Aldehyde and ketone condensation reactions catalyzed by boric acid

Offenhauer, Robert D.; Nelsen, Stephen F.

doi:10.1021/jo01266a059

Cited by 37 publications

(9 citation statements)

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“…Boric acid and boron oxide are reported as highly efficient catalysts for selective aldol condensation of aldehydes in hexane. In the presence of small concentrations of water, however, B 2 O 3 is hydrated forming strong acidic Brønsted acid sites that favored over‐condensation reactions . For B–MgO catalysts prepared by combustion, B cations are located in different chemical environments depending on the concentration as revealed by 11 B NMR spectroscopy.…”

Section: Resultsmentioning

confidence: 99%

Fine‐Tuning the Acid–Base Properties of Boron‐Doped Magnesium Oxide Catalyst for the Selective Aldol Condensation

et al. 2016

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Controlled incorporation of dopants into the structure of metal oxide catalysts can be used to fine‐tune their topological, chemical, and electronic properties. Conventional preparation methods (coprecipitation and impregnation) tend to produce materials with a limited extent of chemical interaction between metal oxide and dopant, small pore volume, and disconnected pore structure. Herein, we describe a combustion method to optimize both the porous structure of metal oxides and the chemical interaction with dopants. By exploiting the differences in melting points between metal oxide (MgO) and dopant (B), it is possible to create hierarchical mixed oxides with tailored chemical structure. As a model reaction, we employed the aldol condensation of acetaldehyde to crotyl alcohol, a key intermediate step in the conversion of bioethanol to 1,3‐butadiene, to show the unique characteristics of these materials. The B–Mg mixed oxide prepared by combustion exhibits an order of magnitude higher productivity of C4 products than conventional MgO and B–MgO. We anticipate that our approach could be extended to the development of other dual oxides with open structure for unrestricted diffusion and enhanced chemical interaction of acid and basic metal oxides.

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Section: Resultsmentioning

confidence: 99%

Fine‐Tuning the Acid–Base Properties of Boron‐Doped Magnesium Oxide Catalyst for the Selective Aldol Condensation

et al. 2016

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“…We would make use of this nov- el transformation in synthetic objectives which are difficult to achieve relying on the previous acid-catalyzed method. 3 These extraordinarily simple conditions without benzoic acid also provided an opportunity for cross aldol condensation reaction between, for instance, nonanal 1f and acetone to afford enone 7, though accompanied by the homo-aldol product 2f. We will undoubtedly pick up the more sophisticated modern protocol of Horner-Emmons reaction if we are asked to synthesize the enone 7.…”

Section: Methodsmentioning

confidence: 99%

“…2). To our surprise, however, no reaction of this class has been described so far except for one example of homocoupling of heptanal which was promoted by boric acid in xylene under reflux for 18 h. 3 This protocol was employed for the preparation of 2-butyl-2E-octenal (2a) from hexanal (1a) (eq. 3) which was required as one of the segments for the total synthesis of an elastase inhibitor, elastin.…”

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confidence: 99%

Pyrrolidine-Catalyzed Homo-Aldol Condensation Reactions of Aldehydes

Ishikawa¹,

Uedo²,

Okada³

et al. 1999

Synlett

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“…12 Yields were much higher than those reported with other acid or base catalysts. 12 Yields were much higher than those reported with other acid or base catalysts.…”

Section: Condensationmentioning

confidence: 58%