Dipole carboxylate catalysts

Arndtsen and coworkers [154] described the first Pd-catalyzed synthesis of miinchnones 6/1-318 from an imine 6/1-316, a carboxylic acid chloride 6/1-317 and CO. The formed 1,3-dipol 6/1-318 can react with an alkyne 6/1-319 present in the reaction mixture to give pyrroles 6/1-321 via 6/1-320, in good yields. The best results in this four-component domino process were obtained with the preformed catalyst 6/1-322 (Scheme 6/1.83). 

An interesting transformation involving the indole nucleus was found from propargylic carboxylates to give tetracychc compounds with Au(I) (equation 85). This reaction proceeds by an allene-gold complex in equilibrium with the aUcenyl-gold species, which reacts intramolecularly with the indole to form the product. When the reaction of these substrates is performed with dichloro(pyridine-2-carboxylato)gold(III) or Pt(II) as catalysts, products in equation (86) are obtained instead. This new reactivity can be explained by a formal [3 + 2] cycloaddition of 1,3-dipole... 

TSE-NH2 (3) has been utilized for the formation of 1,3-dipoles. Thus, treatment of 3 with the N-acy imidazole derived from the carboxylic acid 12 generated the TSE amide 13, which was acylated and diazotized to yield the diazo amide 14 (eq 4). Exposure of intermediate 14 to a Rh(II) catalyst produced isomiinch-none (15), which participated in an intramolecular [3 + 2] cycloaddition to afford the bridged bicycle 16 in 85% yield. Subsequent removal of the TSE protecting group using potassium f-butoxide afforded the lactam 17 in 50% yield. 

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