First cobalt(I)-catalyzed [6 + 2] cycloadditions of cycloheptatriene with alkynes.
[reaction: see text] The CoI2(dppe)/Zn/ZnI2 system effectively catalyzes the [6 + 2] cycloaddition of cycloheptatriene with terminal alkynes to afford 7-alkyl-bicyclo[4.2.1]nona-2,4,7-trienes in fair to excellent yields. The catalyst proved to be tolerant toward functional groups such as ketone, sulfone, ester, ketal, ether, alcohol, imide, and nitrile. The enantioselective cycloaddition of CHT and phenylacetylene with BINOL phosphoramidite ligand 4 afforded the cycloadduct 3a (R = Ph) in 91% yield and 74% ee.
Achard
Mathieu
M
Laboratoire de Synthèse Asymétrique, UMR 6180 CNRS Chirotechnologies: Catalyse et Biocatalyse, Université d'Aix-Marseille P. Cézanne, Faculté des Sciences et Techniques de St. Jérôme, EGIM, 13397 Marseille, France.
Tenaglia
Alphonse
A
Buono
Gérard
G