Chromoselective Synthesis of Sulfonyl Chlorides and Sulfonamides with Potassium Poly(heptazine imide) Photocatalyst

Article abstract of DOI:10.1002/anie.202106183

Among external stimuli used to promote a chemical reaction, photocatalysis possesses a unique one—light. Photons are traceless reagents that provide an exclusive opportunity to alter chemoselectivity of the photocatalytic reaction varying the color of incident light. This strategy may be implemented by using a sensitizer capable to activate a specific reaction pathway depending on the excitation light. Herein, we use potassium poly(heptazine imide) (K-PHI), a type of carbon nitride, to generate selectively three different products from S-arylthioacetates simply varying the excitation light and otherwise identical conditions. Namely, arylchlorides are produced under UV/purple, sulfonyl chlorides with blue/white, and diaryldisulfides at green to red light. A combination of the negatively charged polyanion, highly positive potential of the valence band, presence of intraband states, ability to sensitize singlet oxygen, and multi-electron transfer is shown to enable this chromoselective conversion of thioacetates.

Full text of DOI:10.1002/anie.202106183

Angewandte
Research Articles
Chemie
How to cite:
International Edition: doi.org/10.1002/anie.202106183
German Edition: doi.org/10.1002/ange.202106183
Photoredox Catalysis
Hot Paper
Chromoselective Synthesis of Sulfonyl Chlorides and Sulfonamides
with Potassium Poly(heptazine imide) Photocatalyst
Yevheniia Markushyna,* Christoph M. Schꢀßlbauer, Tobias Ullrich, Dirk M. Guldi,
Markus Antonietti, and Aleksandr Savateev*
Abstract: Among external stimuli used to promote a chemical
reaction, photocatalysis possesses a unique one—light. Pho-
tons are traceless reagents that provide an exclusive oppor-
tunity to alter chemoselectivity of the photocatalytic reaction
varying the color of incident light. This strategy may be
implemented by using a sensitizer capable to activate a specific
reaction pathway depending on the excitation light. Herein, we
use potassium poly(heptazine imide) (K-PHI), a type of
carbon nitride, to generate selectively three different products
from S-arylthioacetates simply varying the excitation light and
otherwise identical conditions. Namely, arylchlorides are
produced under UV/purple, sulfonyl chlorides with blue/white,
and diaryldisulfides at green to red light. A combination of the
negatively charged polyanion, highly positive potential of the
valence band, presence of intraband states, ability to sensitize
singlet oxygen, and multi-electron transfer is shown to enable
this chromoselective conversion of thioacetates.
breakthroughs in the history of medicine, and the sulfonamide
linkage is an omnipresent motif in numerous biologically
active compounds (Figure S1).[3] Sulfa drugs are broadly used
for the treatment of a wide variety of indications, such as high
blood pressure, diabetes, bacterial infections, and even human
immunodeficiency due to HIV.[4]
In fact, intense efforts have been focused on the develop-
ment of methods for sulfonyl amides synthesis.[5] Tradition-
ally, formation of sulfonyl amide groups is the endpoint of
a synthetic route, in which other sulfonyl derivatives serve as
a point for derivatization. The common strategy for the
synthesis of complex sulfonamides is the addition-elimination
process, and sulfonyl chlorides are the most common sub-
strates in this type of reactions (Figure 1a).[6] Apart from the
main application in the synthesis of sulfonyl amides, sulfonyl
chlorides are commonly used precursors for several important
functional groups including sulfonate esters, sulfones, and
sulfinic acids.[7] In photocatalysis, upon one-electron reduc-
tion, they give alkyl- and aryl radicals, which are valuable
intermediates in organic synthesis.[8]
Introduction
Sulfur is one of the earliest known elements, and its
healing power was known to the Greeks since antiquity.
Nowadays, sulfur-containing compounds are widely used as
pharmaceuticals and agrochemicals next to their role in
material science and food industries.[1] Ever since Prontosil
became the basis of antibiotics (for which Gerhard Domagk
was awarded with the Nobel Prize in 1939),[2] sulfonamide-
containing drugs turned out to be one of the greatest
Although many methodologies have been reported for the
synthesis of sulfonyl chlorides, their synthesis is still largely
dominated by the dehydration of sulfonic acids with strongly
oxidizing and unselective reagents, such as POCl3 or SO2Cl2
(Scheme 1b).[9] A viable alternative is the Sandmeyer type
reaction proposed by Meerwein et al., where arenediazonium
salts react with gaseous SO2 to yield sulfonyl chlorides in low-
to-moderate yields.[10] Recently, a photocatalytic version of
this approach using a molecular transition metal complex was
reported.[11]
[*] Dr. Y. Markushyna, Prof. M. Antonietti, Dr. A. Savateev
Department of Colloid Chemistry, Max Planck Institute of Colloids
and Interfaces
Photocatalysis is considered to be a milder method of
synthesis, which might help to overcome selectivity problems
and poor tolerance to other functional groups.[12] Overall,
enhanced chemoselectivity is one of the main advantages of
catalytic methods. Photocatalysis, in turn, possesses a unique
tool to select the reaction pathway—light. Several works
dedicated to chromoselective catalysis represent an exclusive
possibility of photocatalysis to tune the reaction outcome by
simply changing the color of light.[13]
Among the heterogeneous photocatalysts, polymeric
carbon nitride, a metal free semiconductor, has been reported
to enable multiple organic reactions.[14] It has been used to
synthesize azo- and azoxy-compounds or to enantioselective-
ly oxidize ethylbenzene by means of varying the wavelength
of excitation light.[13a,15] Besides, potassium poly(heptazine
imide) (K-PHI), a more refined carbon nitride semiconduc-
tor, possesses extra features especially useful in organic
photocatalysis. In particular, one gram of K-PHI stores up to
Am Mꢀhlenberg 1, 14476 Potsdam (Germany)
E-mail: Yevheniia.Markushyna@mpikg.mpg.de
Oleksandr.Savatieiev@mpikg.mpg.de
C. M. Schꢀßlbauer, T. Ullrich, Prof. D. M. Guldi
Department of Chemistry and Pharmacy, Interdisciplinary Center for
Molecular Materials(ICMM), Friedrich-Alexander University of Er-
langen-Nꢀrnberg
Egerlandstrasse 3, 91058 Erlangen (Germany)
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.202106183.
ꢁ 2021 The Authors. Angewandte Chemie International Edition
published by Wiley-VCH GmbH. This is an open access article under
the terms of the Creative Commons Attribution Non-Commercial
License, which permits use, distribution and reproduction in any
medium, provided the original work is properly cited and is not used
for commercial purposes.
&&&&
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Figure 1. Literature overview and novelty of the present work. a) Classical route to sulfonyl amides; b) Common approaches in sulfonyl chlorides
synthesis; c) Proposed methods of sulfonyl chlorides and sulfonamides synthesis with K-PHI semiconductor using chromoselective catalysis.
Scheme 1. Chromoselective oxidation of thioacetate with K-PHI. Conditions: S-Arylthioacetate 0.04 mmol; K-PHI 4 mg; HCl (36 wt. %) 0.1 mL;
H2O 0.1 mL; MeCN 0.5 mL; T=258C; electron scavenger—O2; irradiation with an LED of specific wavelength. lmax denotes the maximum
emission wavelength of the LED declared by the manufacturer or determined from emission spectra (Figure S2). W stands for LED emitting white
light. (Detailed results can be found in Scheme S1).
1 mmol of electrons via IDEAS (Illumination-Driven Elec-
tron Accumulation in Semiconductors),[16] which allows for
completing multi-electron reactions,[17] activation of CO2,[18]
and design of hybrid nanomaterials for sensing.[19]
In the present work, we investigate the reactivity of
thioacetates in chromoselective catalysis using K-PHI semi-
conductor under 5 quasi-monochromatic light sources ranging
from the UVup to the near IR and white light. Three reaction
pathways for S-arylthioacetates exist: 1) formation of aryl-
chloride, 2) formation of diaryldisulfide, and 3) formation of
sulfonyl chloride (Figure 1c). Changing the wavelength of
incident photons enables selectivity toward one of the three
possible products. Using photons of the optimal energy, we
present a method for the synthesis of sulfonyl chlorides from
a variety of precursors, such as, thiols, thioacetates and
isothiouronium salts, as well as a one-pot synthesis of sulfonyl
amides.
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
www.angewandte.org
&&&&
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Results and Discussion
reaction under illumination with direct sunlight, which led to
the full conversion of the substrate in only 5 hours (entry 12).
Considering the chromoselective catalysis by carbon
nitrides and molecular catalysts[13a–c,15] and the multiple
reaction paths feasible for S-phenylthioacetates[21–24] under
redox conditions, we explored the impact of excitation
wavelength on the selectivity of S-arylthioacetates conver-
sion. To this end, three substrates with different electronic
properties were selected, that is, electron rich 4-methoxyphe-
nylthioacetate, electron deficient 2-trifluoromethylphenylth-
ioacetate, and bare phenylthioacetate. Three different prod-
ucts were formed and their formation depended on the
applied light. The corresponding results are presented in
Scheme 1.
Considering that S-substituted thioacetates are common
substrates for oxidative sulfonylchlorination, S-phenylthioa-
cetate was chosen as a model compound. Under 465 nm blue
light irradiation, which matches the optical gap of K-PHI,
using HCl in a water/acetonitrile mixture and O2 as electron
acceptor, phenylsulfonyl chloride was obtained in 93% yield
(Table 1, entry 1). Analysis of the reaction conditions showed
that all components and light are necessary (Tables S3,4).
Table 1: Screening of semiconductors and molecular photoredox com-
plexes[a]
Scheme 1 infers that the selectivity of the reaction can be
tuned by optimizing the wavelength of the incident light. It is
shown that irradiation with 365 and 410 nm is necessary to
yield arylchlorides. A 465 nm as well as white LED light is
needed for producing sulfonyl chlorides, while irradiation
with 525/625 nm light generates disulfides.
Entry
Catalyst
Light
Time
Yield
(Conversion), %*
Using this approach, various aromatic sulfonyl chlorides
were synthesized under irradiation with an appropriate light
source (Scheme 2a). The proposed method also allows for
using different thio-derivatives as starting substrates: bare
thioles, thioacetates, and isothiouronium salts. The nature of
the thio-precursor affects the reaction only slightly and the
product can be obtained in a good yield and selectivity. For
example, phenylsulfonyl chloride was synthesized from thio-
phenol with a 90% yield and from phenylthioacetate with
a 93% yield under the same conditions.
Despite the synthesis of sulfonyl chlorides is the most
challenging step towards sulfonyl amides, it is certainly
beneficial to obtain them in one step. A slight modification,
that is, using NH4Cl instead of HCl, led to several sulfonyl
amides in a single step, however blue light irradiation was
required for all (Scheme 2b).
To increase the value and to broaden the possible
application of our method next to changing the corresponding
thiol, we studied reactions using different amines. Thus,
primary amines, such as ethylamine and butylamine hydro-
chlorides, gave N-substituted sulfonamides. In contrast,
photocatalytic tests with secondary amines, such as diethyl-
amine, failed in terms of forming the desired product.
Overall, sulfonyl chlorides and sulfonamides derived from
electron rich and electron poor thiols and their derivatives
could be synthesized by the developed method.
1
2[b]
3[c]
4
5
6
7
8
9
K-PHI
K-PHI
K-PHI
mpg-CN
g-CN
H-PHI
Na-PHI
RFT
465 nm
465 nm
465 nm
465 nm
465 nm
465 nm
465 nm
465 nm
465 nm
465 nm
465 nm
sunlight
20 h
20 h
20 h
20 h
20 h
20 h
20 h
20 h
20 h
20 h
20 h
5 h
93 (100)
10 (15)
91 (100)
0
0
0
0
0
0
0
(0)
(0)
(0)
(0)
(0)
(0)
(0)
Ru(bpy)3Cl2
Ir(ppy)3
K-PHI
10
11[d]
12[e]
90 (100)
95 (100)
KPHI
[a] S-Phenylthioacetate 0.04 mmol; photocatalyst 4 mg; HCl (36 wt.%)
50 mL; H2O 0.2 mL; MeCN 0.5 mL; T=258C; electron scavenger—O2;
LED module 465 nm; [b] recycled catalyst; [c] catalyst recovered with
KOH; [d] p-bromothiophenol 0.55 mmol, K-PHI 50 mg. Isolated yield;
[e] S-phenylthioacetate 0.04 mmol; K-PHI 4 mg; HCl (36 wt.%) 0.1 mL;
H2O 0.1 mL; MeCN 0.5 mL; T=258C; electron scavenger—O2; sunlight
70 mWcmÀ2. *Yields and conversion were evaluated by NMR.
With regards to the heterogeneous nature of K-PHI, we
recycled the semiconductor after the photocatalytic reaction.
In the second run, using recycled K-PHI we observed that the
yield of phenylsulfonyl chloride dropped to 10% (entry 2). In
our previous work, we found that under acidic conditions loss
of potassium and partial hydrolysis takes place.[20] Consider-
ing the zeolite-like nature of K-PHI, potassium cations were
back-inserted into the poly(heptazine imide) framework by
treating it with KOH solution. This led to the recovery of the
initial K-PHI activity (entry 3).
For comparison, performances of other carbon nitrides
and several common homogeneous photoredox complexes in
this reaction were evaluated. Surprisingly, we found that other
carbon nitride materials and molecular photoredox com-
plexes only led to the recovery of the starting phenylthioa-
cetate (entries 4–10). Scaling-up of the reaction was per-
formed on a 0.55 mmol scale with a 90% yield (entry 11).
Furthermore, efficiency of the method was proven by the
Irradiation of S-phenylthioacetate with 365, 465, and
525 nm without K-PHI lacks any substrate conversion, which
suggests that chlorobenzene, phenylsulfonyl chloride, and
disulfide evolve only in a photocatalytic process. Likewise,
irradiation of phenylsulfonyl chloride with 365, 465, and
525 nm with or without K-PHI also gave no conversion to any
products. This suggests that chlorobenzene and diphenyldi-
sulfide do not directly derive from phenylsulfonyl chloride,
but the path of their formation is photocatalytic (Ta-
bles S5,S6).
Higher flux of 410 nm photons, that is, 0.2 mmolsÀ1 cmÀ2,
versus 0.05 mmolsÀ1 cmÀ2 of 365 nm photons is likely to
contribute to the higher yield of arylchlorides at 410 nm
&&&&
www.angewandte.org
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
These are not the final page numbers!

Angewandte
Research Articles
Chemie
observed at + 1.58 V, while that for bare S-phenylthioacetate
occurs at + 1.94 V and that for electron-deficient CF3-
substituted S-acetate at + 1.99 V vs. NHE. Therefore, the
photocatalytic oxidation of thioacetates requires a valence
band (VB) potential of at least + 2.0 V vs. NHE. Among the
studied catalysts, only poly(heptazine imide)s fulfill this
requirement (Table S2).
Steady state fluorescence measurements were performed
for K-PHI suspension and the reaction mixture using the
series of excitation wavelengths like in the photocatalytic
experiments (Figure S11). Excitation of just K-PHI suspen-
sion at different wavelengths leads to an invariable position of
emission maximum. When, however, the reaction mixture was
photo-excited with incident light of longer wavelengths, the
emission maximum shifted and the emission intensity in-
creased. Additionally, a faster separation of excitons was
observed when shorter wavelengths were used, as document-
ed in time-resolved fluorescence measurements (Figures 2b,
S17–19). This phenomenon underlines the dependence of the
K-PHI excited state dynamics on the wavelength of incident
light.
Next, fluorescence measurements were employed to
probe the interactions between S-thioacetates and K-PHI
(Figure S12). Addition of thioacetates led to the quenching of
the K-PHI fluorescence. The quenching effect becomes more
pronounces when using electron-rich rather than electron-
deficient substrates and decreases in the following order: 4-
MeOC6H4SAc > PhSAc > 2-CF3C6H4SAc (see Scheme 1 for
chemical structures). This trend correlates well with their
oxidation potentials determined in the CV measurements
(Figure S10).
Oxygen plays crucial role in the studied reaction. Re-
cently, we have shown that intraband states in K-PHI are
responsible for the sequential energy transfer to O2 and,
subsequent, 1O2-sensitization.[25] In the context of the sulfonyl
chloride synthesis, Na-PHI failed to give any desired product.
Indeed, in this system there are no intraband states that could
be involved in 1O2 sensitization and would otherwise be
observed as bands in the visible region of the absorption
spectrum (Figure 2c). K-PHI, in stark contrast, shows two
bands in the diffuse reflectance UV-vis (DRUV-Vis) spec-
trum that are related to energy gaps, that is, an intrinsic band
gap (BG) typical for carbon nitrides of 2.71 eV (previously
assigned to p-p* transitions) and a band of ca. 1.9 eV related
to intraband states (IBS) (previously assigned to n-p*
transitions). K-PHI compared to Na-PHI also shows lower
fluorescence quantum efficiency as another piece of evidence
for more surface states available for trapping excitons (Fig-
ure S16).
Scheme 2. Scope of substrates used in oxidative synthesis of sulfonyl
chlorides (a) and sulfonyl amides (b). a) Conditions: Substrate
0.04 mmol; K-PHI 4 mg; HCl (36 wt.%) 0.1 mL; H2O 0.1 mL; MeCN
0.5 mL; T=258C; electron scavenger—O2; irradiation with LED mod-
ule. a irradiation with LED module 465 nm (46.2 mWcmÀ2); b irradiation
with white LED (139.3 mWcmÀ2); c irradiation with LED module
465 nm (22.6 mWcmÀ2). b) Conditions: Substrate 0.04 mmol; K-PHI
4 mg; NH4Cl 0.19 mmol or RNH3Cl 0.23 mmol; H2O 0.2 mL; MeCN
0.5 mL; T=258C; electron scavenger—O2; irradiation with blue LED
465 nm (46.2 mWcmÀ2). Yield and conversion (given in parentheses)
are given in % and were determined by 1H NMR or GC-MS.
Due to these structural features, a significantly higher
1
concentration of O2 is produced by K-PHI. This summary
was corroborated in near-infrared (nIR) phosphorescence
measurements with a 360 nm photo-excitation (Figures 2d,
S20).[26]
The different behavior of K-PHI and Na-PHI was also
evidenced in transient absorption spectroscopy (TAS) meas-
urements. The excited state dynamics in the case of Ar-purged
dispersions of K-PHI and Na-PHI are very similar. Here,
directly after photoexcitation a negative transient stemming
irradiation (Figures 2a, S9). Nevertheless, the energy of
a photon rather than the overall flux define the path of S-
phenylthioacetate conversion.
Redox properties of the starting S-acetates were eval-
uated by cyclic voltammetry (CV) (Figure S10). For the
electron-rich 4-methoxyphenylthioacetate, the oxidation is
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
www.angewandte.org
&&&&
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Figure 2. Rationale behind the activity of K-PHI in sulfonyl chloride synthesis and chromoselective synthesis of arylchlorides and diaryldisulfides.
a) Correlation of the arylchloride, sulfonyl chloride, and disulfide yields with the photon flux of different LEDs; b) Investigation of exciton lifetime
dependence on excitation light; c) DRUV-vis spectra of K-PHI and Na-PHI powders; d) Singlet oxygen fluorescence measurements for K-PHI and
Na-PHI (lex =360 nm); Sub-picosecond (e) and nanosecond (f) pump-probe transient absorption measurements (lex =387 nm/2 mJ) of K-PHI
suspension in MeCN purged with O2.
from the ground state bleaching (GSB) forms up to 600 nm
together with the formation of a positive absorption in the
nIR region starting, which starts at 900 nm and, which reaches
all the way up to 1350 nm (Figure S21). Within 2 ps, a sharp
440 nm maximum is formed. It quickly turns negative and is
buried by the GSB, which signal dominates the whole visible
region after 300 ps.
In stark contrast, O2-purged solutions behave rather
differently. In the spectrum of K-PHI, a positive transient
forms directly after photoexcitation with maxima at around
630 and 750 nm (Figure 2e,f). Within 3 ps, both maxima
transform into a single maximum at 690 nm. On longer
timescales, that is, after 1 ms, a positive transient forms
between 850 and 1000 nm. We ascribe our observation to
the quenching of the K-PHI excited state by oxygen. This
turns out to be diffusion-controlled. No similar transient was
detected for Na-PHI, whose spectral changes are the same
either in argon or oxygen atmosphere (Figure S21).
fides is sketched in Figure 3. Considering the absorption
spectrum, photons of low energy at 535 nm lead to the
excitation of electrons from the intraband state to the
conduction band, that is, an “IBS-CB” electron transfer
(Figures S23, 24 and discussion in Supporting Information).[25]
Formation of diaryldisulfides is, therefore, rationalized by
deacetylation of arylthioacetate followed by coupling of thiyl
radicals to disulfides. This process is likely to be triggered by
1O2 stemming from an energy transfer pathway as photons of
2.38 eV (green light) and 2.0 eV (red light) are insufficient to
effectively separate excitons considering the K-PHI optical
1
band gap of 2.71 eV. Formation of O2 was verified in EPR
experiments with 2,2,6,6-tetramethylpiperidine (TEMP),
where under 530 nm irradiation, the rising signal of TEMPO
was detected due to trapped 1O2 (Figure 3a, S25).
Irradiation of K-PHI with photons of higher energy (with
410 or 465 nm) allows for the excitation of electrons from the
valence to conduction band, that is, a “VB-CB” electron
transfer, which represents an intrinsic band gap of CN
materials. Such a K-PHI excited state may undergo either
energy or electron transfer pathways. Considering the photo-
catalytic cycle, which rests upon electron transfer, one-
electron oxidation of thioacetate yields the radical-anion of
K-PHI and radical-cation of thioacetate. The latter decom-
Mechanism Discussion
The mechanism of chromoselective conversion of thio-
derivatives to arylchlorides, sulfonyl chlorides, and aryldisul-
&&&&
www.angewandte.org
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Figure 3. The proposed mechanism of chromoselective conversion of thio-derivatives to sulfonyl chlorides, arylchlorides, and disulfides. a) EPR
spectra under 530 nm irradiation and in dark of K-PHI 4 mg and TEMP 5 mL in 0.5 mL MeCN. b) EPR spectra under 455 nm irradiation and in
dark of K-PHI 4 mg and DMPO 5 mL in 0.5 mL H2O:MeCN (1:10). c) Experimental and simulated EPR spectra of the DMPO-thiyl radical adduct
(K-PHI 4 mg, PhSAc 5 mg, DMPO 5 mL in 0.5 mL deaerated MeCN under 415 nm irradiation). d) Detection of Cl2 with QuantofixꢂChlor test
strips.
poses to the corresponding thiyl radical that couples with
chlorine to give sulfenyl chloride. Formation of the phenyl-
thiyl radical was confirmed by EPR and reaction with DMPO
(Figure 3c, detailed discussion in Supporting information). In
particular, a signal with the coupling constants of ab-H = 12.84
G and aN = 10.35 G (g = 2.0062) stems from an adduct of
DMPO with the phenylthiyl radical. This was supported by
GC-MS analysis (Figure S28–31).[27] The K-PHI radical-
anion, in turn, is oxidized by O2 to form peroxide, which
reacts with HCl and give a rise of Cl2.[28]
Under irradiation with blue light of 465 nm, K-PHI
mediates the oxidation of sulfenyl chloride to sulfonyl
chloride by O2 (Figure S32). As such, we propose that
465 nm irradiation activates O2 via both energy and electron
transfer. Electron transfer to O2 was probed in EPR experi-
ments with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Evi-
dence for DMPO-OH was gathered in irradiation experi-
ments with 415 and 455 nm LEDs. It failed, however, when
green light (530 nm) was used (Figure S25). In EPR experi-
ments with TEMP, the formation of TEMPO confirmed
energy transfer when irradiated at 415 and 455 nm (Fig-
ure S25).
The selectivity of 410 nm irradiation to produce aryl
chlorides is rationalized as follows. Under 365 or 410 nm
irradiation, which correspond to energies of 3.02 or 3.4 eV,
respectively, a two-electron oxidation of ClÀ by K-PHI* takes
place. The excess of chlorine leads to over-chlorination of
sulfenyl chloride with formation of unstable arylsulfur
trichlorides, which quickly decompose to afford arylchlor-
ides.[29]
Therefore, two different oxidations are possible in the
reaction mixture. On one hand, it is the oxidation of
thioacetate and, on the other hand, it is the oxidation of
ClÀ. Under 465 nm irradiation, the one-electron oxidation of
thioacetate is favored, while irradiation with 365 nm renders
a high-energy two-electron process, such as the oxidation of
ClÀ, possible. Our mechanistic proposal was backed-up by
determining the Cl2-concentrations with QuantofixꢀChlor
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
www.angewandte.org
&&&&
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Biotechnology, Vol. 55 (Ed.: R. G. Berger), Springer, Berlin,
Heidelberg, 1997, pp. 1 – 49; c) R. J. McGorrin, in Volatile Sulfur
Compounds in Food, Vol. 1068, American Chemical Society,
Washington, 2011, pp. 3 – 31; d) P. Devendar, G. F. Yang, Top.
Curr. Chem. 2017, 375, 82.
stripes. Significantly higher Cl2-concentrations were detected
under 365 nm irradiation, namely 3–10 mgLÀ1 (Figure 3d,
S26), than under 465 nm with 1 mgLÀ1, while none was
detected under 530 nm irradiation.
Next to the high oxidation potential and the ability to
form 1O2, the reason for K-PHI as the only active material in
the discussed reaction (Table 1) might be its negatively-
charged polymeric anion. It enables the temporary storage of
the oxidation product of ClÀ. The local structure of the adduct
between the polyanion of poly(heptazine imide) and active
chlorine resembles that of N-chlorosuccinimide (NCS), which
is a common source of active chlorine in organic synthesis
(Scheme S27).[21] Taking into account that the potassium
content in K-PHI is 8% and using the results from Table 1
(entry 11), the turnover number (TON) is 85, we conclude
that unlike to a reaction with NCS, a path of N-H recovery to
N-K in poly(heptazine imide) exists, that is, a previously non-
catalytic process could be turned catalytic.
[2] F. Bosch, L. Rosich, Pharmacology 2008, 82, 171 – 179.
[3] K. A. Scott, J. T. Njardarson, in Sulfur Chemistry (Ed.: X. Jiang),
Springer, Cham, 2019, pp.1 – 34.
[4] J. J. Li, E. J. Corey, Drug Discovery: Practices, Processes, and
Perspectives, Wiley, Hoboken, New Jersey, 2013.
[5] a) M. Feng, B. Tang, S. H. Liang, X. Jiang, Curr. Top. Med. Chem.
2016, 16, 1200 – 1216; b) P. J. Hogan, B. G. Cox, Org. Process Res.
Dev. 2009, 13, 875 – 879; c) J. Hoyle, in Sulphonic Acids, Esters
and their Derivatives (Eds.: S. Patai, Z. Rappoport), Wiley, New
York, 1991, pp. 351-399..
[6] K. K. Anderson, in Comprehensive Organic Chemistry, Vol. 3
(Eds.: D. H. R. Barton, W. D. Ollis, D. N. Jones), Pergamon
Press, Oxford, 1979, pp. 331 – 350.
[7] a) E. D. Weil, J. Polym. Sci. Part A 1995, 33, 2091; b) G. H.
Whitham, Organosulfur Chemistry, Oxford University Press,
Oxford, New York, 1995; c) K. Tanaka, in Sulphonic Acids,
Esters and their Derivatives (Eds.: S. Patai, Z. Rappoport), Wiley,
New York, 1991, pp. 401-452..
[8] R. Chaudhary, P. Natarajan, ChemistrySelect 2017, 2, 6458 – 6479.
[9] a) S. Fujita, Synthesis 1982, 423 – 424; b) E. E. Gilbert, Synthesis
1969, 1, 3 – 10.
[10] H. Meerwein, G. Dittmar, R. Gçllner, K. Hafner, F. Mensch, O.
Steinfort, Chem. Ber. 1957, 90, 841 – 852.
[11] M. Mꢁjek, M. Neumeier, A. Jacobi von Wangelin, ChemSu-
sChem 2017, 10, 151 – 155.
[12] L. Marzo, S. K. Pagire, O. Reiser, B. Kçnig, Angew. Chem. Int.
Ed. 2018, 57, 10034 – 10072; Angew. Chem. 2018, 130, 10188 –
10228.
[13] a) Y. Dai, C. Li, Y. Shen, T. Lim, J. Xu, Y. Li, H. Niemantsver-
driet, F. Besenbacher, N. Lock, R. Su, Nat. Commun. 2018, 9, 60;
b) A. M. Martꢂnez-Gualda, R. Cano, L. Marzo, R. Pꢃrez-Ruiz, J.
Luis-Barrera, R. Mas-Ballestꢃ, A. Fraile, V. A. de la PeÇa O’Sh-
ea, J. Alemꢁn, Nat. Commun. 2019, 10, 2634; c) I. Ghosh, B.
Konig, Angew. Chem. Int. Ed. 2016, 55, 7676 – 7679; Angew.
Chem. 2016, 128, 7806 – 7810.
[14] a) Y. Markushyna, C. A. Smith, A. Savateev, Eur. J. Org. Chem.
2020, 2020, 1294 – 1309; b) A. Savateev, M. Antonietti, ACS
Catal. 2018, 8, 9790 – 9808.
[15] L. Schmermund, S. Reischauer, S. Bierbaumer, C. K. Winkler, A.
Diaz-Rodriguez, L. J. Edwards, S. Kara, T. Mielke, J. Cartwright,
G. Grogan, B. Pieber, W. Kroutil, Angew. Chem. Int. Ed. 2021,
60, 6965 – 6969; Angew. Chem. 2021, 133, 7041 – 7045.
[16] Y. Markushyna, P. Lamagni, C. Teutloff, J. Catalano, N. Lock, G.
Zhang, M. Antonietti, A. Savateev, J. Mater. Chem. A 2019, 7,
24771 – 24775.
Conclusion
In the present work, we have thoroughly studied chro-
moselective photocatalysis on the example of oxidative
chlorination of thiobenzenes with carbon nitride K-PHI.
Three products, that are, sulfonyl chlorides, aryl chlorides, and
aryldisulfides, are selectively formed from the same reaction
mixture just by adjusting the wavelength of incident light.
Moreover, for the first time, photocatalytic methods for the
synthesis of aromatic sulfonyl chlorides and amides from
thioderivatives have been developed. High performance of
the proposed method is also shown by probing the reaction at
direct sunlight with a yield of 95% within a time-period of
5 hours. The mechanism of chromoselective catalysis is rather
complex, however rationalized by the combination of several
unique properties of K-PHI, namely the presence of intra-
band states that allows for energy as well as electron transfer,
high oxidation potential, ability for multi-electron trans-
formations, and negatively charged polymeric structure.
Acknowledgements
AS, YM and MA gratefully acknowledge Max Planck Society
for financial support. Open access funding enabled and
organized by Projekt DEAL.
[17] Y. Markushyna, A. Vçlkel, A. Savateev, M. Antonietti, S.
Filonenko, J. Catal. 2019, 380, 186 – 194.
[18] Y. Markushyna, P. Lamagni, J. Catalano, N. Lock, G. Zhang, M.
Antonietti, A. Savateev, ACS Catal. 2020, 10, 7336 – 7342.
[19] A. Savateev, Y. Markushyna, C. M. Schꢄßlbauer, T. Ullrich,
D. M. Guldi, M. Antonietti, Angew. Chem. Int. Ed. 2021, 60,
7436 – 7443; Angew. Chem. 2021, 133, 7512 – 7520.
[20] Y. Markushyna, C. Teutloff, B. Kurpil, D. Cruz, I. Lauermann, Y.
Zhao, M. Antonietti, A. Savateev, Appl. Catal. B 2019, 248, 211 –
217.
Conflict of Interest
The authors declare no conflict of interest.
Keywords: carbon nitride · chromoselective catalysis ·
organic synthesis · photoredox catalysis · sulfonyl chloride
[21] A. Nishiguchi, K. Maeda, S. Miki, Synthesis 2006, 2006, 4131 –
4134.
[22] J. Choi, N. M. Yoon, Synlett 1995, 1073 – 1074.
[23] H. M. Meshram, A. Bandyopadhyay, G. S. Reddy, J. S. Yadav,
Synth. Commun. 1999, 29, 2705 – 2709.
[1] a) M. Feng, B. Tang, S. H. Liang, X. Jiang, Curr. Top. Med. Chem.
2016, 16, 1200 – 1216; b) P. S. J. Cheetham, in Biotechnology of
Aroma Compounds. Advances in Biochemical Engineering/
[24] H. M. Meshram, Tetrahedron Lett. 1993, 34, 2521 – 2522.
&&&&
www.angewandte.org
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
These are not the final page numbers!

Angewandte
Research Articles
Chemie
[25] A. Savateev, N. V. Tarakina, V. Strauss, T. Hussain, K. ten Brum-
[28] R. S. Livingston, W. C. Bray, J. Am. Chem. Soc. 1925, 47, 2069 –
2082.
[29] I. B. Douglass, B. S. Farah, E. G. Thomas, J. Org. Chem. 1961, 26,
melhuis, J. M. Sꢁnchez Vadillo, Y. Markushyna, S. Mazzanti,
A. P. Tyutyunnik, R. Walczak, M. Oschatz, D. M. Guldi, A.
Karton, M. Antonietti, Angew. Chem. Int. Ed. 2020, 59, 15061 –
15068; Angew. Chem. 2020, 132, 15172 – 15180.
1996 – 1999.
[26] Excitation with 460 nm and 620 nm lead to the lower or no signal
of 1O phosphorescence due to the very low K-PHI amount, short
irradiation time and weaker light source used for the measure-
ment (Figure S20).
[27] O. Sala, N. Santschi, S. Jungen, H. P. Luthi, M. Iannuzzi, N.
Hauser, A. Togni, Chemistry 2016, 22, 1704 – 1713.
Manuscript received: May 7, 2021
Revised manuscript received: June 22, 2021
Accepted manuscript online: July 5, 2021
Version of record online: && &&
,
&&&&
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
www.angewandte.org
&&&&
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Research Articles
Photoredox Catalysis
Photons are traceless reagents in the
photocatalytic system, able to control the
reaction pathway. Herein, the carbon
nitride photocatalyst is used to obtain
three products from the same reaction
mixture only varying the excitation light.
The developed method is optimized for
the synthesis of sulfonyl chlorides and
amides. Finally, through different phys-
ico-chemical methods, the rationale
behind the chromoselective synthesis is
explained.
Y. Markushyna,* C. M. Schꢀßlbauer,
T. Ullrich, D. M. Guldi, M. Antonietti,
A. Savateev*
&&&& — &&&&
Chromoselective Synthesis of Sulfonyl
Chlorides and Sulfonamides with
Potassium Poly(heptazine imide)
Photocatalyst
&&&&
www.angewandte.org
ꢁ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
These are not the final page numbers!