56
3 The Reactivity of Nitrile Imines
N
Cl
NH
Ph
Ph
AlCl 3 , o-dichlorobenzene
120
o C, 0.5 h
85 %
N
N
N
Ph
Ph
Me
MeCN
N
Cl
NH
MeO 2 C
Et 3 N, DCM
40
o C, 3 h
86 %
N
N
N
MeO 2 C
Ph
Cl
OMe
Ph
NH
OEt
PhCN, EtOH
PhCN
EtOH
HCl
Scheme 3.27 The use of exogenous reagents in the activation of nitriles towards NI 1,3-dipolar
cycloaddition
3.1.6 Carbon-Sulfur Bonds
As with imines and nitriles, carbon-sulfur double bonds have been utilised as NI
dipolarophiles. The first examples emerged from a publication from Huisgen in 1962
(Scheme 3.28) [105].
Carbon disulfide has proven to be a somewhat popular NI dipolarophile within
the literature, although the stoichiometries involved must be controlled. In some
cases, this can lead to the intended syntheses of a 5,5-spirocycle using excess NI
(Scheme 3.29), particularly useful in NI polymerisation reactions (see Sect. 4.3.1 for
further details) [100]. There are also multiple other examples which document the
N
Cl
NH
Ph
Ph
Et 3 N, PhH
80
o
C, 20 h
72 %
N
S
N
Ph
Ph
Ph
Ph
S
Ph
Ph
Scheme 3.28 One of the first examples of the reaction of NIs with a C–S double bond
N
Cl
NH
Ph
Ph
Et 3 N
50
o C, 1 h
63 %
CS 2
N N
Ph
Ph
N
N
Ph
Ph
S
S
N
Cl
NH
EtO 2 C
Py
120
o
C, 2 h
83 %
CS 2
HN
N
Ph
N N
EtO 2 C
H
N
N
Ph
S
S
Scheme 3.29 The reactions of NIs with carbon disulfide