Onno Graalmann

The bicyclobutylidene to bicyclooctene rearrangement: Formal syntheses of (±)-ceratopicanol and (±)-hirsutene ☆

Abstract The bicyclobutylidenes 2 and 5 have been rearranged to the bicyclooctenes 3 and 6, respectively, and further transformed to the tricyclic ketones 16 and 21, respectively, as known precursors of (±)-ceratopicanol (4) and (±)-hirsutene (7). For the cyclopentane annelation, a [3+2]cycloaddition with cyclopropane-1,1-dicarboxylic acid ester, followed by an alkaline hydrolysis and an oxidative decarboxylation of the diacids formed was used (3-8-14-16, 6-18-20-21). The structures of the cycloadduct 9, the diacid 15 and the ketone 17 followed from an X ray analysis of the ditosylate 13, itself obtained by reduction and tosylation (9-12-13). The new syntheses of 16 and 21 represent short entries to 4 and 7.

Neuartige synthese von halogensilanolen und halogenfluorsilanen

Abstract Silanols of the type R 3 SiOH, RuSi(OH) 2 and R 2 Si(OH)OSiFR 2 react selectively with phosphorus pentahalides (PCl 5 , PBr 5 ) by hydroxy-halide exchange. Halosilanols (R 2 Si(OH)Hal, Hal = Cl, Br) and mixed halosubstituted fluorosilanes (R 2 SiFHal, Hal = Cl, Br) have been prepared. Di-butylchlorofluorosilane reacts with elemental lithium to give a 1,2-difluorodisilane.