General Photoinduced Sequential Electrocyclization/[1,9]-Sigmatropic Rearrangement/Ring-Opening Reaction of Diarylethenes

Article abstract of DOI:10.1021/acs.joc.5b02237

A novel and efficient photochemical transformation of diarylethenes comprising a five-membered heterocyclic ring and phenyl moiety is described. This reaction provides a simple method for the preparation of functionalized naphthalene derivatives via photorearrangement reaction of diarylethenes, and the process is characterized by high efficiency that was determined by NMR monitoring. Some mechanistic aspects of this process have been also explored. It was found that the reaction includes tandem transformation of three basic processes: the photocyclization of the hexatriene system, [1,9]-sigmatropic rearrangement, and heterocyclic ring opening. Diarylethenes with different heterocycle moieties (thiophene, benzo[b]thiophene, furan, indole, imidazole, thiazole, oxazole, pyrazole) have been involved into this process, and the target naphthalenes with good yields have been obtained. The opportunity for use in the transformation of diarylethenes with different heterocyclic residues permits synthesis of naphthalenes with desired functional groups. The general character and high efficiency of the reaction promise that the transformation can be an effective synthetic route for the annulation of benzene rings to various aromatic systems, including heterocycles.

Full text of DOI:10.1021/acs.joc.5b02237

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Article
A GENERAL PHOTO-INDUCED SEQUENTIAL
ELECTROCYCLIZATION / [1,9]-SIGMATROPIC REARRANGEMENT /
RING-OPENING REACTION OF DIARYLETHENES
Andrey G. Lvov, Valerii Z. Shirinian, Alexey V. Zakharov,
Mikhail M. Krayushkin, Vadim V Kachala, and Igor V. Zavarzin
J. Org. Chem., Just Accepted Manuscript • Publication Date (Web): 02 Nov 2015
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A GENERAL PHOTO-INDUCED SEQUENTIAL
ELECTROCYCLIZATION / [1,9]-SIGMATROPIC REARRANGEMENT /
RING-OPENING REACTION OF DIARYLETHENES
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Andrey G. Lvov, Valerii Z. Shirinian,* Alexey V. Zakharov, Mikhail M. Krayushkin,
Vadim V. Kachala, and Igor V. Zavarzin
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47, Leninsky prosp.,
119991 Moscow, Russian Federation
GRAPHIC ABSTRACT
ABSTRACT
A novel and efficient photochemical transformation of diarylethenes comprising fiveꢀ
membered heterocyclic ring and phenyl moiety is described. This reaction provides a simple
method for the preparation of functionalized naphthalene derivatives via photorearrangement
reaction of diarylethenes and the process is characterized by high efficiency that was determined
by NMR monitoring. Some mechanistic aspects of this process have been also explored. It was
found that the reaction includes tandem transformation of three basic processes: the
photocyclization of hexatriene system, [1,9]ꢀsigmatropic rearrangement and heterocyclic ring
opening. Diarylethenes with different heterocycle moieties (thiophene, benzo[b]thiophene, furan,
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indole, imidazole, thiazole, oxazole, pyrazole) have been involved into this process and the target
naphthalenes with good yields have been obtained. The opportunity to use in the transformation
of diarylethenes with different heterocyclic residues permits synthesis of naphthalenes with
desired functional groups. The general character and high efficiency of the reaction promise that
the transformation can be an effective synthetic route for the annulation of benzene ring to
various aromatic systems, including heterocycles.
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Keywords: photoreaction, electrocyclization, diarylethene, naphthalene, sigmatropic shift,
NMRꢀmonitoring, 2,3ꢀdiarylcyclopentꢀ2ꢀenꢀ1ꢀone.
INTRODUCTION
Photochemical transformations have long ceased to represent only of a fundamental
interest, now are actively used for the synthesis of a various classes of organic compounds that
are difficult to achieve by conventional chemical methods.1ꢀ3 However these reactions are
underutilized in the development of novel scaffolds for medicines, technology and material
chemistry, although they can provide access to products with rich structural complexity and
stereochemical diversity. Among the photochemical reactions the photocyclization of stilbenes
(diarylethenes) is a subject of long standing interest.4ꢀ6 This reaction is known for more than fifty
years and different physical and chemical features have been also explored (Scheme 1).5ꢀ7 The
stilbenes (diarylethenes) photocyclization not only provides a convenient access to novel
polyaromatic systems, their heterocyclic derivatives have a significant interest as photochromic
compounds which for the last decades have been widely studied in the development of data
storage devices and molecular switches.8
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Scheme 1. Photochemical transformations of stilbenes / diarylethenes.
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The first step of this reaction involves the formation of cyclohexadiene derivatives II by
6πꢀelectrocyclic reaction. The subsequent transformations of the resulting intermediate II depend
strongly on the nature of substituents R1 and R2. When both substituents are alkyl or aryl, such
compounds typically exhibit photochromic properties which photoꢀinduced form is a thermally
metastable.8 Such diarylethenes are chemically inert and do not represent an interest for
photochemical organic synthesis. However the reactivity of compounds II varies drastically if at
least one of these substituents is hydrogen. Several ways of their chemical transformations which
proceed through aromatization stage of cyclohexadiene system of molecule II are described over
the past decades. Among them it should be noted the oxidation and elimination reactions,
resulting in the same products, phenanthrene derivatives or relative polyaromatic systems. In
addition it was also reported a number of skeletal rearrangement reactions of the molecule II,
leading to polyaromatic systems with different substituents. Thus, the cyclization of stilbenes
(diarylethenes) can lead to formation of the polycyclic systems both with the same number
(Route 1, Scheme 1) or more than one aromatic rings (Route 2) in depending on the nature of the
substituents (R1 and R2) and structure core.
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The photocyclization followed by oxidation or elimination has become a respected
synthetic protocol for the preparation of phenanthrenes or analogs thereof.5,6 When the
substituents at C1 and C2 are hydrogen atom, the aromatization of intermediate II occurs in the
presence of oxidants (O2, I2). In the event that one of the substituents is a hydrogen atom, and
the other is halogen, or methoxy group etc, the aromatization process occurs via the elimination
reaction (leaving groups ꢀ HHal, MeOH). These methods are widely used in practice for the
preparation of polyarenes,9 including biologically active compounds,10 organic semiconductors,11
fluorophores,12 DNA intercalators,13 and for photogeneration of acid agents.14
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When the above processes are not possible, and one of the substituents is hydrogen, the
aromatization of the central core can proceed via sigmatropic rearrangement involving of C2ꢀX3
bond cleavage (Scheme 1). This way leads to the formation of polyaromatic hydrocarbons
through the formal ringꢀopening of one of the aromatic residues and to date, in contrast to
oxidation or elimination protocol, only a few random examples are described (Scheme 2). To the
best of our knowledge, the first type of this reaction had been described for styrylfurans and
styrylthiophenes (reaction A, Scheme 2), the photorearrangement of which results in benzofurans
and benzothiophenes, respectively.15 In the continuation of these works authors have studied the
photoreaction of styrylfurans in the presence of acids16 and bases.17 It has been also reported18
the rearrangement of 3,3'ꢀbis(arylbenzofurans) resulting in benzofuranꢀannulated naphthalenes in
high yields (reaction B in Scheme 2, synthetic protocols A and B were performed under an inert
conditions). Recently, in the course of our studies directed toward the synthesis and the
investigation of spectral properties of photochromic diarylethenes19 we have found a photoꢀ
induced rearrangement of diarylethenes comprising benzene and oxazole derivatives as aryl
moieties, the UVꢀirradiation of which results in functionalized naphthalenes with medium to
high yields (reaction C in Scheme 2).20 An important feature of this transformation is its
amenability to scale up (scalable process) and enables to carry out the reaction at the high
concentrations and in the presence of oxygen. Finally, more recently Kawai et al. have published
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the photorearrangement of diarylethenes where their tandem photocyclization and thiophene
ringꢀopening processes lead to the formation of benzothiazole derivatives (reaction D in Scheme
2).21 The high yields of the reaction have been demonstrated by 1H NMRꢀmonitoring.
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Scheme 2. Family of diarylethene photorearrangements.
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The foregoing examples indicate that all these reactions include tandem
photocyclization/sigmatropic rearrangement/ring opening processes (Scheme 2). The reaction
begins by photocyclization of hexatriene system with followed Hꢀshift and the opening of lateral
heterocyclic moiety. The sequence of these processes and their efficiency highly dependent on
some structural features, namely, the lability of the migrating hydrogen atom and the ability to
opening of aromatic (heteroaromatic) ring. However the scarcity of available examples does not
allow assessing the importance and the potential of this reaction. To elucidate these issues and
the opportunity of applications of the reaction in organic synthesis the exploration of the features
and scopes of the process is required. The aim of this research is to study the photorearrangement
of diarylethenes comprising various heterocyclic moieties along with phenyl residue. The design
and elaboration of a new general and effective synthetic process is one of the major challenges in
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modern organic synthesis having a high priority in the development of new technologies, smart
materials and medicines.22
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RESULTS AND DISCUSSION
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To clarify some features of the phototransformation of diarylethenes, namely on the role
and the effect of heterocyclic moiety on the process, a series of diarylethenes that differ only by
the heterocyclic residues was explored. The choice of diarylcyclopentenone derivatives as basic
core for the starting diarylethenes (compounds of general formula 3, Scheme 3) has been caused
by some factors. Firstly, recently we have demonstrated that diarylethenes of this type bearing
oxazole and phenyl residues readily undergo photorearrangement reaction.20 Moreover it was
found that the presence of carbonyl group in the geminal position with respect to phenyl
fragment promotes the process leading to increase in yields of the final products. Another
important argument in favor of such structures is their availability by previously our developed
synthetic protocol.19b To explore the photorearrangement reaction we have synthesized series of
previously unknown (except 3a19b) 2,3ꢀdiarylcyclopentꢀ2ꢀenꢀ1ꢀones 3 starting from ethyl 3ꢀoxoꢀ
4ꢀphenylbutanoate 1 and 2ꢀbromoꢀ1ꢀhetarylethanones 2 (Scheme 3). It was prepared the
diarylethenes comprising 5ꢀmembered heterocycles with both one heteroatom (thiophene, furan,
benzo[b]thiophene, indole) 3a-d, h, and two heteroatoms (imidazole, thiazole, pyrazole) 3e-g, i
with yields ranged from 20 to 53% for two stages.
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Scheme 3. Synthesis and structures of starting compounds.
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The photoreaction of diarylethenes has been performed in conventional glass reactors
(no need to use only quartz glassware, details see in section I in Supporting Information) with
stirring in dichloromethane or toluene solutions under irradiation by UV light (λ = 365 nm, c ≈ 6
* 10ꢀ2 M). In most cases, the irradiation of diarylethene solution leads to the formation of only
product ꢀ 2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthalenꢀ1ꢀone derivatives with good yields (Table 1,
for more clarity, the previously published data for oxazole derivative 3j are also included). The
use of various heterocyclic systems has allowed us to synthesize an indanone analogous of
naphthalene with various functional substituents. The formal opening of the thiophene or
benzothiophene rings (attached to the central double bond of diarylethene by βꢀposition) results
in the formation of the corresponding thiols 4a,c, in the first case the photoreaction product 4a is
a mixture of Eꢀ and Zꢀ isomers. The photoreaction of 3b leads to naphthalene 4b with 2ꢀ
oxopropyl substituent. Similarly with benzothiophene derivative the photorearrangment of indole
diarylethene 3d results in the formation of corresponding amine 4d. The phototransformation of
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azole derivatives with two heteroatoms is similar to the reaction of diarylethenes with one
heteroatom and proceeds with cleavage of carbonꢀheteroatom bond giving amidines 4e,f for
imidazole derivatives, and thioimide 4g for thiazole diarylethene.
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Table 1. Structures of starting compounds 3, photoproducts 4 and their isolated yields.*
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Isolated
Entry No Diarylethene 3 Photoproduct 4
yields
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70%
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69%
55%
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77%**
75%
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80%
g
j
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* Photoreaction was performed in dichloromethane solutions.
** Photoreaction was performed in toluene solution
*** Recently published data [ref. 20]
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As mentioned above the photoreaction products were obtained with sufficiently high
yields that were confirmed by 1H NMR monitoring of reaction process. (1H NMR monitoring of
the process was performed for all substrates; see section IV in Supporting Information). The
monitoring of the reaction process for indole derivative is illustrated in Figure 1. As can be seen
from the figure, the photoreaction proceeds with quantitative conversion of the starting
compound leading to photoproduct and the formation of any byꢀproducts is not observed. A
similar pattern is observed for all other diarylethenes.
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Figure 1. 1H NMR monitoring of diarylethene 3d photoreaction under UVꢀirradiation (λ = 365 nm) in
CDCl3 solution: before irradiation (A) and after 1 h irradiation (B).
The interesting results have been obtained in the irradiation of diarylethene solutions
comprising pyrazole moiety 3i (Scheme 4). Instead of the expected Schiff base 5 aldehyde 6 has
been isolated, wherein the yields in methylene chloride solution (15%) are significantly lower
than in toluene solution (71%). In methylene chloride solution along with aldehyde 6, it was also
observed the formation of numerous side products. The inconsistent result could be explained by
the instability of the photoreaction product 5 in methylene chloride by action of acidic impurities
formed by the decomposition of the solvent.
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Scheme 4. Photoreaction of pyrazole derivative 3i.
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O
O
O
H2O traces
H
O
UV(365 nm)
solvent
N NH
N
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Me
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Ph
Ph
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: 15% (dichloromethane)
71% (toluene)
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unstable
A more complicated pattern was observed in the irradiation of αꢀsubstituted thiophene
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derivative 3h (Scheme 5). H NMR monitoring of the photoprocess showed the formation of
only two photoproducts: dihydronaphthalene 7 and naphtho[2,1ꢀb]thiophene 8 (see section IV in
Supporting Information). These compounds were isolated and their structures were proved by
different spectral methods including 2D NMR experiments (for complete assignments see the
Supporting Information). The mechanism of those products formation is discussed below.
Scheme 5. Photoreaction of thiophene derivative 3h.
To expand the scope of the reaction and to synthesize other polyaromatic systems, we
have performed the photorearrangement of diarylethenes 9 and 10 (Scheme 6). In the first case
instead naphthalene system it has been prepared its isosteric analogue, benzo[b]thiophene
derivative 11. The photoreaction of diarylethene 10 leads to the formation of furanꢀ2(5H)ꢀoneꢀ
annulated naphthalene 12, the structure of the latter was proven by Xꢀray analysis (see Figure S4
in the Supporting Information).23 Both reactions proceed without side processes and the yields of
the final products are rather high. These examples demonstrate the ample opportunities of the
rearrangement including the introduction in the reaction of novel types of diarylethenes leading
to the formation of benzeneꢀannulated heterocycles.
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Scheme 6. Photorearrangement of different substrates.
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The structures of starting diarylethenes 3,9,10 and photoproducts 4,6-8,11,12 have been
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proved by H and 13C NMR and mass spectrometry methods. To prove the structures of some
photoproducts 2D NMR experiments have been also used (compounds 4a and 4e, see Supporting
Information). Furthermore, the structure of compound 4g was unambiguously confirmed by Xꢀ
ray analysis (see Figure S3 in the Supporting Information).23
The foregoing results indicate that the photorearrangement of the diarylethenes with
different heterocycles has a general nature and the formation of a polyaromatic system with
simultaneous opening of heterocyclic ring proceeds by the same mechanism. The proposed
mechanism of the reaction is shown in Scheme 7.
Scheme 7. Proposed mechanism of photorearrangement.
The first stage of the process is 6πꢀelectron conrotatory photocyclization leading to the
formation of intermediate 13. This cyclization is a direct reaction of wellꢀknown photochromic
isomerization which is a typical for diarylethenes.8 At the next stages we propose [1,9]ꢀ
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sigmatropic shift, leading to intermediate 14, and the spontaneous rearomatization of the latter as
a result of migration of a proton and a fiveꢀmembered heterocycle opening.
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This mechanism has been proposed in our previous work.20 In this study, it was found
some evidences in favor of the mechanism, namely regarding the step of sigmatropic
rearrangement. It has been shown that this [1,9]ꢀrearrangement proceeds thermally through
suprafacial shift. In addition the rearrangement product has been isolated and its structure has
been proved by NMR and mass spectrometry methods.
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To study the rearrangement stage we have synthesized diarylethene 3k (Scheme 8) and
its photoreaction under similar conditions has been explored. In previous work it was found that
the photorearrangement of diarylethenes bearing phenyl group at third position compared to
structural isomer compounds (2ꢀphenyl attached diarylethenes) proceeds rather slowly and with
relatively low yields.20
Scheme 8. Photochemical transformation of diarylethene 3k.
In the structure 15 the carbonyl group is not conjugated with cyclohexadiene moiety
which increases the lifetime of this intermediate and allows detecting it by electron spectroscopy
(Figure 2). It was found that the irradiation of the solution of 3k with UV light (λ = 365 nm)
results in the formation of intermediate 15 with absorption maximum at 525 nm. The kinetic
study showed the fast bleaching of the colored intermediate 15 in the absence of irradiation (see
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Figure 2, inset). This result indicates that the rearrangement proceeds thermally via suprafacial
[1,9]ꢀsigmatropic shift, that is in agreement with WoodwardꢀHoffmann rule of conservation of
orbital symmetry.24 According to this rule the [1,9]ꢀH shift is permitted thermally in the case of
suprafacial shift and photochemically only when there is an antarafacial shift.
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Figure 2. UVꢀVis spectra of diarylethene 3k before and after irradiation with UV light (λ = 365 nm) for
10 s in acetonitrile (c = 1.1 × 10−3 M) and thermal decomposition of colored intermediate 15 observed at
525 nm (on inset).
The additional confirmation of the proceeding of [1,9]ꢀsigmatropic shift was obtained by
the photoreaction of diarylethene 3h, containing αꢀthienyl substituent at the central double bond.
As noted above, in the photoreaction of this diarylethene instead of the expected product 19 it
was isolated two products: dihydronaphthalene 7 and naphtho[2,1ꢀb]thiophene 8 (Scheme 9).
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Scheme 9. Photoreaction of inverse thiophene derivative.
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The first two stages of diarylethene 3h photoreaction are also electrocyclization and
[1,9]ꢀsigmatropic shift of a hydrogen atom, leading to the intermediate 18 with antiꢀ
configuration of hydrogen atom and methyl group. The product 7 and intermediate 18 are
diastereoisomers, the conversion of the latter to 7 is likely occurs as a result of the ketoꢀenol
isomerization, leading to a more stable synꢀisomer. Similar transformations have been previously
described for a number of structurally related compounds.25,26 The formation of 8 is the result of
the elimination of a molecule of methane from compound 17 or 7. In particular, by a separate
experiment, it has been shown that the irradiation of solution of 7 under similar conditions leads
to 8.
Thus an expansion of the reaction scope and a more detailed study of separate stages of
this transformation allowed us to clarify some aspects of the process. The driving force of this
rearrangement is the restoration initially of aromaticity of the benzene ring and then of
naphthalene system leading to thermodynamically more stable structure. Another important
condition for the proceeding of this reaction is the opening of a heterocyclic ring with the
cleavage of carbonꢀheteroatom bond. It should be noted that the presence of carbonꢀcarbon bond
instead of carbonꢀheteroatom (diarylethene 3h) prevents the ring opening process and leads to
restoration of aromaticity by elimination of methane molecule, although in the scientific
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literature there is described a close example of carbonꢀcarbon bond cleavage reaction leading to
ring opening.27
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CONCLUSIONS
9
In summary, we have studied a novel photochemical transformation of diarylethenes
comprising fiveꢀmembered heterocyclic ring (thiophene, benzo[b]thiophene, furan, indole,
imidazole, pyrazole, thiazole, pyrazole and oxazole) and benzene derivatives. It was found that
the reaction includes tandem photocyclization/sigmatropic rearrangement/ring opening
processes. Based on this transformation a general and efficient method for the preparation of
functionalized naphthalene derivatives has been proposed. NMR monitoring has indicated that
the process proceeds without side products and with good yields of final products. A high
efficiency of the reaction and opportunity to carry out under mild conditions promises that the
transformation can be an effective practical synthetic protocol for the annulation of the benzene
ring to various aromatic systems, including heterocycles.
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EXPERIMENTAL SECTION
General information. Proton nuclear magnetic resonance spectra (1H NMR) and
carbon nuclear magnetic resonance spectra (13C NMR) were recorded in deuterated solvents on
spectrometers working at 200 MHz or 300 MHz or 400 MHz or 600 MHz for 1H, 75 MHz or 101
MHz or 151 MHz for 13C. Data are represented as follows: chemical shift, multiplicity (s,
singlet; d, doublet; m, multiplet; br, broad), coupling constant in hertz (Hz), integration, and
assignment. Melting points (Mp) were recorded using an apparatus and not corrected. Mass
spectra were obtained on a mass spectrometer (70 eV) with direct sample injection into the ion
source. High resolution mass spectra were obtained from a TOF mass spectrometer with an ESI
source. All chemicals and solvents were purchased from commercial sources and used without
further purification. Silica column chromatography was performed using silica gel 60 (70−230
mesh); TLC analysis was conducted on silica gel 60 F254 plates.
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Photochemical studies. UV−Vis spectra were recorded in 1.0 cm quartz cuvettes. The
experimental measurements were performed at 293 K in the presence of air in solutions of
acetonitrile.
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Photochemical synthesis. Photochemical reactions were performed in the commercial
10 ml flatꢀbottomed glass vessels (for details see section I in Supporting Information). The
irradiation was carried out by 6W UVꢀlamp (365 nm light).
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Synthesis and characterization of starting diarylethenes. Diarylethenes 3a and 3k
were prepared according to literature procedures.19b Diarylethenes 3b-i and 9 were prepared
according previously reported method19b from corresponding ethyl 3ꢀoxoꢀ4ꢀarylbutanoates28 and
corresponding 2ꢀbromoꢀ1ꢀarylethanones. 2ꢀBromoꢀ1ꢀarylethanones were prepared from
corresponding ketones by bromination with Br2 in CHCl3. Diarylethene 10 was synthesized from
phenylacetic acid and 2ꢀbromoꢀ1ꢀ(5ꢀmethylꢀ2ꢀphenylꢀ1,3ꢀoxazolꢀ4ꢀyl)ethanone according
previously reported method.29
2,3-Diarylcyclopent-2-en-1-ones (General procedure). To a solution of ketoester 1
(10 mmol) in absolute benzene (30 mL) sodium (0.23 g, 10 mmol) was added. The reaction
mixture was stirred for 2 h and bromoketone 2 or 23 (10 mmol) was added portionwise. The
mixture was kept overnight, then poured into water (150 mL) and extracted with ethyl acetate (3
× 50 mL). The combined organic phases were washed with water (100 mL) and evaporated in
vacuum. The residue was dissolved in ethanol (37 mL), and a solution of KOH (2.80 g, 50
mmol) in water (37 mL) was added. The reaction mixture was refluxed until completion of the
reaction (monitored by TLC), then cooled, poured into water (100 mL), and extracted with ethyl
acetate (3 × 50 mL). The combined organic phases were washed with water (100 mL), dried with
magnesium sulfate, and evaporated in vacuum. The residue was purified by column
chromatography by petroleum ether/ethyl acetate (2:1 or 3:1 or 4:1).
3ꢀ(2,5ꢀDimethylfuranꢀ3ꢀyl)ꢀ2ꢀphenylcyclopentꢀ2ꢀenꢀ1ꢀone (3b). Yellow amorphous
1
powder, 20% yield (504 mg). H NMR (300 MHz, CDCl3): δ = 2.04 (s, 3H, CH3), 2.18 (s, 3H,
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CH3), 2.61ꢀ2.70 (m, 2H, CH2), 2.90ꢀ3.00 (m, 2H, CH2), 5.69 (s, 1H, Hfuran), 7.22ꢀ7.45 (m, 5H,
Harom). 13C NMR (75 MHz, CDCl3): δ = 13.2, 14.2, 30.0, 34.7, 106.3, 117.8, 127.5, 128.3, 129.3,
133.0, 138.2, 150.4, 150.5, 162.5, 207.2. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C17H17O2
253.1223; Found 253.1220. MS (EI): m/z (%) = 252 (15) [M]+, 237 (10) [MꢀCH3]+, 43 (100).
3ꢀ(2ꢀHeptylꢀ1ꢀbenzothiophenꢀ3ꢀyl)ꢀ2ꢀphenylcyclopentꢀ2ꢀenꢀ1ꢀone (3c). White powder,
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26% yield (1.01 g). Mp 95ꢀ98 °C. H NMR (300 MHz, CDCl3): δ = 0.89 (t, J = 6.9 Hz, 3H,
CH3), 1.03ꢀ1.51 (m, 10H, (CH2)5), 2.31ꢀ2.65 (m, 2H, CH2), 2.73ꢀ2.91 (m, 3H, ½ CH2+CH2),
3.16ꢀ3.33 (m, 1H, ½ CH2), 7.13ꢀ7.40 (m, 7H, Harom), 7.50ꢀ7.59 (m, 1H, Harom), 7.76ꢀ7.87 (m, 1H,
Harom). 13C NMR (75 MHz, CDCl3): δ = 14.1, 22.6, 29.0, 29.3, 29.4, 31.3, 31.7, 35.4, 51.0,
121.8, 122.4, 124.0, 124.5, 127.1, 127.9, 128.1, 128.5, 128.8, 129.4, 131.4, 134.3, 138.5, 138.9,
142.6, 143.0, 166.3, 207.2. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C26H29OS 389.1934;
Found 389.1928. MS (EI): m/z (%) = 388 (95) [M]+, 289 (100) [MꢀC7H15]+.
3ꢀ(1,2ꢀDimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ2ꢀphenylcyclopentꢀ2ꢀenꢀ1ꢀone (3d). Yellow powder,
29% yield (873 mg). Mp 196ꢀ198 °C. 1H NMR (300 MHz, CDCl3): δ = 1.81 (s, 3H, CH3), 2.71ꢀ
2.83 (m, 2H, CH2), 3.18ꢀ3.28 (m, 2H, CH2), 3.62 (s, 3H, CH3), 7.13ꢀ7.37 (m, 8H, Harom), 7.61 (d,
J = 7.8 Hz, 1H, Harom). 13C NMR (75 MHz, CDCl3): δ = 11.9, 29.8, 31.3, 35.5, 109.2, 109.7,
119.7, 120.3, 121.5, 126.3, 127.0, 128.2, 129.1, 133.5, 135.8, 137.5, 137.8, 167.0, 207.5. HRMS
(ESIꢀTOF) m/z: [M + H]+ Calcd for C21H20NO 302.1539; Found 302.1543. MS (EI): m/z (%) =
301 (50) [M]+, 45 (100).
3ꢀ(1,5ꢀDimethylꢀ2ꢀphenylꢀ1Hꢀimidazolꢀ4ꢀyl)ꢀ2ꢀphenylcyclopentꢀ2ꢀenꢀ1ꢀone
(3e).
1
Yellow powder, 53% yield (1.74 g). Mp 148ꢀ150 °C. H NMR (300 MHz, CDCl3): δ = 1.50 (s,
3H, CH3), 2.61ꢀ2.71 (m, 2H, CH2), 3.12ꢀ3.22 (m, 2H, CH2), 3.48 (s, 3H, CH3), 7.24ꢀ7.38 (m, 5H,
Harom), 7.41ꢀ7.52 (m, 3H, Harom), 7.62 (d, J = 6.7 Hz, 2H, Harom). 13C NMR (75 MHz, CDCl3): δ =
10.4, 29.9, 31.9, 34.9, 127.2, 128.3, 128.6, 128.7, 128.9 (2C), 129.2, 130.5, 133.6, 133.9, 137.0,
148.4, 165.1, 207.9. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C22H21N2O 329.1648; Found
329.1643. MS (EI): m/z (%) = 328 (100) [M]+, 313 (40) [MꢀCH3]+.
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3ꢀ(1,2ꢀDiphenylꢀ5ꢀmethylꢀ1Hꢀimidazolꢀ4ꢀyl)ꢀ2ꢀphenylcyclopentꢀ2ꢀenꢀ1ꢀone (3f). White
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powder, 49% yield (1.91 g). Mp 155ꢀ157 °C. H NMR (300 MHz, CDCl3): δ = 1.32 (s, 3H,
CH3), 2.69ꢀ2.80 (m, 2H, CH2), 3.30ꢀ3.43 (m, 2H, CH2), 7.06ꢀ7.58 (m, 15H, Harom). 13C NMR (75
MHz, CDCl3): δ = 10.9, 29.8, 35.0, 127.3, 127.8, 128.2 (2C), 128.3, 128.4, 129.0, 129.3, 129.7,
130.1, 130.4, 133.5, 134.4, 136.8, 137.6, 147.5, 164.9, 207.9. HRMS (ESIꢀTOF) m/z: [M + H]+
Calcd for C27H23N2O 391.1805; Found 391.1804. MS (EI): m/z (%) = 390 (30) [M]+, 180 (95),
77 (100) [C6H5]+.
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3ꢀ(4ꢀMethylꢀ2ꢀphenylꢀ1,3ꢀthiazolꢀ5ꢀyl)ꢀ2ꢀphenylcyclopentꢀ2ꢀenꢀ1ꢀone (3g). Yellow
1
crystals, 39% yield (1.29 g). Mp 92ꢀ94 °C. H NMR (200 MHz, CDCl3): δ = 2.04 (s, 3H, CH3),
2.68ꢀ2.81 (m, 2H, CH2), 2.99ꢀ3.14 (m, 2H, CH2), 7.23ꢀ7.54 (m, 8H, Harom), 7.82ꢀ7.97 (m, 2H,
H
arom). 13C NMR (75 MHz, CDCl3): δ = 17.6, 32.1, 35.0, 126.5, 127.8, 128.3, 128.7, 129.0,
129.2, 130.5, 131.9, 133.0, 140.8, 152.9, 159.5, 168.2, 206.2. HRMS (ESIꢀTOF) m/z: [M + H]+
Calcd for C21H18NOS 332.1104; Found 332.1098. MS (EI): m/z (%) = 331 (85) [M]+, 316 (50)
[MꢀCH3]+, 77 (100) [C6H5]+.
3ꢀ(3,5ꢀDimethylthiophenꢀ2ꢀyl)ꢀ2ꢀphenylcyclopentꢀ2ꢀenꢀ1ꢀone (3h). Yellow powder,
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37% yield (992 mg). Mp 114ꢀ117 °C. H NMR (300 MHz, CDCl3): δ = 1.67 (s, 3H, CH3), 2.45
(s, 3H, CH3), 2.64ꢀ2.77 (m, 2H, CH2), 2.95ꢀ3.08 (m, 2H, CH2), 6.48 (s, 1H, Hthiophene), 7.23ꢀ7.41
(m, 5H, Harom). 13C NMR (75 MHz, CDCl3): δ = 15.4, 16.0, 32.0, 35.0, 127.7, 128.4, 129.3,
130.2, 131.1, 132.8, 138.1, 138.6, 142.3, 162.8, 206.8. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd
for C17H17OS 269.0995; Found 269.0995. MS (EI): m/z (%) = 268 (90) [M]+, 253 (30) [Mꢀ
CH3]+, 211 (100).
3ꢀ(5ꢀMethylꢀ1ꢀphenylꢀ1Hꢀpyrazolꢀ4ꢀyl)ꢀ2ꢀphenylcyclopentꢀ2ꢀenꢀ1ꢀone
(3i).
White
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crystals, 44 % yield (1.38 g). Mp 138ꢀ141 °C. H NMR (300 MHz, CDCl3): δ = 1.82 (s, 3H,
CH3), 2.67ꢀ2.78 (m, 2H, CH2), 3.01ꢀ3.13 (m, 2H, CH2), 7.24ꢀ7.50 (m, 10H, Harom), 7.64 (s, 1H,
Hpyrazole). 13C NMR (75 MHz, CDCl3): δ = 12.6, 30.3, 34.7, 117.5, 125.2, 127.7, 128.3, 128.6,
129.2 (2C), 133.1, 137.7, 138.1, 139.0, 139.8, 161.9, 206.8. HRMS (ESIꢀTOF) m/z: [M + H]+
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Calcd for C21H19N2O 315.1492; Found: 315.1486. MS (EI): m/z (%) = 314 (35) [M]+, 299 (10)
[MꢀCH3]+, 77 (100) [C6H5]+.
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3ꢀ(5ꢀMethylꢀ2ꢀphenylꢀ1,3ꢀoxazolꢀ4ꢀyl)ꢀ2ꢀthiophenꢀ3ꢀylcyclopentꢀ2ꢀenꢀ1ꢀone (9). Yellow
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powder, 25% yield (803 mg). Mp 155ꢀ157 °C. H NMR (300 MHz, CDCl3): δ = 1.91 (s, 3H,
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CH3), 2.65ꢀ2.72 (m, 2H, CH2), 3.05ꢀ3.12 (m, 2H, CH2), 7.13 (d, J = 5.0 Hz, 1H, Hthiophene), 7.26ꢀ
7.33 (m, 1H, Hthiophene), 7.43ꢀ7.52 (m, 3H, Harom), 7.62ꢀ7.68 (m, 1H, Hthiophene), 8.00ꢀ8.10 (m, 2H,
Harom). 13C NMR (75 MHz, CDCl3): δ = 11.7, 29.3, 34.6, 125.0, 125.2, 126.2, 127.0, 127.7,
128.8, 130.5, 131.9, 133.2, 134.6, 148.0, 159.6, 160.7, 207.2. HRMS (ESIꢀTOF) m/z: [M + Na]+
Calcd for C19H15NO2SNa 344.0716; Found 344.0705. MS (EI): m/z (%) = 321 (20) [M]+, 43
(100).
4ꢀ(5ꢀMethylꢀ2ꢀphenylꢀ1,3ꢀoxazolꢀ4ꢀyl)ꢀ3ꢀphenylfuranꢀ2(5H)ꢀone (10). Yellow crystals,
1
56% yield (890 mg) obtained from 5 mmol of initial phenylacetic acid. Mp 197ꢀ200 °C. H
NMR (300 MHz, CDCl3): δ = 1.79 (s, 3H, CH3), 5.24 (s, 2H, CH2), 7.33ꢀ7.67 (m, 8H, Harom),
7.91ꢀ8.11 (m, 2H, Harom). 13C NMR (75 MHz, CDCl3): δ = 12.0, 70.8, 125.3, 126.2, 126.4, 126.7,
128.6, 128.8, 128.9, 129.1, 129.3, 130.7, 148.9, 149.3, 160.9, 173.3. HRMS (ESIꢀTOF) m/z: [M
+ H]+ Calcd for C20H16NO3 318.1125; Found 318.1121. MS (EI): m/z (%) = 317 (100) [M]+.
Photochemical rearrangement of diarylethenes (General Procedure). Diarylethene
(0.5 mmol) was dissolved in 8 ml of appropriate solvent (dichloromethane or toluene) and the
reaction mixture was irradiated (UV, λ = 365 nm, 6W) with stirring in 10 ml flatꢀbottomed glass
vessel. After completion of the reaction (TLC control) the solution was evaporated under
vacuum, the residue was purified by column chromatography eluting by light petroleum ꢀ ethyl
acetate (compounds 4a-d,6-8,19) or by recrystallization from small amount of CH2Cl2
(compounds 4e-g,11,12).
5ꢀMethylꢀ4ꢀ(2ꢀsulfanylpropꢀ1ꢀenꢀ1ꢀyl)ꢀ2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthalenꢀ1ꢀone
(4a). Diarylethene 3a, solvent: dichloromethane, irradiation time: 6 h. It was isolated mixture of
Eꢀ and Zꢀ isomers (for more details see section II.4 in Supporting Information). Light yellow
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powder (93 mg, 70%). Mp 97ꢀ100 °C. Zꢀisomer (65%). 1H NMR (300 MHz, CDCl3): δ = 2.31 (s,
3H, CH3), 2.70 (s, 3H, CH3), 2.72ꢀ2.80 (m, 2H, CH2), 2.76 (s, 1H, SH), 3.02ꢀ3.10 (m, 2H, CH2),
6.43 (s, 1H, CH), 7.55ꢀ7.71 (m, 2H, Harom), 8.11 (d, J = 7.9 Hz, 1H, Harom), 9.24 (d, J = 8.1 Hz,
1H, Harom). 13C NMR (75 MHz, CDCl3): δ = 16.6, 25.5, 26.4, 36.7, 120.2, 124.3, 124.7, 126.5,
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128.2, 128.8, 129.4, 132.2, 132.4, 133.3, 141.1, 158.4, 207.5. Eꢀisomer (35%). H NMR (300
MHz, CDCl3): δ = 1.83 (s, 3H, CH3), 2.66 (s, 3H, CH3), 2.72ꢀ2.80 (m, 2H, CH2), 2.95ꢀ3.02 (m,
2H, CH2), 3.10 (s, 1H, SH), 6.58 (s, 1H, CH), 7.55ꢀ7.71 (m, 2H, Harom), 8.09 (d, J = 7.3 Hz, 1H,
Harom), 9.24 (d, J = 8.1 Hz, 1H, Harom). 13C NMR (75 MHz, CDCl3): δ = 16.9, 22.5, 25.8, 36.7,
122.8, 124.2, 124.6, 126.6, 128.2, 128.6, 128.8, 132.1, 132.3, 133.3, 140.5, 158.3, 207.4. HRMS
(ESIꢀTOF) m/z: [M + H]+ Calcd for C17H17OS 269.0995; Found 269.0997. MS (EI): m/z (%) =
268 (100) [M]+, 253 (10) [MꢀCH3]+.
5ꢀMethylꢀ4ꢀ(2ꢀoxopropyl)ꢀ2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthalenꢀ1ꢀone
(4b).
Diarylethene 3b, solvent: dichloromethane, irradiation time: 8 h. White powder (87 mg, 69%).
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Mp 155ꢀ157 °C. H NMR (300 MHz, CDCl3): δ = 2.29 (s, 3H, CH3), 2.65 (s, 3H, CH3), 2.71ꢀ
2.85 (m, 2H, CH2), 2.96ꢀ3.11 (m, 2H, CH2), 4.02 (s, 2H, CH2), 7.55ꢀ7.73 (m, 2H, Harom), 8.10 (d,
J = 8.2 Hz, 1H, Harom), 9.25 (d, J = 8.0 Hz, 1H, Harom). 13C NMR (75 MHz, CDCl3): δ = 16.1,
25.5, 29.8, 36.6, 44.8, 124.3 (2C), 126.7, 128.1, 128.2, 128.8, 129.5, 132.2, 141.3, 157.9, 204.9,
207.2. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C17H17O2 253.1223; Found 253.1225. MS
(EI): m/z (%) = 252 (45) [M]+, 209 (100).
5ꢀHeptylꢀ4ꢀ(2ꢀsulfanylphenyl)ꢀ2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthalenꢀ1ꢀone (4c).30
Diarylethene 3c, solvent: dichloromethane, irradiation time: 7 h. Yellow amorphous powder (107
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mg, 55%). H NMR (300 MHz, CDCl3): δ = 0.88 (t, J = 6.8 Hz, 3H, CH3), 1.13ꢀ1.40 (m, 8H,
(CH2)4), 1.51ꢀ1.78 (m, 2H, CH2), 2.68ꢀ3.11 (m, 6H, CH2), 3.17 (s, 1H, SH), 7.18ꢀ7.37 (m, 3H,
Harom), 7.46ꢀ7.49 (m, 1H, Harom), 7.62ꢀ7.75 (m, 2H, Harom), 8.17 (d, J = 8.3 Hz, 1H, Harom), 9.35
(d, J = 7.8 Hz, 1H, Harom). 13C NMR (75 MHz, CDCl3): δ = 14.1, 22.6, 25.6, 28.7, 30.1, 30.5,
30.8, 31.6, 36.8, 124.6, 124.9, 125.7, 126.7, 128.5, 128.6, 128.8, 129.1, 129.8, 130.2, 131.6,
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131.9, 135.1, 136.5, 146.0, 157.9, 207.4. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C26H29OS:
389.1934; Found: 389.1935; m/z: [M + H2O + H]+ Calcd for C26H31O2S 407.2039; Found
407.2033. MS (EI): m/z (%) = 388 (65) [M]+, 247 (100).
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5ꢀMethylꢀ4ꢀ[2ꢀ(methylamino)phenyl]ꢀ2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthalenꢀ1ꢀone
(4d). Diarylethene 3d, solvent: toluene, irradiation time: 5 h. White powder (116 mg, 77%). Mp
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180ꢀ183 °C. H NMR (300 MHz, CDCl3): δ = 2.55 (s, 3H, CH3), 2.66ꢀ2.85 (m, 4H, CH2), 2.80
(s, 3H, CH3), 6.81ꢀ6.94 (m, 2H, Harom), 7.02 (d, J = 7.3 Hz, 1H, Harom), 7.35ꢀ7.44 (m, 1H, Harom),
7.60ꢀ7.76 (m, 2H, Harom), 8.15 (d, J = 8.4 Hz, 1H, Harom), 9.30 (d, J = 8.2 Hz, 1H, Harom). 13C
NMR (75 MHz, CDCl3): δ = 16.7, 25.7, 30.8, 36.7, 110.3, 117.4, 123.7, 124.4, 124.7, 126.6,
128.5, 129.1, 129.2, 129.6, 129.8, 132.3, 133.7, 142.0, 145.9, 159.1, 207.6. HRMS (ESIꢀTOF)
m/z: [M + H]+ Calcd for C21H20NO 302.1539; Found 302.1537. MS (EI): m/z (%) = 301 (100)
[M]+, 286 (20) [MꢀCH3]+.
NꢀMethylꢀN'ꢀ(5ꢀmethylꢀ1ꢀoxoꢀ2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthalenꢀ4ꢀ
yl)benzenecarboximidamide (4e). Diarylethene 3e, solvent: dichloromethane, irradiation time: 5
h. White crystals (123 mg, 75%). Mp 165–167°C. For 2D NMR HSQC and NOESY data see
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section II.5 in Supporting Information. H NMR (600 MHz, DMSOꢀd6): δ = 2.39 (s, 3H, CH3),
2.57ꢀ2.66 (m, 2H, CH2), 2.69ꢀ2.83 (m, 1H, ½ CH2), 2.96 (br s, 3H, CH3), 2.90ꢀ3.02 (m, 1H, ½
CH2), 7.14ꢀ7.35 (m, 6H, NH+Harom), 7.40ꢀ7.54 (m, 2H, Harom), 7.84ꢀ7.95 (m, 1H, Harom), 8.90ꢀ
9.01 (m, 1H, Harom). 13C NMR (75 MHz, DMSOꢀd6): δ = 14.5, 25.0, 29.2, 36.9, 123.4, 124.2,
125.5, 125.7, 126.5, 127.8, 128.6, 128.7, 128.9, 129.8, 133.1, 136.0, 146.0, 154.9, 158.2, 207.5.
HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C22H21N2O 329.1648; Found 329.1651. MS (EI):
m/z (%) = 328 (10) [M]+, 313 (10) [MꢀCH3]+, 119 (100).
NꢀPhenylꢀN'ꢀ(5ꢀmethylꢀ1ꢀoxoꢀ2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthalenꢀ4ꢀ
yl)benzenecarboximidamide (4f). Diarylethene 3f, solvent: dichloromethane, irradiation time: 5
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h. White crystals (119 mg, 61%). Mp 217ꢀ220 °C. (The temperatureꢀdependence of H NMR
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spectrum of 4f see section V in Supporting Information). H NMR (400 MHz, CDCl3, 333 K): δ
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= 2.62 (s, 3H, CH3), 2.63ꢀ2.70 (m, 2H, CH2), 2.93ꢀ3.15 (m, 2H, CH2), 6.99ꢀ7.10 (m, 1H, Harom),
7.16ꢀ7.59 (m, 11H, Harom), 7.93ꢀ8.03 (m, 1H, Harom), 9.10ꢀ9.19 (m, 1H, Harom). 13C NMR (100
MHz, CDCl3, 333 K): δ = 14.2, 24.6, 36.7, 123.6, 123.7, 124.2, 126.3, 126.7, 128.5, 128.9,
129.2, 129.6, 129.7, 130.0, 130.1, 133.1, 134.9, 153.0, 154.9, 206.9. HRMS (ESIꢀTOF) m/z: [M
+ H]+ Calcd for C27H23N2O 391.1805; Found 391.1799. MS (EI): m/z (%) = 390 (20) [M]+, 298
(75) [MꢀCH3ꢀC6H5]+, 77 (100) [C6H5]+.
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5ꢀMethylꢀ1ꢀoxoꢀ2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthalenꢀ4ꢀyl
benzenecarbimidothioate (4g). Diarylethene 3g, solvent: dichloromethane, irradiation time: 5 h.
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Light yellow powder (130 mg, 79%). Mp 136ꢀ138 °C. H NMR (300 MHz, CDCl3): δ = 2.75ꢀ
2.88 (m, 2H, CH2), 2.99 (s, 3H, CH3), 3.14ꢀ3.26 (m, 2H, CH2), 7.50ꢀ7.89 (m, 5H, Harom), 8.15ꢀ
8.30 (m, 3H, Harom), 9.33 (d, J = 8.4 Hz, 1H, Harom). 13C NMR (75 MHz, CDCl3): δ = 18.0, 26.5,
36.6, 121.9, 124.7, 125.5, 127.5, 128.8, 130.3, 130.4, 131.4, 131.9, 132.4, 132.7, 135.8, 137.2,
151.5, 161.1, 206.6. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C21H18NOS 332.1104; Found
332.1107. MS (EI): m/z (%) = 331 (5) [M]+, 316 (10) [MꢀCH3]+, 228 (90) [MꢀPhCN]+, 103 (100)
[PhCN]+.
5ꢀMethylꢀ4ꢀ(2ꢀoxopropyl)ꢀ1,2ꢀdihydroꢀ3Hꢀcyclopenta[a]naphthalenꢀ3ꢀone
(4k).
Diarylethene 3k, solvent: dichloromethane, irradiation time: 20 h. Yellow powder (31 mg, 25%).
Mp 150 °C. 1H NMR (300 MHz, CDCl3): δ = 2.35 (s, 3H, CH3), 2.57 (s, 3H, CH3), 2.75ꢀ2.86 (m,
2H, CH2), 3.34ꢀ3.44 (m, 2H, CH2), 4.55 (s, 2H, CH2), 7.58ꢀ7.75 (m, 2H, Harom), 8.07 (d, J = 8.0
Hz, 1H, Harom), 8.14 (d, J = 8.5 Hz, 1H, Harom). 13C NMR (75 MHz, CDCl3): δ = 14.2, 23.4, 29.8,
36.6, 42.9, 124.7, 125.3, 126.3, 127.4, 129.4, 129.8, 132.0, 133.4, 135.7, 155.8, 206.1, 207.9.
HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C17H17O2 253.1223; Found 253.1239. MS (EI): m/z
(%) = 252 (25) [M]+, 210 (100).
5ꢀMethylꢀ1ꢀoxoꢀ2,3ꢀdihydroꢀ1Hꢀcyclopenta[a]naphthaleneꢀ4ꢀcarbaldehyde
(6).
Diarylethene 3i, solvent: dichloromethane, irradiation time: 15 h. (17 mg, 15%); solvent: toluene,
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irradiation time: 10 h. (80 mg, 71%). White powder. Mp 172ꢀ175 °C. H NMR (300 MHz,
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CDCl3): δ = 2.71ꢀ2.87 (m, 2H, CH2), 3.10 (s, 3H, CH3), 3.44ꢀ3.57 (m, 2H, CH2), 7.60ꢀ7.87 (m,
2H, Harom), 8.27 (d, J = 8.2 Hz, 1H, Harom), 9.32 (d, J = 8.4 Hz, 1H, Harom), 10.85 (s, 1H, CH). 13C
NMR (75 MHz, CDCl3): δ = 14.6, 26.4, 36.7, 124.5, 125.2, 127.4, 128.7, 129.7, 130.2, 131.2,
132.0, 148.2, 157.5, 191.8, 207.1. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C15H13O2
225.0910; Found 225.0919. MS (EI): m/z (%) = 224 (100) [M]+.
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2,10bꢀDimethylꢀ3a,9,10,10bꢀtetrahydroꢀ8Hꢀcyclopenta[3,4]naphtho[2,1ꢀb]thiopheneꢀ8ꢀ
one (7), racemic mixture of (R,S) and (S,R) isomers. Diarylethene 3h, solvent: dichloromethane,
irradiation time: 10 h. Yellow powder (26 mg, 20%). Mp 185ꢀ7 °C. 1H NMR (600 MHz, CDCl3):
δ = 1.46 (s, 3H, CH3), 1.96ꢀ1.98 (m, 3H, CH3), 2.59ꢀ2.67 (m, 3H, CH2 + ½CH2), 2.75ꢀ2.83 (m,
1H, ½CH2), 4.63 (s, 1H, CH), 5.60ꢀ5.62 (m, 1H, CH), 7.25ꢀ7.34 (m, 3H, Harom), 8.48 (d, J = 7.5
Hz, 1H, Harom). 13C NMR (150 MHz, CDCl3): δ = 16.7, 28.6, 29.1, 35.8, 54.1, 58.1, 124.2, 125.8,
126.2, 126.7, 127.6, 129.0, 133.0, 136.5, 140.0, 167.3, 206.2. HRMS (ESIꢀTOF) m/z: [M + H]+
Calcd for C17H17OS 269.0995; Found 269.0990. MS (EI): m/z (%) = 268 (85) [M]+, 253 (70) [Mꢀ
CH3]+, 211 (100).
2ꢀMethylꢀ9,10ꢀdihydroꢀ8Hꢀcyclopenta[3,4]naphtho[2,1ꢀb]thiopheneꢀ8ꢀone
(8).
Diarylethene 3h, solvent: dichloromethane, irradiation time: 10 h. Yellow crystals, (57 mg,
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45%). Mp 179ꢀ181°C. H NMR (400 MHz, CDCl3): δ = 2.78 (s, 3H, CH3), 2.85ꢀ2.91 (m, 2H,
CH2), 3.21ꢀ3.27 (m, 2H, CH2), 7.60ꢀ7.67 (m, 2H, Harom), 7.71 (s, 1H, Harom), 8.25 (d, J = 8.3 Hz,
1H, Harom), 9.29 (d, J = 7.4 Hz, 1H, Harom). 13C NMR (100 MHz, CDCl3): δ = 16.7, 24.9, 36.5,
121.5, 123.6, 124.7, 126.6, 127.2, 127.3, 127.4, 128.3, 133.2, 141.9, 146.0, 153.5, 206.2. HRMS
(ESIꢀTOF) m/z: [M + H]+ Calcd for C16H13OS 253.0682; Found 253.0683. MS (EI): m/z (%) =
252 (100) [M]+.
Nꢀ(4ꢀMethylꢀ8ꢀoxoꢀ7,8ꢀdihydroꢀ6Hꢀindeno[5,4ꢀb]thiophenꢀ5ꢀyl)benzamide
(11).
Diarylethene 9, solvent: dichloromethane, irradiation time: 5 h. Yellow crystals, (136 mg, 85%).
Mp 264ꢀ266 °C. 1H NMR (300 MHz, DMSOꢀd6): δ = 2.55 (s, 3H, CH3), 2.66ꢀ2.82 (m, 2H, CH2),
3.00ꢀ3.20 (m, 2H, CH2), 7.50ꢀ7.71 (m, 3H, Harom), 7.96ꢀ8.19 (m, 4H, Harom), 10.25 (s, 1H, NH).
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13C NMR (75 MHz, DMSOꢀd6): δ = 17.4, 24.6, 36.5, 122.0, 128.1, 128.2, 129.0, 129.4, 130.7,
132.3, 133.3, 134.5, 136.7, 141.2, 153.7, 166.2, 205.6. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd
for C19H15NO2SNa 344.0716; Found 344.0708. MS (EI): m/z (%) = 321 (50) [M]+, 105 (100)
[C6H5CO]+.
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Nꢀ(5ꢀmethylꢀ1ꢀoxoꢀ1,3ꢀdihydronaphtho[1,2ꢀc]furanꢀ4ꢀyl)benzamide (12). Diarylethene
10, solvent: dichloromethane, irradiation time: 5 h. White crystals, (142 mg, 90%). Mp 242ꢀ244
°C. 1H NMR (300 MHz, DMSOꢀd6): δ = 2.70 (s, 3H, CH3), 5.43 (s, 2H, CH2), 7.50ꢀ7.90 (m, 5H,
Harom), 7.99ꢀ8.19 (m, 2H, Harom), 8.22ꢀ8.38 (m, 1H, Harom), 8.81ꢀ9.00 (m, 1H, Harom), 10.47 (s,
1H, NH). 13C NMR (75 MHz, DMSOꢀd6): δ = 14.9, 69.0, 118.0, 123.0, 126.1, 127.7, 127.8,
128.3, 128.4, 128.8, 129.0, 132.4, 133.3, 134.1, 139.2, 148.3, 166.2, 171.3. HRMS (ESIꢀTOF)
m/z: [M + H]+ Calcd for C20H16NO3 318.1125; Found 318.1125. MS (EI): m/z (%) = 317 (100)
[M]+.
ASSOCIATED CONTENT
Supporting Information
This material is available free of charge via the Internet at http://pubs.acs.org.
1H, 13C NMR and HRMS spectra for new compounds; 2D NMR characterization of
1
photoproducts 4a, 4e, 7, 8; H NMR monitoring of photoreaction for diarylethenes 3 (PDF).
Crystallographic files for compounds 4g and 12 (CIF).
AUTHOR INFORMATION
Corresponding Author:
Prof. Valerii Shirinian
*Eꢀmail: svbegunt@mail.ru
*Eꢀmail: shir@ioc.ac.ru
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ACKNOWLEDGMENT
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Authors thank the Russian Foundation for Basic Research (RFBR grant 15ꢀ03ꢀ05546) for
financial support of this study. This work was also partly financially supported by the Russian
Science Foundation (RSF grant 14ꢀ50ꢀ00126) in regard with the characterization of the
compounds obtained.
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23. Crystallographic data were deposited with the Cambridge Crystallographic Data Centre
(CCDC No. 1420922 (4g) and 1420923 (12)). For details see section III in Supporting
Information.
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30. Photoproduct 4c is unstable in the air due to oxidation and forming of appropriate disulfide.
This was proved by MS characterization of decomposition product: HRMS (ESIꢀTOF) m/z:
[M+H]+ Calcd for C52H55O2S2 775.3638; Found 775.3612. For spectrum see section VIII in
Supporting Information.
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