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Palladium- or nickel-catalyzed sequential reaction of organic bromides, bicyclo[2.2.1]hept-2-ene or bicyclo[2.2.1]hepta-2,5-diene and alkynes

1984; Elsevier BV; Volume: 275; Issue: 1 Linguagem: Inglês

10.1016/0022-328x(84)80586-0

1872-8561

Marta Catellani, Gian Paolo Chiusoli, Aristodemo Mari,

Catalytic Alkyne Reactions

The reactions of various types of organic bromides with a mixture of bicycloheptene or bicycloheptadiene and alkynes are reported. The products are bicyclic compounds, containing an organic chain and an alkynyl group in adjacent positions. In the presence of a Pd0 catalyst, aromatic and vinylic bromides react smoothly in ethereal solvents. Allylic bromides are much less reactive and require protic solvents and arylacetylenes to give satisfactory results. With Ni0 catalysts the situation is reversed: aromatic and vinylic bromides show little or no tendency to undergo the desired reaction and allylic bromides give better results, although the occurrence of secondary reactions between allylic bromides and bicycloheptene derivatives or between allylic bromides and alkynes limits the synthetic value of the reaction. With both Pd and Ni catalysts electron-withdrawing substituents in the arylacetylenes accelerate the reaction. Formation of a Pd complex able to effect reductive coupling of bicycloheptyl and alkynyl groups or of a Ni complex able to abstract hydrogen from the organic chain (resulting from double bicycloheptene and arylacetylene insertion into an allyl-Ni bond) are possibly involved as critical steps, which drive the preceding ones to completion.