Ralf Gerke

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.

Tetrakis (1-Methylcyclopropyl) Ethylen

Zusammenfassung Tetrakis(1-methylcyclopropyl)ethylene, a potential precursor for the synthesis of tetra-tert-butylethylene, has been prepared and spectral properties are described.

New indigo chromophores containing disulfide donor groups

Abstract Oxidative dimerization of a mixture of the thiolanone 5 and the dithiolanone 4 yields 2c as chromophore of thioindigo 1c, and 6 and 7 as chromophores of still unknown indigo dyes. As compared to 2c, the first ionization potential of the new indigo chromophore 7 is higher, but the calculated HOMO-LUMO splitting is lower. Accordingly, its longest wavelength absorption maximum surpasses that of 2c distinctly.

A rearrangement approach to (±)-cerapicol☆

Abstract The synthesis and rearrangement of the cyclobutyl methanol 4 is described. The synthesis has been achieved by addition of the Grignard reagent 16 to the bicyclic ketone 22 . Experimental procedures for the preparation of both compounds are given. Upon treatment with trifluoroacetic acid and subsequent reduction, 4 yields the norbornanes 24 and 25 and (±)-cerapicol ( 8 ). Some consequences concerning the search for other potential precursors of 8 are discussed.