Chemistry Reference
In-Depth Information
70
) than the corresponding
singlet sulfonyl nitrenes are significantly smaller (
90
).
Calculations at all levels of theory predict that the triplet state is the ground state of
the sulfonyl nitrenes
NCO bond angles in the singlet carbonyl nitrenes (
61b,d
. However, the singlet-triplet splitting is low and equal to
4-7 kcal/mol at
the highest
levels of theory employed (MP2/6-311G(3
df
,2
p
)//
B3LYP/6-31G(
d
,
p
) for
). Similar to
the carbonyl nitrenes, the reason is the N
O bonding interaction, which stabilizes
significantly the singlet state of sulfonyl nitrenes.
61b,d
and MCSCF(22,15)/6-31G(
d
,
p
) for
61b
12.5 GENERATION AND PROPERTIES OF PHOSPHINYL-
AND PHOSPHORYL NITRENES
Properties of phosphinyl- (
) are discussed in this
section (Scheme 12.38). Thermolysis and photolysis of corresponding phosphinyl
(
78
) and phosphoryl nitrenes (
79
) azides were mainly used to generate these acyl nitrenes.
155-166
The evidence of the diethoxyphosphoryl nitrene (
80
) and phosphoryl (
81
) formation was
obtained upon refluxing a solution of diethyl
N
,
N
-dibromophosphoramidate in
benzene in the excess of activated zinc dust.
167
The products from insertion of
nitrene
79a
H bond of benzene were isolated.
167
Formation of phosphonyl
nitrenes in a small yield was also proposed in the phototransformation of trialky-
lammonio-
N
-diphenylphosphinoylimides.
168
79a
into a C
12.5.1 Phosphinyl Azides and Nitrenes
78
80
Phosphinyl nitrenes and azides (
) have not attracted much attention in the
literature; only product studies
155-159
and quantum chemical calculations of the
properties of dimethylphosphinyl azide and nitrene
169
have been performed. In 1964,
Reichle carried out vacuum pyrolysis (680
) of diphenylphosphinyl azide
80a
, which
gave polymeric residues in a high yield (72%).
155
This polymer contained phenyl
group bound to nitrogen, which is the indication of a Curtius-like rearrangement of
phosphinyl azide
,
.
Later,
156
Harger synthesized cyclic analogues of phosphinyl azides, namely,
1-azidophosphetan oxides
80a
82
and
83
. Photolysis of azides
82
and
83
in methanol
O
O
P
N
P
N
R
1
R
2
R
1
O
OR
2
78
79
R
1
, R
2
= alkyl, aryl
SCHEME 12.38.
Structures of phosphinyl- (
78
) and phosphoryl nitrenes (
79
) discussed in
this section.
