84
3 The Reactivity of Nitrile Imines
N
N
N
N
N
N
N
N
N
N
- 1,1-cyclo
-addition
- nucleophilic
vinyl group
R
1
R
1
R
1
R
1
R
1
- stepwise
- propargylic NI
- concerted
- carbenic NI
Scheme 3.74 The two potential mechanisms of intramolecular cyclopropylcinnoline formation
from the NI species shown
indicated that these products may in fact be formed through an intramolecular 1,5rearrangement with aryl ring, with the high temperatures involved permitting the
normally unfavourable disruption of aromaticity (Scheme 3.75) [241].
N
N
N
N
O
i Pr
N
H
N
O
i Pr
350
o C
N N
O
i Pr
N N
O
i Pr
H
via
1,5-rearrangment
C-H insertion
or
Scheme 3.75 The formation of indazoles via pyrolysis of 2,5-tetrazoles, which may proceed
through either a carbenic C–H insertion or a 1,5-rearrangement
3 The Reactivity of Nitrile Imines
N
N
N
N
N
N
N
N
N
N
- 1,1-cyclo
-addition
- nucleophilic
vinyl group
R
1
R
1
R
1
R
1
R
1
- stepwise
- propargylic NI
- concerted
- carbenic NI
Scheme 3.74 The two potential mechanisms of intramolecular cyclopropylcinnoline formation
from the NI species shown
indicated that these products may in fact be formed through an intramolecular 1,5rearrangement with aryl ring, with the high temperatures involved permitting the
normally unfavourable disruption of aromaticity (Scheme 3.75) [241].
N
N
N
N
O
i Pr
N
H
N
O
i Pr
350
o C
N N
O
i Pr
N N
O
i Pr
H
via
1,5-rearrangment
C-H insertion
or
Scheme 3.75 The formation of indazoles via pyrolysis of 2,5-tetrazoles, which may proceed
through either a carbenic C–H insertion or a 1,5-rearrangement