2021
DOI: 10.1002/chem.202101890
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Allenes and Dienes as Chiral Allylmetal Pronucleophiles in Catalytic Enantioselective C=X Addition: Historical Perspective and State‐of‐The‐Art Survey

Abstract: 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 covere… Show more

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Cited by 54 publications
(25 citation statements)
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“…Here, by understanding halide counterion effects , and exploiting trifluoroethanol (TFE)-enhanced turnover, we report an improved catalytic system for alkyne−alcohol C−C coupling, as illustrated by the regio- and enantioselective conversion of ethanol (the most abundant renewable small-molecule carbon source) to enantiomerically enriched homoallylic alcohols. Specifically, using a ruthenium catalyst modified by JOSIPHOS in the presence of TFE, diverse 1-aryl-1-propynes react with ethanol to form branched secondary homoallylic alcohols through a tandem catalytic cycle in which alkyne-to-allene redox isomerization is followed by allene−​aldehyde reductive coupling via hydrogen auto-transfer. As corroborated by DFT calculations and crystallographic characterization of a series of halide-bound complexes, RuX­(CO)­(η 3 -C 3 H 5 )­(JOSIPHOS), where X = Cl, Br, or I, there exists a halide-dependent diastereomeric preference that defines metal-centered stereogenicity and, therefrom, the absolute stereochemical course of C−C coupling. Whereas the chloride- and bromide-bound catalysts exist as stereoisomeric mixtures, the iodide-bound catalyst exists as a single stereoisomer, enforcing superior levels of enantioselectivity.…”
Section: Introductionmentioning
confidence: 99%
“…Here, by understanding halide counterion effects , and exploiting trifluoroethanol (TFE)-enhanced turnover, we report an improved catalytic system for alkyne−alcohol C−C coupling, as illustrated by the regio- and enantioselective conversion of ethanol (the most abundant renewable small-molecule carbon source) to enantiomerically enriched homoallylic alcohols. Specifically, using a ruthenium catalyst modified by JOSIPHOS in the presence of TFE, diverse 1-aryl-1-propynes react with ethanol to form branched secondary homoallylic alcohols through a tandem catalytic cycle in which alkyne-to-allene redox isomerization is followed by allene−​aldehyde reductive coupling via hydrogen auto-transfer. As corroborated by DFT calculations and crystallographic characterization of a series of halide-bound complexes, RuX­(CO)­(η 3 -C 3 H 5 )­(JOSIPHOS), where X = Cl, Br, or I, there exists a halide-dependent diastereomeric preference that defines metal-centered stereogenicity and, therefrom, the absolute stereochemical course of C−C coupling. Whereas the chloride- and bromide-bound catalysts exist as stereoisomeric mixtures, the iodide-bound catalyst exists as a single stereoisomer, enforcing superior levels of enantioselectivity.…”
Section: Introductionmentioning
confidence: 99%
“…The synthesis of fragment B began with conversion of prenyl alcohol 5 to prenyl methyl carbonate (not shown), which was subjected to Riley-type oxidation to provide enal 6 . syn -Diastereo- and enantio­selective crotylation of enal 6 was achieved via 2-propanol-mediated reductive coupling with silyl-substituted diene 7 using a ruthenium catalyst modified by ( R )-SEGPHOS. , Desilylation of vinyl­silane 8 could be accomplished in situ or as a separate manipulation in roughly equivalent overall yield.…”
Section: Resultsmentioning
confidence: 99%
“…The controlled catalytic elaboration of dienes is thus of great synthetic importance. 23 On the other hand, methanol is produced in large volume each year (>30 × 10 6 tons/year). The direct conversion of methanol to higher alcohols is particularly attractive.…”
Section: Acyclic Quaternary Carbon Stereocenters Through Functionaliz...mentioning
confidence: 99%