stereochemistry

CARLO THILGEN, ISABELLE GOSSE, AND FRANÇOIS DIEDERICH 33
MeO
MeO
OMe
MeO
MeO
O
MeO
O OMe
O
EtO2C MeO
O
O
O
EtO 2C
OMe
O
O
(P, f A)-42
(e,e,e; C3)
OMeO
O
O
MeO O
O
(M, f A)-43
(e,e,e; C3)
OMe
O O
CO2Et O
MeO
O
O
O
EtO2C CO 2Et
s
EtO2C
O
O
(M, f C)-42
(e,e,e; C3)
O
OMe O
O OMe
O
O
(P, f C)-43
(e,e,e; C3)
O
OMe
MeO O
CO2Et O
OMe
O
O
O
CO2Et Figure 1.17. The four classical stereoisomers of a CTV-C60 tris-adduct conjugate with an e,e,e
addition pattern, and their planar representations. Each structure corresponds to a unique topological
stereoisomer.
On the other hand, the four stereoisomers of the trans-3,trans-3,trans-3 trisadduct
((P , f A)-44, (M, f C)-44, (M, f A)-45, and(P , f C)-45) are formally
interconvertible pairwise ((P , f A)-44 and (M, f A)-45), and ((M, f C)-44 and
(P , f C)-45), respectively (Figure 1.18) by a continuous deformation making
the C60 ball pass through the nine-membered ring of the CTV unit. In conclusion,
there are four classical, but only two topological stereoisomers for
the trans-3,trans-3,trans-3 tris-adduct. 18 This appears plausible by considering
the fact that the plane including the three methano bridge C-atoms divides the
fullerene spheroid into two equal halves in the trans-3,trans-3,trans-3 adduct,
but into two different fractions in the e,e,e adduct.
MeO
OMe
OMe
OMe
MeO
OMe