Tetrabutylammonium fluoride (TBAF) is an efficient catalyst in the [3 + 2] cycloaddition reaction of organic nitriles 1 with trimethylsilyl azide (TMSN(3)) in solventless conditions. The corresponding 5-substituted 1H-tetrazoles 2 were obtained under mild conditions and in 80-97% yields.
TBAF-catalyzed [3 + 2] cycloaddition reactions of 2-aryl-1-cyano- or 2-aryl-1-carbethoxy-1-nitroethenes 1 with TMSN3 under SFC allow the corresponding 4-aryl-5-cyano- or 4-aryl-5-carbethoxy-1H-1,2,3-triazoles 2 to be prepared under mild reaction conditions and with good to excellent yields (70-90%). The proposed protocol does not require dried glassware or inert atmosphere.
(R)-4-Hydroxy-, -4-fluoro-, -4-bromo-, and
-4-iodo[2.2]paracyclophanes have been prepared and
their
absolute configuration assigned on the basis of chemical correlations.
Different relationships
between the specific optical rotation and the group polarizability have
been found depending on
the ability of the substituents to conjugate with the aromatic ring.
At least for 4,7-disubstituted
[2.2]paracyclophanes, the effects of the substituents on the
specific rotation seem to be additive,
independent of the wavelength used. An equation has been derived
which allows to predict, to a
satisfactory approximation, the [α] values of
4-X-7-methyl[2.2]paracyclophanes whenever the
group
polarizability of the substituents is known.
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