Substituierte 9-Oxabicyclo[4.2.1]- und 9-Oxabicyclo[3.3.1]nonane III. neue ergiebige synthese von 2, 7-dioxatwistan und endo-2-hydroxy-9-oxabicyclo[3.3.1]nonen-(6)

Iodine cleavage of the 3.3.1]-iodomercuri compound 4 , easily prepared from cis, cis-cyclooctadiene-(1,5) by oxymercuration of the monoepoxide 1 (→ 3 ) followed by treatment with potassium iodide, leads to three isomeric iodides 6, 7 , and 8 , the 3.3.1]-exo-iodo isomer 8 being the predominant product. Intramolecular substitution in 8 opens an attractive new route to unsubstituted 2,7-dioxatwistane ( 19 ) 2], whereas dehydrohalogenation of 7 and 8 yields the unsaturated alcohol 17 2], a suitable starting material for the preparation of substituted 2,7-dioxatwistanes 2], 2,7-dioxaisotwistanes ( e ) 2], and 2,8-dioxa-homotwistbrendanes ( f ).