Chemistry Reference
In-Depth Information
-NSO
2
CH
3
+
S
S
h
v, 266 nm
+
1
NSO
2
CH
3
1
61b
72
71b
S
S
77
N
N
H
3
CO
2
S
H
3
CO
2
S
SCHEME 12.37.
Proposed scheme of the sulfonyl azepine
77
formation.
26
with a
trans
/
cis
ratio about 2 in both cases. Raising the
cis
-4-octene concentration
from 12 to 890mM increased the aziridine yield from 74% to 97% but increased the
retention of stereochemistry only slightly.
26
However, it was not possible to detect any IR bands attributable to the singlet or
triplet mesyl nitrene
with TRIR spectroscopy.
26
Only, the instantaneous
formation of two IR bands at 1330 and 1150 cm
1
was observed. These bands
were tentatively assigned to the sulfonyl azepine 77 (Scheme 12.37) arising from
insertion of
1
61b
61b
onto the dibenzothiophene nucleus.
Toscano and coworkers
26
also performed calculations of the singlet-triplet
splitting for the mesyl nitrene and benzenesulfonyl nitrene (
). The calculations
at all levels of theory employed to predict that the SON fragment of singlet sulfonyl
nitrenes have a cyclic structure similar to the other acyl nitrenes investigated
(Fig. 12.19). The length of the weak O
61b
,
d
N bond is close to the similar bond in
carbonyl nitrenes (Fig. 12.6) and nitrene esters (Fig. 12.18). As the SO and SN bonds
are significantly longer than the CO and CN bonds, the NSO bond angles in the
FIGURE 12.19.
Selected bond lengths (A
) and bond angles of singlet and triplet states of
mesyl nitrene optimized at the B3LYP/6-31G(
d
) level.
26
