Oxidative transformations of cembrane diterpenoids III. Epoxycembrenes
Summary1. It has been established that the epoxidation of cembrene with perbenzoic and peracetic acids takes place stereospecifically at each of the trisubstituted double bonds with the formation of 4S,5R-, 7S,8S-, and 11S,12S-monoepoxycembrenes, the structures and absolute configurations of which have been established by spectral methods.2. Epoxidation of cembrene at the C11–C12 double bonds under the conditions used takes place preferentially as compared with epoxidation at the C7–C8 double bond.
New methods for the preparation of 1-phenyl-trans-cyclohexane-1,2-diol
Abstract In contrast with previous reports, it was found that the reaction of 1-phenylcyclohexene with peroxyformic acid is not entirely stereospecific, but gives some trans -1-phenylcyclohexane-1, 2-diol (IV) beside the cis -isomer (III). The reaction of 1-phenylcyclohexene oxide (II) with formic acid yielded a similar mixture of III and IV, while addition of trichloroacetic acid in benzene was entirely cis -stereospecific. Reaction of the epoxide II with potassium hydroxide took place only under very drastic conditions to give a small yield of III, while sodium 2-dimethylaminoethoxide added exclusively in a trans way, leading to the amino ether X, which was easily transformed into the trans -glycol IV. The latter compound was also the main product of the borohydride reduction of 2-hydroxy-2-phenylcyclohexanone (IX). Possible explanations of the observed stereochemical results are discussed.
Über eine neue Epoxyd‐Isomerisierung mit Diisobutylaluminiumhydrid
1.2-Epoxy-cyclododecan und -cyclododecadien-(5.9) werden mit Diisobutylaluminiumhydrid zu α.β-ungesattigten Alkoholen isomerisiert. Es entstehen cis-trans-Isomere des 1-Hydroxy-cyclododecens-(2) bzw. 1-Hydroxy-cyclododecatriens-(2.5.9). Aus den Gemischen konnten die Isomeren mit der cis-Konfiguration der neu eingefuhrten Doppelbindung isoliert werden.