Handbook of Functionalized Organometallics Applications in S

24
2 Polyfunctional Lithium Organometallics for Organic Synthesis
2.4
c-Functionalized Organolithium Compounds
Organolithium compounds with a functional group at the c position can be represented
by a great number of general structures (XI±XX) depending on the hybridization
of the carbon atoms bearing both the lithium and the functional group.
Li
Li X Li X
X
X
Li
X
Li
Li
X
XI XII XIII XIV XV
XVI
X
Li
X
XVII
2.4.1
c-Functionalized Alkyllithium Compounds
X
Li
XVIII
Functionalized organolithium compounds of type XI can be accessible through a
large number of methodologies. They are accessible by halogen±, sulfur±, or selenium±lithium
exchange, tin±lithium transmetallation, reductive opening of fourmembered
heterocycles and also by carbolithiation of cinnamyl systems.
Enantiomerically pure oxygen functionalized organolithium compounds 135±138
have been prepared by halogen±lithium exchange. The precursor of 135 was the
corresponding chlorohydrin and lithium naphthalenide the lithiating reagent [86],
meanwhile intermediates 136 [112], 137 [113] and 138 [114] were prepared by
iodine±lithium exchange by means of t-BuLi. All of them reacted with electrophiles
to yield polyfunctionalized compounds, compound 137 being used in the
synthesis of scopadulcic acid A.
OLi
Li
OBn
Li
O
O
() 3
OLi
Li O O
CF3 Li
135 136 137 138
The carbolithiation of cinnamyl methyl ether 139 with an alkyllithium in the
presence of TMEDA led to the corresponding benzylic organolithium intermediates
140, which by reaction with electrophiles gave compounds 141 with high diastereoselectivity
(Scheme 2.19) [115].
X
Li
XIX
X
Li
XX
X