Diastereoselective Cobalt-Catalyzed Alkylative Aldol Cyclizations Using Trialkylaluminum Reagents

Rudkin, Mairi E.; Joensuu, Pekka M.; MacLachlan, William S.; Lam, Hon Wai

doi:10.1021/ol800883b

Cited by 11 publications

(3 citation statements)

References 46 publications

(18 reference statements)

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“…Based on the obtained results, including significant ligand effects, we propose a plausible reaction pathway in Figure . Since Co catalysts with different valences (Co(I), Co(II), Co(III)) equally promoted the carboxylation, a low-valent methyl-Co(I) species I would first be generated from the Co salt, Xantphos, and AlMe 3 . Dialkyl-Co(II) is known to undergo disproportionation to form Co(I) and Co(III); the latter further produces Co(I) through reductive elimination.…”

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confidence: 99%

Cobalt-Catalyzed Allylic C(sp³)–H Carboxylation with CO₂

2017

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Catalytic carboxylation of the allylic C(sp)-H bond of terminal alkenes with CO was developed with the aid of a Co/Xantphos complex. A wide range of allylarenes and 1,4-dienes were successfully transformed into the linear styrylacetic acid and hexa-3,5-dienoic acid derivatives in moderate to high yields, with excellent regioselectivity. The carboxylation showed remarkable functional group tolerability, so that selective addition to CO occurred in the presence of other carbonyl groups such as amide, ester, and ketone. Since styrylacetic acid derivatives can be readily converted into optically active γ-butyrolactones through Sharpless asymmetric dihydroxylation, this allylic C(sp)-H carboxylation showcases a facile synthesis of γ-butyrolactones from simple allylarenes via short steps.

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Cobalt-Catalyzed Allylic C(sp³)–H Carboxylation with CO₂

2017

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“…This methodology was extended towards intra-and intermolecular alkylative aldol reactions of α,β-unsaturated amides with a keto functionality using cobalt acetylacetonate as catalyst in combination with alkylzinc and alkylaluminum reagents. 328,329 An enantioselective aldol reaction between cyclic as well as acyclic ketones and aldehydes using L-proline and cobalt chloride as catalyst system has been described by Reiser (Scheme 93). 330 Although the reaction proceeds without any metal salt, the combination of the cobalt chloride with the organocatalyst increased the diastereo-and enantioselectivity observed in 170 significantly, presumably through chelation of both the proline enamine and the aldehyde.…”

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confidence: 99%

Cobalt-Catalysed Bond Formation Reactions; Part 2

Röse

Hilt

2015

Synthesis

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This review summarises the cobalt-catalysed reactions of the years 2008 through 2014. Covered are addition reactions, such as the hydrogenation of double bonds, the addition of C-H bonds to double and triple bonds, C-H activation reactions, cobalt-catalysed cross-coupling reactions and selected additions of H-B and H-Si bonds to unsaturated starting materials. The cobalt-catalysed cycloadditions range from cyclopropanations, [2+2], Pauson-Khand reactions, [2+2+2], [4+2], [6+2] cycloadditions as well as benzannulations. Also covered are Nicholas reactions, cobalt-catalysed Jacobsen's kinetic resolution of epoxides as well as selected miscellaneous cobalt-catalysed processes mainly for carbon-carbon bond formations. 1 Introduction 2 Addition Reactions 3 Homo-and Cross-Coupling Reactions 4 Jacobsen Kinetic Resolution of Epoxides 5 Nicholas Reactions 6 Cycloaddition Reactions 7 Miscellaneous 8 Conclusion

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“…A proposed mechanism for this reaction is depicted in Figure . First, a low-valent methylcobalt(I) species would be generated from a cobalt salt and AlMe 3 . Dimethylcobalt(II) is known to undergo disproportionation to form methylcobalt(I) and trimethylcobalt(III), and the latter is further reduced to methylcobalt(I) via reductive elimination.…”

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Co-Catalyzed Direct Addition of Allylic C(sp³)–H Bonds to Ketones

et al. 2017

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By using Co(acac)/Xantphos with AlMe, the C(sp)-H bonds of allylarene derivatives were cleaved for reaction with various ketones, affording the homoallylic alcohols in moderate to good yields. The branch/linear selectivity depended on the steric and electronic factors of the ketone electrophiles. The intermediate in this reaction is thought to be a low-valent allylcobalt(I) species, which exhibits high nucleophilicity toward ketones.

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Diastereoselective Cobalt-Catalyzed Alkylative Aldol Cyclizations Using Trialkylaluminum Reagents

Abstract: Co(acac)2.2H2O serves as an effective precatalyst for alkylative aldol cyclizations of alpha,beta-unsaturated amides with ketones using trialkylaluminum reagents. These reactions provide beta-hydroxylactams containing three contiguous stereocenters with high levels of diastereoselection.

Cited by 11 publications

References 46 publications

Cobalt-Catalyzed Allylic C(sp³)–H Carboxylation with CO₂

Cobalt-Catalyzed Allylic C(sp³)–H Carboxylation with CO₂

Cobalt-Catalysed Bond Formation Reactions; Part 2

Co-Catalyzed Direct Addition of Allylic C(sp³)–H Bonds to Ketones

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Diastereoselective Cobalt-Catalyzed Alkylative Aldol Cyclizations Using Trialkylaluminum Reagents

Abstract: Co(acac)2.2H2O serves as an effective precatalyst for alkylative aldol cyclizations of alpha,beta-unsaturated amides with ketones using trialkylaluminum reagents. These reactions provide beta-hydroxylactams containing three contiguous stereocenters with high levels of diastereoselection.

Cited by 11 publications

References 46 publications

Cobalt-Catalyzed Allylic C(sp3)–H Carboxylation with CO2

Cobalt-Catalyzed Allylic C(sp3)–H Carboxylation with CO2

Cobalt-Catalysed Bond Formation Reactions; Part 2

Co-Catalyzed Direct Addition of Allylic C(sp3)–H Bonds to Ketones

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Product

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Cobalt-Catalyzed Allylic C(sp³)–H Carboxylation with CO₂

Cobalt-Catalyzed Allylic C(sp³)–H Carboxylation with CO₂

Co-Catalyzed Direct Addition of Allylic C(sp³)–H Bonds to Ketones