A general approach to 5-substitution of 3-furaldehydes

Lee, Gary C. M.; Holmes, J. M.; Harcourt, D.; Garst, Michael E.

doi:10.1021/jo00037a032

Cited by 32 publications

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“…[32] The formed 2-furyllithium derivative b, when treated with benzaldehyde, yielded 2-(phenylhydroxymethyl)-4-furancarboxaldehyde c. The reaction with a phenyl Grignard reagent was applied to convert this aldehyde into the targeted compound 3.…”

Section: Resultsmentioning

confidence: 99%

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Pyrrole‐Appended Derivatives of O‐Confused Oxaporphyrins and Their Complexes with Nickel(II), Palladium(II), and Silver(III)

Pawlicki

Latos‐Grażyński

2003

Chemistry A European J

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Condensation of 2,4-bis(phenylhydroxymethyl)furan with pyrrole and p-toluylaldehyde formed, instead of the expected 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin, a pyrrole addition product [(H,pyr)OCPH]H(2); this product can formally be considered as an effect of hydrogenation of 3-(2'-pyrrolyl)-5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-21-carbaporphyrin ([(pyr)OCPH]H). The new oxacarbaporphyrinoid presents the (1)H NMR spectroscopy features of an aromatic molecule, including the upfield shift of the inner H21 atom. Insertion of NiCl(2) or PdCl(2) into [(H,pyr)OCPH]H(2) gave two structurally related organometallic complexes, [(pyr)OCP]Ni(II)] and [(pyr)OCP]Pd(II)], in which the metal ions are bound by three pyrrolic nitrogens and the trigonally hybridized C21 atom of the inverted furan. The reaction of [(H,pyr)OCPH]H(2) with silver(I) acetate yields a stable Ag(III) complex [(C(2)H(5)O,pyr)OCP]Ag(III)] substituted at the C3 position by the ethoxy and pyrrole moieties. The macrocyclic frame of [(H,pyr)OCPH]H(2) is conserved. Addition of trifluoroacetic acid to [(C(2)H(5)O,pyr)OCP]Ag(III)] yielded a new aromatic complex [(pyr)OCP]Ag(III)](+). The structures of [(pyr)OCP]Ni(II)] and [(C(2)H(5)O,pyr)OCP]Ag(III)] have been determined by X-ray crystallography. In both molecules the macrocycles are only slightly distorted from planarity and the nickel(II) and silver(III) are located in the NNNC plane. The dihedral angle between the macrocyclic and appended-pyrrole planes of [(pyr)OCP]Ni(II)] reflects the biphenyl-like arrangement with the NH group pointing out toward the adjacent phenyl ring on the C5 position. Tetrahedral geometry around the C3 atom was detected for [(C(2)H(5)O,pyr)OCP]Ag(III)]. The Ni[bond]C and Ag[bond]C bond lengths are similar to other nickel(II) or silver(III) carbaporphyrinoids where the trigonal carbon atom coordinates the metal ion. The trend detected in the (13)C chemical shifts for the appended-pyrrole resonances has been rationalized by the extent of effective conjugation between the macrocycle and the appended pyrrole moiety controlled by the hybridization of the C3 atom and the metal ion oxidation state. The dianionic or trianionic macrocyclic core of the pyrrole-appended derivatives is favored to match the oxidation state of nickel(II), palladium(II), or silver(III), respectively.

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Section: Resultsmentioning

confidence: 99%

“…[32] 3-Furaldehyde (3 mL, 36.4 mmol) was added after 20 min, to be followed after a further 20 min by sBuLi (29.4 mL, 38.25 mmol, 1m solution in hexanes). The resulting mixture was stirred for 4 h at À 78 8C.…”

Section: Methodsmentioning

confidence: 99%

Pyrrole‐Appended Derivatives of O‐Confused Oxaporphyrins and Their Complexes with Nickel(II), Palladium(II), and Silver(III)

Pawlicki

Latos‐Grażyński

2003

Chemistry A European J

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“…The C-4 lithiation of a 3-substituted furan, however, has not been successful to date; only products resulting from a C-2 and/or C-5 lithiation have been isolated . Recently, Lee and Garst have reported that the in situ lithiation of an α-amino alkoxide from 3-furaldehyde provided some 3,4-disubstituted furan (3−13%) in addition to the expected 2,3- (24−36%) and 3,5- (2−8%) disubstituted products. Until recently, the lithiation of a 2,3-disubstituted furan had provided the C-5 lithiated species exclusively. 8g,h,k, …”

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“…As previously mentioned, 2,4-disubstituted furans are also difficult to prepare. They have been synthesized by (a) the formation of the furan ring from acyclic precursors, (b) a double electrophilic aromatic substitution of a 2-substituted furan (to give a 2,3,5-trisubstituted furan) followed by removal of the initial C-2 group; or (c) the direct C-5 lithiation of a 2,3-disubstituted furan followed by the removal of the initial C-2 group. 8g,h,, Both a bromine atom 16,18 and a phenylthio group 8g,h,17 have been successfully removed from the C-2 position of a 2,3,5-trisubstituted furan ( i.e. , replaced by a hydrogen atom) thereby producing a 2,4-disubstituted furan.…”

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Regioselective Preparation of 2,4-, 3,4-, and 2,3,4-Substituted Furan Rings. 2.¹ Regioselective Lithiation of 2-Silylated-3-substituted Furan Rings

Bures

Nieman

et al. 1997

J. Org. Chem.

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A new method for the preparation of 3,4-and 2,5-disubstituted furan rings is described. A variety of 2-silylated-3-(hydroxymethyl)furans and 2-silylated-3-furoic acids lithiate exclusively at C-4 when treated with 2.2 equivs of BuLi. The resulting dianions were quenched with a variety of electrophiles to provide 2-silylated-3-(hydroxymethyl)-4-substituted furans and 2-silylated-4-substituted 3-furoic acids in good to excellent yields. Removal of the silyl group (n-Bu 4 NF) provided a variety of 4-substituted-3-(hydroxymethyl)furans and methyl 4-substituted-3-furoates, respectively. The latter esters were prepared due to difficulties encountered in isolating 4-substituted-3-furoic acids. The site of lithiation was altered by protecting the 3-hydroxyl group with a triethylsilane. Lithiation of 2-silylated-3-(((triethylsilyl)oxy)methyl)furan with 1.2 equivs of BuLi followed by the addition of electrophiles provided 2-silylated-3-(((triethylsilyl)oxy)methyl)-5-substituted furan rings. Subsequent removal of both silyl groups provided 2,4-disubstituted furan rings in moderate to good yields. A rationale is provided to explain why protection of the hydroxyl group at C-3 leads to a change in lithiation from the C-4 to the C-5 position of the furan ring. In addition, an explanation for the observed effect of adding HMPA or LiCl to the solution during the lithiation of 2-(tertbutyldimethylsilyl)-3-(hydroxymethyl)furan is provided.In the preceding paper, 1 the difficulty in preparing 3,4and 2,4-disubstituted furan rings due to the preference for furan rings to lithiate 2 and add electrophiles 3 in the C-2 or C-5 positions was discussed. New synthetic routes toward the preparation of furan rings which contain groups in the 3 and/or 4 positions are useful, since many natural products incorporate furan rings with either a 3,4-or 2,4-disubstituted or 2,3,4-trisubstituted pattern. 4 This paper describes a full account of our work in this area.Some previous reports on the preparation of 3,4disubstituted furans have involved using Diels-Alder/ retro-Diels-Alder chemistry, 5 chemical modifications of 3,4-furandicarboxylic acid, 6 and the synthetic modification of acyclic precursors. 7 An alternative approach to the preparation of 3,4-disubstituted furans is the direct lithiation of substituted furan rings. The C-4 lithiation of a 3-substituted furan, however, has not been successful

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“…E-mail: p.kocienski@chem.gla.ac.uk † 5-Triethylsilyl-3-furaldehyde was prepared in one pot from commercial 3-furaldehyde in 73% yield by (i) addition of lithium morpholide to the aldehyde; (ii) metallation of the resultant adduct with Bu s Li, and (iii) addition of chlorotriethylsilane (ref 15)…”

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Synthesis of manoalide using a 1,2-metallate rearrangement

Pommier¹,

Kocieński²

1997

Chem. Commun.

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A general approach to 5-substitution of 3-furaldehydes

Cited by 32 publications

References 0 publications

Pyrrole‐Appended Derivatives of O‐Confused Oxaporphyrins and Their Complexes with Nickel(II), Palladium(II), and Silver(III)

Pyrrole‐Appended Derivatives of O‐Confused Oxaporphyrins and Their Complexes with Nickel(II), Palladium(II), and Silver(III)

Regioselective Preparation of 2,4-, 3,4-, and 2,3,4-Substituted Furan Rings. 2.¹ Regioselective Lithiation of 2-Silylated-3-substituted Furan Rings

Synthesis of manoalide using a 1,2-metallate rearrangement

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A general approach to 5-substitution of 3-furaldehydes

Cited by 32 publications

References 0 publications

Pyrrole‐Appended Derivatives of O‐Confused Oxaporphyrins and Their Complexes with Nickel(II), Palladium(II), and Silver(III)

Pyrrole‐Appended Derivatives of O‐Confused Oxaporphyrins and Their Complexes with Nickel(II), Palladium(II), and Silver(III)

Regioselective Preparation of 2,4-, 3,4-, and 2,3,4-Substituted Furan Rings. 2.1 Regioselective Lithiation of 2-Silylated-3-substituted Furan Rings

Synthesis of manoalide using a 1,2-metallate rearrangement

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Regioselective Preparation of 2,4-, 3,4-, and 2,3,4-Substituted Furan Rings. 2.¹ Regioselective Lithiation of 2-Silylated-3-substituted Furan Rings