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Ester Rearrangement (ester + rearrangement)

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Chemistry100%

Selected Abstracts

Synthesis of cis-Hedione® and Methyl Jasmonate via Cascade Baylis,Hillman Reaction and Claisen Ortho Ester Rearrangement

HELVETICA CHIMICA ACTA, Issue 12 2005
Christian Chapuis
The exocyclically unsaturated conjugated keto esters 10, obtained via a Claisen ortho ester rearrangement of the allylic hydroxy ketones 9, were either directly hydrogenated or partially isomerized into the endocyclically unsaturated tetrasubstituted didehydrojasmonoid intermediates 14, prior to a more selective hydrogenation with Pd/C in cyclohexane to the disubstituted oxocyclopentaneacetates 15 (Scheme,2). The key intermediates 9 were obtained either by a four-step sequence, including acetal protection/deprotection from enone 1, in the specific case of hydroxy ketone 9a (Scheme,1), or more directly and generally by a Baylis,Hillman reaction from cyclopent-2-en-1-one (16) and the appropriate aldehydes 17 (Scheme,2). The judicious choice of these aldehydes opens versatile modifications for the stereoselective introduction of the partially cis - or epimerized trans -C(2) jasmonoid side chain, while the Baylis,Hillman reaction, catalyzed by chiral [1,1,-binaphthalene]-2,2,-diols (BINOLs) 19 (Scheme,3), may be efficiently conducted in a one-pot cascade fashion including the ortho ester Claisen rearrangement. [source]

ChemInform Abstract: Synthesis of Bicyclic Orthoesters by Epoxy Ester Rearrangements and Study of Their Ring-Opening Reactions.

CHEMINFORM, Issue 25 2001
Peter Wipf
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Synthesis of cis-Hedione® and Methyl Jasmonate via Cascade Baylis,Hillman Reaction and Claisen Ortho Ester Rearrangement

HELVETICA CHIMICA ACTA, Issue 12 2005
Christian Chapuis
The exocyclically unsaturated conjugated keto esters 10, obtained via a Claisen ortho ester rearrangement of the allylic hydroxy ketones 9, were either directly hydrogenated or partially isomerized into the endocyclically unsaturated tetrasubstituted didehydrojasmonoid intermediates 14, prior to a more selective hydrogenation with Pd/C in cyclohexane to the disubstituted oxocyclopentaneacetates 15 (Scheme,2). The key intermediates 9 were obtained either by a four-step sequence, including acetal protection/deprotection from enone 1, in the specific case of hydroxy ketone 9a (Scheme,1), or more directly and generally by a Baylis,Hillman reaction from cyclopent-2-en-1-one (16) and the appropriate aldehydes 17 (Scheme,2). The judicious choice of these aldehydes opens versatile modifications for the stereoselective introduction of the partially cis - or epimerized trans -C(2) jasmonoid side chain, while the Baylis,Hillman reaction, catalyzed by chiral [1,1,-binaphthalene]-2,2,-diols (BINOLs) 19 (Scheme,3), may be efficiently conducted in a one-pot cascade fashion including the ortho ester Claisen rearrangement. [source]

The atmospheric oxidation of ethyl formate and ethyl acetate over a range of temperatures and oxygen partial pressures

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2010
John J. Orlando
The Cl-atom-initiated oxidation of two esters, ethyl formate [HC(O)OCH2CH3] and ethyl acetate [CH3C(O)OCH2CH3], has been studied at pressures close to 1 atm as a function of temperature (249,325 K) and O2 partial pressure (50,700 Torr), using an environmental chamber technique. In both cases, Cl-atom attack at the CH2 group is most important, leading in part to the formation of radicals of the type RC(O)OCH(O,)CH3 [R = H, CH3]. The atmospheric fate of these radicals involves competition between reaction with O2 to produce an anhydride compound, RC(O)OC(O)CH3, and the so-called ,-ester rearrangement that produces an organic acid, RC(O)OH, and an acetyl radical, CH3C(O). For both species studied, the ,-ester rearrangement is found to dominate in air at 1 atm and 298 K. Barriers to the rearrangement of 7.7 ± 1.5 and 8.4 ± 1.5 kcal/mole are estimated for CH3C(O)OCH(O,)CH3 and HC(O)OCH(O,)CH3, respectively, leading to increased occurrence of the O2 reaction at reduced temperature. The data are combined with those obtained from similar studies of other simple esters to provide a correlation between the rate of occurrence of the ,-ester rearrangement and the structure of the reacting radical. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 397,413, 2010 [source]