Versatile synthesis of bicyclo[4.3.0]nonenes and bicyclo[4.4.0]decenes by a domino Heck-Diels-Alder reaction

Palladium-catalyzed cross-coupling reactions and electrocyclizations—efficient combinations for new cascade reactions

“…Since alkenylpalladium halides, which have proved to rapidly carbopalladate the double bond in bicyclopropylidene (8), cannot only be generated intermolecularly by oxidative addition of an alkenyl halide to a palladium(0) species, but also intramolecularly by carbopalladation of an alkyne [18], one may extrapolate the allintermolecular cascades involving 8 to intra-intermolecular variants. Indeed, 2-bromo-1,6-eneynes of type 30, under palladium catalysis react with bicyclopropylidene (8) to yield cross-conjugated tetraenes 31 or their electrocyclization products 32, depending on the reaction temperature (Scheme 8).…”

Intramolecular Heck Couplings and Cycloisomerizations of Bromodienes and Enynes with 1′,1′‐Disubstituted Methylenecyclopropane Terminators: Efficient Syntheses of [3]Dendralenes

“…In this latter context, we noticed that the intramolecular Heck reaction even proceeds with 2-bromo-1,n-dienes containing highly strained methylenecyclopropane end groups or (bromomethylene)cyclopropane starters [8] to yield spirocyclopropanebicyclo [4.3.0]nonene skeletons without opening of the three-membered ring.…”

Synthesis of Bis(enolnonaflates) and their 4-exo-trig-Cyclizations by Intramolecular Heck Reactions

“…1 The cyclization of 2-halo-1,w-alkenes using Heck type reactions in general leads to the construction of exo-dimethylenecycloalkanes, which in turn can be trapped in a Diels-Alder fashion to give bicyclic systems. 6,7 However, the formation of cyclobutanes by this protocol has not been observed, due to the competing Cope rearrangement and/or polymerization of the starting materials. 6 As a part of a study to examine enantioselective desymmetrization reactions, the synthesis of non-chiral substrates with enantiotopic leaving groups were necessary.…”

“…6,7 However, the formation of cyclobutanes by this protocol has not been observed, due to the competing Cope rearrangement and/or polymerization of the starting materials. 6 As a part of a study to examine enantioselective desymmetrization reactions, the synthesis of non-chiral substrates with enantiotopic leaving groups were necessary. Since cycloalkanes might serve as a useful platform for this process, it was therefore decided to use 1,5-dienes with an annelated cycloalkane system upon which to conduct intramolecular Heck reaction.…”