In Situ Generation of Vinyl Allenes and Its Applications to One-Pot Assembly of Cyclohexene, Cyclooctadiene, 3,7-Nonadienone, and Bicyclo[6.4.0]dodecene Derivatives with Palladium-Catalyzed Multicomponent Reactions

A novel tandem Pd-catalyzed cross-coupling and [4 + 4] cycloaddition sequence allows the
rapid synthesis of eight-membered carbocycles starting from α-bromovinyl arenes and propargyl bromides
in one reaction vessel. It is noteworthy that four components are assembled into one molecule via this
procedure. In contrast to α-bromovinyl arenes, α-bromovinyl alkanes afforded tandem cross-coupling and
homo [4 + 2] cycloaddition products. Subjecting an equimolar mixture of α-bromostyrene and 2-bromo-1-octene to propargyl bromides furnished the tandem Pd-catalyzed cross-coupling and hetero [4 + 2]
cycloaddition product. Exposure of equimolar mixtures of α-bromovinyl arenes to allenylindium resulted in
tandem a Pd-catalyzed cross-coupling and hetero [4 + 4] cycloaddition products. Synthesis of vinylallene
from the reaction of vinyl triflate with allenylindium followed by Pd-catalyzed carbon monoxide insertion
reaction gave the corresponding 3,7-nonadienone product via tandem Pd-catalyzed cross-coupling and [4
+ 4 + 1] annulation. Tandem Pd-catalyzed cross-coupling, [4 + 4] cycloaddition, and [4 + 2] cycloaddition
provided the rapid synthesis of bicyclo[6.4.0]dodecene derivatives starting from α-bromovinyl arenes,
propargyl bromides, and dienophiles in one operation, in which five components were integrated into one
molecule.