Oxepine, III. Ein neuer Syntheseweg ausgehend von 2,5‐Cyclohexadien‐1,4‐diolen

Abstract

Die Dehydratisierung von 1-R-4-R-2,6-di-tert-butyl-2,5-cyclohexadien-l,4-diolen 9 fuhrt bei konsequenter Ausnutzung der Substituenteneffekte von R und R erstmals zu 2-R-5-R-3,7-di-tertbutyloxepinen 1. Einige chemische Reaktionen sowie die Umlagerung der Oxepine 1 iiber 2.4-Cyclohexadienone 7 in Phenole 15 und die damit verbundenen mechanistischen Konsequenzen (NlH-Shift) werden untersucht. Oxepins, III1.*)A New Synthesis from 2,5-Cyclohexadiene-l,4diolsThe dehydration of 1-R-4-R-2,6-di-tert-butyl-2,5-cyclohexadiene-1,4-diols 9 for the first time yields 2-R-5-R-3,7-di-tert-butyloxepins 1 if the substituents R and R' are properly chosen. Some chemical reactions including the rearrangements of the oxepins 1 via 2,4-cyclohexadienones 7 to the phenols 15 and their mechanistic consequences (NIH shift) are investigated. A. Bisherige Synthesen

1,4-Addition of Lithium Organyls to para-Quinols / Structure Determination of 2,6-Di-tert-butyl-4-hydroxy-4,5-diphenylcyclohex-2-en-1-one

“…The reaction sequence generally is in the order 2 -^4 -> 6^7 or 2 -> 6^7 . The step 4 -> 6 can also be perform ed therm ally w ithout acid [3]. M eantim e, sim ilar observations have been reported by other authors [ 7 -1 0 ] .…”

“…The structure o f the 1,2-adducts 2, the oxepins 4 and cyclohexadienones 6 has already been dis cussed [3]. The 1,4-adducts 3 are isom ers of 2, as shown by elem ental analysis and m ass spectro metry.…”

“…Indeed, after alcaline hydrolysis o f the reaction m ixture, the 1.2-adducts 2 (R 1 =M e) are isolated in 84-92% yield [3,6]. W ith larger groups in the lithium organyls (phenyl, 4-tolyl, 3-tolyl) the yields o f 1,2-adducts 2 are sm aller (generally 45-60% ) [3 -6], and the 1,4-adducts are form ed as byproducts (8-13% ) (see Table I); w ith 2-tolyl-or m esityllithium neither pri mary 1,2-nor 1,4-adducts could be obtained; the structure o f the reaction products has not yet been determ ined.…”