Mechanism of the acyloin condensation

Bloomfield, Jordan J.; Owsley, Dennis C.; Ainsworth, C.; Robertson, R. E.

doi:10.1021/jo00892a001

Cited by 49 publications

(17 citation statements)

References 16 publications

(23 reference statements)

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“…This paper deals with the first synthesis of cyclobutene nucleosides unsubstituted at the vinylic position ( 5 ). The synthetic way started from anhydride 6 prepared by photocycloaddition of acetylene to maleic anhydride . In early experiments the carboxylic group of the hemiester 7 , obtained by methanolysis of 6 , was converted into amide or acyl azide in the usual experimental conditions but the subsequent Hofmann or Curtius rearrangements failed to yield the amino ester 8 , or a protected related product, due to the high thermal unstability of the intermediates and the product.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Norcarbovir Analogues, the First Examples of Cyclobutene Nucleosides Unsubstituted at the Vinylic Position

Gourdel-Martin

Huet

1997

J. Org. Chem.

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Two cyclobutene nucleosides, 27 and 29, analogous to the yet unknown norcarbovir, and with adenine and hypoxanthine as the base moieties, respectively, were synthesized starting from cis-3-cyclobutene-1,2-dicarboxylic anhydride (6). Its reduction to lactone 9 followed by reaction with ammonia and then Hofmann rearrangement led to cyclic carbamate 15 which was the key intermediate of these syntheses. Its tert-butoxycarbonyl derivative 17 led to the ring opening of the heterocyclic moiety at low temperature. Compound 18 was thus obtained, and the successive benzylation and then treatment with hydrochloric acid yielded hydrochloride 21. Construction of bases was achieved in satisfying overall yields provided that mild experimental conditions from 21 to 27 or 29 were used to restrict the unwanted electrocyclic ring opening. Nitropyrimidine 31 was also prepared from 21 via the intermediate 23.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Norcarbovir Analogues, the First Examples of Cyclobutene Nucleosides Unsubstituted at the Vinylic Position

Gourdel-Martin

Huet

1997

J. Org. Chem.

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“…This has been disputed (1 1) and is almost certainly not the complete mechanism. Bloomfield, Owsley et al propose an alternative mechanism (12), which is given in Scheme 2. Both mechanisms, however, require that the reacting carbonyl carbons be joined (C-C bond in 15, Scheme 1 , and C-0-C bridge in 18, Scheme 2) prior to expulsion of the alkoxide groups, i.e., the tether would bring the reaching centres together and then be expelled.…”

Section: Discussionmentioning

confidence: 99%

“…loomf field and Owsley suggest that fragmentation of the radical intermediate 19 can account for the radical products observed. Also, fragmentation of the anion 20 could, they suggest, result in anion formation, which would be particularly favourable with tertiary, benzylic, and allylic systems (12). Thus, in some cases, free radicals may not be involved other than as very transient radical anion intermediates.…”

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confidence: 99%

The acyloin reaction using tethered diesters

Daynard¹,

Eby²,

Hutchinson³

1993

Can. J. Chem.

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A study of the intramolecular acyloin condensation using diesters tethered by their alkoxide groups was undertaken. The goal was to provide a method for optimizing the yield of mixed acyloin products from the reaction of two different esters by utilizing tethered dissimilar esters as substrates. The results of the study show that the yield of the acyloin condensation is dependant on the tether length. Tethers of 8 and 14 carbons in length give yields comparable to those obtained from an intermolecular control reaction while shorter tethers give reduced yields of product. However, the use of mixed tethered diesters and a crossover experiment between two different tethered substrates provides a statistical distribution of products. These observations have been interpreted as resulting from a fragmentation of the initially formed radical anion intermediate that destroys the tethered nature of the substrate(s).

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“…The temperature rose to about 10°d uring the 2 min required; the color changed from dark green to dark brown. After 2-5 min ice water was added and the pH adjusted to [5][6][7] with 6 M hydrochloric acid. The organic products were isolated by extraction with ether, washing with water, and drying over magnesium sulfate.…”

Section: Methodsmentioning

confidence: 99%