Chemistry Reference
In-Depth Information
SCHEME 11.22.
Pandurangi et al.
91
prepared the first example of a compound BFCA1 containing in
the same molecule a photochemical nitrene precursor for labeling (perfluorophenyl
azide) and a bifunctionality for complexation with a transition metal (Scheme 11.22).
In a recent article, Pandurangi et al.
8a
reported the preparation of novel BFCAs
with improved properties for covalent attachment to biomolecules. The Re chelate
BFCA2 was prepared and its photochemical properties (insertion to C
H and
N
H) were tested with organic solvents like hexane and diethylamine. They
extended their experiments to labeling of human serum albumin and antibody
fragments under aqueous conditions. The insertion efficiency of BFCAs was found
to increase when the metal center was connected far enough from the photolabile aryl
azide to avoid perturbance of the photochemical properties.
8a
11.8 CONCLUSIONS AND OUTLOOK
The complex photochemistry of aryl azides has fascinated scientist for many years.
Much time has been devoted to elucidate the actual mechanism of the photochemical
process for a simple aryl azide like phenyl azide and fluorosubstituted aryl azides.
Spectroscopists have investigated the means to characterize short-live intermediates
formed (like singlet nitrene and triplet nitrene) by different analytical techniques.
Their lifetimes and reaction rates have been determined by new and highly sensitive
techniques such as laser flash photolysis. The intermediates, formed on photolysis of a
given azide under different conditions, have been trapped by reaction with nucleo-
philes. Theoretical calculations have explained the intrinsic interplay of the several
intermediates present in solution.
In spite of the extensive research on the photochemistry of aryl azides, there are
some areas that remain to be investigated. The application of this reaction in the
synthesis of novel heterocyclic compounds has not been studied. Since fluorophenyl
