Thermal racemization of (+)-bicyclo[2.2.1]hept-5-ene-trans-2,3-dicarboxylic acid in the melted and solid states

Pincock, Richard E.; Tong, Min-Min; Wilson, Keith R.

doi:10.1021/ja00736a018

Cited by 16 publications

(3 citation statements)

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“…Examples are cis-stilbenes (20-80 ∘ C) [113] or cis-1,2-dibenzoylethenes (30-60 ∘ C) [114] that form the trans-isomers. The bicyclic (+)-Diels-Alder trans-adduct of cyclopentadiene with fumaric acid (mp 176 ∘ C) racemizes without catalyst upon heating to 130-155 ∘ C (eutectic T = 165 ∘ C) [115] presumably via diradical and the cis-isomers (Scheme 13) [90]. However, a local cycloreversion and recycloaddition after changed orientation of the components mechanism in the bulk of the crystal was assumed in Ref.…”

Section: Geometrical Isomerizationsmentioning

confidence: 99%

“…However, a local cycloreversion and recycloaddition after changed orientation of the components mechanism in the bulk of the crystal was assumed in Ref. [115] where this racemization was compared with the solid-state endo to exo isomerization of the tricyclic maleic Numerous cis-alkenes undergo photoisomerization to trans-alkenes. For example, the cis-1,2-di(1-naphthyl)ethene crystals neither photodimerize nor photocyclize, but they isomerize unidirectionally upon photolysis to give the trans-isomer that does not photoisomerize or photodimerize (despite 4.06 Å distance of the putative reaction centers) [116].…”

Section: Geometrical Isomerizationsmentioning

confidence: 99%

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Organic Solid-State Reactions

Kaupp

2016

Encyclopedia of Physical Organic Chemistry, 5 Volume Set

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Section: Geometrical Isomerizationsmentioning

confidence: 99%

Section: Geometrical Isomerizationsmentioning

confidence: 99%

Organic Solid-State Reactions

Kaupp

2016

Encyclopedia of Physical Organic Chemistry, 5 Volume Set

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“…Preparation of optically pure substances by resolving racemates combined with readily available chiral compounds using repeated crystallization is still a procedure widely used in practice, since it ensures high purity of the products and good reproducibility of results . Several examples of resolving racemic trans ‐norborn‐5‐ene‐2,3‐dicarboxylic acid by repeated crystallization with chiral amines have been described, but no similar examples pertaining to its monoesters were reported. At the same time, the presence of diversified groups in organic compounds opens the way for its selective transformation that has importance for organic synthesis.…”

Section: Introductionmentioning

confidence: 99%

A Simple Method for Resolution ofEndo‐/Exo‐Monoesters ofTrans‐Norborn‐5‐Ene‐2,3‐Dicarboxylic Acids Into Their Enantiomers

Kovalenko

Kozyrkov

2014

Chirality

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Separation of optical isomers obtainable from trans-norborn-5-ene-2,3-dicarboxylic acid methyl and tert-butyl monoesters was performed by crystallization of the respective salts prepared with (R)- and (S)-1-phenylethylamine. Starting from racemic endo-monomethyl ester of trans-norborn-5-ene-2,3-dicarboxylic acid, prepared by partial hydrolysis of the cyclopentadiene-dimethyl fumarate adduct, the corresponding (2R,3R)-endo-monoester was isolated in 97% enantiomeric excess (ee) yield after seven repeated crystallizations from tetrachloromethane. Starting from exo-mono-tert-butyl ester of the same acid, prepared by alcoholysis of the cyclopentadiene-maleic anhydride adduct followed by isomerization, (2R,3R)-exo-monoester was isolated in >98% ee yield after four repeated crystallizations from ethanol. Crystallization of the acids from the mother liquor containing (S)-1-phenylethylamine yielded products with inverse stereochemical configuration.

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Solid-State Isomerization of Atropodiastereomers: Effective Diastereoselection through Polymorphic Transformations

et al. 2001

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The Â re Á se Averbuch, and Jacques Einhorn* Polymorphism is a fascinating phenomenon accompanied by a lot of strange manifestations. [1] It is generally defined as the existence of a given compound in more than one crystalline form. In conformational polymorphs, [2] a given molecular compound adopts different conformations in different polymorphs. But, at a molecular level, conformational changes may involve quite high energy barriers, allowing in some cases the isolation of separate stereoisomers (atropisomers) which do not interconvert rapidly in solution at room temperature, but do so if enough energy is supplied. Herein we report solid-state thermal isomerizations of compounds 1, which present such a type of atropisomerism. These isomerizations have features reminiscent of polymorphic transformations, although not involving polymorphs in the usual sense of the word. [3] As depicted in Scheme 1, the synthesis of 1 has been achieved by Diels ± Alder reactions between isobenzofuran 2 and maleimide or N-benzylmaleimide, giving adducts 3 a or 3 b in good yields. Their aromatization under strongly acidic conditions furnished 1 a and 1 b quantitatively. Demethylation of 1 a and 1 b gave diphenols 1 c and 1 d in high yields. Scheme 1. Reagents, conditions, and yields: a) for 3 a: 1 equiv maleimide, toluene, RT, 6 h, 96 %; for 3 b: 1 equiv N-benzylmaleimide, toluene, RT, 6 h, 81 %; b) 6 equiv MeSO 3 H, CH 2 Cl 2 , RT, 12 h, b 99 % for 1 a, b 99 % for 1 b; c) 3 equiv BBr 3 , CH 2 Cl 2 , À 78 8C to RT, 15 h, 98 % for 1 c, 99 % for 1 d. Full details can be found in the Supporting Information. RT room temperature.16: m.p. 81 ± 83 8C (hexane). A referee proposed that we examine the reaction of S 8 O with trapping reagents, with regard to the mechanism of the reactions reported here. The reaction of S 8 O, prepared by a reported method, [4b] with 2,3dimethyl-1,3-butadiene in dichloromethane at room temperature for 1 h gave 2 in only 1.4 % yield, while that carried out under reflux gave 2 in 25 % yield. At present we do not have direct evidence for the existence of free S 2 O in solution, so that ªS 2 Oº should be read as ªS 2 O equivalentº throughout this paper.

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Thermal racemization of (+)-bicyclo[2.2.1]hept-5-ene-trans-2,3-dicarboxylic acid in the melted and solid states

Cited by 16 publications

References 0 publications

Organic Solid-State Reactions

Organic Solid-State Reactions

A Simple Method for Resolution ofEndo‐/Exo‐Monoesters ofTrans‐Norborn‐5‐Ene‐2,3‐Dicarboxylic Acids Into Their Enantiomers

Solid-State Isomerization of Atropodiastereomers: Effective Diastereoselection through Polymorphic Transformations

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