No abstract

Die Rolle von Cu‐Salzen als Katalysatoren bei der Arylierung nach Meerwein wird untersucht [Substrate sind Cyclooctadien (COD), Allylalkohol u.a. Allylderivate sowie 4‐Butenol‐(l); als Arylierungsreagenz dient p‐Chlorbenzoldiazoniumchlorid].

A dilution effect shows that the proline-catalysed Robinson cyclisation involves both enantioselective and non-enantioselective processes, with a different dependence on amino acid concentration.The Hajos-Parrish reaction1 presents a most interesting mechanistic problem in the field of enantioselective synthesis (Scheme l), but only indirect mechanistic studies have been carried out so far, mainly through structural modifications of the catalyst2 and/or the substrate.3 We report here direct

The previously discovered rearrangement of a-santonin to isophoto-asantonic lactone has been shown to be a general phenomenon. p-Santonin, 6-epi-ct-santonin, 6-epi-P-santonin, artemisin acetate, 6-epi-8-epiartemisin acetate, and 8-epiartemisin acetate all undergo the corresponding rearrangements. With the aid of X-ray crystallography the stereochemistry of this transformation has been elucidated. Differential hydrogenation or hydrogenolysis reactions in these compounds have been observed depending upon the quasi-equatorial or quasi-axial character of the alkyl-oxygen atom of the lactone ring.

Tour 45, 11, quai Saint-Bernard 75-Paris 5eme) Szcmmary From the ketol (2), previously synthesised from (-)-dihydrocarvone, (+)-daucene, (+)-carotol, and (-)daucol have been prepared.