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Desymmetrization of cyclic 1,3-diketones via Ir-catalyzed hydrogenation: an efficient approach to cyclic hydroxy ketones with a chiral quaternary carbon.

ABSTRACT: We herein report an efficient method to synthesize cyclic hydroxy ketones with a chiral quaternary center. Catalyzed by an Ir/f-ampha complex, cyclic ?,?-disubstituted 1,3-diketones were hydrogenated, giving mono-reduced products with both high enantioselectivities and diastereoselectivities. In addition, C[double bond, length as m-dash]C and C[triple bond, length as m-dash]C bonds could survive in this catalytic system. This method was applied in the preparation of (+)-estrone. No diols were observed in this chemical transformation. The enantiomeric and diastereomeric induction were achieved as a result of steric hindrance.

SUBMITTER: Gong Q

PROVIDER: S-EPMC6601421 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Desymmetrization of cyclic 1,3-diketones <i>via</i> Ir-catalyzed hydrogenation: an efficient approach to cyclic hydroxy ketones with a chiral quaternary carbon.

Gong Quan Q Wen Jialin J Zhang Xumu X

Chemical science 20190521 25

We herein report an efficient method to synthesize cyclic hydroxy ketones with a chiral quaternary center. Catalyzed by an Ir/f-ampha complex, cyclic α,α-disubstituted 1,3-diketones were hydrogenated, giving mono-reduced products with both high enantioselectivities and diastereoselectivities. In addition, C[double bond, length as m-dash]C and C[triple bond, length as m-dash]C bonds could survive in this catalytic system. This method was applied in the preparation of (+)-estrone. No diols were ob ...[more]

PMID: 31341590

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Project description:Acetone is the expected ketone product of an acetic acid decarboxylative ketonization reaction with metal oxide catalysts used in the industrial production of ketones and for biofuel upgrade. Decarboxylative cross-ketonization of a mixture of acetic and isobutyric acids yields highly valued unsymmetrical methyl isopropyl ketone (MIPK) along with two less valuable symmetrical ketones, acetone and diisopropyl ketone (DIPK). We describe a side reaction of isobutyric acid with acetone yielding the cross-ketone MIPK with monoclinic zirconia and anatase titania catalysts in the absence of acetic acid. We call it a reketonization reaction because acetone is deconstructed and used for the construction of MIPK. Isotopic labeling of the isobutyric acid's carboxyl group shows that it is the exclusive supplier of the carbonyl group of MIPK, while acetone provides only methyl group for MIPK construction. More branched ketones, MIPK or DIPK, are less reactive in their reketonization with carboxylic acids. The proposed mechanism of reketonization supported by density functional theory (DFT) computations starts with acetone enolization and proceeds via its condensation with surface isobutyrate to a β-diketone similar to β-keto acid formation in the decarboxylative ketonization of acids. Decomposition of unsymmetrical β-diketones with water (or methanol) by the retrocondensation reaction under the same conditions over metal oxides yields two pairs of ketones and acids (or esters in the case of methanol) and proceeds much faster compared to their formation. The major direction yields thermodynamically more stable products-more substituted ketones. DFT calculations predict even a larger fraction of the thermodynamically preferred pair of products. The difference is explained by some degree of a kinetic control in the opposite direction. Reketonization has lower reaction rates compared to regular ketonization. Still, a high extent of reketonization occurs unnoticeably during the decarboxylative ketonization of acetic acid as the result of the acetone reaction with acetic acid. This degenerate reaction is the major cause of the inhibition by acetone of its own rate of formation from acetic acid at high conversions.

Dataset Information

Desymmetrization of cyclic 1,3-diketones via Ir-catalyzed hydrogenation: an efficient approach to cyclic hydroxy ketones with a chiral quaternary carbon.

Publications

Desymmetrization of cyclic 1,3-diketones <i>via</i> Ir-catalyzed hydrogenation: an efficient approach to cyclic hydroxy ketones with a chiral quaternary carbon.

Similar Datasets

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