Synthesis of multisusbstituted cyclopentadienes by zirconocene-mediated cyclization of dienynes

U okviru ovog diplomskog rada razvijena je metodologija priprave višesupstituiranih ciklopentadiena u nekoliko konvergentnih sintetskih koraka pri čemu postoji mogućnost selektivnog uvođenja i variranja veličine pojedinih supstituenata na ciklopentadienskom prstenu. Sintetski put započinje regioselektivnom bromalilacijom disupstituiranih alkina pri čemu nastaju odgovarajući bromdieni s reaktivnom ugljik-halogen vezom. To je ključno za provedbu Sonogashirine reakcije s terminalnim acetilenima kako bi se generirali nekonjugirani dienini. Ciklizacijom dienina pomoću niskovalentnog organocirkonija (Negishijev reagens) pripravljeni su ciklopentadieni s exo-cikličkom dvostrukom. U posljednjem koraku, kiselinom kataliziranom exo-to-endo izomerizacijom exo-cikličke dvostruke veze ciklopentadiena pripravljeni su tetrasupstituirani ciklopentadieni. Strukture pripravljenih spojeva potvrđene su analitičkim tehnikama i postupcima (NMR, MS).The methodology for the preparation of multisubstituted cyclopentadienes in several convergent synthesis steps was developed within this master's thesis. This allows for the selective introduction and varation of the size of individual substituents on the cyclopentadienyl ring. The synthetic route starts with the regioselective bromallylation of disubstituted alkynes, yielding the corresponding bromodienes with a reactive carbon-halogen bond, which is crucial for carrying out the Sonogashira reaction with terminal acetylenes to generate non-conjugated dienynes. By cyclizing the dienyne using low-valent zirconium compounds (Negishi reagent), cyclopentadienes with an exo-cyclic double bond were prepared. In final step, through acid catalyzed exo-to-endo isomerisation of the exo-cyclic double bond of the cyclopentadiene, tetrasubstituted cyclopentadienes were prepared. The structures of the prepared compounds were confirmed using analytical techniques and procedures such as (NMR, MS)