A New, Mild Heterogeneous Catalyst for the Tetrahydropyranylation of Alcohols and Phenols

Johnston, Rich D.; Marston, Charles R.; Krieger, Paul E.; Goe, Gerald L.

doi:10.1055/s-1988-27587

Cited by 55 publications

(12 citation statements)

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“…Acid catalysts play a predominant role in organic synthesis, in particular tetrahydropyranylation. Due to its ease of handling and recovering, various solid acids were introduced, which include protic acids [2,3], Lewis acids [4,5], ion exchange resins [6,7], solid silica-based sulfonic acid [8], zeolites [9,10], hetropolyacids [11,12], and clays [13,14]. The main problems associated with solid acids are the complicated preparation procedure, corrosiveness, the expense, the harsh reaction conditions, the need for solvents such as CH 2 Cl 2 , as well as unsatisfactory product yields, etc.…”

Section: Introductionmentioning

confidence: 99%

Solvent-free tetrahydropyranylation of alcohols catalyzed by amine methanesulfonates

2010

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A comparative study of tetrahydropyranylation of alcohols under various solvents or solvent-free conditions using different amine methanesulfonates as catalysts shows that tetrahydropyranyl ethers of alcohols are obtained under solvent-free conditions in good yields using catalytic amounts of triethylenediamine methanesulfonate, 1,6-hexanediamine methanesulfonate, diethylenetriamine methanesulfonate and pyridine methanesulfonate, respectively. The reaction occurs readily in short times at room temperature catalyzed by these catalysts, especially triethylenediamine methanesulfonate. Some of the major advantages of this procedure are that the catalysts are environmentally friendly, highly effective, and easy to prepare and handle. The reaction is also clean and needs no solvent, and the work-up is very simple.

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Section: Introductionmentioning

confidence: 99%

Solvent-free tetrahydropyranylation of alcohols catalyzed by amine methanesulfonates

2010

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“…Stirring the free alcohols with 3,4-dihydro-2H-pyran (DHP) under acidic conditions can easily produce THP-protected alcohols. [1][2][3][4][5][6][7][8] Also, THP-protected alcohols are generally stable under a wide range of reaction conditions and reagents, such as metal hydrides, alkyllithiums, Grignard reagents, and catalytic hydrogenation. [9][10][11][12][13] For the THP ethers, a number of deprotecting methods have been introduced.…”

Section: Notesmentioning

confidence: 99%

One-Step Transformation of Tetrahydropyranyl Ethers Using Indium(III) Triflate as the Catalyst

Mineno

Nikaido

Kansui

2009

CHEMICAL & PHARMACEUTICAL BULLETIN

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NotesTetrahydropyranyl (THP) group is a well-utilized moiety, mainly as a tool to protect alcohol units due to its feasibility of installation and low cost. Stirring the free alcohols with 3,4-dihydro-2H-pyran (DHP) under acidic conditions can easily produce THP-protected alcohols.1-8) Also, THP-protected alcohols are generally stable under a wide range of reaction conditions and reagents, such as metal hydrides, alkyllithiums, Grignard reagents, and catalytic hydrogenation. O, 19,20) and CuSO 4 · 5H 2 O, 21) has also been reported.Previously, we have reported a couple of convenient reaction methods using indium or indium-related reagents. [22][23][24][25] The authors have recently developed a practical approach to tetrahydropyranylation and depyranylation of various alcohols using indium(III) triflate.26) It is worth noting that with the same catalyst, the reactions proceed in directions of both protection and deprotection. In the presence of a catalytic amount of indium(III) triflate, protection of alcohols is carried out using CH 2 Cl 2 as the solvent, whereas deprotection uses MeOH/H 2 O as the solvent. Kamal et al. also reported that tetrahydropyranylation can be controlled using catalytic aluminum(III) triflate. 27) Another report has shown the cleavage of THP ethers using titanium(III) triflate in good yields.28) According to our earlier experiments, indium(III) triflate was revealed to be an efficient catalyst for the transformation of THP ethers into their corresponding acetates. In further intensive work, we have developed a useful transforming reaction of THP ethers using various anhydride moieties with indium(III) triflate as the catalyst. Herein, we report the details of this one-step transformation. Results and DiscussionTHP-protected benzyl alcohol and N-(2-hydroxyethyl)-phthalimide were used as the starting materials. First, the suitability of the catalysts was examined by reactions with acetic anhydride (Chart 1). In both cases, the reaction proceeded and produced excellent yields in a shorter time when indium(III) triflate was employed as the catalyst (Table 1, entries 1 and 3), as compared with indium(III) chloride (Table 1, entries 2 and 4). Giving the satisfactory results with indium(III) triflate, we then expanded our investigation to the other types of anhydrides. The reactions were carried out with THP-protected benzyl alcohol, N-(2-hydroxyethyl)phthalimide, and a wide range of anhydrides (Chart 2).As expected, the reactions with another aliphatic anhydride of isobutyric anhydride generated similar satisfactory results (Table 2, entries 1 and 7). In the case of benzoic anhydride, the reaction required an extended period of time, although acceptable results were obtained (Table 2, entries 2 and 8). With the exception of entry 5, these conditions were then applied to the cyclic anhydrides, and the reactions produced entirely poor yields. These results were presumably due to the low reaction temperature. When reactions were resumed at reflux using THF as the solvent, good to excellent out...

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“…In order to overcome this limitation, the selective monoprotection of symmetrical diols has been typically performed using an excess of diol. Moreover, catalysts with a relatively small catalytic surface such as ion-exchange resins (namely, Amberlite IR-120 [21], Amberlist H-15 [22], Rellex 425 [23], Dowex 50 [24], and Nafion-H [25]), iodine [26], ZrO 2 -pillared clay [27], zinc chloride [28], and aqueous acids [29] have been reported to be effective for selective monotetrahydropyranylation.…”

Section: Introductionmentioning

confidence: 99%

Selective Monoprotection of Symmetrical Diols in a Flow Reactor

Masui¹,

Takizawa²,

Sakai³

et al. 2018

IJOC

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Desymmetrization reactions provide a powerful approach for the construction of complex molecules. Various methods have been developed for the selective monoprotection of symmetrical diols; however, their application to large-scale operations is limited. In this study, the monotetrahydropyranylation of symmetrical diols in a flow reactor has been developed, whereby the length of the flow reactor tube and the amount of acid were optimized. A higher selectivity for the monoprotected derivative was observed when the reaction was performed in a flow reactor compared with that observed in a conventional batch experiment. The efficient flow method developed herein can be applied to large-scale synthesis by numbering up the flow reactor without affecting the selectivity and yield. Since monoprotection can be achieved without using a large excess of diol, our developed flow method is effective when expensive diol must be used.

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A New, Mild Heterogeneous Catalyst for the Tetrahydropyranylation of Alcohols and Phenols

Cited by 55 publications

References 0 publications

Solvent-free tetrahydropyranylation of alcohols catalyzed by amine methanesulfonates

Solvent-free tetrahydropyranylation of alcohols catalyzed by amine methanesulfonates

One-Step Transformation of Tetrahydropyranyl Ethers Using Indium(III) Triflate as the Catalyst

Selective Monoprotection of Symmetrical Diols in a Flow Reactor

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