Chemistry Reference
In-Depth Information
Scheme 8 Synthesis of 1,3,4,7,9,10-substituted diones 35a-d [
43
]
Scheme 9 Synthesis of 12 via terphenyl tricarboxylic acid precursor 42 [
45
]
2
Indeno[1,2-
a
]fluorenes
2.1
Indeno[1,2-
a
]fluorene-7,12-diones
The synthetic route utilizing Friedel-Crafts acylation via terphenyldicarboxylic
acid precursors to reach the pentacyclic diketone has been applied for the assembly
of a multitude of indeno[1,2-
a
]fluorene diones [
44
]. In most cases, a mixture of
[1,2-
a
] and [2,1-
b
] species was formed during the cyclization stage, although in
some instances the [1,2-
a
] isomer was the exclusive product. One such example
involves tricarboxylic acid precursor 36, so that the acylation step forms in
the correct configuration regardless of direction (Scheme
9
)[
45
]. To achieve
this,
cis
-1,3-diphenylpropene (37) was reacted with 3-pentanone (38) to yield
