Biomedical Engineering Reference
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O
O
O
O
O
O
AuL
(JohnPhos)AuCl (5 mol%)
AgNTf
2
(5 mol%)
AuL
MeO
Boc
Boc
MeO
MeO
N
O
N
MeOH (5 equiv)
- MeOH
OMe
NHBoc
Me
CH
2
Cl
2
, rt, 24 h
98%
MeO
MeO
MeO
OMe
OMe
OMe
129
130
- MeOH
O
O
O
O
O
O
LiAlH
4
Dioxane, 100°C, 5 h
71%
Boc
N
N
N
MeO
MeO
MeO
OMe
OMe
OMe
Nitidine
133
132
131
SCHEME 4.38
Formal synthesis of nitidine by Takemoto and coworkers.
AuL
AuL
AuL
O
O
O
IPrAuNTf
2
(5 mol%)
THF, 45°C, 2 h
78%
N
N
N
H
134
135
136
H
O
H
2
, PtO
2
N
N
6 N HCl
Indolizidine 167B
138
137
SCHEME 4.39
Formal synthesis of indolizidine 167B by Zhang and coworkers.
4.3.2. Cyclizations Involving the Formation
of a New C-C Bond
4.3.2.1. Alkyne-Ene and Allene-Ene Cyclizations In addition to the
transformations presented in the previous section that involved the initial addition
of a nitrogen nucleophile on an unsaturation, nitrogen-containing heterocycles can
also be accessed by a ring closure involving the formation of a new C-C bond.
The gold(I)-catalyzed cycloisomerizations of enynes and allene-enes represent a
powerful synthetic tool for this purpose [31].
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