Addition-elimination reactions of an arylaluminum reagent with vinylarenes is achieved mediated by ar hodium catalyst. The reaction of dimethyl(phenyl)aluminum with ar hodium(I) catalystt akes place to afford (E)-stilbene. The reaction is promoted by the addition of ketone as an addi-tive to give (E)-stilbenei naquantitative yield. An ickel complex bearing cyclopentadienyl (Cp) and N-heterocyclicc arbene (NHC) ligandsa lso catalyzes the reaction to afford 1,2diarylethenes accompanied by as mall amount of the saturated byproduct, 1,2-diarylethanes.Scheme1.Addition-eliminationreaction of arylaluminum reagents with styrene.

One-pot halogen dance/Negishi cross-coupling of readily available 2,5-dibromothiophenes is described. A lithium diisopropylamide (LDA)-mediated halogen dance reaction resulted in the formation of thermodynamically stable α-lithiodibromothiophenes, which were transmetalated with ZnCl and subjected to Negishi cross-coupling to provide the corresponding arylated dibromothiophenes in one pot. The resultant β-bromo group was much less reactive than the remaining α-bromo group, which was used in a one-pot double Suzuki-Miyaura cross-coupling, enabling facile synthesis of multiply arylated thiophenes.

A magnesium bisamide-mediated halogen dance of bromothiophenes is described. The thienylmagnesium species generated in situ is more stable than the corresponding thienyllithium species, which was applied to trap the transient anion species with several electrophiles, such as allyl iodide, phenyl isocyanate, and tributylstannyl chloride. The utility of the magnesium bisamide-mediated halogen dance is useful in the concise synthesis of a medicinally advantageous compound via a one-pot, ester-directed halogen dance/Negishi cross coupling.

Deprotonative metalation of 2-chloro-3-substituted thiophene at the 5-position of the thiophene ring is performed by a bulky magnesium amide 2,2,6,6-tetramethylpiperidin-1-yl magnesium chloride lithium chloride salt (TMPMgCl•LiCl). The obtained metallic species reacts with bromothiophene to afford the regioregular head-to-tail-type chlorobithiophene, which is subjected to further end functionalization by the coupling reaction with C-Cl bond. Deprotonative C-H coupling polycondensation of differently-substituted chlorobithiophene gives polythiophene of the formal alternating copolymer.

Treatment of an organoaluminum reagent bearing aryl and ethyl groups furnishes 1,2-diarylethene derivatives in good to excellent yields by the catalysis of a rhodium complex, in which the ethyl group of the aluminum reagent serves as an ethylene source in the product formation.