Two synthetic approaches have been investigated for the syntheses of model
angucyclinones related to ochromycinone. The first involves a
Diels–Alder/Friedel–Crafts strategy in which the
Diels–Alder adduct formed between dimethyl acetylenedicarboxylate and
3-ethenyl-5,5-dimethylcyclohex-2-en-1- one was converted into
6,6-dimethyl-8-oxo-5,6,7,8-tetrahydronaphthalene-1,2-dicarboxylic anhydride,
which was then reacted with benzene in a Friedel–Crafts reaction.
Acid-catalysed cyclization of the Friedel–Crafts products gave
3,3-dimethyl-3,4-dihydrobenz[a]anthracene-1,7,12(2H)-trione
(3) in poor yield. Angucyclinones related to (3) are formed (in
40–50% overall yield) by aromatization of the adduct formed
between the appropriate 1,4-naphthoquinone and
3-[(E)-2-methoxyethenyl]-
5,5-dimethylcyclohex-2-en-1-one (this dienone reacts with itself by a
Diels–Alder process to yield an adduct which decomposes to
3,3,8,8-tetramethyl-3,4,7,8-tetrahydroanthracene-1,6(2H,5H)-dione).
When the substituted 1,4-naphthoquinone is unsymmetrical, a boron triacetate
assisted Diels–Alder reaction gives a single regioisomer (e.g. X-ray
investigations indicate that
8-hydroxy-3,3-dimethyl-3,4-dihydrobenz[a]anthracene-1,7,12(2H)-trione
is the product from 5-hydroxy-1,4-naphthoquinone). An X-ray structural study
of the Diels–Alder adduct in the above reaction confirms the operation
of an endo cyclization.
研究了两种合成方法,以合成模型
angucyclinones。第一种是
Diels-Alder/Friedel-Crafts 策略,其中
乙炔二
羧酸二甲酯与 3-
乙烯基-5,5-二甲基-2-
丙酮之间形成的 Diels-Alder 加合物。
3-
乙烯基-
5,5-二甲基环己-2-烯-1-酮之间形成的 Diels-Alder 加合物转化为
6,6-二甲基-8-氧代-5,6,7,8-四氢
萘-1,2-二
羧酸酐、
然后与苯发生弗里德尔-卡夫斯反应。
在酸催化下,Friedel-Crafts 反应产物环化生成了
3,3-二甲基-
3,4-二氢苯并[a]蒽-1,7,12(2H)-三酮(3)
(3) ,收率较低。与(3)相关的 Angucyclinones 由芳香族化合物生成(总收率为 40-50%)。
的加合物发生芳香化反应而形成(总收率为 40-50%)。
之间的加合物发生芳香化反应,生成与 (3) 相关的 Angucyclinones(总收率为 40-50%)。
3-[(E)-2-methoxyethenyl]-
5,5-二甲基环己-2-烯-1-酮之间形成的加合物进行芳香化反应(这种二烯酮通过
Diels-Alder 反应生成加合物,加合物分解为
3,3,8,8-四甲基-3,4,7,8-四氢
蒽-1,6(2H,5H)-二酮)。
当取代的
1,4-萘醌不对称时,
三乙酸硼
三乙酸硼辅助的 Diels-Alder 反应会产生单一的区域异构体(例如,X 射线
研究表明
8-羟基-3,3-二甲基-
3,4-二氢苯并[a]蒽-1,7,12(2H)-三酮
是 5-羟基-
1,4-萘醌的产物)。X 射线结构研究
对上述反应中的 Diels-Alder 加合物进行的 X 射线结构研究证实了
内环化反应。