Chemistry Reference
In-Depth Information
nucleophilic aniline. HF elimination, heterocyclic ring closure, and further HF
elimination would give the phenazine. A similar mechanism has been proposed
in the oxidation of PFA to DFAB with sodium hypochlorite.
34
Consistent with the
proposed intermediacy of fluorophenyl nitrene in this oxidation is the reported
formation of both products, DFAB and octafluorophenazine, in the thermal decom-
position of PFPhN
3
in the presence of PFAwhere singlet nitrene is considered to be
the intermediate.
18
11.6 NOVEL FLUORO ARYL NITRENE PRECURSORS
11.6.1 Fluorinated 2-Nitrophenyl Azides and 2-Nitroanilines
Phenyl azide derivatives with an unsaturated
ortho
substituent (Scheme 11.16) are
useful starting materials for heterocyclic-ring synthesis by pyrolysis or photolysis.
39
Thereby, anchoring assistance of the
ortho
substituent plays an important role in
decreasing the activation energy.
40
o
-Nitrophenyl azide (NPA) is a well-studied
precursor for heterocyclic-ring synthesis of benzofuran via photolysis and pyrolysis
in both liquid and gas phases.
41
Benzofuroxans comprise a well-known class of heterocyclic compounds with
important biological applications.
42
They have gained interest as cardiovascular
agents (like nitroglicerol) due to their ability to generate nitric oxide which plays an
important role as a biological messenger.
42
The property of benzofuroxans to be
involved in the synthesis of DNA and peptides has stimulated a search to develop
anticancer compounds.
43
A wide range of biological activity has been claimed for
benzofuroxans and derivatives.
44
Some present nematocidal, antimicrobial, fungici-
dal, herbicidal, and algicidal properties. Others are depressants of the central nervous
system, muscle relaxants, and anticonvulsants.
Benzofuroxans have been reported to serve as intermediates in the synthesis of a
large number of commercially available pharmaceuticals and veterinary medical
products such as benzimidazole-3-oxides.
44
They react very easily with carbonyl
compounds in basic media to give quinoxaline-1,4-dioxides with strong antibacterial
activity.
45
SCHEME 11.16.
