Palladium catalysis Claisen rearrangements

Late transition-metal-catalyzed asymmetric Claisen rearrangement takes place in a different mode from that of Lewis-acid-catalyzed Claisen rearrangement Late transition metal catalysis is based on affinity for the Claisen diene system. Among late transition metals, palladium complexes are the most useful and effective for the Claisen rearrangement. 

Palladium (0) catalysis promised to be an efficient tool to accelerate aza-Claisen rearrangements. Indeed, the reaction temperatures could be kept between 50 and 100 °C using a Pd(0) catalyst and a strong proton acid. The major drawback reported was that the palladium-assisted aza-Claisen reaction delivered 1,3 as well as 3,3 rearrangement products [21a,b]. The least hindered allyl terminus always formed the new C-C bond restricting the process to symmetric allyl systems. 

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