Stereoselective Acetate Aldol Reactions

Romea, Pedro; Urpı́, Fèlix

doi:10.1002/9783527656714.ch1

Cited by 18 publications

(7 citation statements)

References 424 publications

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“…Acetate-type enolates generally display lower stereoselectivity, presumably because a smaller steric bias at the α-position of the enolate makes stereocontrol less tractable . Given the ubiquitous nature of the chiral β-aminoacetate unit in natural products and biologically active compounds, direct enolization of acetamides coupled with the subsequent Mannich-type reaction is an important objective .…”

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confidence: 99%

“…Intriguingly, L9 having dialkyl and diarylphosphino groups outperformed L8, which has two diphenylphosphino groups (entries 10, 11). In contrast to 7azaindoline amide 1a, six-and seven-membered analogs 1b and 1c failed in the reaction under the optimized conditions for an anti-selective reaction (entries 12,13). NMR studies of the Cu(I)/L1 complex revealed that ca.…”

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Direct Catalytic Asymmetric Mannich-Type Reaction of Alkylamides

et al. 2016

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Direct enolate formation coupled with subsequent enantioselective C-C bond formation remains a topic of intense interest in asymmetric catalysis. This methodology is achieved even with low acidic amides without an electron-withdrawing group at the α-position in the context of a Mannich-type reaction. Acetate-, propionate-, and butyrate-type 7-azaindoline amides served as enolate precursors to afford the desired Mannich adducts with high stereoselectivity, and ligand-enabled diastereo-divergency provided access to both anti/syn diastereomers. The facile transformation of the amide moiety ensures the synthetic utility of the Mannich adducts.

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Direct Catalytic Asymmetric Mannich-Type Reaction of Alkylamides

et al. 2016

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“…groups were introduced in 12 steps, and in Krische's synthesis of (+)-roxaticin, 12 six hydroxyl groups were introduced but in just 9 steps by taking advantage of bidirectional chain synthesis. Acetate aldol reactions have also been developed, 14 such as Carreira's silyl ketene acetal addition reaction (Figure 1b). [15][16][17] Although highly enabling, the iterative aldol and allylation reaction sequences described above require three steps per hydroxyl group, suggesting that general approaches that provide more expediated routes to these motifs would have broad impact.…”

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Iterative Synthesis of 1,3-Polyboronic Esters with High Stereocontrol: Applications to Bahamaolide A and Polyfunctionalised Hydrocarbons

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Liao

et al. 2022

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Polyketide natural products often contain common repeat motifs, e.g., propionate, acetate and deoxypropionate, and so can be synthesized by using iterative processes. We report a highly efficient iterative strategy for the synthesis of polyacetates based on boronic ester homologation that does not require functional group manipulation between iterations. This process involves sequential asymmetric diboration of a terminal alkene, forming a 1,2-bis(boronic ester), followed by regio- and stereoselective homologation of the primary boronic ester with a butenyl metallated carbenoid to generate a 1,3-bis(boronic ester). Each transformation independently controls stereochemical configuration, making the process highly versatile, and the sequence can be iterated prior to stereospecific oxidation of the 1,3-poly(boronic ester) to reveal the 1,3-polyol. The methodology was applied to a 14-step synthesis of the oxopolyene macrolide bahamaolide A, and the versatility of the 1,3-polyboronic esters was demonstrated in various stereospecific transformations, leading to poly-alkenes, -alkynes, -ketones, and -aromatics with full stereocontrol.

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“…Mukaiyama-type aldol reactions 1 are some of the most powerful tools for the formation of carbon-carbon bonds. 2 These reactions are widely used in medicinal chemistry and in the total synthesis of natural products. 2,3 The classic catalytic systems for these reactions operate through the activation of the carbonyl group by strong Lewis acids [4][5][6] such as BX 3 , 7,8 Sn(II), 9,10 Ti(IV), 11 Cu(II), 12,13 Pd(II), 14 or lanthanide complexes.…”

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“…2 These reactions are widely used in medicinal chemistry and in the total synthesis of natural products. 2,3 The classic catalytic systems for these reactions operate through the activation of the carbonyl group by strong Lewis acids [4][5][6] such as BX 3 , 7,8 Sn(II), 9,10 Ti(IV), 11 Cu(II), 12,13 Pd(II), 14 or lanthanide complexes. 15,16 These Lewis-acidic catalysts are often incompatible with other functional groups present.…”

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confidence: 99%