| The dihalocyclopropanation of the endocyclic double bond, the exocyclic double bond or the extra ring double bond constitutes an essential step to realize the rearrangement of the resulting cyclopropanation products. The cyclopropane rearrangement, with Hiyama's reagent presence of cationic system of two oxidation state, for example: Cr+2/Cr+3, produced the elongation of alkenes chains (see the sequence proposed in Scheme-3). The gem-dihalocyclopropane pathway to obtain the dihalomethylvinyl compounds, starting with the monocyclopropanes, then gem-diols, aldehydes, and alpha,beta-unsaturated acid is proposed.; However, the analogous rearrangement of dichlorocyclopropanes on the exocyclic double bond produced the allenic compounds. This rearrangement is a new pathway to introduce an aldehyde or a carboxylic acid functions on the natural products.; The prenylation of indolic and imidazolic bases offered a possibility to use the isoprene and its auxiliaries as "linkers" enabling the attachment of isoprene units to the natural products skeleton, in particular for those with physiological activity (via the epoxide opening or via the attachment to the double bond). The synthetic analogue of isoprene, such as 2-methyl-2-vinyloxirane, seems to be an excellent synthon for this study because it has a potential to form the opening products with various nucleophilic agents.; In organic synthesis, the prenylation could be realized by thermal or by microwave assisted pathways. In this study we compare these two methods. |
