The selective synthesis of 1,2,3,4-tetrasubstituted carbazoles can be performed effectively through the palladium-catalyzed oxidative coupling reactions of N-substituted indoles or their carboxylic acid derivatives with alkynes. Unsymmetrically octasubstituted carbazoles can also be obtained by the stepwise couplings of 1-methylpyrrole-2-carboxylic acid with two different alkynes. In addition, the present coupling procedure is applicable to the synthesis of other various heteroarenes possessing di-, tri-, and tetracyclic cores. Some of the products exhibit intense fluorescence in the solid state.

Abstract:The intermolecular oxidative coupling of arylboronic acids with internal alkynes efficiently proceeds in a 2:2 manner in the presence of palladium acetate, a triaryl phosphite or phosphate, and silver carbonate as catalyst, ligand, and oxidant, respectively, to produce the corresponding 1,4-diaryl-1,3-butadiene derivatives.

1,4-Addition of arylboronic acids to acrylic acid derivatives proceeds efficiently in the presence of a palladium catalyst system of Pd(OAc)2/(PhO)3P to produce the corresponding 3-arylpropionic acid derivatives. The use of the phosphite ligand is the key to conducting the addition smoothly with suppressing the competing Mizoroki-Heck-type oxidative coupling.

Abstract:The intermolecular three-component coupling of aryl iodides, diarylacetylenes, and alkenes effectively proceeds in the presence of palladium acetylacetonate and silver acetate as catalyst and base, respectively, to give the corresponding 1:2:1 coupling products, 1,3,5-hexatriene derivatives. A further homologation of the oligoene chain of the three-component coupling products by a simple procedure is also presented.

Polyphenylalkene derivatives Q 0740Palladium-Catalyzed Three-Component 1:2:1 Coupling of Aryl Iodides, Alkynes, and Alkenes to Produce 1,3,5-Hexatriene Derivatives. -The coupling products are predominantly formed as (E,E)-isomers. A further homologation of triene (IVa) is presented. The attempt to prepare a higher oligoene from bromostyrene affords pentaphenylfulvene (XIII) without participation of butyl acrylate instead of the desired 1:2:1 coupling product. -(HORIGUCHI, H.; HIRANO, K.; SATOH*, T.; MIURA, M.; Adv.