Beilstein J. Org. Chem. 2018, 14, 2799–2804.
S-diazocine reported in the Cambridge Structural Database er, the overall yields and the reliability of the formation of the
(CSD; version 5.39; Feb. 2018) [28].
azo group are superior to previously reported methods. All
S-diazocines 1–5 are thermodynamically more stable in their
This compound crystallizes in the monoclinic space group P21/c cis configuration. Irradiation with violet light (405 nm) converts
with Z = 4 and all atoms in general positions (specification see the cis into the trans isomer with 50–70% yield. Back-reaction
conformation with an dihedral angle of 72.24(8)° between both half-lives of the metastable trans isomer are between 1–7 days.
phenyl rings (Figure 3). Each of these rings is planar with These properties are ideal for applications in photopharma-
maximum deviations from the mean plane calculated through cology where the more bulky cis state is the inactive form and
the C atoms of 0.014(2) and 0.009(2) Å. The N=N bond lengths the trans isomer is the active configuration.
of the azo group of 1.251(4) Å corresponds to literature values
and the CNNC torsion angle amounts to 3.7(4)°, which proves
Supporting Information
that this unit is nearly coplanar. In contrast, the CCSC fragment
is twisted by 22.9(3)°. The structure of the title compound 3 can
CCDC-1857720 (3) contains the supplementary
be compared with the structure of 5,6-dihydrobenzo[c,g][1,2]-
crystallographic data for this paper. These data can be
diazocine (18) already reported in the literature [8]. In this com-
obtained free of charge from the Cambridge
pound the CNNC fragment is more planar with an torsion angle
Crystallographic Data Centre via
of 0.7(2)°. The dihedral angle between the phenyl rings of
85.00(6)° is larger compared to the S-diazocine 3. The ethylene
Supporting Information File 1
Analytical equipment, experimental procedures, spectral
data and crystallographic data.
group in the 8-membered ring is disordered in two orientations
with torsion angles of 47.9(1) and 37.7(1)°, which means that
the overall molecule is more distorted in the C-diazocine than in
the sulfur analogue.
Acknowledgements
The authors gratefully acknowledge financial support by the
Deutsche Forschungsgesellschaft (DFG) within the Sonder-
forschungsbereich 677, “Function by Switching”.
ORCID® iDs
Figure 3: Left: crystal structure of the iodo-functionalized S-diazocine
3. Right: crystal structure of the unfunctionalized C-diazocine 18 [8].
References
Conclusion
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