Environmental Engineering Reference
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guidedly using triazoles are used to evaluate the biological effects of other com-
pounds in the database. Cycloaddition of azido compounds and alkyne or active
alkene produces triazoles. Available azido compounds include hydragoic acid,
metal azides, organic azido compounds. Alkene only reacts with organic azido
compounds. In the cycloaddition of azido compounds and alkyne, the types of
azido compounds and alkyne impact triazoles. Aromatic and aliphatic azides react
with active alkyne to generate 1,2,3-triazoles. Sulfonyl azides react with active
alkyne, which produces N-sulpyl triazoles. After rearrangements, the mixtures of
triazoles, its isomers with open loops, and
finally [ 10 ].
Being catalyzed by Cu(I), the cycloaddition selectively generates 4-substituted 1-
(N-sulfonyl-)-1,2,3-triazoles. Adamo et al. [ 11 ] discovered another special method
to synthesize triazoles. This method is the cycloaddition of
α
-diazoimides are produced
-unsaturated ami-
noketones and diethylaluminum azide. After reduction of azides, amine-group
compounds are obtained. Thoils, complex hydrides, and borane with Lindlar cat-
alyst can reduce azide into amine-group compounds. Li/2-tertbutyl biphenyl
reduces azido group into primary amine at room temperature. Under catalysis of
FeCl 3 , N,N-dimethylhydrazine is a mild reductant of azides. Trimethyl chlorosilane
can reduce aliphatic, romatic, and benzoyl azides into amine with severe reaction
conditions. Catalyst samarium diodide (SmI 2 ) helps the reactions conducted in a
moderate condition. Huang et al. [ 12 ] reduced alkyl, aryl, acyl, and sulfonyl azides
into amines using samarium diodide as catalyst with mild reaction conditions. The
yields of amines were very high. Under catalysis of Cu(II), zinc borohydride and
sodium borohydride can reduce azido group into amine. Iron salt Fe(II) and stan-
naimine Sn(II) [ 13 ] (acryl substituted tin (II) thiolate) are very good reductants.
Acyl azides are not stable. In inert hot solvents, they like to rearrange and release
nitrogen gas. The parsed intermediate isocyanates hydrolyze to primary amine. This
is the famous Curtius rearrangement (below equation).
α
,
ʲ
O
RNCO hydrolysi s
-CO 2
R
N
N N
RNH 2
Curtius
Rearrangement
6.1.2.3 Application of Azido Compounds in Azene Chemistry
Azene is a kind of reactive intermediates in organic synthesis, which is produced
through the decomposition azido compounds under illumination or heat. Azene is
the nitrogen analogs of carbene; it is high electrophilic. Azene is widely applied in
cycloaddition,
rearrangement,
ring expansion,
ring contraction, and insertion
reactions.
Cycloadditions of azido compounds and various functional groups are a classic
synthesis of triazoles with nitrogen containing rings. Their intramolecular cyc-
loadditions derive a lot of organic compounds. Lukina et al. [ 14 ] synthesized
 
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