Die Epoxysulfoncyclofragmentierung, eine neue Ringerweiterungsmethode. Synthese von rac.‐Muskon

A new ring expansion method using the cyclofragmentation of epoxysulfones; a synthesis of rac. muscone. Starting from the readily available cyclododecanone 1 the hydroxy sulfone 5 has been prepared using standard procedures. Subsequent dehydration followed by an acidic equilibration resulted in a mixture of two endocyclic olefines, from which the olefin 7 showing the ( E )‐configuration could be isolated by fractional crystallization. Oxidation of 7 produced the epoxy sulfones 8 and 9 . The epoxy sulfone 8 was cyclized to the hydroxy sulfone 10 without any detectable amount of the corresponding epimer 11 . Fragmentation of the intermediate 10 using KOTB produced pure ( E )‐4‐muscenone 12 . The epoxy sulfone 9 was cyclized to a mixture of the two epimeric hydroxy sulfones 14 and 15 . Fragmentation of the two crystalline hydroxy sulfones 14 or 15 with KOTB produced a mixture of 12 and 16 . The ‘one‐pot’ preparation of ( E )‐4‐muscenone 12 starting from 8 could also be accomplished. The configurational assignements within this serie are based upon the data of an X‐ray analysis of the hydroxy sulfone 10 .