A very efficient route toward the 4a-methyltetrahydrofluorene skeleton: short synthesis of (+/-)-dichroanone and (+/-)-taiwaniaquinone H.
A very expedient and efficient new route toward taiwaniaquinoids, bearing the 4a-methyltetrahydrofluorene skeleton, is reported. Key steps are the intramolecular Friedel-Crafts alkylation of an aryldiene and the degradative oxidation of a methylenedioxy group; the latter process could also be utilized for building the 2-hydroxy-1,4-benzoquinone unit, which is frequently found in natural products. Utilizing this new methodology, (+/-)-dichroanone (7) (three steps, 77% overall yield) and (+/-)-taiwaniaquinone H (6) (four steps, 70% overall yield) have been synthesized from commercial alpha- (11a) or beta-cyclocitral (11b).
Alvarez-Manzaneda
Enrique
E
Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain. eamr@ugr.es
Chahboun
Rachid
R
Cabrera
Eduardo
E
Alvarez
Esteban
E
Alvarez-Manzaneda
Ramón
R
Meneses
Ricardo
R
Es-Samti
Hakima
H
Fernández
Antonio
A
D000478:Alkylation; D004224:Diterpenes / Q000138:chemical synthesis* / Q000737:chemistry; D005449:Fluorenes / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism
D004224:Diterpenes; D005449:Fluorenes; C516091:dichroanone; C516088:taiwaniaquinone H