Second Generation Copper-Catalyzed Aerobic Oxidation Protocol

Second Generation Copper-Catalyzed Aerobic Oxidation Protocol 

The previous observation strongly suggested that the regeneration of the active copper(I) species was a serious predicament in the oxidation of aliphatic alcohols. It was therefore decided to test the effect of various reductants in this aerobic oxidation reaction. Naturally, we turned to the hydrazine family of reducing agents (Table I) (14). 

Interestingly, the corresponding azo dicarboxylate (DEAD) could be substituted to the hydrazide derivative (DEAD-H2) with equal efficiency. Unfortunately, both primary and secondary aliphatic alcohols proved to be poor substrates and only modest conversions could be achieved under these conditions, even when a larger amount of the CuCl Phen catalyst was employed (Table II, Entries 7 and 8). 

Copper-Catalysed Aerobic Oxidation of Alcohols Using DEAD H2 

A plausible mechanism, involving both the azo and hydrazide derivatives can be formulated as shown in Fig. 5. 

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III. Second Generation Copper-Catalyzed Aerobic Oxidation Protocol... 

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