Molecular Recognition of Carbonyl Compounds Using Aluminum Tris(2,6-diphenylphenoxide) (ATPH): New Regio- and Stereoselective Alkylation of α,β-Unsaturated Carbonyl Compounds

Saitō, Susumu; Shiozawa, Masahito; Nagahara, Takashi; Nakadai, and Masakazu; Yamamoto, Hisashi

doi:10.1021/ja000789d

Cited by 35 publications

(16 citation statements)

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“…We were therefore very pleased to find (after a search in the Cambridge Structural Database) that aluminum tris(2,6-diphenylphenoxide) (ATPH, Scheme 2) forms conglomerates with both cinnamaldehyde [14] and benzaldehyde. [15] Yamamoto and co-workers have reported remarkable regioand stereoselective reactions of ATPH complexes in solution, [16][17][18][19][20][21][22] and we were intrigued to learn that ATPH has a chiral pocket because the phenoxide ligands are wrapped around the metal, much like in a helicate ( Figure 3 and Figure 4). Moreover, these complexes should be stereochemically labile, which would set the stage for total spontaneous resolution and (thereafter) enantioselective alkylation.…”

Section: Introductionmentioning

confidence: 99%

Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Johansson

Håkansson

2005

Chemistry A European J

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Helical complexes formed between aluminum tris(2,6-diphenylphenoxide) (ATPH) and five different aldehydes have been prepared and structurally characterized by X-ray diffraction. It was found that [Al(OC6H3Ph2)3PhCHO] (2), [Al(OC6H3Ph2)3(4-CH3C6H4CHO)] (3), [Al(OC6H3Ph2)3(4-tBuC6H4CHO)] (4), and [Al(OC6H3Ph2)3(p-CH3OC6H4CHO)] (5) all crystallize as conglomerates, while crystals of [Al(OC6H3Ph2)3(o-CH3OC6H4CHO)] (6) are racemic. Supramolecular CH/pi interactions between molecules in crystals of 2-5 that enable stereochemical information to be mediated in three dimensions have been identified and explain the high frequency of conglomerate formation among ATPH helicates. Since 2-5 are stereochemically labile and thus enantiomerize rapidly in solution, the conglomerates can be resolved by crystallization-induced asymmetric transformation. The determination of the enantiomeric excess (ee) in solid samples of stereochemically labile molecules is not trivial, but solid-state CD spectroscopic data, anomalous dispersion data, and the ee values in alkylation reactions all indicate that preferential crystallization of 2-5 yields an essentially enantiopure product. Thus the preparation of 2-5 constitute new examples of absolute asymmetric synthesis. The helical chirality can be transferred (and thus trapped) to alcohols (with ee values of up to 16%) in crystal-to-crystal reactions with achiral organometallic reagents.

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Section: Introductionmentioning

confidence: 99%

Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Johansson

Håkansson

2005

Chemistry A European J

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“…In recent years, the reaction has gained significant attention from the organic community, and an important advance was described by Hisashi Yamamoto with the use of the very bulky Lewis acid, aluminum tris(2,6-diphenylphenoxide) (ATPH 1, Scheme 1). 3 ATPH is used in reactions of lithium enolates and aldehydes, and it is thought to bind to both the dienolate and the aldehyde components of the reaction. Due to its bulk, it prevents reaction at the α-carbon of the dienolate, thereby forcing the reaction to occur at the distal γ-carbon (Scheme 1).…”

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confidence: 99%

“…Remarkably, Yamamoto has used ATPH to direct reactivity to the terminal carbon in substrates as large as hexaenolates derived from pentaenoates. 3b …”

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confidence: 99%

The Vinylogous Aldol Reaction of Unsaturated Esters and Enolizable Aldehydes Using the Novel Lewis Acid Aluminum Tris(2,6-di-2-naphthylphenoxide)

Gazaille

Sammakia

2012

Org. Lett.

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The synthesis of the novel Lewis acid, aluminum tris(2,6-di-2-naphthylphenoxide) (ATNP), and its use in the vinylogous aldol reaction between methyl crotonate and enolizable aldehydes are described. ATNP is related to Yamamoto’s Lewis acid, aluminum tris(2,6-diphenylphenoxide) (ATPH), but the 2-naphthyl groups more effectively block the α-position of aldehydes, enabling the selective enolization of crotonate esters in the presence of enolizable aldehydes. Vinylogous aldol reactions then proceed smoothly and in high yields with a variety of substrates.

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“…This idea is based upon related enolization studies demonstrating that, under certain conditions, the selective formation of the thermodynamic exo-cyclic enolate of type III is strongly favored over both the endo-isomer and the kinetic cross-conjugated dienolate (41)(42)(43)(44)(45). This inherent behavior of β-substituted cyclohexenones has found a wonderful application in the conceptually unique, direct, vinylogous aldol reaction reported by Yamamoto and coworkers (46,47): The complete γ-site selectivity induced by the nonchiral, bulky aluminum-based catalyst has been rationalized on the basis of catalyst steric effects (48,49), which inhibit base deprotonation at the α′ position, whereas thermodynamic factors account for the formation of the reactive exo-dienolate isomer of the β-methyl 2-cyclohexen-1-one (46). On these grounds, we considered the unique Scheme 1.…”

Section: Microbiologymentioning

confidence: 99%

Direct asymmetric vinylogous Michael addition of cyclic enones to nitroalkenes via dienamine catalysis

Bencivenni

Galzerano

Mazzanti

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

186

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In spite of the many catalytic methodologies available for the asymmetric functionalization of carbonyl compounds at their α and β positions, little progress has been achieved in the enantioselective carbon–carbon bond formation γ to a carbonyl group. Here, we show that primary amine catalysis provides an efficient way to address this synthetic issue, promoting vinylogous nucleophilicity upon selective activation of unmodified cyclic α,β-unsaturated ketones. Specifically, we document the development of the unprecedented direct and vinylogous Michael addition of β-substituted cyclohexenone derivatives to nitroalkenes proceeding under dienamine catalysis. Besides enforcing high levels of diastereo- and enantioselectivity, chiral primary amine catalysts derived from natural cinchona alkaloids ensure complete γ-site selectivity: The resulting, highly functionalized vinylogous Michael adducts, having two stereocenters at the γ and δ positions, are synthesized with very high fidelity. Finally, we describe the extension of the dienamine catalysis-induced vinylogous nucleophilicity to the asymmetric γ-amination of cyclohexene carbaldehyde.

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Molecular Recognition of Carbonyl Compounds Using Aluminum Tris(2,6-diphenylphenoxide) (ATPH): New Regio- and Stereoselective Alkylation of α,β-Unsaturated Carbonyl Compounds

Cited by 35 publications

References 1 publication

Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

Absolute Asymmetric Synthesis of Stereochemically Labile Aldehyde Helicates and Subsequent Chirality Transfer Reactions

The Vinylogous Aldol Reaction of Unsaturated Esters and Enolizable Aldehydes Using the Novel Lewis Acid Aluminum Tris(2,6-di-2-naphthylphenoxide)

Direct asymmetric vinylogous Michael addition of cyclic enones to nitroalkenes via dienamine catalysis

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