Claisen rearrangement Lewis acid catalysis

Recently, Hiersemann reported the first catalytic enantioselective Claisen rearrangement (Scheme 2.4) [11]. The 2-alkoxycarbonyl-substituted allyl vinyl ethers 11 are reactive under the Lewis acid catalysis. Therefore, the Claisen rearrangements proceed catalytically [12]. Usually the Lewis-acid-catalyzed Claisen rearrangement does not proceed catalytically because of a higher affinity of the carbonyl product for the Lewis acids than the ether substrate. But this 2-alkoxycarbo-nyl-substituted substrate 11 can coordinate to metals in a bidentate fashion. This 2-alkoxycarbonyl substrate has higher affinity for Lewis acidic Cu complexes than the simple ether substrate. In this system, chiral copper (II) bisoxazoline Cu (box) complex 13 is effective for the enantioselective Claisen rearrangement. 

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. 

Lewis acid catalysis of Ireland-Claisen rearrangements by TiCl4 has been observed.251 This methodology was employed in the synthesis of a novel type of anti-inflammatory drug candidate.252... 

Catalysis of Claisen rearrangements has been achieved using highly hindered bis(phenoxy)methylaluminum as a Lewis acid.156 Reagents of this type also have the ability to control the E Z ratio of the products. Very bulky catalysts tend to favor the Z-isomer by forcing the a substituent of the allyl group into an axial conformation. 

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