Chemistry Reference
In-Depth Information
MTBD (
3
)
(10 mol%)
Me
Me
Me
Me
(a)
+
CO
2
O
N
Bn
H
Bn
MeCN
O
O
O
1. PS-TosMIC reagent
BTMG (
2
)
N
H
(b)
2. filtration
3. evaporation
X
X
Ph
n
PS-TosMIC
reagent
SO
2
NC
Scheme 4.29
Guanidine catalysed formation of oxazolidinone and oxazole ring systems
Pyrrole
Pyrrole derivatives were given in 80% yield by treatments of
-nitrostyrene with iso-
cyanoacetate and DBU [80] (Scheme 4.30). The reaction was slightly faster and the yield
better (90%) whenDBUwas replaced by BTMG (2), inwhichMichael addition, cyclization
through internal attack of the nitronate on the isocyano group, elimination of a nitronate ion
through a vinylogous E1
CB
mechanism after proton exchange and aromatization by a [1.5]-
sigmatropic shift of hydrogen could be successively occurred.
b
4.3.3.2 Horner-Wadsworth-Emmons Reaction
TMG (1) is used as a base in Horner-Wadsworth-Emmons (HWE) reactions [81]. For
example, the sequential reaction of 1,3-diformylbenzene with different phosphorylglycines
OMe
OMe
BTMG (
2
)
t
BuO
2
C
t
BuO
2
C
+
CN
HN
O
2
N
Me
Me
Scheme 4.30
BTMG (2) catalysed formation of pyrrole ring system
