A Facile and Selective SyntheticMethod for the Preparation of Aromatic Dialdehydes from Diesters­ viathe Amine-Modified SMEAH Reduction System

Hagiya, Kazutake; Mitsui, Sunao; Taguchi, Hiroaki

doi:10.1055/s-2003-38677

Cited by 12 publications

(7 citation statements)

References 10 publications

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“…With a straightforward method for the synthesis of 4-methyl-5-vinylthiazole ( 6 ) in hand, we turned our attention to its conversion into the corresponding aldehyde 9 in order to overcame drawbacks related to the reductive/oxidative pathways previously described. – Thus, crude vinylthiazole 6 was diluted with MeOH and subjected to ozonolysis at −78 °C. After quenching with aqueous Na 2 SO 3 and a standard workup, the desired aldehyde was isolated in 84% overall yield.…”

Section: Discussionmentioning

confidence: 99%

“…The pure aldehyde 9 can be obtained by sublimation (0.3 mmHg, yield 60%) or crystallisation (AcOEt at −20 °C, yield 75%), mp 74.8–75.2 (lit., 71 °C) 1 H NMR (CDCl 3 ): δ 2.79 (3 H, s), 8.96 (1 H, s), 10.14 (1 H, s).…”

Section: Methodsmentioning

confidence: 99%

“…The aldehyde 9 has also been prepared through reduction of 4-methylthiazole-5-carboxylic acid ethyl ester ( 7 ) with NaBH 4 −AlCl 3 followed by oxidation of the alcohol 8 thus obtained . The direct reduction of ester 7 to aldehyde 9 has been carried out with Red-Al in moderate yield . All these methods suffer from limitations derived from the use of hydride reducing agents or metal reagents that produce significant waste.…”

mentioning

confidence: 99%

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Concise Synthesis of Vinylheterocycles through β-Elimination under Solventless Phase Transfer Catalysis Conditions

Albanese

Ghidoli

Zenoni

2008

Org. Process Res. Dev.

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Various vinylheterocycles compounds have been prepared in excellent yields through -elimination of the corresponding sulfonate esters with 50% aq NaOH under phase transfer catalysis conditions without organic solvent. The new approach provides an economic and environmentally friendly solution to removal of hazardous bases as well as toxic and expensive dipolar aprotic solvents.The development of environmentally friendly synthetic procedures has seen a steadily growing interest in the past few years in academic and industrial chemistry. 1 In particular, it is of increasing interest to avoid solvents by carrying out reactions under solvent-free conditions or by replacing them with greener alternatives. 2 Vinylthiazoles are useful intermediates for the synthesis of pharmaceuticals, 3 flavoring materials, 4 insect repellents 5 and lubricant additives. 6 For example 4-methyl-5-vinylthiazole (6), a widely employed vinylthiazole, has been prepared by treating thiamine 1 with saturated aqueous HBr, followed by quaternarization of the resulting bromide 2 with trimethylamine. The vinylthiazole 6 was generated by the sequential treatment of the ammonium salt 3 with Ag 2 O and hot KOH (Scheme 1). 7 This procedure suffers from low atom efficiency since the (4-amino-2-methyl-5-pyrimidinyl)methyl] portion of thiamine is lost. Moreover, the use of corrosive HBr, expensive Ag 2 O and toxic benzene severely hinders the scale-up.More recently vinylthiazoles have also been prepared from the corresponding sulfonate ester 5 through -elimination promoted by strong bases such as NaH, t-BuOK or DBU in DMF (Scheme 1). 5 Although this procedure affords the desired vinylthiazoles in good yields, it also suffers from limitations derived from using strong but expensive bases that require careful handling. Moreover, process unfriendly solvents such as DMF are required; therefore, additional steps are needed for its removal and disposal.On the other hand, 5-formyl-4-methylthiazole (9) is an important starting material for manufacturing Cefditoren, a wide spectrum antibiotic ( Figure 1). 8 5-Formyl-4-methylthiazole (9) has usually been prepared by oxidation of 4-methyl-5-(2-hydroxyethyl)thiazole (4) with pyridinium dichromate 9 or other chromium derivatives, 10 or by oxidation of alcohol 8 with MnO 2 11 or NaOCl (Scheme 2). 12 The aldehyde 9 has also been prepared through reduction of 4-methylthiazole-5-carboxylic acid ethyl ester (7) with NaBH 4 -AlCl 3 followed by oxidation of the alcohol 8 thus Rubi, E.; Arnal, P.; Boisbrun, M.; Carcel, C.; SalomRoig, X.; Maynadier, M.; Wein, S.; Vial, H.; Calas, M. Sukegawa, M.; Watanabe, T.; Iwasawa, H.; Murai, Y.; Iinuma, K.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Concise Synthesis of Vinylheterocycles through β-Elimination under Solventless Phase Transfer Catalysis Conditions

Albanese

Ghidoli

Zenoni

2008

Org. Process Res. Dev.

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“…Absolute ethanol was purchased from Fisher Scientific. Fluorene-2,7-diamine (FDA) was purchased from Aldrich, and naphthalene-2,6-dicarboxaldehyde (NDC) was synthesized as in the literature . The compound was a light yellow solid and was recrystallized in acetone/H 2 O with 72% overall yield.…”

Section: Methodsmentioning

confidence: 99%

Transition from Tunneling to Hopping Transport in Long, Conjugated Oligo-imine Wires Connected to Metals

et al. 2010

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We report the electrical transport characteristics of conjugated oligonaphthalenefluoreneimine (ONI) wires having systematically varied lengths up to 10 nm. Using aryl imine addition chemistry, ONI wires were built from gold substrates by extending the conjugation length through imine linkages between highly conjugated building blocks of alternating naphthalenes and fluorenes. The resistance and current-voltage characteristics of ONI wires were measured as a function of molecular length, temperature, and electric field using conducting probe atomic force microscopy (CP-AFM). We have observed a transition in direct current (DC) transport from tunneling to hopping near 4 nm as previously established for oligophenyleneimine (OPI) wires. Furthermore, we have found that long ONI wires are less resistive than OPI wires. The single-wire conductivity of ONI wires is approximately 1.8 +/- 0.1 x 10(-4) S/cm, a factor of approximately 2 greater than that of OPI wires, and consistent with the lower transport activation energy ( approximately 0.58 eV versus 0.65 eV or 13 versus 15 kcal/mol). Quantum chemical calculations reveal that charge is preferentially localized on the fluorene subunits and that the molecules are substantially twisted. Overall, this work confirms that imine addition chemistry can be used to build molecular wires long enough to probe the hopping transport regime. The versatility of this chemistry, in combination with CP-AFM, opens up substantial opportunities to probe the physical organic chemistry of hopping conduction in long conjugated molecules.

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“…The solvent was removed on a rotary evaporator, and the crude product was subjected to column chromatography on silica gel using CH 2 Cl 2 /hexane (1:1) as eluent to afford the dialdehyde product 15 (27 mg, 15%) in the form of an off-white solid; MP=170-172 °C [lit. 173.4-174.0 °C]; 17…”

Section: Naphthalene-26-dicarbaldehyde 15mentioning

confidence: 99%

Steric hindrance to the syntheses and stabilities of 1,5- and 2,6-naphthalene N-permethylated diammonium salts

et al. 2016

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A series of naphthalene-1,5-and 2,6-diamines and their N-methyl derivatives were synthesized and characterized. 1 H NMR spectroscopy showed that an aqueous solution of naphthalene-2,6di(NMe3I) (2) underwent considerable demethylation over a 24 hour period after its initial preparation. Exchange of the iodide nucleophilic anion by the triflate non-nucleophilic counterion afforded a stable quaternary aminium salt. H/D -position exchange in D2O solutions of naphthalene-2,6-di(NH2MeCl) (3•HCl) and naphthalene-2,6-di(NHMe2Cl) (4•HCl) with acidic + NH protons was observed, but not in those of naphthalene-2,6-di(NMe3I) or triflate (2 or 5). Exhaustive per-N-methylation of naphthalene-1,5-di(NMe2) (7) afforded only the mixed naphthalene-1-NMe3I-5-NHMe2I quaternary aminium-tertiary ammonium salt due to severe 1,8type peri-strain.

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A Facile and Selective SyntheticMethod for the Preparation of Aromatic Dialdehydes from Diesters viathe Amine-Modified SMEAH Reduction System

Cited by 12 publications

References 10 publications

Concise Synthesis of Vinylheterocycles through β-Elimination under Solventless Phase Transfer Catalysis Conditions

Concise Synthesis of Vinylheterocycles through β-Elimination under Solventless Phase Transfer Catalysis Conditions

Transition from Tunneling to Hopping Transport in Long, Conjugated Oligo-imine Wires Connected to Metals

Steric hindrance to the syntheses and stabilities of 1,5- and 2,6-naphthalene N-permethylated diammonium salts

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A Facile and Selective SyntheticMethod for the Preparation of Aromatic Dialdehydes from Diesters­ viathe Amine-Modified SMEAH Reduction System

Cited by 12 publications

References 10 publications

Concise Synthesis of Vinylheterocycles through β-Elimination under Solventless Phase Transfer Catalysis Conditions

Concise Synthesis of Vinylheterocycles through β-Elimination under Solventless Phase Transfer Catalysis Conditions

Transition from Tunneling to Hopping Transport in Long, Conjugated Oligo-imine Wires Connected to Metals

Steric hindrance to the syntheses and stabilities of 1,5- and 2,6-naphthalene N-permethylated diammonium salts

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A Facile and Selective SyntheticMethod for the Preparation of Aromatic Dialdehydes from Diesters viathe Amine-Modified SMEAH Reduction System