18326-13-1Relevant articles and documents
Enantioselective, Lewis Base-Catalyzed Sulfenocyclization of Polyenes
Tao, Zhonglin,Robb, Kevin A.,Zhao, Kuo,Denmark, Scott E.
supporting information, p. 3569 - 3573 (2018/03/21)
A sulfenium-ion-initiated, catalytic, enantioselective polyene cyclization is described. Homogeranylarenes and ortho-geranylphenols undergo polycyclization in good yield, diastereoselectivity, and enantioselectivity. The stereodetermining step is the generation of an enantiomerically enriched thiiranium ion from a terminal alkene and a sulfenylating agent in the presence of a chiral Lewis basic catalyst. The use of hexafluoroisopropyl alcohol as the solvent is crucial to obtain good yields. The thioether moiety resulting from the reaction can be subsequently transformed into diverse oxygen and carbon functionality postcyclization. The utility of this method is demonstrated by the enantioselective syntheses of (+)-ferruginol and (+)-hinokiol.
Synthesis of (+)-Hinokiol, (+)-Hinokione, (+)-Salviol, and (+)-2-Oxoferruginol
Matsumoto, Takashi,Usui, Shuji,Kawashima, Hiroyuki,Mitsuki, Masanori
, p. 581 - 584 (2007/10/02)
Reduction of abieta-5,8,11,13-tetraen-3-one with lithium aluminium hydride afforded the corresponding alcohol, which was submitted to catalytic hydrogenation to yield abieta-8,11,13-trien-3β-ol (7) together with its 5βH-isomer.Acetylation of 7, followed by the Friedel-Crafts acylation, afforded 3β-acetoxy-12-acetylabieta-8,11,13-triene.This compound was converted into 3β,12-diacetoxyabieta-8,11,13-triene (11) by the Baeyer-Villiger oxidation.Treatment of 11 with lithium aluminium hydride yielded hinokiol, which was oxidized to hinokione.Subsequently, hinokiol was methylated and the resulting 12-methyl ether was dehydrated to afford 12-methoxyabieta-2,8,11,13-tetraene.The tetraene was then submitted to hydroboration-oxidation to give 12-methoxyabieta-8,11,13-trien-2α-ol (15) which, on demethylation with ethanethiol and anhydrous aluminium chloride, afforded salviol.Oxidation of 15 with pyridinium chlorochromate, followed by demethylation, gave 2-oxoferruginol.
Cyclisation Reactions: Part VI - Further Study in Biogenetic-type Cyclisation of Epoxy-Olefins
Nasipuri, Dhanonjoy,Samaddar, Ashis K.,Das, Gautam
, p. 727 - 734 (2007/10/02)
(6E)-9-p-Methoxyphenyl-2,6-dimethylnona-2,6-diene (I) on mono-epoxidation affords mainly 2,3-epoxyolefin (IV) admixed with some 6,7-isomer.IV on cyclisation with boron trifluoride etherate furnishes three ketones: 7-oxo-9-p-methoxyphenyl-2,6-dimethylnon-2-ene (XIII) presumably formed from 6,7-epoxyolefin (XII), cis-3-(2-p-methoxyphenylethyl)-2,2,4-trimethylcyclohexanone (XIV) arising out of 1,4-hydride transfer in an intermediate cyclohexyl cation (XVII), and cis-3-(2-p-methoxyphenylethyl)-2,3,4-trimethylcyclohexanone (XV) resulting from three consecutive 1,2-H, Me shifts in the same intermediate.In addition, 12-methoxypodocarpa-8,11,13-trien-3β-ol (IX) is obtained in 10 percent yield.The mono-epoxide (V) from the corresponding 3-isopropyl-4-methoxyphenyldiene (II) on similar cyclisation affords, among others, hinokiol methyl ether (X) and another crystalline compound characterised by PMR and MS as 12-methoxy-13-isopropyl-A-homo-4a-oxapodocarpa-8,11,13-trien-3β-ol (XXII).The latter is formed by a concerted cyclisation of the di-epoxide (XXI) present in the starting material.Contrary to a previous report from this laboratory, it is now found that trans-podocarpa-8,11,13-trienes (XXV) are more stable than the cis-isomers and are almost the sole products of cyclisation of 2-(2-arylethyl)-1,3,3-trimethylcyclohexyl cations (XXIV) and their analogues under thermodynamically controlled condition.
