text: The product scope of this reaction is extremely broad with the use of different substrates; however development of different functionalities has required accompanied studies to determine the proper catalyst system. The most typical class of reactions involves coupling between C–COOH and C–X bonds, however C–COOH and C–M cross-coupling, homo-coupling of carboxylic acids, heck coupling, and dehydrogenative cross-coupling can also be including in this class as they release CO. Heteroatom cross coupling reactions involving formation of C–N, C–S, C–P, and C–X bonds have also been demonstrated.