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