Handbook of Functionalized Organometallics Applications in S

2.3 b-Functionalized Organolithium Compounds 23
Dianions 126, alkenyllithium compounds of type VIII, have been obtained by
halogen±lithium exchange from the corresponding chlorinated or brominated
precursors 125 using lithium naphthalenide; it was necessary to carry out a previous
deprotonation with PhLi. The reaction of 126 with electrophiles gave regioselective
functionalized allyl amines 127 (Scheme 2.17) [106].
Hal
NHR
1. PhLi, THF, -78ºC
2. LiC 10H 8,-78ºC
E=H2O, D2O, Me2S2,R 1 R 2 Hal = Cl, Br
CO, CH2=CH2CH2Br Li
Li
NR
1. E
2. H 2O
X
NHR
125 126 127 (68-93%)
Scheme 2.17
Vinyllithium derivatives 128±131 have been generated through a bromine±lithium
exchange with t-BuLi. In the case of 128, used in the synthesis of (±)-wodeshiol,
a deprotonation of the alcohol functionality was performed prior lithiation
[107]. Intermediates 129 were also used in the synthesis of triquinanes [102,108],
meanwhile 130 acted as an intermediate in a synthetic route to (+)-pericosine B
[109]. Dianionic species 131 showed an unexpected intramolecular carbometallation
upon addition of TMEDA to give dilithiated dihydropyrroles, which finally
reacted with different electrophiles [110].
O
O
OLi
Li
OR
( ) n
Li
Li
TESO
TESO
OMe
OTES
128 129 (n = 0, 1) 130 131
Vinyllithium acetals 133, compounds of type IX, were prepared from the corresponding
chlorinated precursor 132 by a DTBB-catalyzed lithiation at low temperature.
They reacted with electrophiles to give compounds 134. In the case of using
chiral starting materials (132, R = Me), the reaction with prostereogenic carbonyl
compounds took place with almost null stereoselectivity (Scheme 2.18) [111].
R
O
R
O
Cl
Li, DTBB (5 mol%)
THF, -78ºC
R
O
R
O
Li
1. E
2. H 2O
132 133 134 (51-98%)
[E = H2O, D2O, Me3SiCl, RCHO, R1R2CO] Scheme 2.18
R
RN
O
R
O
Li
Li
X