Molecular Recognition of α,β-Unsaturated Carbonyl Compounds Using Aluminum Tris(2,6-diphenylphenoxide) (ATPH):  Structural and Conformational Analysis of ATPH Complexes and Application to the Selective Vinylogous Aldol Reaction

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

doi:10.1021/ja0205941

Cited by 43 publications

(31 citation statements)

References 62 publications

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“…The ASU also contains three independent molecules of toluene of crystallisation. 2 showed the presence of two single resonances for the methyl groups of the phenolic moieties and two well defined resonances for the AB spin system for the CH 2 protons. The ethoxy unit (-CH 2 CH 2 -) is also clearly defined as two well-separated triplet resonances.…”

Section: Synthesis Of Ligands and Complexesmentioning

confidence: 99%

Synthesis and structure of aluminium amine-phenolate complexes

et al. 2009

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Reaction of Al(OiPr)3 with the tris-phenol amine ligand L1H3 in toluene at ambient temperature results in the formation of the iso-propanol adduct [HOiPr.Al(L1)]. Single crystal X-ray diffraction analysis reveals the structure to be a hydrogen bonded dimer. Reaction of Al(OiPr)3 (or AlMe3) with L1H3 in THF affords the related, and structurally characterised THF adduct, [THF.Al(L1)]. Similar reaction of Al(OiPr)3 (or AlMe3) with the bis-phenol amine and tetra-phenol diamine ligands, L2H3 and L3H4, results in the formation and isolation of the complexes [Al(L2)]2 and [Al(L3)H] respectively, both of which have been structurally characterised via single crystal X-ray diffraction studies. Reaction of the alkoxide bridged dimer [Al(L2)]2 with the strong Lewis base HMPA results in the formation of the monomeric HMPA adduct [HMPA.Al(L2)] which was also structurally characterised. The adduct [HOiPr.Al(L1)] and the dimer [Al(L2)]2 were tested for their activity in the ring-opening polymerisation (ROP) of rac-lactide under solvent-free conditions (130 degrees C). Under the conditions employed [Al(L2)]2 failed to produce polymer after 48 h, in stark contrast to [HOiPr.Al(L1)] which after 24 h and 48 h produced narrow molecular weight polymer (24 h: yield=25%, Mn=14500 and PDI=1.05; 48 h: yield=65%, Mn=47700 and PDI=1.06).

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Section: Synthesis Of Ligands and Complexesmentioning

confidence: 99%

Synthesis and structure of aluminium amine-phenolate complexes

et al. 2009

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“…Thus, treatment of a mixture of methyl crotonate and chiral epoxy alcohol 85 with 8 mol equiv of 2,6-lutidine and 4 mol equiv of TBSOTf triggered a tandem aldol sequence involving in situ generation of the Scheme 51. Aldolization of r,β-Unsaturated Carbonyl Compounds with Aldehydes Using ATPH (275) and Me-ATPH (276) 121,122 activated aldehyde species, as well as γ-enolization of the crotonate ester (not shown). In such cases, excellent facial and simple diastereocontrol were witnessed, giving rise to useful chiral non racemic all-syn aldol fragments.…”

Section: Diastereoselective and Unselective Processesmentioning

confidence: 99%

The Vinylogous Aldol and Related Addition Reactions: Ten Years of Progress

et al. 2011

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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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Molecular Recognition of α,β-Unsaturated Carbonyl Compounds Using Aluminum Tris(2,6-diphenylphenoxide) (ATPH): Structural and Conformational Analysis of ATPH Complexes and Application to the Selective Vinylogous Aldol Reaction

Cited by 43 publications

References 62 publications

Synthesis and structure of aluminium amine-phenolate complexes

Synthesis and structure of aluminium amine-phenolate complexes

The Vinylogous Aldol and Related Addition Reactions: Ten Years of Progress

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

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