Chemistry Reference
In-Depth Information
SCHEME 11.8.
11.4 PHOTOCHEMISTRY OF FLUORINATED PHENYL AZIDES
IN AMINES
11.4.1 Reactions in Diethylamine
It is well-established that irradiation of an aryl azide at room temperature in the
presence of a nucleophile (HNuc) such as diethylamine (Scheme 11.8) gives a variety
of products; among them, the ring expanded azepine.
12,13,24
This reaction has been studied for more than 60 years and a variety of reaction
pathways have been proposed to explain the products formed. Short-lived intermedi-
ates, with a lifetime of nanoseconds or picoseconds, have been monitored by improved
spectroscopic techniques such as LFP.
21,22,25
The
1
PhN is considered to be the first
intermediate formed on photolysis of PhN
3
.
12,13,26
However, the nature of the
intermediate involved in the ring expansion is still under debate (shown as segmented
arrows, to or from DA, in Scheme 11.9). Early studies on the photolysis of PhN
3
by
Huisgen and Vossius
27
suggested that the first intermediate formed from the
1
PhN was
BA. Later studies in the photochemistry of matrix isolated PhN
3
by Chapman and Le
Roux
28
gave IR spectroscopic evidence for the formation of DA.
SCHEME 11.9.
