Handbook of Functionalized Organometallics Applications in S

Ar
OR
Scheme 6.42
N
H
SnBu 3
n-BuLi (2 eq.)
THF, -78ºC
MOMO
Ar=
R=MOM
O
O
Ar
H
N
H
6.5 Transmetallations
HO
O
O
N
H
Crinine
The tin-to-lithium exchange can be applied to aziridin chemistry, as illustrated
by the reported synthesis of the Aziridinomitrosene skeleton (Scheme 6.43), by an
intramolecular Michael addition after lithiodestannylation followed by a spontaneous
aromatization [360].
OTIPS
OMe CO2 Et
Scheme 6.43
N
D
NTr
SnBu 3
1) MeLi
2) PhSeCl
OTIPS
OMe CO2 Et
N NTr
Finally, an aza-Wittig rearrangement of acyclic enantio-enriched N,N-diallyllic
a-amino alkylithium prepared via a tin-to-lithium exchange was reported, the process
proceeding predominantly with inversion of configuration at the lithiumbearing
carbon terminus [361].
6.5.2.2 Alkenyltins
The tin-to-lithium exchange in alkenyltins is characterized by the preservation of
the alkene stereochemistry and is compatible with several functionalities on the
alkene moiety such as amino, hydroxyl and ester groups. The transmetallation of
functionalized vinyltins has found an application in the synthesis of complexmolecules
such as unsaturated fatty acids [362], prostaglandin side-chain [363], various
antibiotics [364] and a biotoxin [365].
1,1- and 1,2-distannnylalkenes are also lithiated. An interesting example
involved the bis stannylated enyne, prepared from an unsymmetrical butadiene.
A subsequent regioselective lithiation of the internal tin residue followed by a 1,4retro-Brook
rearrangement afforded the functionalized vinylsilane in a stereoselective
fashion [366] (Scheme 6.44), which can also be considered as a masked
triyne.
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