NbCl 3-catalyzed [2+ 2+ 2] intermolecular cycloaddition of alkynes and alkenes to 1, 3-cyclohexadiene derivatives

Y Obora, K Takeshita, Y Ishii

Index: Obora, Yasushi; Takeshita, Keisuke; Ishii, Yasutaka Organic and Biomolecular Chemistry, 2009 , vol. 7, # 3 p. 428 - 431

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Citation Number: 16

Abstract

As for the catalyst precursor of this reaction, the low-valent Nb(III) complex, NbCl 3 (DME), is highly efficient. When the Ta(III) analog, TaCl 3 (DME), was used as a catalyst, preferential formations of the alkyne cyclotrimerization products (5a) (33% yield) as well as the dimerization product, 1,4-di-tert-butyl-1-buten-3-yne (9% yield), were observed, but the desired 1,3-cyclohexadiene adduct was not produced at all (entry 8). Other Nb(IV), Nb(V) and V(III) complexes such as ...