Sililujące sprzęganie : użyteczne narzędzie selektywnej syntezy organicznej

The design and development of highly selective methods for the synthesis of functionalized olefins based on sequential catalytic reactions using organosilicon reagents have been the subject of extensive study because of their versatile application in organic and organometallic synthesis. The ruthenium-catalyzed silylative coupling of olefins with vinyl-substituted organosilicon compounds (discovered by professor Bogdan Marciniec and co-workers in Poznań) represents one of the most efficient methods for the synthesis of stereodefined alkenylsilanes and isomeric bis(silyl)alkenes, which are particularly attractive scaffolds for further transformations including palladium-catalyzed cross-coupling with organic halides (Hiyama coupling) or substitution with organic and inorganic electrophiles. The unique feature of these methodologies is that the stereochemistry of the overall processes can be controlled during the initial step as the subsequent desilylation usually proceeds with retention of the configuration at the carbon atom and allows the formation of stereodefined products. The sequential silylative coupling - Hiyama coupling has been successfully used for stereoselective synthesis of (E)-stilbenes, bis-(E)-styrylarenes, stilbenoid dendrimers and poly(arylene-vinylene)s. On the other hand, the combination of silylative coupling with electrophilic halodesilylation reaction has been applied for the selective preparation of synthetically useful alkenyl halides (e.g. (E)-styryl halides, (E)-N-2-iodovinylcarbazole, (E)-N-2-iodovinylamides) - versatile coupling partners in palladium-catalyzed Suzuki and Sonogashira couplings, leading to vide variety of stereodefined ß-substituted (E)-enimides, (E,E)-dienimides and (E)- enynimides as well as related л-conjugated derivatives of N-substituted carbazole. The discovery of sequential silylative coupling and rhodium- or iridium-catalyzed acylation reactions is of great importance in the synthesis of (E)-α,ß-unsaturated ketones. The article highlights recent developments and covers literature mainly from the last decade in the sequential (also one-pot) synthetic strategies including ruthenium-catalyzed silylative coupling followed by desilylative cross-coupling, acylation and halogenation, leading to stereodefined я-conjugated organic derivatives which are widely applied as fine chemicals, functional materials or building blocks in organic synthesis.