stereochemistry

CARLO THILGEN, ISABELLE GOSSE, AND FRANÇOIS DIEDERICH 31
EtO
O
O
O
O
OEt
O
O
O
O
O
O
O
O
O
(±)-35 . O
O
EtO
O
4PF O
6
(trans-4, C1) O
O
(±)-37/(±)-38
(trans-2, C 2)
O
N
N
O
O
O
O
EtO
O
O
O
O
N
N
4PF6
O
O
O
O
O
O
OEt
OEt
O
O
O
O
O
O
O
O
O
O
O
O
(±)-36
(trans-1, C 2)
(±)-39
(trans-3, C 1)
Figure 1.16. Macrocyclic bis-malonate adducts of C60 including planar chiral units ((±)-35–
(±)-38).
configuration of the methano bridge C-atoms lowers the overall symmetry of
(±)-39 to C1. 135
Planar chirality was finally combined with the achiral cis-2 addition pattern
in a tethered Bingel type bis-adduct including a trans-configured ethene unit
as planar chiral element in the macrocyclic bridge. 118
Even tris- and tetrakis-adducts of C60 were accessible in a regioselective
way by sequential tether-directed macrocyclization steps. A clipping reaction
starting from mono-adduct 40 with two tether-linked malonate residues thus
yielded tris-adduct (±)-41 (Scheme 1.5). 125 Under the assumption that both
m-xylylene tethers enforce the expected cis-2 addition, the C2-symmetry of
O
EtO
EtO
O
O
O
O
O