A c T A -V O I .~~, Fas.4(1983)-Nr. 109 I002 HI.LV~I.ICA CHIMICA ACTA -Vol. 66, Fasc. 4 ( I 9833 -Nr. 109 11 Scheme 3 12 13 14 Scheme 4 15 13 16 the hexahydroindenes 13 and 16 by the intermediacy of the a-chlorosulfone 14 and the corresponding a , a-dichlorosulfone [17].In spite of the discouraging examples above, chances are still intact that base treatment of an a-bromo-(ora-chloro-)sulfone 17 may lead to 5 by Ramberg-Bucklund reaction. It is true that the a-H-, S-and Br-atoms cannot adopt a favorable W-type arrangement in any conformation of the isomers of 17, but on the other hand, competing 1,2-elimination of HBr is also disfavored because the P-H-atom at the bridgehead and the Br-atom bisect under a dihedral angle of 20-40", or 80loo", respectively (estimated from molecular models). In addition, the unsaturated sulfone 18 with a bridgehead double bond is likewise strained, although considerably less than the Bredt olefin 5. 18Intramolecular Ramberg-Backlund reaction of 2-bromo-l-thiadecalin-1, l-di-oxide3). -In order to shed more light on the question of competing Ramberg-Bucklund reaction and 1,2-elimination in a-halosulfones and to solve some confusing inconsistencies found by Kattenberg et al. with the decalin-type sulfones 11, 15 and related compounds [ 161 [ 171, the preparation and base treatment of 2-bromo-

Aus den Oxidationsprodukten (Ic) bzw. (Id) der Thiadecaline (Ia), (Ib) werden die Halogensulfone (IIa) bzw. (IIb) [+ (III)] dargestellt, die den Bedingungen der Ramberg‐ Bäcklund‐Reaktion unterworfen werden: Nur (IIa) reagiert dabei unter entsprechender 1,3‐Eliminierung und SO2 ‐Ausstoßung [→ (IV)] aus (IIb) oder den Isomeren (III) wird dagegen jeweils das 1,2‐Eliminierungsprodukt (V) gebildet.