The Acyloxylation of Furan with Lead Tetraacyloxylates: Cis-Trans Isomerism of 2,5-Diacyloxy-2,5-dihydrofurans and 2,5-Diacyloxytetrahydrofurans.

Elming, Niels; Clauson-Kaas, Niels; Rottenberg, Max; Stenhagen, Einar; Östling, Sven

doi:10.3891/acta.chem.scand.06-0535

Cited by 28 publications

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“…The yellow solution was then concentrated in vacuo to give a yellow oil, and the colourless crystals and yellow oil were then analysed separately (see Results and discussion). The crystals were found to have a melting point of 51–53°C, in excellent agreement with that reported by Elming & Clauson-Kaas [13] after recrystallization from methanol (51–52°C).…”

Section: Methodssupporting

confidence: 89%

“…This was passed through a silica plug (eluting in dichloromethane) and the solvent removed in vacuo to give a pale yellow oil; the 1 H NMR spectrum of this oil showed it to consist of a mixture of the cis and trans isomers of 2,5-dibutoxy-2,5-dihydrofuran. This compound has been reported and characterized before [13] but no NMR data were reported. Hence we can now report these data as follows: 1 H NMR (CDCl 3 , 400 MHz), δ = 7.01 (s, 2H, trans- H a ), 6.78 (s, 1.8H, cis- H a ), 6.24 (s, 1.8H, cis- H b ), 6.21 (s, 2H, trans- H b ), 2.34–2.29 (m, ∼8H, ROOC–C H 2 –CH 2 –CH 3 ( cis and trans signals overlap)), 1.71–1.61 (m, ∼8H, ROOC–CH 2 –C H 2 –CH 3 ( cis and trans signals overlap)), 0.97–0.93 (m, ∼12H, ROOC–CH 2 –CH 2 –C H 3 ( cis and trans signals overlap)).…”

Section: Methodsmentioning

confidence: 99%

“…All 1 H and 13 C nuclear magnetic resonance (NMR) spectra were recorded on a Bruker AV 400 instrument (unless otherwise stated), at a constant temperature of 300 K. Chemical shifts are reported in parts per million from low to high field. Standard abbreviations indicating multiplicity were used as follows: m, multiplet; s, singlet.…”

Section: Experimental Section 21 General Experimental Remarksmentioning

confidence: 99%

“…In the majority of cases, these 2,5-dicarboxy-2,5-dihydrofurans are prepared by reaction of furan with the appropriate tetracarboxy salt of lead according to the general method of Elming & Clauson-Kaas [13]. An attractive route for obtaining such products without the use of toxic lead salts is the electrochemical oxidation of furan in the presence of acetate to give 2,5-diacetoxy-2,5-dihydrofuran.…”

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confidence: 99%

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Towards a better understanding of the electrosynthesis of 2,5-dicarboxy-2,5-dihydrofurans: structure, mechanism and influence over stereochemistry

et al. 2019

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2,5-Dicarboxy-2,5-dihydrofurans are key constituents of a number of natural products and have roles as intermediates in the formation of other such compounds of interest. Typically, these species are synthesized using toxic Pb(IV) salts. Electrochemical syntheses of 2,5-diacetoxy-2,5-dihydrofuran that do not require the use of lead have been reported, but a general lack of experimental detail has prevented these procedures from being more widely adopted. Moreover, no electrochemical study has yet reported the ratio of cis and trans isomers produced. Herein, we compare the chemical, lead-based route to 2,5-diacetoxy-2,5-dihydrofuran with a fully described electrosynthesis method. In doing so, we have discovered that the cis and trans isomers of this compound were previously incorrectly assigned in the literature, an error that we correct by obtaining the crystal structure of cis- 2,5-diacetoxy-2,5-dihydrofuran. This allows the ratios of the isomers as prepared by the chemical (2 : 1 cis : trans ) and electrochemical (7 : 5 cis : trans ) methods to be obtained. Through experimental and computational insights, we propose a mechanism for the electrochemical synthesis of 2,5-dicarboxy-2,5-dihydrofurans and go some way towards validating this mechanism by synthesizing 2,5-dibutoxy-2,5-dihydrofuran electrochemically for the first time. We hope that these findings will provide some greater clarity to the literature surrounding the electrosynthesis and potential applications of 2,5-dicarboxy-2,5-dihydrofurans.

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Section: Methodssupporting

confidence: 89%

Section: Methodsmentioning

confidence: 99%

Section: Experimental Section 21 General Experimental Remarksmentioning

confidence: 99%

mentioning

confidence: 99%

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Towards a better understanding of the electrosynthesis of 2,5-dicarboxy-2,5-dihydrofurans: structure, mechanism and influence over stereochemistry

et al. 2019

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“…Scheme illustrates the retrosynthetic analysis of 2 in which the furanoside part comes from two AAAs on the bis‐benzoate 3 ,7 one involving an acetyl nucleophile equivalent, the other involving a phenol, either 4 or 5 , as nucleophile 8. Additionally, the aminocyclitol 6 derives from deracemization of the racemic conduritol B tetraester 7 .…”

Section: Methodsmentioning

confidence: 99%