A Facile Synthesis of Tetra- and Dihydronaphthalene Derivatives by Excimer Laser Photolysis of 1,2-Bis(substituted-methyl)benzenes in the Presence of Olefins and Acetylene

Article abstract of DOI:10.1021/jo970953o

o-Quinodimethane (3A) was generated effectively by excimer laser photolyses of 1,2-bis(phenoxymethyl)benzene (1-O), 1,2-bis[(phenylthio)methyl]benzene (1-S), and 1,2-bis[(phenylseleno)methyl]-benzene (1-Se) in acetonitrile solutions via a two-photon process, which was followed by cycloaddition of 3A with several dienophlles-maleic anhydride (4a), dimethyl maleate (4b), dimethyl fumarate (4c), fumaronitrile (4d), and dimethyl acetylenedicarboxylate (4e) - to give corresponding cycloadducts 5. Three kinds of excimer lasers, namely, KrF (248 nm), XeCl (308 nm), and XeF (351 nm) excimer lasers were used for the reaction. The KrF excimer laser was found to be most effective for obtaining high consumption of 1-(O, S, Se) and yield of 5; the maximum yield of the cycloadduct obtained was 48%.

Full text of DOI:10.1021/jo970953o

7376
J . Org. Chem. 1997, 62, 7376-7383
A F a cile Syn th esis of Tetr a - a n d Dih yd r on a p h th a len e Der iva tives
by Excim er La ser P h otolysis of
1,2-Bis(su bstitu ted -m eth yl)ben zen es in th e P r esen ce of Olefin s a n d
Acetylen e†
Akihiko Ouchi* and Yoshinori Koga
National Institute of Materials and Chemical Research, AIST, MITI, Tsukuba, Ibaraki 305, J apan
Received May 29, 1997X
o-Quinodimethane (3A) was generated effectively by excimer laser photolyses of 1,2-bis(phenoxy-
methyl)benzene (1-O), 1,2-bis[(phenylthio)methyl]benzene (1-S), and 1,2-bis[(phenylseleno)methyl]-
benzene (1-Se) in acetonitrile solutions via a two-photon process, which was followed by cycloaddition
of 3A with several dienophilessmaleic anhydride (4a ), dimethyl maleate (4b), dimethyl fumarate
(4c), fumaronitrile (4d ), and dimethyl acetylenedicarboxylate (4e)sto give corresponding cycload-
ducts 5. Three kinds of excimer lasers, namely, KrF (248 nm), XeCl (308 nm), and XeF (351 nm)
excimer lasers were used for the reaction. The KrF excimer laser was found to be most effective
for obtaining high consumption of 1-(O, S, Se) and yield of 5; the maximum yield of the cycloadduct
obtained was 48%.
Sch em e 1
In tr od u ction
Recent studies on the application of lasers to organic
photochemistry have revealed the occurrence of many
reactions which only proceed by the use of lasers.1 The
difference between such laser reactions and conventional
photolyses is that the former can provide more precise
control over the reactions of intermediates2-5 and/or
excited states6,7 which are involved in the photochemical
processes. However, in spite of the findings of the laser
specific reactions only a few can be employed as useful
synthetic purposes.
† Dedicated to Professor Waldemar Adam on the occasion of his 60th
birthday.
X Abstract published in Advance ACS Abstracts, August 15, 1997.
(1) Reviews: (a) Kleinermanns, K.; Wolfrum, J . Angew. Chem., Int.
Ed. Engl. 1987, 26, 38-58. (b) Wilson, R. M.; Schnapp, K. A.;
Hannemann, K.; Ho, D. M.; Memarian, H. R.; Azadnia, A.; Pinhas, A.
R.; Figley, T. M. Spectrochim. Acta, Part A 1990, 46, 551-558. (c)
Wilson, R. M.; Adam, W.; Schulte Oestrich, R. Spectrum 1991, 4, 8-17.
(d) Wilson, R. M.; Schnapp, K. A. Chem. Rev. 1993, 93, 223-249. (e)
J ohnston, L. J . Chem. Rev. 1993, 93, 251-266.
(2) Laser-jet photolysis: e.g. (a) Wilson, R. M.; Romanova, T. N.;
Azadnia, A.; Bauer, J . A. K.; J ohnson, R. P. Tetrahedron Lett. 1994,
35, 5401-5404. (b) Adam, W.; Kita, F. J . Am. Chem. Soc. 1994, 116,
3680-3683. (c) Adam, W.; Kita, F.; Schulte Oestrich, R. J . Photochem.
Photobiol. A 1994, 80, 187-197. (d) Adam, W.; Patterson, J . J . Org.
Chem. 1995, 60, 7769-7773. (e) Wilson, R. M.; Patterson, W. S.;
Austen, S. C.; Ho, D. M.; Bauer, J . A. K. J . Am. Chem. Soc. 1995, 117,
7820-7821. (f) Adam, W.; Walther, B. Tetrahedron 1996, 52, 10399-
10404. (g) Schnapp, K. A.; Motz, P. L.; Stoeckel, S. M.; Wilson, R. M.;
Bauer, J . A. K.; Bohne, C. Tetrahedron Lett. 1996, 37, 2317-2320.
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Chem. Soc. 1993, 115, 6409-6413. (b) Scaiano, J . C.; Banks, J . T. J .
Braz. Chem. Soc. 1995, 6, 199-210. (c) Banks, J . T.; Scaiano, J . C. J .
Phys. Chem. 1995, 99, 3527-3531. (d) Banks, J . T.; Scaiano, J . C. J .
Photochem. Photobiol. A. 1996, 96, 31-33.
(4) Two-color, two-pulse photolysis: (a) Netto-Ferreira, J . C.;
Wintgens, V.; Scaiano, J . C. Tetrahedron Lett. 1989, 30, 6851-6854.
(b) Bendig, J .; Mitzner, R. Ber. Bunsen-Ges. Phys. Chem. 1994, 98,
1004-1008. (c) Ouchi, A.; Yabe, A. Chem. Lett. 1995, 945-946. (d)
Ouchi, A.; Koga, Y. Tetrahedron Lett. 1995, 36, 8999-9002.
(5) Laser photolysis: e.g. (a) Alkenings, B.; Bettermann, H.; Dasting,
I.; Schroers, H.-J . Vib. Spectrosc. 1993, 5, 43-49. (b) Pe´rez-Prieto, J .;
Miranda, M. A.; Font-Sanchis, E.; Ko´nya, K.; Scaiano, J . C. Tetrahedron
Lett. 1996, 37, 4923-4926. (c) Pe´rez-Prieto, J .; Miranda, M. A.; Garc´ıa,
H.; Scaiano, J . C. J . Org. Chem. 1996, 61, 3773-3777. (d) Ouchi, A.;
Koga, Y.; Adam, W. J . Am. Chem. Soc. 1997, 119, 592-599.
(6) Reactions from higher excited states: e.g. (a) Pola, J .; Taylor, R.
Tetrahedron Lett. 1994, 35, 2799-2800. (b) Ichinose, N.; Kawanishi,
S. J . Chem. Soc., Chem. Commun. 1994, 2017-2018. (c) North, S. W.;
Blanck, D. A.; Gezelter, J . D.; Longfellow, C. A.; Lee, Y. T. J . Chem.
Phys. 1995, 102, 4447-4460. (d) Kawamata, K.; Kikuchi, K.; Okada,
K.; Oda, M. J . Phys. Chem. 1995, 99, 3548-3553.
In the course of our research on the laser photochem-
istry, we have found an efficient double homolytic C-X
(X ) O, S, Se) bond cleavage by the use of excimer lasers,
which proceeds through a two-photon process;8 the reac-
tion is the laser photolysis of 1,8-bis(substituted-meth-
yl)naphthalenes (substituent: OPh, SPh, SePh), which
generates acenaphthene in 72% yield by a stepwise two-
photon process with use of KrF excimer laser (248 nm)
and SePh radical leaving groups (Scheme 1).
This efficient reaction can be applied to the generation
of o-quinodimethane [3A; 5,6-bis(methylene)cyclohexa-
1,3-diene] by the laser photolysis of 1,2-bis(phenoxymeth-
yl)benzene (1-O), 1,2-[bis(phenylthio)methyl]benzene (1-
S), and 1,2-[bis(phenylseleno)methyl]benzene (1-Se)
through a two-photon process (Scheme 2). o-Quino-
dimethane (3A) has attracted much attention of both
theoretical and synthetic chemists and it is known as a
versatile building block for organic synthesis.9 The major
synthetic utilization is cycloaddition reactions between
(7) Reactions by nonresonant two-photon excitation: (a) Kira, M.;
Miyazawa, T.; Koshihara, S.; Segawa, Y.; Sakurai, H. Chem. Lett. 1995,
3-4. (b) Miyazawa, T.; Koshihara, S.; Segawa, Y.; Kira, M. Ibid. 1995,
217-218.
(8) (a) Ouchi, A.; Adam, W. J . Chem. Soc., Chem. Commun. 1993,
628-629. (b) Ouchi, A.; Yabe, A.; Adam, W. Tetrahedron Lett. 1994,
35, 6309-6312. (c) Reference 4d.
(9) Reviews: (a) McCullough, J . J . Acc. Chem. Res. 1980, 13, 270-
276. (b) Charlton, J . L.; Alauddin, M. M. Tetrahedron 1987, 43, 2873-
2889. (c) Scaiano, J . C.; Wintgens, V.; Netto-Ferreira, J . C. Pure Appl.
Chem. 1990, 62, 1557-1564. (d) Martin, N.; Seoane, C.; Hanack, M.
Org. Prep. Proced. Int. 1991, 23, 237-272.
S0022-3263(97)00953-5 CCC: $14.00 © 1997 American Chemical Society

Synthesis of Tetra- and Dihydronaphthalene Derivatives
J . Org. Chem., Vol. 62, No. 21, 1997 7377
Sch em e 2
F igu r e 1. Absorption spectra of 1,2-bis(phenoxymethyl)ben-
zene (1-O)[s], 1,2-[bis(phenylthio)methyl]benzene (1-S)[----],
and 1,2-bis[(phenylseleno)methyl]benzene (1-Se)[-‚-‚-]. Con-
centration 10-4 M in acetonitrile, optical path 10 mm. The
wavelength of the excimer laser emissions are marked in the
figure.
Ta ble 1. Mola r Absor p tivities of 1, 4, 5, a n d 6 a t 248, 308,
a n d 351 n m a
molar absorptivity (ꢀ) (M-1‚cm-1
)
3A and dienophiles, and many synthetic applications
have been attempted,10,11 especially in the field of steroids
synthesis.10 Several methods have been developed for the
efficient generation of o-quinodimethane (3A), which can
be used for preparative purposes;12 however, most of
these methods require long synthetic steps for the
preparation of its precursors and/or time-consuming
synthetic procedures. Our method shown in Scheme 2
provides a fast and simple preparation of o-quino-
dimethane (3A) from easily accessible precursors 1;
compound 1 (X ) O, S, Se) can be prepared by a one-
step procedure in an excellent yield (89-99%) from
commercially available 1,2-bis(bromomethyl)benzene, and
3A is generated efficiently from 1-(O, S, Se) within a
pulse of an excimer laser. o-Quinodimethane (3A) is then
trapped with various dienophiles 4 to give the corre-
sponding cycloadducts 5 (Scheme 2).
compound
248 nm
308 nm
351 nm
1-O
1-S
1-Se
4a
4b
4c
4d
4e
5a
5b
5c
5d
5e
6-S
6-Se
670
13600
16800
160
30
40
1800
10
0
0
0
20
0
470
0
0
0
0
0
0
0
0
400
6
0
0
230
6
140
0
160
0
160
0
110
0
1630
7800
14500
70
1020
790
0
120
840
a
Measured by a UV-vis spectrophotometer in acetonitrile
solutions.
In this paper we report a full detail on the generation
of o-quinodimethane (3A) by using KrF (248 nm),13 XeCl
(308 nm), and XeF (351 nm) excimer lasers and the
trapping of 3A with several dienophiles under various
photolysis conditions.
each substrate at 248, 308, and 351 nm are summarized
in Table 1. The dienophiles used in the reaction were
maleic anhydride (4a ), dimethyl maleate (4b), dimethyl
fumarate (4c), fumaronitrile (4d ), and dimethyl acety-
lenedicarboxylate (4e). The molar absorptivities of the
dienophiles 4a -e, corresponding cycloadducts 5a -e, and
the coupling products of the radical leaving groups, i.e.,
diphenyl disulfide (6-S) and diphenyl diselenide (6-Se),
are also summarized in Table 1.
Transmittance of the reactant solutions (10-4 M 1, 10-3
M 4) was measured by an UV-vis spectrophotometer and
by excimer laser irradiations (Table 2). The transmit-
tance of the lasers were calculated from the energies of
the transmitted light between sample solutions and
acetonitrile. As seen in Table 2, >90% of photons were
absorbed at 248 nm in the spectroscopic measurements
and >80% of photons were absorbed in the KrF laser
irradiation with 10-mm optical path except for the
solution of 1-O and 4a ; however, >70% of the photons
were transmitted in the cases of the KrF laser irradiation
with 1-mm optical path. On the other hand, the spec-
troscopic measurements at 308 nm showed that only <4%
of the photons were absorbed for the solution of 1-(O, S)
and 4a , and 33% of absorption for 1-Se and 4a ; in the
case of the laser irradiations, practically no absorption
Resu lts
Absor p tion sp ectr a of 1,2-bis(phenoxymethyl)ben-
zene (1-O), 1,2-[bis(phenylthio)methyl]benzene (1-S), and
1,2-bis[(phenylseleno)methyl]benzene (1-Se) in acetoni-
trile are shown in Figure 1. The molar absorptivities of
(10) Reviews: (a) Oppolzer, W. Angew. Chem., Int. Ed. Engl. 1977,
16, 10-23. (b) Oppolzer, W. Synthesis 1978, 793-802. (c) Funk, R. L.;
Vollhardt, K. P. C. Chem. Soc. Rev. 1980, 9, 41-61. (d) Kametani, T.;
Nemoto, H. Tetrahedron 1981, 37, 3-16.
(11) e.g. (a) Charlton, J . L.; Bogucki, D.; Guo, P. Can. J . Chem. 1995,
73, 1463-1467. (b) Bogucki, D. E.; Charlton, J . L. J . Org. Chem. 1995,
60, 588-593. (c) Nemoto, H.; Satoh, A.; Fukumoto, K.; Kabuto, C. J .
Org. Chem. 1995, 60, 594-600.
(12) (a) Kambe, N.; Tsukamoto, T.; Miyoshi, N.; Murai, S.; Sonoda,
N. Bull. Chem. Soc. J pn. 1986, 59, 3013-3018. (b) Sano, H.; Ohtsuka,
H.; Migita, T. J . Am. Chem. Soc. 1988, 110, 2014-2015. (c) Hoey, M.
D.; Dittmer, D. C. J . Org. Chem. 1991, 56, 1947-1948. (d) Fujihara,
H.; Yabe, M.; Furukawa, N. J . Org. Chem. 1993, 58, 5291-5292. (e)
Sato, H.; Isono, N.; Okamura, K.; Date, T.; Mori, M. Tetrahedron Lett.
1994, 35, 2035-2038; and see references cited therein.
(13) Preliminary results with a KrF excimer laser: Ouchi, A.; Koga,
Y. Chem. Commun. 1996, 2075-2076.

7378 J . Org. Chem., Vol. 62, No. 21, 1997
Ta ble 2. Tr a n sm itta n ce of th e Rea cta n t Mixtu r e Solu tion s a t 248 a n d 308 n m a
transmittance (%)
Ouchi and Koga
248 nm
KrF excimer laserb
308 nm
precursor
(10-4 M)
dienophile
(10-3 M)
spectrophotometer
op:c 10 mm
spectrophotometer
XeCl excimer laserb
op:c 1 mm
op:c 10 mm
op:c 1 mm
op:c 10 mm
1-O
1-S
4a
4a
4a
4b
4c
4d
4e
63
5
2
1
1
52
8
7
4
6
91
78
71
71
72
87
71
97
96
67
-
99
99
96
-
1-Se
1-Se
1-Se
1-Se
1-Se
-
-
8
2
16
6
-
-
-
-
a
b
Measured in acetonitrile solutions. Laser fluence: 1.25 × 1021 photons‚m-2‚pulse-1
.
c op: optical path.
F igu r e 2. The dependence of the KrF excimer laser fluence on the consumption of 1-O (a), 1-S (b), 1-Se (c) and the yields of 5a
and 6-(S, Se). Substrates: 1-(O, S, Se) (9), 5a (b), 6 -(S, Se) ([); concentration in acetonitrile: 10-4 M 1-(O, S, Se) and 10-3
M
4a ; optical path 10 mm; number of KrF laser shots 1 shot. The results are the average of two independent runs; the experimental
errors are given as Supporting Information.
was observed for the solutions of 1-(O, S) and 4a , and
only 4% for 1-Se and 4a . The solutions of 1-(O, S, Se)
and 4a showed practically no absorption at 351 nm, both
for the spectroscopic and the XeF laser irradiation
measurements.
tigated by conducting the photolysis with high concentra-
tion (HC; 10-2 M) 4a [type ii mode] [Figures 3b (1-S) and
3e (1-Se)]; other reaction conditionssthe concentration
of 1-(S, Se), optical path, and the fluence of the KrF
laserswere the same as those of the standard condition.
Thirdly, the effect of the laser fluence was examined by
the reaction with high fluence (HF; 3.12 × 1022
photons‚m-2‚pulse-1) laser photolysis [type iii mode]
[Figures 3c (1-S) and 3f (1-Se)]; other conditions were
the same as those of the standard condition. Finally, the
effect of optical path was studied by changing the optical
path from 10 mm to 1 mm [type iv mode] [Figures 4a
(1-O), 4b (1-S), and 4c (1-Se)].
In the standard photolysis condition [type i mode], the
consumption rate of 1 is almost the same between 1-S
(Figure 3a) and 1-Se (Figure 3d). Under this photolysis
condition, the photons are mostly absorbed by 1-(S, Se)
because the molar absorptivity of 1-(S, Se) is two orders
of magnitude larger than that of 4a (cf. Table 1).
However, the formation rate of 5a was faster for 1-Se
than for 1-S, and the yield of 5a was higher in the case
of 1-Se. The similar trend was observed on the reactivity
of 1-S and 1-Se in the other photolysis conditions, i.e. in
type ii-iv modes.
The increase of the dienophile concentration [type ii
mode] resulted in the decrease of the consumption rate
of 1-(S, Se) and of the formation rate of 5a and 6-(S, Se)
compared with those of the standard condition [Figure
3a vs 3b (1-S); Figure 3d vs 3e (1-Se)]. The decrease can
be rationalized by the innegligible absorption of photons
by 4a which became comparable to that of 1-(S, Se) (cf.
Table 1) since the concentration of 4a is 100-fold more
than that of 1-(S, Se); thus, the number of photons
absorbed by 1-(S, Se) is diminished and the decrease in
F lu en ce d ep en d en ce on the reactions between 1-(O,
S, Se) and maleic anhydride (4a ) is shown in Figure 2
for the fluence range of 0.2 × 103 to 1.4 × 103 J ‚
m-2‚pulse-1 (0.25 × 1021 to 1.75 × 1021 photons‚m-2
‚
pulse-1). As seen in Figure 2a-c, the slopes of the
consumption of 1-(O, S, Se) and the yield of 6-(S, Se) vs
laser fluence for a double-logarithmic plot were unity,
whereas that of the yield of 5a was two. This result
indicates one-photon processes for the consumption of 1
and the formation of 6, and a two-photon process for the
formation of 5. However, the saturation of the consump-
tion of 1-(S, Se) (Figure 2b and c), and the yields of 5a
and 6-Se in the reaction with 1-Se (Figure 2c) was
observed at high laser fluence. In the cases of the
photolyses with 1-mm optical path, the saturation of the
consumption of 1-(S, Se) and the yields of 5a and 6-(S,
Se) were observed even from lower fluence.14
P h otolysis Con d ition . In order to study the effect
of reaction conditions, four types of photolysis conditions
were applied to the reactions of 1-(S, Se) and 4a . Firstly,
standard photolysis was conducted with low fluence (LF,
1.25 × 1021 photons‚m-2‚pulse-1) KrF excimer laser
irradiation on a solution of 10-4 M 1-(S, Se) and low
concentration (LC; 10-3 M) 4a with 10-mm optical path
[type i mode] [Figures 3a (1-S) and 3d (1-Se)]. Secondly,
the effect on the concentration of dienophile was inves-
(14) Original data are given as Supporting Information.

Synthesis of Tetra- and Dihydronaphthalene Derivatives
J . Org. Chem., Vol. 62, No. 21, 1997 7379
F igu r e 3. The consumption of substrate 1-(S, Se) and the yields of cycloadduct 5a and 6-(S, Se) as a function of the number of
KrF excimer laser shots. Substrate, laser fluence, and concentration of 4a : (a)1-S, LF, LC; (b) 1-S, LF, HC; (c) 1-S, HF, LC; (d)
1-Se, LF, LC; (e) 1-Se, LF, HC; (f) 1-Se, HF, LC. Substrates 1-(S, Se) (9), 5a (b), 6-(S, Se) ([); concentration in acetonitrile:
10-4 M 1-(S, Se), and 10-3 M (LC) or 10-2 M (HC) 4a ; laser fluence 1.25 × 1021 (LF) or 3.12 × 1022 (HF) photons‚m-2‚pulse-1
;
optical path 10 mm. The results are the average of two independent runs; the experimental errors are given as Supporting
Information.
F igu r e 4. The consumption of (a) 1-O, (b) 1-S, (c) 1-Se and the yields of 5a and 6-(S, Se) as a function of the number of KrF
excimer laser shots. Substrates 1-(O, S, Se) (9), 5a (b), 6-(S, Se) ([); concentration 10-4 M 1-(O, S, Se) and 10-3 M 4a ; laser
fluence 1.25 × 1021 photons‚m-2‚pulse-1; optical path 1 mm. The results are the average of two independent runs; the experimental
errors are given as Supporting Information.
the consumption rate of 1-(S, Se), and the formation rate
of 5a and 6-(S, Se) is expected.
Additional photolysis condition, high fluence (HF) and
high 4a concentration (HC), was applied on the solution
of 1-(S, Se) and 4a . The decrease in the consumption
rate of 1-(S, Se) and the yields of 5a and 6-(S, Se) was
observed; the yield of 5a was lower than those in type
i-iii modes.14
The application of shorter optical path (1 mm)[type iv
mode] showed the increase in both the consumption of
1-(S, Se), and the yields of 5a and 6-(S, Se) compared
with those in the standard condition [Figure 3a vs 4b (1-
S); Figure 3d vs 4c (1-Se)]. In the case of 1-Se, the best
yield of 5a was obtained by this photolysis condition
among type i-iv modes. In the case of 1-S, however, the
best yield of 5a was obtained in type iii mode. The
decrease in the yield of 6-(S, Se) was observed by the
subsequent laser pulses, similar to that in type iii mode,
which indicates the decomposition of 6-(S, Se) by the
By changing the laser fluence from 1.25 × 1021 to 3.12
× 1022 photons‚m-2‚pulse-1 [type iii mode] the large
increase in the consumption rate of 1-(S, Se) and the
formation rate of 5a and 6-(S, Se) was observed [Figure
3a vs 3c (1-S); Figure 3d vs 3f (1-Se)]. As seen in Figures
3c and 3f, the yield of 6-(S, Se) decreased with the
increase of laser pulses, which indicates the decomposi-
tion of 6-(S, Se) by the laser. On the contrary, the
saturation of the yield of 5a indicates that 5a is not
decomposed by the subsequent laser pulses. During the
laser irradiation, ablation of liquid was observed from
the surface of the solution; however, the weight loss after
one laser shot was 0.4% for the solution of 1-S and 4a
and 0.5% for that of 1-Se and 4a , which shows that the
weight loss of the solution by the ablation was negligible.

7380 J . Org. Chem., Vol. 62, No. 21, 1997
Ta ble 3. Con su m p tion of P r ecu r sor 1 a n d Yield of Cycloa d d u cts 5a
Ouchi and Koga
precursor
dienophile
reaction
number of
laser pulses
yield of 5
consumption
of 1 (%)
1
4
temp (°C)b
(%)
1-O
1-S
4a
4a
4a
rt
rt
rt
rt
rt
rt
60
60
rt
60
rt
1
13 ( 0.3
28 ( 1.4
13 ( 0.6
30 ( 2.3
43 ( 2.2
48 ( 0.6
44 ( 1.9
60 ( 7.7
4.7 ( 0.3
4.9 ( 0.7
16 ( 1.9
20 ( 2.7
17 ( 0.9
20 ( 1.0
39 ( 4.2
40 ( 0.3
44 ( 1.7
2.3 ( 0.3
4.0 ( 0.1
1.3 ( 0.6
3.9 ( 0.6
30 ( 1.9
77 ( 2.9
90 ( 0.2
99 ( 0.1
91 ( 0.7
∼100 ( 0.3
96 ( 1.5
∼100 ( 0.2
89 ( 1.7
92 ( 1.6
88 ( 1.6
∼100 ( 0.1
93 ( 1.5
99 ( 0.2
93 ( 0.4
95 ( 1.2
99 ( 0.6
94 ( 0.8
∼100 ( 0.2
95 ( 0.2
99 ( 0.2
5c
1
3c
1
1-Se
5c
1
3d
1c
1d
1
1-Se
1-Se
4b
4c
rt
5c
1
60
60
rt
60
60
rt
rt
60
60
3d
1c
1
1-Se
1-Se
4d
4e
2d
1
5c
1
3d
a
KrF excimer laser fluence: 1.25 × 1021 photons‚m-2‚pulse-1; optical path: 1 mm; concentration: 10-4 M 1 and 10-3 M 4 in acetonitrile;
the results are the average of two independent runs. rt: room temperature. c Highest yield of 5 at room temperature obtained among
1-, 2-, 3-, and 5-laser-pulse photolyses. Highest yield of 5 at 60 °C obtained among 1-, 2-, and 3-laser-pulse photolyses.
b
d
laser. No decomposition of 5a occurred by the subse-
quent laser irradiations, which is consistent with the
result of type iii mode.
The reaction of 1-O and 4a was also conducted in type
iv mode (Figure 4a). As seen in Figures 4a-c, the
consumption of 1-O was much slower than those of 1-(S,
Se); the consumption rate was 1-Se ≈ 1-S . 1-O.
However, in spite of the slow consumption rate, the yield
of 5a was comparable to that in the case of 1-S; the yield
of 5a was 1-Se . 1-S ≈ 1-O.
The same trend was observed in the reaction of 1-(S,
Se) and 4d in type i and iii modes,14 and of 1-Se and 4b
in type i mode.14 The consumption rate of the starting
F igu r e 5. The consumption of 1-Se and the yields of 5a and
material 1-(S, Se) and the formation rate of 6-(S, Se) in
6-Se as a function of the number of XeCl excimer laser shots.
these reactions were identical with those of 1-(S, Se) and
4a .
Substrates 1-Se (9), 5a (b), 6-Se ([); concentration 10-4
M
1-Se and 10-3
M
4a ; laser fluence 1.25
×
1021
photons‚m-2‚pulse-1; optical path 1 mm. The results are the
average of two independent runs; the experimental errors are
given as Supporting Information.
Wa velen gth d ep en d en ce on the reactions of 1-(O,
S, Se) and 4a in type iv mode was studied by using KrF,
XeCl, and XeF excimer lasers. The results on the KrF
excimer laser photolyses are already shown in Figures
4a-c. No reaction took place for 1-O with the use of XeCl
practically negligible;14 this is also explained by a very
weak absorption at 351 nm.
14
laser, which is explained by the lack of absorption at
Cycloa d d ition w ith Va r iou s Dien op h iles. The
reaction of 1-Se and the other dienophiles 4b-e was
conducted in type iv mode,14 whose results are sum-
marized in Table 3. The consumption rate of 1-Se and
the formation rate of 6-Se in these photolyses were
almost the same as those of 1-Se and 4a . As seen in
Table 3, the consumption of 1-Se was not dependent on
the type of dienophiles used; this is consistent with the
fact that the most of the photons were absorbed by 1-Se
under this reaction condition, which is due to the large
difference in the molar absorptivities between 1-Se and
4 (cf. Table 1). In the case of the reaction of 1-Se and
4c, obtained cycloadduct was only 5c, and no stereoiso-
mer 5b was observed.15 In the reaction of 1-Se and 4e a
small amount of dehydrogenated product, 2,3-bis(methoxy-
carbonyl)naphthalene (7) was detected in addition to the
expected cycloadduct 5e.
308 nm (cf. Table 1). Slight consumption of 1-S (9.4% at
the fifth laser shots) and the formation of 6-S (1.5% at
the fifth laser shots) were observed for 1-S but practically
no 5a was formed.14 As seen in Figure 5, the reaction
proceeded in the case of 1-Se but with slower consump-
tion rate of 1-Se and lower yield of 5a compared with
those in the KrF laser photolyses [Figure 4c (KrF laser)
vs 5 (XeCl laser)]. The yield of 6-Se reached to the same
level as that of KrF laser; however, in contrast to the
case of KrF laser photolysis, 6-Se showed no decrease
with additional laser pulses. This is explained by the
lower molar absorptivity of 6-Se at 308 nm compared
with that at 248 nm (cf. Table 1).
With use of XeF excimer laser, no reaction took place
for 1-S due to the absence of absorption at 351 nm (cf.
Table 1). In the case of 1-Se, only a slight consumption
of the starting material (3.6% at the fifth laser shots) was
observed, and the yields of 5a (0.7% at the fifth laser
shots) and 6-Se (1.0% at the fifth laser shots) were
(15) The stereoisomer 5b obtained from 4c in Table 1 of ref 13 was
found to be a different compound.

Synthesis of Tetra- and Dihydronaphthalene Derivatives
J . Org. Chem., Vol. 62, No. 21, 1997 7381
Ta ble 4. P la u sible Absor p tion s of 1-O, 1-S, a n d 1-Se for th e F ir st a n d th e Secon d P h oton s
absorption chromophoresa
first photon
308 nm
second photon
308 nm
substrate
248 nm
351 nm
248 nm
351 nm
1-O
P h O (π-π*: 1Lb)
Bn (π-π*: 1Lb)
P h S (π-π*: 1Lb)
Bn (π-π*: 1Lb)
none
P h S (π-π*: 1Lb)
none
none
P h O (π-π*: 1Lb)
Bz (π-π*)
-
-
-
1-S
P h S (π-π*: 1Lb)
Bz (π-π*)
P h S (π-π*: 1Lb)
Bz (π-π*)
2B (π-π*)
2B (π-π*)
S (n, π*)
S (n, π*)
1-Se
P h Se (π-π*: 1Lb) P h Se (π-π*: 1Lb) P h Se (π-π*: 1Lb) P h Se (π-π*: 1Lb) P h Se (π-π*: 1Lb) P h Se (π-π*: 1Lb)
Bn (π-π*: 1Lb)
Se (n, π*)
Bz (π-π*)
2B (π-π*)
Se (n, π*)
Bz (π-π*)
2B (π-π*)
Bz (π-π*)
2B (π-π*)
a
P h O: phenoxy group; P h S: phenylthio group; P h Se: phenylseleno group; Bn : o-dialkylbenzene; S: sulfur atom; Se: selenium
atom; Bz: substituted benzyl radical of 2A; 2B: bridged-form monoradical.
The reactions were also conducted at 60 °C in order to
investigate the temperature effect on the yield of cycload-
ducts 5a -e by facilitating the thermal reaction of o-
quinodimethane (3A) and dienophiles 4a -e;14 the results
are also shown in Table 3. As seen in the table, only
dienophiles 4a and 4d showed slight increase in the yield
of 5a and 5d , but no change was seen in the reactions
with other dienophiles. The consumption of 1-Se was the
same between the reactions at room temperature and at
60 °C.
1-(S, 1-Se) have an absorption which is attributed to the
π-π* (1Lb) excitation of the two PhX (X ) S, Se) groups,
but no absorption is expected from Bn group. Therefore,
the photolyses of 1-(S, 1-Se) at this wavelength proceed
solely by the excitation of the PhX leaving groups. In
the cases of XeF (351 nm) laser photolyses (cf. Table 4),
only 1-Se has absorption at the laser wavelength which
is due to the PhSe groups, but no absorption was
observed for 1-(O, S).
The probable species for the absorption of the second
photon is monoradical 2.20 Transient spectrum of the
photolysis of 1-(O, S, Se) contained the same absorption
as that of parent benzyl radicalsa strong absorption in
the region of 300-330 nm and terminating at ca. 370 nm
due to the Dn(2A2) f D0(1B2) excitation,21 which is not
much affected by alkyl substitutions. This is an evidence
for the involvement of the substituted benzyl radical 2A.
Semiempirical MO calculations of the monoradical 2,
however, predicted the existence of two possible forms,
a benzyl-type open-form 2A and a bridged-form 2B. The
calculations showed the heats of formation of 80.9 and
72.1 kcal‚mol-1 for 2A-S and 2B-S, and 59.2 and 36.8
kcal‚mol-1 for 2A-Se and 2B-Se. In the case of 2-O, the
heat of formation for 2A-O was calculated to be 44.6
Discu ssion
Absor p tion of P h oton s. The fluence dependence
experiments on the formation of 5a from 1-(O, S, Se) and
4a (Figures 2a-c) showed that 5a was formed by a two-
photon process. The absorption of the first photon by
1-(O, S, Se) is much dependent on the kind of heteroatom
involved in the molecule. Each substrate, 1-(O, S, Se),
is comprised of three chromophores, i.e., two PhX (X )
O, S, Se) leaving groups and one o-dialkylbenzene ring.
The kind of excitations which correspond to the absorp-
tion of the chromophores at the three laser wavelength
is summarized in Table 4.
In the cases of KrF (248 nm) laser irradiations (cf.
Table 4), two PhX (X ) O, S, Se) groups and one
o-dialkylbenzene (Bn ) are responsible for the absorption
of photons. The absorptions of PhX and Bn chro-
mophores are both attributed to the secondary absorption
band (1Lb) of the benzene ring.16 In the case of 1-(S, Se),
additional absorption corresponding to n f π* excitation
of S and Se atoms17 is also present in the photolysis.
During the photolysis, the photons are mainly absorbed
by PhX rather than Bn because in the case of 1-O, the
molar absorptivity of the two PhO groups is estimated
to be ca. 12-fold larger than that of Bn ;18 in the case of
1-S the molar absorptivity of the two PhS groups is
estimated to be at least 85-fold larger than that of Bn ,19
and a similar trend is expected for 1-Se in analogy with
the cases of 1-O and 1-S.
kcal‚mol-1 22
however, the calculation starting from the
;
bridged-form 2B-O did not gave stable structure but led
to the open-form 2A-O. The result indicates that mono-
radicals 2-S and 2-Se favor the bridged-forms 2B-S and
2B-Se, whereas the 2-O can only take the open-form 2A-
O.
The probable excitations which are responsible for the
second photon absorption is also summarized in Table
4. The difference of the absorbing species between the
first and the second photon is the participation of the
intermediate radical 2A and/or 2B instead of the o-
dialkylbenzene (Bn ) group. The absorption of the bridged-
form 2B is expected to show a significant red shift20,23
compared with that of the open-form 2A, which is due to
a highly extended conjugation of the π-electron system.
In the cases of XeCl (308 nm) laser photolyses (cf. Table
4), 1-O has no absorption at this wavelength. However,
(20) Preliminary experiments on the flash photolysis of 1-S and 1-Se
showed λmax at ca. 320 nm, corresponding to open-form monoradical
2A, and broad absorption in the range 430-500 nm, corresponding to
bridged-form monoradical 2B and PhX radical.
(21) e.g. Tokumura, K.; Udagawa, M.; Ozaki, T.; Itoh, M. Chem.
Phys. Lett. 1987, 141, 558-563.
(22) Calculated by using PM3 method (RHF, CI) in the MOPAC
version 6.0: cf. Stewart, J . J . P. QCPE Bull. 1989, 9, 10.
(23) The bridged-form of the monoradical generated from 1,8-
bis(substituted-methyl)naphthalene (substituent: SPh, SePh) showed
broad absorption at 400-520 nm, whereas the absorption of the open-
form monoradical was observed at 330-380 nm: Ouchi, A.; Koga, Y.;
Alam, M. M.; Ito, O. J . Chem. Soc., Perkin Trans. 2 1996, 1705-1709.
(16) J affe´, H. H.; Orchin, M. Theory and Application of Ultraviolet
Spectroscopy; J ohn Wiley & Sons: New York, 1962; Chapter 12, section
12.2.
(17) Reference 16; Chapter 17, section 17.2.
(18) The molar absorptivity and λmax of the 1Lb absorption band are
reported to be 204 M-1‚cm-1 and 254 nm for benzene, 225 M-1‚cm-1
and 261 nm for toluene, and 1480 M-1‚cm-1 and 269 nm for anisole:
ref 16; Table 12.4.
(19) The molar absorptivity and λmax of thioanisole is reported to be
9550 M-1‚cm-1 and 254 nm: ref 16; Table 17.1.

7382 J . Org. Chem., Vol. 62, No. 21, 1997
Ouchi and Koga
This conjugation is possible because, according to the MO
calculations, the bond order of the two C(benzylic)-X and
one C(phenyl)-X bonds were calculated to be ca. 0.7 so
that a π electron is expected to exist on the two benzylic
carbons; this is confirmed by the spin density obtained
by the MO calculation. Therefore, the feature of the
monoradical 2B might be better considered as a single
chromophore rather than two independent ones. Higher
stability of the bridged-form 2B to the open-form 2A can
be also explained by such conjugation.
(S, Se) rather than the open-form 2A-(S, Se), whereas
only the open-form 2A-O is allowed for 1-O. The stable
bridged-form 2B-(S, Se) increases the dissociation energy
for the second C-X bond cleavage, 2 f 3, which hinders
the formation of 3. Thus, the order in the yield of 5a
was reversed between 1-O and 1-S; the order of the yield
between 1-Se and 1-O was not reversed probably because
of the low dissociation energy of C-Se bond even in the
bridged-form.
Effect of La ser F lu en ce. It is clear from Figure 2
that the consumption of 1-(O, S, Se) and the formation
of 6-(S, Se) proceeded by one-photon processes, but a two-
photon process was operating in the formation of 5a ,
which is consistent with the mechanism shown in Scheme
1. The two-photon process is largely affected by the
fluence of light since, theoretically, the yield of the two-
photon product is proportional to the square of the light
intensity. In the standard condition [type i mode] the
result on the transmission of the KrF excimer laser at
10-mm optical path (cf. Table 2) showed that most of the
photons were absorbed when 1-(S, Se) was used, and
about a half of the photons was absorbed in the case of
1-O. This result indicates the presence of a large
difference in the photon density between incident-side
and exit-side of the photolysis cell; thus, the photon
density near the exit-side of the laser becomes too low
for conducting the two-photon processes. A simple
calculation shows that, under this photolysis condition,
the number of photons per molecule of 1 is 2.1
photons‚molecule-1‚pulse-1, which is not sufficient for the
efficient formation of 5a , although a large consumption
of 1 was observed.
In the case of KrF laser photolysis (cf. Table 4), the
second photon absorption of 1-O occurs at the remaining
PhO group and the benzyl radical (Bz) of open-form 2A-
O, whereas the absorption of 1-(S, Se) is attributed to
the π-π* excitation of PhX (X ) S, Se) group and Bz of
open-form 2A-(S, Se), and bridged-form monoradical 2B-
(S, Se), and to the n f π* excitation of S and Se atoms.
Contribution of the open-form monoradical absorption
becomes more important in the cases of XeCl laser
photolyses. In the case of 1-(S, Se), the absorption occurs
at the PhX (X ) S, Se) group and Bz of 2A-(S, Se), and
2B-(S, Se), all through the π-π* excitations. The same
excitation is responsible in the case of XeF laser pho-
tolyses of 1-Se. However, 2A and 2B cannot be gener-
ated in the cases of XeCl laser photolysis of 1-O and XeF
laser photolysis of 1-(O, S) because of the lack of the first
photon absorption.
The competition of the first photon absorption between
substrate 1 and dienophile 4 can be assessed from the
molar absorptivities (cf. Table 1). In the standard
photolysis condition [type i mode], 10-4 M 1 and 10-3
M
4 were employed so that the most of the photons are
absorbed by 1 in the case of 1-(S, Se); in the case of 1-O,
however, the absorption of photons between 1 and 4
becomes comparable and is much dependent on the type
of 4 used. For the second photon, the competition of the
photon absorption between 2A/B and 4 is somewhat
difficult to estimate because the molar absorptivity of 2A
and 2B at each laser wavelength have not been measured
so far.
Effect of Heter oa tom s. The rate of the consumption
of 1-(O, S, Se) in the type iv KrF laser photolysis with
4a (Figures 4a-c) was found to be in the order 1-Se ≈
1-S . 1-O. The order is in good accord with the order of
the molar absorptivities, 1-Se > 1-S . 1-O (cf. Table 1).
The molar absorptivity of 1-S and 1-Se had almost the
same value but that of 1-O was two orders of magnitude
smaller than the others. In contrast to the consumption
of 1-(O, S, Se) the yield of 5a was in the order 1-Se .
1-S ≈ 1-O. A prominent difference between the tendency
of the consumption of 1-(O, S, Se) and the yield of 5a is
that a big difference was observed between 1-S and 1-O
in the consumption, whereas large difference was ob-
served between 1-Se and 1-S in the yield.
The simple way to improve the efficiency of the two-
photon process is to increase the laser fluence. By
increasing the laser fluence by 25-fold [type iii mode],
ca. 2-fold increase in the yield of 5a was achieved
compared with that of the standard condition [Figure 3a
vs 3c (1-S); Figure 3d vs 3f (1-Se)]. A simple calculation
shows that the number of photons per molecule of 1 is
53 photons‚molecule-1‚pulse-1. However, such high flu-
ence photolysis has disadvantage for practical purposes
because the quartz window of the reaction vessel (or
simply a quartz cuvett) is often damaged by such high
fluence photolysis.
Another way to increase the efficiency is to decrease
the optical path of the laser. When 1-mm optical path
was used, 70-90% of photons are transmitted in most
cases (cf. Table 2) so that the photon density at the exit-
side is still sufficiently high for conducting efficient two-
photon reactions. By decreasing the optical path to 1 mm
[type iv mode] ca. 2-fold increase in the yield of 5a was
obtained compared with the standard condition [Figure
3a vs 4b (1-S); Figure 3d vs 4c (1-Se)] even with the low
fluence (LF) laser photolysis; the effect of decreasing the
optical path from 10 mm to 1 mm was similar to that of
increasing the laser fluence by 25-fold [type iii mode]. A
simple calculation shows that the number of photons per
molecule of 1 is 21 photons‚molecule-1‚pulse-1; the
number of photons is in the same order as that of the
high fluence (HF) photolysis with 10-mm optical path
[type ii mode].
This contrast in the tendency becomes more clear when
the reaction was conducted in type i mode (cf. Figure 2a-
c); the order of the yield of 5a became 1-Se > 1-O > 1-S.
This unexpected order in the yield of 5a seems to reflect
the facility of the second bond cleavage. A naive com-
parison of C-X (X ) O, S, Se) bond dissociation energies
gives the expected order 1-Se > 1-S > 1-O.24 However,
the semiempirical MO calculation, as shown before,
revealed that the monoradical favors bridged-form 2B-
Cycloa d d ition Rea ction of o-Qu in od im eth a n e.
Singlet diradical 3B is in resonance with the ground state
o-quinodimethane (3A), which undergoes cycloaddition
reaction with the dienophiles. Triplet diradical 3B and
o-quinodimethane (3A) might be involved during the
(24) Baff, L. The chemistry of organic selenium and tellurium
compounds; Patai, S., Rappoport, Z., Ed.; Wiley: Chichester, 1986; vol.
1, chapter 4, p 159.

Synthesis of Tetra- and Dihydronaphthalene Derivatives
J . Org. Chem., Vol. 62, No. 21, 1997 7383
formation of singlet 3A/B; however, intersystem crossing
of triplet to singlet 3A/B is expected to be fast.25
In the case of the reaction between 1-Se and 4c, the
obtained cycloadduct was only 5c; the result is the same
as that obtained by thermal reactions.9,12 According to
the orbital-symmetry rules, this result indicates that
cycloaddition of 3A and dienophile 4 proceeded by a
concerted thermal process because the stereoisomer 5b
should have been the major product if the reaction
proceeded photochemically, and the mixture of 5b and
5c should have been obtained by stepwise processes. Two
attempts were made in order to increase the efficiency
of the thermal process and thus the yield of cycloaddition
product 5.
increase of laser fluence and the decrease of the optical
path showed the same effect on the yield of 5. The type
of the heteroatoms (O, S, Se) in the leaving groups also
showed a significant difference in the yield of 5; this
difference was interpreted in terms of the participation
of a stable bridged-form monoradical as an intermediate,
which hindered the second bond cleavage and thus giving
a lower yield of 5. The phenylseleno group was found to
be the best among the three heteroatoms tested. Three
kinds of excimer laserssKrF, XeCl, and XeF lasersswere
tested, and the maximum yield of the cycloadduct, 48%,
was obtained by the use of KrF laser.
Exp er im en ta l Section
The first attempt was to increase the concentration of
dienophile in order to facilitate the trapping of o-
quinodimethane (3A) generated by the laser photolysis.
However, the result obtained was found to be the opposite
to the expectation; by the 10-fold increase of the concen-
tration of 4a [type ii mode], the rates of the consumption
of 1-(S, Se) and the formations of 5a and 6-(S, Se) have
decreased compared with those of standard condition
[type i mode] [Figure 3b vs 3a (1-S); Figure 3e vs 3d (1-
Se)]. Furthermore, the final yield of 5a have also
decreased. These decreases are ascribed to the consider-
able absorption of the photons by dienophile 4a . Al-
though the molar absorptivity of 4a is ca. 1/100 of that
of 1-(S, Se), the total absorption of 4a becomes compa-
rable to that of 1-(S, Se) in type ii mode because the
concentration of 4a is 100-fold higher than that of 1-(S,
Se). Therefore, the effective fluence of the laser for the
photolysis of 1-(S, Se) is considered to be about a half of
that of the standard condition [type i mode]. This is
evidenced by the fact that the consumption rate of 1-(S,
Se), which proceeds by an one-photon process, in type ii
mode becomes about half of that of type i mode [Figure
3b vs 3a (1-S) and Figure 3e vs 3d (1-Se); at the first
laser shot].
Detailed descriptions on the preparation of the starting
materials 1-(O, S, Se) and the authentic compounds 5a -e and
7 are given as Supporting Information.
Excim er La ser P h otolyses. Laser photolyses were con-
ducted in acetonitrile solution [1: 10-4 M; 4: 10-3 M (LC) and
10-2 M (HC)] under a nitrogen gas atmosphere. High-fluence
photolyses (HF, 3.12 × 1022 photons‚m-2‚pulse-1) were con-
ducted by using an ca. 15-mm glass capillary of 1-mm
diameter, one of whose ends was closed. A 10-µL aliquot of
the solution was placed into a horizontally placed capillary,
and the laser light was focused at the opening of the capillary.
Low-fluence photolyses (LF, 1.25 × 1021 photons‚m-2‚pulse-1
)
were conducted on ca. 0.5-mL solution with 10-mm optical path
or on ca. 0.1-mL solution with 1-mm optical path under a
nitrogen gas atmosphere by using synthetic quartz cuvettes
of 10-mm width. The experiments on the laser fluence
dependence were conducted on ca. 0.5-mL solution (1: 10-4
M; 4a : 10-3 M) under a nitrogen gas atmosphere by using a
synthetic quartz cuvette of 10-mm width and 10-mm optical
path. The excimer lasers used were Lambda Physik EMG 201
MSC [pulse width (fwhm) 30 ns (KrF) and 26 ns (XeF)] and
Lambda Physik EMG 102 MSC [pulse width (fwhm) 14 ns
(XeCl)]. The laser pulse energy was measured by means of a
Gentec joulemeter ED-500 and a Tektronix T912 10 MHz
storage oscilloscope.
An a lysis of th e P h otolysis P r od u cts. The yields of the
two-photon products 5a -e, diphenyl disulfide (6-S), diphenyl
diselenide (6-Se), and the consumption of the starting material
1-(O, S, Se) were determined by HPLC analysis and their
retention times compared with the authentic samples.
The second attempt is to raise the reaction tempera-
ture. However, the increase of the reaction temperature,
from room temperature to 60 °C, showed practically no
effect on the rate of the consumption of 1-Se and the
yields of 5a and 6-Se.
Ack n ow led gm en t. We thank the Agency of Indus-
trial Science and Technology (MITI J apan) for financial
support.
Con clu sion s
Su p p or tin g In for m a tion Ava ila ble: Preparation of com-
pounds 1-O, 1-S, 1-Se, 5a -e, and 7; KrF laser fluence depen-
dence on the reaction of 1-(S, Se) and 5a with 1-mm optical
path; photolyses of 1-(S, Se) and high concentration 4a by high
fluence KrF laser with 10-mm optical path; photolyses of 1-(S,
Se) and 4d by high and low fluence KrF lasers with 10-mm
optical path; photolyses of 1-Se and 4b by low fluence KrF
laser with 10-mm optical path; original data on the photolysis
of 1-(O, S) and 4a by low fluence XeCl laser with 1-mm optical
path; original data on the photolysis of 1-Se and 4a by low
fluence XeF laser with 1-mm optical path; original data on
the photolyses of 1-Se and 4b-e by low fluence KrF laser with
1-mm optical path at room temperature; original data on the
photolyses of 1-Se and 4a -e by low fluence KrF laser with
1-mm optical path at 60 °C (29 pages). This material is
contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
o-Quinodimethane (3A) was generated effectively by
excimer laser photolyses of 1,2-bis(phenoxymethyl)ben-
zene (1-O), 1,2-bis[(phenylthio)methyl]benzene (1-S), and
1,2-[bis(phenylseleno)methyl]benzene (1-Se) in acetoni-
trile solutions via a two-photon process. Cycloaddition
of 3A was conducted with several dienophilessmaleic
anhydride (4a ), dimethyl maleate (4b), dimethyl fuma-
rate (4c), fumaronitrile (4d ), and dimethyl acetylenedi-
carboxylate (4e)swhich gave corresponding cycloadducts
5a -e. Four kinds of reaction conditions were tested by
using a KrF excimer laser: (i) standard condition, (ii)
high dienophile concentration, (iii) high laser fluence, and
(iv) short optical path. The results obtained from these
conditions revealed that the photon density was the most
important factor for the efficient formation of 5; the
(25) Wintgens, V.; Netto-Ferreira, J . C.; Casal, H. L.; Scaiano, J . C.
J . Am. Chem. Soc. 1990, 112, 2363-2367.
J O970953O