Cross dehydrogenative couplings CDCs

As illustrated in this chapter, oxidative cross-dehydrogenative coupling (CDC) has provided the opportunity to simplify organic synthesis by presenting an alternative to the separate steps of prefunctionalization and defunctionalization that have traditionally been part of synthetic design. In the near future, we anticipate the development of CDC reactions that will be more efficient and effective to provide a positive economical and ecological impact on the next generation of C-C bond formation processes. 

Copper Catalysts Direct oxidative functionalization of tertiary amines is of importance both enzymatically and synthetically. The combination of CuBr—TBHP has proved to be as an efficient system in the oxidative activation of sp3 C—H bonds adjacent to a nitrogen atom [10]. Various types of cross-dehydrogenative coupling (CDC) reactions have been developed, including compounds with activated methylene groups [11], indoles [12], and terminal alkynes (Scheme 11.2) [13]. Because 1,2,3,4-tetrahydroisoquinoline derivatives are important structure motifs of natural... 

Scheme 11.2 Cu-catalyzed cross-dehydrogenative coupling (CDC) reactions.

By building their own vibration ball mill, Shayesteh and coworkers obtained 100% conversion in just 12 min at 30 Hz for cross-dehydrogenative coupling (CDC) of 2-naphthol [62]. In comparison, the Toda s mortar grinding and above described method by Rasmussen et al. needed 2 and 1 h, respectively. On operation condition of 30 Hz vibration ball mill gives better performance in comparison to other commonly used methods such as ball mill and mortar and pestle, due to higher mechanical... 

The synthesis of a-acyloxy ethers (formation of C—O bonds) was achieved by the TBHP oxidation of a mixture of a carboxylic acid (R C02H, R =aryl, heteroaryl, alkyl) and an ether (R, R = alkyl, alkyl halide) in the presence of BU4NI as the catalyst. The transformation involved a cross-dehydrogenative coupling (CDC) reaction of the C-H bond. ... 

Copper-catalyzed cross-dehydrogenative coupling (CDC) reactions of (benzo)thiazoles 49 with cycHc ethers 50 have been developed under mild conditions (130L4600). Notably, the 2-thiazolyl acetals, known as the masked 2-thiazolecarboxaldehydes, could be successfully obtained by this CDC reaction. 

Zhao and Du s group [63] developed a metal-free cross-dehydrogenative coupling (CDC) of various 2-(A -arylamino)aldehydes 79 for direct aryl-aldehyde C (sp )-C(sp ) bond formation to provide a convenient approach for the synthesis of biologically important acridone derivatives 80 (Scheme 19). PIDA was used in combination with a substoichiometric amount of benzoyl peroxide as radical initiator for this oxidative intramolecular annulation reaction which presumably proceeds via the intermediacy of acyl radicals 81. 

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