Double CH bond activation took place efficiently upon treatment of 3-phenylthiophenes with alkynes in the presence of a rhodium catalyst and a copper salt oxidant to form the corresponding naphthothiophene derivatives. Dehydrogenative coupling with alkenes was also found to occur on the phenyl moiety rather than the thiophene ring. These reactions provide straightforward synthetic methods for π-conjugated molecules involving a thiophene unit from readily available, simple building blocks.

Herein, we demonstrate that tritylamines undergo an unprecedented copper-mediated cyclization involving the cleavages of two CH bonds and one CN bond to give 9-arylacridine derivatives. This kind of acridines is of interest due to their biological properties and their unique optical and electro- and photochemical properties. Some of obtained acridine derivatives exhibit intense fluorescence in the solid state.

It has been found that readily available hydroxylated cinnamic acids such as ferulic acid undergo palladium-catalyzed decarboxylative coupling with aryl iodides and internal alkynes in a 1:1:1 manner to produce 1,4-diarylbuta-1,3-dienes. The butadiene synthesis has also been achieved through the coupling of aryl halides with dienoic acids. Some of the products exhibit solid-state fluorescence.

Aromatic substrates with oxygen- and nitrogen-containing substituents undergo oxidative coupling with alkynes and alkenes under rhodium catalysis through regioselective CH bond cleavage. Coordination of the substituents to the rhodium center is the key to activate the CH bonds effectively. Various fused-ring systems can be constructed through these reactions.

The straightforward and efficient synthesis of naphtho[1,8-bc]pyran derivatives and related polycyclic compounds is achieved by the rhodium-catalyzed oxidative coupling of 1-naphthols or other phenolic and alcoholic substrates with alkynes. In these annulation reactions, the hydroxy groups effectively act as the key function for the regioselective CH bond cleavage.

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.

A number of new synthetic methods for π-conjugated oligoene and enyne compounds are described. Thus, diene and higher oligoene derivatives are selectively constructed by palladium-catalyzed arylation reactions of internal alkynes in the presence of arylboronic acids or alkenes as terminators. In contrast, the synthesis of various enyne derivatives is achieved effectively by homo- or cross dimerization of alkynes under rhodium catalysis. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 326–336; 2008: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20158

A direct oxidative coupling of salicylaldehydes with internal alkynes proceeds efficiently with cleavage of the aldehyde CH bond to produce the corresponding chromone derivatives. A rhodium catalyst in combination with a cyclopentadiene ligand and a copper oxidant promote this straightforward annulation reaction. Solid-state luminescence was observed for certain chromone products.