An improved procedure for the two carbon homologation of esters to α, β-unsaturated esters

Takacs, James M.; Helle, Mark; Seely, Franklin L.

doi:10.1016/s0040-4039(00)84232-x

Cited by 66 publications

(34 citation statements)

References 11 publications

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“…Stereochemical assignment of the diastereomeric products was carried out effectively by the analysis of 400 MHz and 13c NMR spectra with reference to those reported in the literature, when available. The results are shown in Tables 1-5. Ethyl trans-1,2-di~~zethylcyclohexanecarboxylate (40)~ The 'H NMR spectra of the major product in the cyclization of ethyl 7-bromo-2,3-dimethylheptanoate (11) agree well with the data reported for the methyl ester corresponding to the trans compound 40, except with regard to the signal due to the Throughout this paper, the cis-trans notation for the relative configuration of substituted cyclohexanecarboxylate derivatives refers to the ester groups. Can ... ester groups (14,15).…”

Section: Synthesis Of Cyclization Substratessupporting

confidence: 59%

“…Ethyl 7-bronzo-2,6-dimetlzylheptanoate (39) was synthesized by the homologation of 4-methyl-6-valerolactone (37) (Scheme 7). The substrates 11,15,19,25,26,30,35, and 39 were all obtained as a mixture of diastereomers, as seen distinctly from their 13c NMR spectra.…”

Section: Synthesis Of Cyclization Substratesmentioning

confidence: 88%

“…Ethyl 7-bromo-2,3-dimethylheptanoate (11) was synthesized by the alkylation of acetoacetate dianion with 3-benzyloxypropyl bromide (7) and subsequent successive introduction of methyl groups at the 3 and 2 positions as shown in Scheme 3. To introduce the 3-methyl group, the combination of Nozaki and Weiler methods (10) was used and the resultant trisubstituted olefin was catalytically hydrogenated.…”

Section: Synthesis Of Cyclization Substratesmentioning

confidence: 99%

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Folding strain stereocontrol in cyclohexane ring formation by means of an intramolecular ester enolate alkylation reaction

Tokoroyama¹,

Kusaka²

1996

Can. J. Chem.

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Diastereoselectivity in the cyclization of ethyl 7-bromo-2-methylheptanoates with an additional substituent at various positions in the chain, by LDA treatment, was investigated in connection with the concept of folding strain stereocontrol. Cyclization of 3-, 4-, and 6-methyl-substituted substrates revealed high selectivity, which demonstrates the prevalence of folding strain stereocontrol and the usefulness of this approach for stereoselective ring construction. In particular, reactions of the latter two substrates resulted in the stereodivergent preparation of diastereomeric 1,3-dimethylcyclohexanecarboxylates. In the case of the 5-methyl-substituted substrate, the selectivity of ring closure was only moderate. 'H and '" NMR spectroscopic data were useful for determining the conformation of 1-methylcyclohexanecarboxylate derivatives. The origin of the diastereoselectivity was examined through the qualitative comparison of the strain in the diastereomeric folding in the transition state. Various factors that might affect stereoselectivity were examined in the cyclization of 5-substituted substrates to better understand this concept. As predicted, the selectivity increased as the substituent became bulkier: Ph < M e = Et < i-Pr < t-Bu. The effects of other factors -solvent, base counter cation, and leaving group -on selectivity agree with results predicted from the reactivity-selectivity relationship.Key words: folding strain stereocontrol; diastereoselectivity in ring-closure reaction; remote asymmetric induction; ethyl 2-methylcyclohexanecarboxylate derivatives, 'H and 13c NMR; stereoselective synthesis of substituted cyclohexane derivatives.Resume : Dans le cadre de travaux sur le concept du stCrCocontr6le par le plissement des chahes, on a CtudiC la diastCrCosClectivitC de la cyclisation, sous l'influence du LDA, de 7-bromo-2-mCthylheptanoates d'Cthyle portant un substituant additionnel dans diverses positions. Les cyclisations des substrats substituCs par des groupes mCthyles en positions 3 , 4 ou 6 se produisent avec une grande sClectivitC; ceci met en Cvidence la prkvalence du stCrCocontr6le par le plissement de la chaine et dCmontre 1'utilitC de cette approche pour la formation stCrCosClective de cycles. Ceci est particulibrement vrai avec les deux derniers substrats qui conduisent a la prCparation stCrCoconvergente des 1,3-dimCthylcyclohexanecarboxylates diastCrCombres. Dans le cas du substrat portant un groupe mCthyle en position 5, la sClectivitC de la formation du cycle n'est que modCrCe. Les donnCes de la spectroscopie RMN du 'H et du I3c se sont avCrCes utiles pour la dktermination de la conformation des dCrivCs 1-mCthylcyclohexanecarboxylates. On a CtudiC l'origine de la diastCrCosClectivitC par le biais d'une comparaison qualitative de la tension dans le plissement diastCrCombre dans 1'Ctat de transition. Dans le but de mieux comprendre ce concept, on a examin6 divers facteurs pouvant affecter la stCrCosClectivitC lors de la cyclisation de substrats substituCs en position 5. Tel qu'on ...

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Section: Synthesis Of Cyclization Substratessupporting

confidence: 59%

Section: Synthesis Of Cyclization Substratesmentioning

confidence: 88%

Section: Synthesis Of Cyclization Substratesmentioning

confidence: 99%

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Folding strain stereocontrol in cyclohexane ring formation by means of an intramolecular ester enolate alkylation reaction

Tokoroyama¹,

Kusaka²

1996

Can. J. Chem.

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“…The ester group was reduced by DIBAH to the trans-configurated allylic alcohol 13 [21]. Epoxidation of 13 under Sharpless conditions [22] led to the epoxide 14 [23], which was esterified with 4-benzyloxybenzoic acid.…”

Section: Synthesismentioning

confidence: 99%

Novel ferroelectric liquid crystals and dopants for induced ferroelectric phases containing 3,4-epoxy-2-octanols as chiral unit

Scherowsky

Hentschel

1996

Liquid Crystals

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“…In order to avoid this stereochemical drawback, the Wittig reagent was exchanged for a Horner-Wadsworth-Emmons (HWE reagent), which is compatible to the use of DIBAL. xvii The use of [(EtO) 2 P(O)CHCOOEt] − Na + exclusively gave the desired E -isomer ( E:Z = > 25:1); xviii however the yield of 3c was disappointingly low (13%) (route A in Scheme 4), although, based on the original Seebach's protocol, the entire DIBAL addition temperature was initially maintained at −78°C to prepare the lactol 6 via an organo-aluminum intermediate 7 . Due to the poor reaction efficiency of route A, an alternative approach through a presumed hydroxyester 8 was then explored by adding the first two equivalents of DIBAL at r.t. (route B in Scheme 4).…”

mentioning

confidence: 99%

DIBAL-Mediated Reductive Transformation of trans-Dimethyl Tartrate Acetonide into ε-Hydroxy α,β-Unsaturated Ester and Its Derivatives

et al. 2011

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An improved procedure for the two carbon homologation of esters to α, β-unsaturated esters

Cited by 66 publications

References 11 publications

Folding strain stereocontrol in cyclohexane ring formation by means of an intramolecular ester enolate alkylation reaction

Folding strain stereocontrol in cyclohexane ring formation by means of an intramolecular ester enolate alkylation reaction

Novel ferroelectric liquid crystals and dopants for induced ferroelectric phases containing 3,4-epoxy-2-octanols as chiral unit

DIBAL-Mediated Reductive Transformation of trans-Dimethyl Tartrate Acetonide into ε-Hydroxy α,β-Unsaturated Ester and Its Derivatives

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