Laser flash photolysis of diphenylsulfonyldiazomethane: Detection of the sulfene and a sulfene-pyridine ylide

Article abstract of DOI:10.1021/ol006463r

(matrix presented) The photochemistry of diphenylsulfonyldiazomethane (DSD) was studied by means of nanosecond laser flash photolysis. The photochemical behavior of this molecule upon UV irradiation is characterized by sulfene formation, presumed to arise via Wolff rearrangement of a carbene. We were able to detect the sulfene and the sulfene ylide formed upon sulfene trapping by pyridine. Sulfene quenching by nucleophiles was also examined.

Full text of DOI:10.1021/ol006463r

ORGANIC
LETTERS
2
000
Vol. 2, No. 23
591-3594
Laser Flash Photolysis of
Diphenylsulfonyldiazomethane:
Detection of the Sulfene and a
Sulfene−Pyridine Ylide
3
†
‡
†
†
‡
‡
F. Ortica, G. Pohlers, C. Coenjarts, E. V. Bejan, J. F. Cameron, A. Zampini,
†
,†
M. Haigh, and J. C. Scaiano*
Department of Chemistry, UniVersity of Ottawa, Ottawa, Canada K1N 6N5,
and Shipley Company, Inc., R&D, Marlborough, Massachusetts 01752-3092
tito@photo.chem.uottawa.ca
Received August 15, 2000
ABSTRACT
The photochemistry of diphenylsulfonyldiazomethane (DSD) was studied by means of nanosecond laser flash photolysis. The photochemical
behavior of this molecule upon UV irradiation is characterized by sulfene formation, presumed to arise via Wolff rearrangement of a carbene.
We were able to detect the sulfene and the sulfene ylide formed upon sulfene trapping by pyridine. Sulfene quenching by nucleophiles was
also examined.
The photochemistry of compounds containing a diazo moiety
invariably involves elimination of molecular nitrogen and
typically yields the corresponding carbenes.1-4 The behavior
bonyls useful photoacid generators for the microlithographic
industry.
1
1,12
Deep-UV lithography requires the formulation of new
photoresists with increased sensitivity. This higher sensitivity
is achieved by generating a strong acid and employing it as
a catalyst. The carboxylic acids produced by R-diazocarbonyl
compounds are not satisfactory for this purpose, and stronger
acids, e.g., sulfonic acids, are frequently the preferred
of carbenes derived from R-diazocarbonyls is dominated by
facile Wolff rearrangement to form ketenes.5
-10
The hy-
drolysis of ketenes to carboxylic acids has made diazocar-
†
University of Ottawa.
Shipley Company, Inc.
‡
1
2
(
1) Moss, R. A.; Jones, M. J. Carbenes; Moss, R. A., Jones, M. J., Eds.;
Wiley-Interscience: New York, 1985; Vol. 3, p 45.
2) Jones, M. J.; Moss, R. A. Carbene Chemistry; John Wiley & Sons:
New York, 1975.
3) Moss, R. A.; Jones, M., Jr. Carbenes; John Wiley & Sons: New
York, 1973.
photogenerated acids. R-Diazosulfones are interesting
because they are potential precursors of sulfonic acids. For
these compounds, the initial formation of the carbene is
followed by a sulfo-Wolff rearrangement to give the sulfene1
(
3
(
14-16
which is hydrolyzed in water to yield the sulfonic acid.
(
(
4) Kirmse, W. Carbenes, 2nd ed.; Academic Press: New York, 1971.
5) Patai, S. The Chemistry of Ketenes, Allenes and Related Compounds;
While the reactions of R-ketocarbenes to yield ketenes have
J. Wiley and Sons: New York, 1980.
(
(
(
6) Tidwell, T. T. Ketenes; J. Wiley and Sons: New York, 1995.
7) Meier, H.; Zeller, K. P. Angew. Chem., Int. Ed. Engl. 1975, 14, 32.
8) Regitz, M.; Maas, G. Diazo Compounds; Academic Press: Orlando,
(11) Reiser, A. PhotoreactiVe Polymers: The Science and Technology
of Resists; John Wiley and Sons: New York, 1989.
(12) Willson, C. G. Organic Resist Materials, 2nd ed.; Thompson, L.
F., Willson, C. G., Bowden, M. J., Eds.; American Chemical Society:
Washington, 1994; p 139.
(13) Mulder, R. J.; van Leusen, A. M.; Strating, J. Tetrahedron. Lett.
1967, 3057.
1
986.
9) Boate, D. R.; Johnston, L. J.; Kwong, P. C.; Lee-Ruff, E.; Scaiano,
J. C. J. Am. Chem. Soc. 1990, 112, 8858.
10) Ortica, F.; Pohlers, G.; Scaiano, J. C.; Cameron, J. F.; Zampini, A.
Org. Lett. 2000, 2, 1357.
(
(
(14) King, J. F.; Gill, M. S. J. Org. Chem. 1998, 63, 808.
1
0.1021/ol006463r CCC: $19.00 © 2000 American Chemical Society
Published on Web 10/21/2000

been the subject of intensive studies (vide infra), the
corresponding reactions of R-sulfonylcarbenes and sulfenes
have received less attention.17 These studies have relied
predominantly on the analysis of products from solvolysis
of reaction intermediates. To the best of our knowledge, no
time-resolved studies on the reactions of R-sulfonylcarbenes
have been performed.
The utility of laser flash photolysis (LFP) with UV/vis
detection in the study of R-diazocarbonyl compounds has
been aided greatly by the use of various amines as “probe”
molecules. These probes, typically pyridine, react with both
carbenes and ketenes to form ylides with absorption in the
optical region of interest, thereby allowing more complete
1
8-25
kinetic analysis.
In this work we report a LFP study of diphenylsulfonyl-
diazomethane (DSD), in which, for the first time, a sulfene
Figure 1. Transient absorption spectra obtained upon nanosecond
LFP of DSD in N -saturated acetonitrile solution, recorded (b) 16
µs and (O) 800 µs after the laser pulse. Inset: decay kinetics
monitored at 290 nm.
26
2
was detected under reactive conditions and a sulfene-py-
ridine ylide was detected by LFP. This allowed the behavior
of the sulfene to be investigated via competition experiments.
DSD was prepared via the diazo transfer route commonly
employed for R-diazoketones, starting from diphenylsulfo-
on transient lifetimes in experiments with tetrabutylammo-
27
nylmethane and p-toluenesulfonyl azide (yield: 80%). The
absorption spectrum of DSD in acetonitrile exhibits a main
peak at 231 nm (log ꢀ ) 4.2) and a weaker band at 376 nm
-
nium chloride, a nucleophilic agent due to Cl anion, tri-
butylgermanium hydride, a hydrogen-donating radical scav-
enger, and anthracene, a triplet state quencher makes the
involvement of cations, radicals, and triplet states unlikely.
(log ꢀ ) 2.0).
The transient absorption spectra28 obtained upon LFP
DSD undergoes nitrogen loss upon photoexcitation, pre-
sumably with formation of a carbene followed by Wolff
rearrangement to form the sulfene. Conceivably, the two
transients observed in the LFP experiments could be assigned
to these species. To determine the nature of these transients,
we performed one of the “classic” experiments in the
detection of carbenes (and sometimes ketenes); their trapping
with pyridine. The transient absorption spectra obtained upon
2
(usually at 308 nm) of DSD in N -saturated acetonitrile at
different delays after the laser pulse are shown in Figure 1.
They show a UV maximum at 290 nm and a weaker band
extending up to 370 nm. From the kinetic analysis, two
transients can be observed and fitted to a biexponential decay.
The shorter lifetime is 50 µs (monitored at 290 nm, see
Figure 1) and the longer one 11 ms. Oxygen does not affect
the lifetime of either transient. Due to the lack of any effect
2
nanosecond LFP of DSD in N -saturated acetonitrile solution
in the presence of 0.15 M pyridine shows an intense
absorption extending from 300 to 600 nm and a well-defined
maximum at 440 nm (Figure 2). This spectrum could be
(
15) King, J. F.; Lam, J. Y. L.; Skonieczny, S. J. J. Am. Chem. Soc.
992, 114, 1743.
16) Powlowski, G.; Dammel, R.; Lindley, C. R.; Merrem, H. J.;
1
(
Roeschert, H.; Lignau, J. AdVances in Resist Technology and Processing
VII, Proceedings of SPIE 1990, 1262, 16.
(
17) King, J. F. Acc. Chem. Res. 1975, 8, 10.
(18) Jackson, J. E.; Soundararajan, N.; Platz, M. S.; Liu, M. T. H. J.
Am. Chem. Soc. 1988, 110, 5595.
19) Barcus, R. L.; Hadel, L. M.; Johnston, L. J.; Platz, M. S.; Savino,
T. G.; Scaiano, J. C. J. Am. Chem. Soc. 1986, 108, 3928.
(
(
(
20) Liu, M. T. H.; Bonneau, R. J. Am. Chem. Soc. 1990, 12, 3915.
21) Toscano, J. P.; Platz, M. S.; Nikolaev, V. J. Am. Chem. Soc. 1995,
1
C. J. Am. Chem. Soc. 1992, 114, 2630.
25) Camara de Luca, N.; Netto-Ferreira, J. C.; Andraos, J.; Lusztyk, J.;
Wagner, B. D.; Scaiano, J. C. Tetrahedron Lett. 1997, 38, 5147.
26) Sander, W.; Kirschfeld, A.; Halupka, M. J. Am. Chem. Soc. 1997,
19, 981.
(
(
1
(
(
27) Regitz, M.; Liedhegener, A. Chem. Ber. 1966, 99, 3128.
28) For the laser flash photolysis work, a Lumonics EX-530 excimer
laser (Xe/HCl, 308 nm, ∼6 ns pulse width, 50-100 mJ/pulse) was used
for excitation. The system is controlled by a Power Macintosh computer
running LabVIEW 4.1 software. A Tektronix 2440 digital oscilloscope
captures the signal from the photomultiplier tube. Further details on a similar
system have been provided elsewhere (Scaiano, J. C. J. Am. Chem. Soc.
Figure 2. Transient absorption spectra obtained upon nanosecond
LFP of DSD in N -saturated acetonitrile solution in the presence
2
of 0.15 M pyridine, recorded (b) 1.8 µs, ()) 6.2 µs, and (O) 16.7
µs after the laser pulse. Inset: kinetic trace monitored at 440 nm.
1
1
980, 102, 7747. Scaiano, J. C.; Tanner, M.; Weir, D. J. Am. Chem. Soc.
985, 107, 4396). The optical densities of the samples were 0.2-0.3 at the
laser wavelength. A flow system (a 7 × 7 mm Suprasil quartz flow cell,
connected with a 100 mL reservoir with Teflon tubing) was used in order
to ensure irradiation of a fresh portion of the sample by each laser shot.
3592
Org. Lett., Vol. 2, No. 23, 2000

tentatively assigned either to a carbene-pyridine or a
sulfene-pyridine ylide.
While the first type of complex is well documented,18-20,29-31
Although sulfenes have been proposed as intermediates
1
7,44
involved in several reactions
their subsequent reactions
are still under investigation. The intermediacy of sulfenes is
usually inferred by identifying the products of nuclephile
the generation and subsequent characterization of a sulfene-
13-15,45-47
trapping.
Although there are many literature reports,
pyridine ylide under LFP conditions has never been reported,
1
7
we could not find any LFP study focused on the sulfene
trapping step. Thus, we decided to use the probe technique
although these species have been known for many years.
The rise time for ylide formation (see inset of Figure 2) is
dependent on the pyridine concentration and allows for the
-
4
(
photolysis in the presence of 2 × 10 M pyridine, rise time
for pyridine ylide formation, 2 ms) to monitor the effects of
different sulfene quenchers on sulfene-pyridine ylide rise
time: the results are summarized in Table 1. In these
determination of a rate constant by plotting the first-order
6
rise rate constant vs pyridine concentration; k
M
q
) 3.9 × 10
-
1
-1
s . Additionally, the intercept yields the lifetime in
the absence of pyridine for the transient responsible for ylide
formation. The value we found, 4 ms, is in fairly good
agreement with the direct measurement, 11 ms, considering
the large error associated with the extrapolation of very long
lifetimes. Therefore, the long-lived transient absorbing at 290
nm is the same one responsible for the ylide formation with
pyridine.
Table 1. Bimolecular Rate Constants (kapp) for Interaction of
Various Nucleophiles with the Sulfene Obtained upon LFP (308
nm) of DSD in N -Saturated Solution, in the Presence of 2 ×
2
-
4
10 M Pyridine as a Probe
kapp (M-1 s-1
nucleophile
)
To establish the nature of this transient, we monitored the
effects of various quenchers on the unimolecular rate constant
for the pyridine ylide growth. This method has already been
7
sodium acetate
sodium azide
sodium thiocyanate
sodium hydroxide
sodium cyanide
methanol
1.1 × 10
7
5
2.4 × 10
5.0 × 10
9,18,19,29
24
applied in the study of carbenes
experiments we used a fixed concentration of pyridine (2 ×
M) as a transient probe. Under these conditions the rise
and ketenes. In our
nonlinear quenching plot
<10 , see text
3
-4
<103
<103
10
water
time for pyridine ylide formation was ∼2 ms. The effects
-
2
-3
of oxygen (10 M) and adamantanethione (up to 10 M)
on the kinetics of pyridine ylide growth were analyzed, since
both are efficient scavengers of triplet carbenes.9
,19,32-38
experiments there is a competition for the sulfene between
nucleophile and the pyridine, which reduces the yield of
sulfene-pyridine ylide as well as its rise time (Scheme 1).
The
lack of an effect upon addition of either reagent excludes a
triplet carbene as the transient responsible for ylide formation.
This is also consistent with the long lifetime observed (11
ms) for the ylide precursor.
Scheme 1
The effects of acetone (up to 0.1 M) and methanol (2.25
M) on the kinetics of pyridine ylide growth were analyzed,
since both are good singlet carbene scavengers.39-43 Again,
the lack of an effect excludes a singlet carbene as the
transient responsible for ylide formation.
At this point, the possibility that the ylide might be formed
by interaction of pyridine with a sulfene must be considered.
29) Liu, M. T. H.; Bonneau, R. J. Am. Chem. Soc. 1989, 111, 6873.
M. T. H. Tetrahedron Lett. 1989, 30, 1335.
31) Bonneau, R.; Liu, M. T. H.; Suresh, R. V. J. Phys. Chem. 1989,
3, 4802.
(
9
(
(
32) Closs, G. L.; Rabinow, B. E. J. Am. Chem. Soc. 1976, 98, 8190.
33) Casal, H. L.; Tanner, M.; Werstiuk, N. H.; Scaiano, J. C. J. Am.
Chem. Soc. 1985, 107, 4616.
(
(
34) Fessenden, R. W.; Scaiano, J. C. Chem. Phys. Lett. 1985, 117, 103.
35) Werstiuk, N. H.; Casal, H. L.; Scaiano, J. C. Can. J. Chem. 1984,
6
2, 2391.
36) Sugawara, T.; Iwamura, H.; Hayashi, H.; Sekiguchi, A.; Ando, W.;
Liu, M. T. H. Chem. Lett. 1983, 1261.
(
For many of the nucleophiles studied, the shortening in
the rise time of the sulfene-pyridine ylide was accompanied
by a disproportionately large decrease in the signal due to
the sulfene-pyridine ylide. The UV/vis spectra of DSD
(
(
(
37) Nazran, A. S.; Griller, D. J. Am. Chem. Soc. 1984, 106, 543.
38) McGimpsey, W. G.; Scaiano, J. C. Tetrahedron Lett. 1986, 27, 547.
39) Griller, D.; Liu, M. T. H.; Scaiano, J. C. J. Am. Chem. Soc. 1982,
1
04, 5549.
40) Chuang, C.; Lapin, S. C.; Schrock, A. K.; Schuster, G. B. J. Am.
Chem. Soc. 1985, 107, 4238.
41) Sugawara, T.; Iwamura, H.; Hayashi, H.; Sekiguchi, A.; Ando, W.;
Liu, M. T. H. Chem. Lett. 1983, 1257.
42) Sitzmann, E. V.; Langan, J. G.; Eisenthal, K. B. Chem. Phys. Lett.
984, 112, 111.
43) Sitzmann, E. V.; Wang, Y.; Eisenthal, K. B. J. Phys. Chem. 1983,
7, 2283.
(
(
(44) Opitz, G. Angew. Chem., Int. Ed. Engl. 1967, 6, 107.
(45) King, J. G.; Piers, K.; Smith, D. J. H.; McIntosh, C. L.; de Mayo,
P. Chem. Commun. 1969, 31.
(46) King, J. F.; de Mayo, P.; McIntosh, C. L.; Piers, K.; Smith, D. J.
H. Can. J. Chem. 1970, 48, 3704.
(
1
(
8
(47) McIntosh, C. L.; de Mayo, P. Chem. Commun. 1969, 32.
Org. Lett., Vol. 2, No. 23, 2000
3593

solutions containing sodium acetate and sodium cyanide
showed the presence of a band (λ∼300 nm) not present in
solutions containing nucleophile or DSD alone. Both of these
observations can be rationalized via an interaction between
the nucleophile and ground state DSD. Given the relative
concentrations of nucleophile (<1 mM) and DSD (>10 mM),
such an interaction may significantly deplete the amount of
nucleophile available for reaction with the sulfene. In fact,
for sodium cyanide there was no observable quenching of
4
8
the sulfene despite its very high nucleophilicity. This is
likely due to a (dark) reaction of sodium cyanide with DSD
prior to laser excitation. This effect is also apparent with
results obtained with sodium acetate, where reversible
complexation may be involved. Attempts to use 355 nm for
excitation, where lower concentrations of DSD are requireds
due to the high extinction coefficient at this wavelengths
led to inconclusive results presumably as a result of the
failure to control the thermal reactions already mentioned.
The rate constants observed for all of the ionic species should
be interpreted as lower limits of the actual rate constant, since
some nucleophile may have been consumed in dark reactions.
Attempts were also made to use the nonionic nucleophiles
water and methanol as sulfene scavengers. Only a small
effect was observed with the concentrations employed (16
and 2.25 M, respectively). Despite the lack of an observable
interaction on the time scale of the laser experiment, the
Figure 3. Kinetic decay traces obtained upon nanosecond LFP of
DSD in N -saturated (O) CH CN, (0) benzene, and (4) dioxane
solutions; monitored at 300 nm and recorded 50 µs after the laser
pulse.
2
3
of the singlet carbene of DSD may be altered dramatically
relative to typical singlet carbenes by the presence of the
electron-withdrawing sulfonyl substituents. The role of elec-
49
tronic effects in the stability of carbenes is well established.
Nitrile ylides, formed from reaction of acetonitrile with a
carbene, are species which have been observed in the
products resulting from the attack of water1 and methanol
4,15
13
50-55
photolysis of other diazo compounds.
To test if this
on sulfenes have been detected in product studies. In fact,
product studies we performed on DSD showed that one of
the main products formed upon photolysis in acetonitrile/
water is the expected sulfonic acid formed via reaction of
the sulfene with water (Scheme 2). Similar products have
transient could be a nitrile ylide, the transient absorption
spectra of DSD in dioxane and benzene solution under N
2
were recorded. A very similar transient was observed in these
solvents. Monitoring at 300 nm, the short-lived transient
shows a lifetime (Figure 3) of ∼200 µs in dioxane and ∼44
µs in benzene, thus ruling out a nitrile ylide as a possible
intermediate. The exact nature of this species remains under
investigation.
Scheme 2
In conclusion, the photolysis of diphenylsulfonyldiazo-
methane (DSD) occurs through nitrogen extrusion, presum-
ably involves a carbene, which undergoes rapid Wolff
rerrangement to a sulfene. The probe technique allowed us
to monitor the absorption spectra and the kinetic behavior
of a sulfene-pyridine ylide. It was characterized by quench-
ing studies employing different nucleophiles. The presence
of carbene intermediates could not be detected in our LFP
experiments, even using the shortest time scale available.
been observed in the photolysis of other R-diazosulfones.16
Therefore, all these results allowed us to conclude that
the long-lived transient observed at 290 nm upon laser flash
photolysis of DSD is due to a sulfene intermediate formed
by Wolff rearrangement.
Acknowledgment. Thanks are due to NSERC for support
under its strategic program.
OL006463R
2
The second transient observed upon LFP of DSD in N -
(
49) Arduengo, A. J., III; Rasika, D.; Harlow, R. L. J. Am. Chem. Soc.
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saturated acetonitrile lives 50 µs and can also be monitored
at 290 nm. The experiments already performed do not
support the presence of radicals, triplet states, cations, and
the triplet carbene, due to the lack of effect by selective
scavengers. However, the possibilility of the transient being
a singlet carbene cannot be entirely eliminated despite its
lack of reactivity with the typical scavengers of singlet
carbenes. This doubt arises from the fact that the reactivity
1
(
(
Lett. 1983, 24, 3955.
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