Aluminium Halide-Thiol System: A Useful Reagent for Demethylation of Aliphatic and Aromatic Methyl Ethers and Demethylenation of Methylenedioxy Compounds

Node, Manabu; Nishide, Kiyoharu; Sai, Masahiro; Ichikawa, Kohei; Fuji, Kaoru; Fujita, Eiichi

doi:10.1246/cl.1979.97

Cited by 48 publications

(22 citation statements)

References 3 publications

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“…The reaction can be accomplished by a number of ether cleaving agents such as BBr 3 , AlCl 3 , Ph 2 PLi, TMSI, MgI 2 , 2‐iodoxybenzoic acid (IBX), and pyridine hydrochloride . Of these reagents, AlCl 3 is well‐known for its low cost, tunable reactivity and ease of handling, and its ether cleaving efficiency could be improved by various nucleophiles such as pyridine, thiourea, dimethyl sulfide, thiol and sodium iodide . Interestingly, the ether cleaving power of this Lewis acid is highly dependent on the reaction media.…”

Section: Introductionmentioning

confidence: 99%

Anchimerically Assisted Cleavage of Aryl Methyl Ethers by Aluminum Chloride‐Sodium Iodide in Acetonitrile

Sang

Tian

et al. 2018

ChemistrySelect

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A practical method is developed for the cleavage of catechol monomethyl ethers and o-carbonylphenyl methyl ethers using aluminum chloride and sodium iodide in acetonitrile. Acid scavengers such as 1,3-diisopropylcarbodiimide and CaO are used to prevent acid-labile functional groups from sidereactions. This method is efficient for the deprotection of various o-hydroxyphenyl methyl ethers such as acetovanillone, eugenol, guaiacol, vanillin, isovanillin and ortho-vanillin. The AlCl 3 -NaI system is less efficient than AlI 3 for the cleavage of other typical aryl alkyl ethers without a neighboring hydroxyl or carbonyl group, or for the removal of bulkier alkyl groups from catechol monoalkyl ethers. This procedure represents a convenient approach for the preparation of catechols. 2 3 4 5 6 7 8

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Section: Introductionmentioning

confidence: 99%

Anchimerically Assisted Cleavage of Aryl Methyl Ethers by Aluminum Chloride‐Sodium Iodide in Acetonitrile

Sang

Tian

et al. 2018

ChemistrySelect

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“…The sodium salt of o-anisic acid was hardly cleaved (Entries 2,3,6,21,22). The presence of acidic proton was necessary at the heteroatom adjacent to the ortho-carbonyl group to cleave the methoxy group.…”

Section: Methodsmentioning

confidence: 99%

“…A number of methods have been reported using reagents such as Brønsted acid, 2 Lewis acid, [3][4][5][6][7] alkali metals or organic metals. [8][9][10][11][12] However, the use of aliphatic amines as a nucleophile has not been reported in the dealkylation of the O-alkyl protective group of phenols.…”

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confidence: 99%

Regioselective Dealkylation of 2-Alkoxybenzoic Acid and Its Amide Derivatives with Aliphatic Amines

Nishioka¹,

Nagasawa²,

Yoshida³

2000

Synthesis

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The methoxy group of o-anisic acid was cleaved with aliphatic amines in aprotic dipolar solvents. This cleavage reaction was especially smooth when piperazine in dimethylacetamide was used. This method was applicable to a variety of dealkylations of o-alkoxybenzoic acid and ist amide derivatives with high regioselectivity.For the demethylation of o-anisic acid (o-methoxybenzoic acid) and amide derivatives, dealkylation methods used for the O-alkyl protective group of phenols 1 can generally be applied. A number of methods have been reported using reagents such as Brønsted acid, 2 Lewis acid, 3-7 alkali metals or organic metals. 8-12 However, the use of aliphatic amines as a nucleophile has not been reported in the dealkylation of the O-alkyl protective group of phenols.Buchanan and coworkers have succeeded in the specific demethylation of o-anisic acid using lithium iodide or pyridinium hydroiodide in boiling pyridine. 14,15 The reaction was explained in terms of nucleophilic attack of the iodide ion on the methyl group with activation of the ether oxygen by intramolecular hydrogen bonding. 16,17 In a preliminary investigation, we found that heating o-anisic acid and hexylamine in 2-methoxyethyl ether at 150°C led to a 30% of salicylic acid accompanied by 28% of N-hexyl-o-anisamide. In order to systematically investigate this interesting cleavage of the methoxy group, we attempted to find the optimal reaction conditions and to clarify the scope and limitations of this useful method for the dealkylation of o-alkoxybenzoic acid and amide derivatives. Table 1 shows the results of the reaction of o-anisic acid with various amines and solvents. In using hexylamine, the cleavage reaction proceeded predominantly in DMSO, DMF and dimethylacetamide (DMA) (Entries 1-3) although the amide formation was only observed in cumene (Entry 4). The results of various amines in DMA revealed that the use of secondary or tertiary amines was superior to that of primary amines in terms of yield and reaction time (Entries 3,8,9). Furthermore, diacidic bases (ethylenediamines) shortened the reaction time (Entries 13, 14) and cyclic amines (piperidine, morpholine) gave higher yields (Entries 15, 16). Consequently, the optimal condition was obtained using piperazine as a diacidic cyclic base in DMA at 150°C (Entry 17). Table 2 shows the results of the reaction of various alkoxybenzoic acids and amides with piperazine in DMA. The amide derivatives required a longer time for completion of this demethylation in comparison with acids. The benzyloxy, methoxymethoxy or even ethoxy group was cleaved at the ortho position, but the isopropoxy group was inactive (Entries 8-11). In addition, o-anisic acid or amide derivatives including a meta-or para-alkoxy group underwent the selective cleavage of the ortho-alkoxy group without affecting other substituents (17)(18)(19)(20). However, 2,6-dimethoxybenzoic acid failed to demethylate, and 6-methyl-o-anisic acid required a longer reaction time for completion (Entries 15, 16). Scheme 1 Scheme 2Ethyl ester ...

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“…Daher wurde vermutet, daû ein Formaldehyd-Fänger sowohl die Ausbeute als auch die Reproduzierbarkeit der Reaktion verbessern könnte; tatsächlich erhöhte die Zugabe von Dimedon im Überschuû die Ausbeute auf 55 % bei ausgezeichneter Reproduzierbarkeit. [16] Die Benzylethereinheiten von 18 wurden unter Fujita-Bedingungen [17] entfernt und das entstandene Tetraol direkt zum Tetraacetat 19 acetyliert. Die Struktur von 19 ist durch spektroskopische Daten belegt (hochauflösende Massenspektrometrie (HR-MS), UV, 1 H-NMR); besonders 1 H-1 H-COSY-und 1 H-1 H-NOESY-Experimente bestätigten eindeutig die Protonenzuordnungen und Konnektivitäten.…”

Section: 'unclassified

Totalsynthese des (+)-Tolyporphin-A-O,O-diacetats mit der vorgeschlagenen Struktur

Minehan

Kishi

1999

Angewandte Chemie

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Aus vier monocyclischen Vorstufen gelang die Totalsynthese der für (+)‐Tolyporphin‐A‐O,O‐diacetat vorgeschlagenen Struktur 1‐A (X = Ac). Ein Vergleich der spektroskopischen Daten ergab, daß das synthetische Tolyporphin‐O,O‐diacetat nicht mit dem aus natürlichem (+)‐Tolyporphin A (X = H) hergestellten O,O‐Diacetat übereinstimmte – eine Korrektur der Struktur dieser Naturstoffklasse war gefordert. Aus einer Reihe von NMR‐Experimenten, unter anderem an synthetischen Zwischenprodukten, ließ sich als wahrscheinliche Struktur für den Naturstoff die Struktur 1‐B folgern, in der die Konfigurationen der quartären Kohlenstoffzentren C7 und C17 umgekehrt wie ursprünglich angenommen sind.

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Aluminium Halide-Thiol System: A Useful Reagent for Demethylation of Aliphatic and Aromatic Methyl Ethers and Demethylenation of Methylenedioxy Compounds

Cited by 48 publications

References 3 publications

Anchimerically Assisted Cleavage of Aryl Methyl Ethers by Aluminum Chloride‐Sodium Iodide in Acetonitrile

Anchimerically Assisted Cleavage of Aryl Methyl Ethers by Aluminum Chloride‐Sodium Iodide in Acetonitrile

Regioselective Dealkylation of 2-Alkoxybenzoic Acid and Its Amide Derivatives with Aliphatic Amines

Totalsynthese des (+)-Tolyporphin-A-O,O-diacetats mit der vorgeschlagenen Struktur

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