Claisen rearrangement with chiral Lewis acids

Some advancement has been described for the development of a catalytic enantioselective ester enolate Claisen rearrangement. The strong Lewis basic carboxylate functionality present in the Claisen product effectively coordinates with Lewis or Bronsted acids prohibiting the catalytic turnover. Corey has reported the use of stoichiometric bromoborane 175 to generate chiral boron enolate which undergoes [3,3]-sigmatropic rearrangement to yield 176. ° Kazmaier relied on excess quinidine 178 to provide for asymmetric induction in the conversion of 177 to amino acid 179. ... [Pg.51]

Several chiral organoaluminum Lewis acids catalyze the Claisen rearrangement of achiral allyl vinyl ethers to furnish chiral (3, y-unsaturated aldehydes with good enantioselectivity. Among the most effective catalysts is ATBN-F, a chiral aluminum tris(P-naphthoxide) species prepared from enantiomerically pure binapthol. ... [Pg.395]

These bulky aluminium aryloxides will also promote a variety of carbon-carbon bond forming reactions with a high degree of regio and stereoselectivity. Examples include Michael addition to a,/S-unsaturated ketones, Diels-Alder additions, and Claisen rearrangements. In the case of Diels-Alder reaction, ATPH promoted the exo-selective condensation of a,/6-unsaturated ketones with dienophiles. The Claisen rearrangement can be catalysed by ATPH and its more Lewis acidic 4-bromo derivative. A series of chiral aluminium aryloxides were also synthesized and have been applied to asymmetric Claisen rearrangements, aldol reactions, and aldehyde alkylations. ... [Pg.635]