Self-Terminated Cascade Reactions That Produce Methylbenzaldehydes from Ethanol

Moteki, Takahiko; Rowley, Andrew T.; Flaherty, David W.

doi:10.1021/acscatal.6b02475

Cited by 33 publications

(72 citation statements)

References 24 publications

(65 reference statements)

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“…The selectivity to 2,4,6‐octatrienal decreases as that for 2‐MB=O and 2‐MB‐OH increases, which together with reported mechanisms for dehydrocyclization reactions, strongly suggests that the 2‐MB products form as secondary products from 2,4,6‐octatrienal. Furthermore, the higher selectivity of 2‐MB=O compared to 2‐MB‐OH within the lower range of conversion (0–50 %) shows that 2‐MB‐OH forms from 2‐MB=O via H‐transfer steps that likely use ethanol as a hydrogen donor (e.g., the MPV reaction) . Overall, these data (Figure and Figure ) together with results from our previous study investigating sequential reactions of acetaldehyde provide a nearly complete description of the series of reactions that form 2‐MB=O primarily by cyclization of 2,4,6‐octatrienal, which is produced by either the cross‐aldol condensation between acetaldehyde and 2,4‐hexadienal or by self‐condensation of 2‐butenal.…”

Section: Resultsmentioning

confidence: 88%

“…Besides the 2‐MB and 4‐MB products and their intermediates, other C 4 –C 6 alcohols and aldehydes (e.g., 1‐butanol, 1‐hexanol, butyraldehyde) form as side products via direct (e.g., the Meerwein‐Ponndorf‐Verley (MPV) reaction) or indirect, surface‐mediated H‐transfer from ethanol . Notably, the Ca‐HAP catalyst and reaction conditions used here do not dehydrogenate C−C bonds of small oxygenates, and therefore, saturated aldehydes and alcohols do not reform the enes or enals needed to create aromatic products …”

Section: Resultsmentioning

confidence: 99%

“…Figure shows that 2‐butenal is the primary product of the aldol condensation of acetaldehyde and that 2‐butenal remains the most abundant product until the conversion of acetaldehyde reaches ≈40 % (0.35 kPa C 2 H 4 O, 1 kPa C 2 H 5 OH, 99 kPa H 2 , 548 K), which agrees with prior investigations . The yield of 2‐butenal decreases with increasing conversion of acetaldehyde (for conversions greater than 15 %), because secondary condensation reactions, which form C 6 and C 8 enal products, consume 2‐butenal.…”

Section: Resultsmentioning

confidence: 99%

“…The yield of 2‐butenal decreases with increasing conversion of acetaldehyde (for conversions greater than 15 %), because secondary condensation reactions, which form C 6 and C 8 enal products, consume 2‐butenal. First, aldol condensation of acetaldehyde to 2‐butenal gives 2,4‐hexadienal and subsequent condensation of acetaldehyde to 2,4‐hexadienal produces 2,4,6‐octatrienal . Once formed, 2,4,6‐octratrienal rapidly undergoes electrocyclization and dehydrogenation to produce 2‐MB=O .…”

Section: Resultsmentioning

confidence: 99%

“…Such coupling reactions continue in a series of steps that consume primary products and form larger species . While the cascades of ethanol coupling (Guerbet reaction) processes produce broad distributions of linear and branched alcohols by numerous self‐ and cross‐condensation reactions, narrower product distributions that provide selectivity to specific species emerge if unsaturated aldehydes (and enals) mainly participate in condensation reactions.…”

Section: Introductionmentioning

confidence: 99%

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Formation Pathways toward 2‐ and 4‐Methylbenzaldehyde via Sequential Reactions from Acetaldehyde over Hydroxyapatite Catalyst

et al. 2017

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Condensation reactions of biomass derived C2 and C4 aldehydes form both ortho‐ and para‐tolualdehydes (2‐MB and 4‐MB, respectively). The complete reaction network and the detailed mechanisms, however, have not been fully described. Here, analysis of the products formed by sequential condensation reactions of acetaldehyde and 2‐butenal suggests that 2‐ and 4‐MB products form via aromatization of 2,4,6‐octatrienal and of highly reactive acyclic intermediate(s) formed via self‐addition of 2‐butenal, respectively. The exact positions at which C−C bonds form between C4 co‐reactants to create 4‐MB products were investigated by using reactant mixtures containing combinations of 2‐butenal, 2‐butenol, and 3‐methyl‐2‐butenal as model reactants. The last two reactants can form products that may be assigned to specific reaction pathways (not distinguishable during self‐addition of 2‐butenal) and also have decreased reactivity at specific carbon atoms. The analysis of the products suggests that 4‐MB species form via 2‐butenal self‐addition by nucleophilic attack of the α‐C to the carbonyl‐C. Additionally, Diels–Alder reactions (between C6 and C2 intermediates) do not contribute in any significant manner to the formation of 4‐MB. These findings complete the description of the reaction network that forms 2‐ and 4‐MB from acetaldehyde on hydroxyapatite.

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Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Formation Pathways toward 2‐ and 4‐Methylbenzaldehyde via Sequential Reactions from Acetaldehyde over Hydroxyapatite Catalyst

et al. 2017

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Hydroxyapatite‐Based Catalysts in Organic Synthesis

Gruselle¹,

Tõnsuaadu²,

Gredin³

et al. 2022

Design and Applications of Hydroxyapatite‐Based Catalysts

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Synthesis of Spirocyclohexadieneyl‐2‐Oxindoles by 6π‐Electrocyclization of Trienes Derived from Wittig Reaction of Morita‐Baylis‐Hillman Carbonates and α,β‐Unsaturated Aldehydes

Min

Seo

Ryu

et al. 2017

Bulletin Korean Chem Soc

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Spirooxindoles exist in a huge number of natural substances and pharmaceutically interesting compounds.1 Thus, tremendous efforts have been devoted to efficient protocols to access these important motifs over the past years. [1][2][3][4][5] Recently, we reported the synthesis of spirocyclohexadienyl-2-oxindoles by 6π-electrocyclic ring closure (6π-ERC) of the trienes, derived from Morita-Baylis-Hillman (MBH) adducts of cinnamaldehyde and isatin (Scheme 1).2e Very recently, we also reported the synthesis of dispirobisoxindole from MBH carbonates of N-methylisatin (Scheme 1).3 During the course of our study, we decided to examine the synthesis of structurally related spirocyclohexadienyl-2-oxindoles 4,5 with different substitution pattern by 6π-ERC of the trienes, derived from MBH carbonates of N-methylsatin and cinnamaldehyde, as shown in Scheme 1.At the outset of our experiment, the reaction of MBH carbonate 1a and trans-cinnamaldenyde (2a, 1.1 equiv) in 1,2-dichlorobenzene (ODCB) was examined at 150 C in the presence of PPh 3 (1.0 equiv).3 To our delight, spirocyclohexa-2,4-dienyl-2-oxindole 3a was obtained in good yield (69%) in short time (2 h). The formation of the other diastereomer (3a 0 , vide infra, Scheme 2) was not observed. The structure of 3a was unequivocally confirmed by its crystal structure (vide infra, Scheme 2).6 However, two diastereomeric dispirobisoxindoles (see, Scheme 1) have been formed as side products in appreciable yield (23%), as in our previous paper.3 When we carried out the reaction in refluxing p-xylene (5 h), the yield of 3a increased to 74%, and the yield of dispirobisoxindoles decreased (18%). The yield of 3a increased slightly (77%) when we carried out the reaction in refluxing toluene; however, a long reaction time (24 h) was required. When we used an excess amount of 2a (2.0 equiv) in refluxing xylene (5 h), the yield of 3a increased up to 85%. In the reaction mixture, the formation of only a trace amount (<5%) of dispirobisoxindole was observed. 7Encouraged by the results we synthesized various spirooxindoles 3b-3l, and the results are summarized in Table 1. Various spirooxindoles 3b-3e were synthesized in good to moderate yields (67-89%) by the reactions of substituted isatin derivatives 1b-1e with 2a. The reaction of 1a and trans-3-(2-furyl)acrolein (2b) afforded 3f in moderate yield (60%). The reaction of crotonaldehyde (2c) gave 3g in good yield (78%). In the reaction, we used an excess amount of 2c (3.0 equiv) because the boiling point of 2c (104 C) was lower than the reaction temperature (138 C). The reactions of 1a with α-methyl-trans-cinnamaldehyde (2d) and α-bromocinnamaldehyde (2e) afforded 3h and 3i in good yields (68% and 84%, respectively). However, the reactions with α-substituted aliphatic aldehydes, trans-2-methyl-2-butenal (2f) and 1-cyclohexene-1-carboxaldehyde (2g), produced the corresponding spirooxindoles 3j (23%) and 3k (33%) in low yields with 3.0 equiv. of 2f or 2g. The result might be due to sluggish reactivity in the Wittig reaction of α-branched α...

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Self-Terminated Cascade Reactions That Produce Methylbenzaldehydes from Ethanol

Cited by 33 publications

References 24 publications

Formation Pathways toward 2‐ and 4‐Methylbenzaldehyde via Sequential Reactions from Acetaldehyde over Hydroxyapatite Catalyst

Formation Pathways toward 2‐ and 4‐Methylbenzaldehyde via Sequential Reactions from Acetaldehyde over Hydroxyapatite Catalyst

Hydroxyapatite‐Based Catalysts in Organic Synthesis

Synthesis of Spirocyclohexadieneyl‐2‐Oxindoles by 6π‐Electrocyclization of Trienes Derived from Wittig Reaction of Morita‐Baylis‐Hillman Carbonates and α,β‐Unsaturated Aldehydes

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