New syntheses of novel arylxanthones
Conference Paper
Overview
Overview
abstract
Xanthones represent an outstanding class of oxyg~1_1ated heterocycles widespread in
nature, commonly distributed in several higher plant families, such as Gentianaceae,
Guttiferae and Polygalaceae and in a few families of fungi and lichens [1]. Both natural
and synthetic derivatives often endowed with interesting pharmacological properties
(e.g. anti-inflammatory, antitumour and antioxidant activities [1,2]. Naturally-occurring
xanthones present different types .of substituents (e.g. hydroxyl, methoxyl and prenyl
groups, among others) in different positions of their scaffold leading to a large variety
of analogues [2]. The presence of an aryl ring attached to the xanthone core has only
been reported in some synthetic derivatives [3 ,4].
We have dedicated our previous work to the development of novel methodologies for
the synthesis of xanthones bearing a 2,3-diaryl substitution pattern [4]. Herein, we
report the latest advances in the synthesis of novel 5-arylbenzo[ c ]xanthones 2 and 1-
aryl-9H-xanthen-9-ones 4 [5]. 5-Arylbenzo[c]xanthones 2 are obtained by the Heck
reaction of 3-bromoflavones 1 with styrene derivatives, leading to (E)-3-styrylflavones,
followed by an one-pot photoinduced electrocyclisation and in situ oxidation of
cycloadducts. The condensation of 2-methylchromone 3 with cinammaldehydes leaded
to (E,E)-2-(4-arylbuta-1,3-dien-1-yl)-4H-chromen-4-ones, which after an one-pot
electrocyclization and in situ oxidation of cycloadducts gave the desired 1-aryl-9Hxanthen-
9-ones 4.
