Takeshi KITAHARA, Kaichi TANIDA and Kenji MORI
(±)-g-Irones (1/9 mixture of cis- and trans-isomers and pure trans-g-irone) were synthesized via the intramolecular Diels-Alder reaction starting from 2,4-hexadienyl aniline derivative and b,b-dimethylacryloyl chloride.
Reagents : a) i. o-aminophenol,
NaHCO3, EtOH; ii. NaBH4, H2O; b)
b,b-dimethylacryloyl
chloride, Bz, K2CO3, Py; c) EtMgBr, 140°C, xylene;
d) MeOH, MeONa; e) H2, Pd/C, THF-AcOEt; f) HNO3,
AcOH; g) i. KOH, THF;
ii. P-TsOH, toluene; h) i. Dibal-H, DME, toluene; ii. Ph3P=CHCOCH3,
Toluene; i) i. KI, H3PO4, CH2Cl2;
ii. NaHCO3; j) NO2C6H4SeCN,
NaBH4, EtOH; ii. H2O2, THF.
| This is the first synthesis of cis-g-irone,
but it's a mixture (1/9).
Unfortunately, the final product consisted mainly of the trans-isomer because of epimerization during the transformation from A. |