Lithium triflate (LiOTf) catalyzed efficient and chemoselective tetrahydropyranylation of alcohols and phenols under mild and neutral reaction conditions

Karimi, Babak; Maleki, Jafar

doi:10.1016/s0040-4039(02)00892-4

Cited by 63 publications

(26 citation statements)

References 24 publications

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“…Reagents & Conditions: (a) for (3g), HCCMgBr, THF, 0 8C, 2 h; RT, 16 h; NH 4 Cl, (aq); (b) Finally, in an effort to apply this methodology to the synthesis of potential ligands for the estrogen receptor containing a phenolic pharmacophore, 4-hydroxybenzaldehyde (6f) was protected as its tetrahydropyranyl (THP) ether (6i) by treatment with dihydropyran and lithium trifluoromethanesulfonate (LiOTf) in 1,2-dichloroethane [21] and elaborated according to our established procedure, by reaction with ethynylmagnesium bromide followed by oxidation with IBX, to give the THP ether derivative of (4-hydroxyphenyl)propynone (4i) (Scheme 3). Microwave irradiation with guanidine (1c) at 120 8C or N,N-dimethylguanidine (1d) at 150 8C gave pyrimidine (7ci) or (7di) in 90 or 82% yield, respectively (Scheme 4).…”

Section: Resultsmentioning

confidence: 99%

Microwave‐Assisted Synthesis of Pyrimidine Libraries

et al. 2004

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Di-or trisubstituted pyrimidine libraries are prepared in good yield by the microwave irradiation of an alkynone and either an amidine or guanidine at 120 ± 150 8C in acetonitrile in the presence of sodium carbonate or at 100 8C after treatment with methanolic sodium methoxide in a sealed tube using a monomodal microwave synthesiser. These rapid and efficient methods often require no chromatographic purification and so are appropriate for automated combinatorial methodology and have been applied in the synthesis of a small library of potentially useful novel ligands for the estrogen receptor based on the pyrimidine template.

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Section: Resultsmentioning

confidence: 99%

Microwave‐Assisted Synthesis of Pyrimidine Libraries

et al. 2004

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“…[10d] 3b, [7] 3c, [40] 3e, [7] 3f, [7] 3g, [10d] 3h, [12] 3i, [10d] 3j, [10b] , 3k, [10d] 3l, [10d] 3m, [41] 3n, [42] 3o, [43] 3p, [43] 3q, [44] 3r, [45] 3s, [11d] 3v, [28] and 3z [12] are all known, and their structures are consistent with their published physical data.…”

Section: Discussionmentioning

confidence: 99%

Solvent‐Free Carbon–Oxygen Bond Formation Catalysed by CeCl₃·7 H₂O/NaI: Tetrahydropyranylation of Hydroxy Groups

et al. 2006

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An efficient and highly chemoselective method fo the protection of free hydroxy compounds with 3,4‐dihydro‐2H‐pyran is reported. Since the deprotection of THP‐ethers occurs very readily at room temperature, the successful use of this type of protecting group depends only upon how readily it can be introduced. For this we have examined the tetrahydropyranylation of alcohols and phenols catalysed by the CeCl3·7 H2O/NaI system surface under solvent‐free conditions. The reaction presents the advantage of being performable under extremely mild conditions by use of catalytic amounts of an interesting Lewis acidic system consisting of the CeCl3·7 H2O/NaI catalyst combination, which can be easily separated from the reaction mixture. The advantages of this procedure, which utilizes cheap and “friendly” reagents, over the previously reported ones are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…[1] A variety of reagents have been reported for tetrahydropyranylation of alcohols including using protic acids, [2] Lewis acids, [3] ion-exchange resins, [4] LiOTf, [5] K 5 CoW 12 O 4 Á 3H 2 O, [6] CuSO 4 Á 5H 2 O, [7] In(OTf) 3 , [8] PdCl 2 (CH 3 CN) 2 , [9] ZnCl 2 , [10] I 2 , [11] silica chloride, [12] tetrabutylammonium tribromide, [13] zirconium sulfophenyl phosphonate, [14] ionic liquids, [15] zeolites, [16] and K-10 clay. [17] Although some of these methods are convenient protocols for tetrahydropyranylation of alcohols with good to high yields, the majority of these methods suffer from at least one disadvantage, such as strongly acidic conditions, long reaction times, high temperature, poor selectivity, expensive reagents, toxicity, and need for excessive amounts of reagents.…”

Section: Introductionmentioning

confidence: 99%