text: Enantioselective carbonyl allylations are frequently applied to the synthesis of polyketide natural products. In 1978, Hoffmann reported the first asymmetric carbonyl allylation using a chiral allylmetal reagent, an allylborane derived from camphor. Subsequently, other chiral allylmetal reagents were developed by Kumada, Roush, Brown, Leighton, and others. These methods utilize preformed allyl metal reagents and generate stoichiometric quantities of metal byproducts.
  In 1991, Yamamoto disclosed the first catalytic enantioselective method for carbonyl allylation, which employed a chiral boron Lewis acid-catalyst in combination with allyltrimethylsilane. Numerous catalytic enantioselective methods for carbonyl allylation followed, including work by Umani-Ronchi and Keck. While these methods had a significant impact, they do not circumvent the use of preformed allylmetal reagents. Catalytic variants of the Nozaki-Hiyama-Kishi reaction represent an alternative method for asymmetric carbonyl allylation, but stoichiometric metallic reductants are required.
  Whereas the allylmetal reagents used in these first-generation technologies are often difficult to prepare and handle, the Krische allylation exploits highly tractable allylic acetates. Additionally, the Krische allylation avoids the use of preformed allyl metal reagents or metallic reductants and chiral auxiliaries, significantly reducing waste generation.