The use of allenes and 1,3-dienes as chiral allylmetal pronucleophiles in intermolecular catalytic enantioselective reductive additions to aldehydes, ketones, imines, carbon dioxide and other C=X electrophiles is exhaustively catalogued together with redox-neutral hydrogen auto-transfer processes. Coverage is limited to processes that result in both CÀ H and CÀ C bond formation. The use of alkynes as latent allylmetal pronucleophiles and multicomponent C=X allylations involving allenes and dienes is not covered. As illustrated in this review, the ability of allenes and 1,3-dienes to serve as tractable non-metallic pronucleophiles has evoked many useful transformations that have no counterpart in traditional allylmetal chemistry.
The
first catalytic enantioselective ruthenium-catalyzed carbonyl
reductive couplings of allene pronucleophiles is described. Using
an iodide-modified ruthenium-BINAP-catalyst and O-benzhydryl alkoxyallene 1a, carbonyl (α-alkoxy)allylation
occurs from the alcohol or aldehyde oxidation level to form enantiomerically
enriched syn-sec,tert-diols. Internal
chelation directs intervention of (Z)-σ-alkoxyallylruthenium
isomers, which engage in stereospecific carbonyl addition.
The use of allenes and 1,3‐dienes as chiral allylmetal pronucleophiles in intermolecular catalytic enantioselective reductive additions to aldehydes, ketones, imines, carbon dioxide and other C=X electrophiles is exhaustively catalogued in this Minireview by M. J. Krische and colleagues, together with redox‐neutral hydrogen auto‐transfer processes. For more details, see the Minireview by Michael J. Krische et al. on page 13107 ff.
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