Search

Easily accessible benzylic esters of 3-butynoic acids in a gold-catalyzed cyclization/rearrangement cascade reaction provided 3-propargyl γ-butyrolactones with the alkene and the carbonyl group not being conjugated. Crossover experiments showed that the formation of the new C- C bond is an intermolecular process. Initially propargylic- benzylic esters were used, but alkyl-substituted benzylic esters worked equally well. In the case of the propargylic- benzylic products, a simple treatment of the products with aluminum oxide initiated a twofold tautomerization to the allenyl-substituted γ-butyrolactones with conjugation of the carbonyl group, the olefin, and the allene. The synthetic sequence can be conducted stepwise or as a one-pot cascade reaction with similar yields. Even in the presence of the gold catalyst the new allene remains intact. [ABSTRACT FROM AUTHOR]

A series of arylynamides with alkyloxy groups at the ortho position of the aryl group was prepared through a short alkylation/cross-coupling/amidation sequence. The gold-catalyzed conversion of these substrates combined both CO and CC formation steps, thus providing benzofurans with amine functionalities at the 2-position and alkyl groups at the 3-position. Cross-over experiments showed that the alkyl-migration step was an intermolecular process. X-ray crystal-structure analysis of two of the products supported our structural assignment. In some cases, the corresponding benzofurans without the alkyl group at the 3-position were obtained as side-products, which were formed through a competing protodeauration process. [ABSTRACT FROM AUTHOR]