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Journal ArticleDOI

Heteroatom-directed allylic substitution and rearrangement reactions

01 Mar 1987-Journal of Organic Chemistry (American Chemical Society)-Vol. 52, Iss: 5, pp 782-787
TL;DR: In this paper, a transposition catalyse par un acide en enol ethers was used for diisopropylethylamine in C-1 en presence of diisOPropyle methoxypropadiene.
Abstract: Les nucleophiles alcooliques, phenoliques et thioliques attaquent le (chloro-3 propenyl methyl) ether exclusivement en C-1 en presence de diisopropylethylamine. Quelques acetals mixtes d'acroleines obtenus de cette facon peuvent etre produits par addition catalysee par un acide d'alcools au methoxypropadiene. Des O,S-acetals d'acroleine subissent une transposition catalysee par un acide en enol ethers
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Journal ArticleDOI
TL;DR: This hypothesis that reactions of anionic nucleophiles with allylic halides are generally S(N)2 is consistent with a variety of computations at the HF, B3LYP, mPW1PW91 and MP2 levels with the 6-31+G(d) basis set of reactions of Li and Na fluoride and chloride with allyl halides and 4-halo-2-pentenes.
Abstract: Various disparate experimental results are explained by the hypothesis that reactions of anionic nucleophiles with allylic halides are generally SN2. The SN2′ reactions that do occur proceed generally with anti stereochemistry. Reactions with ion pair nucleophiles occur preferentially as SN2′ reactions with syn stereochemistry. This hypothesis is consistent with a variety of computations at the HF, B3LYP, mPW1PW91 and MP2 levels with the 6-31+G(d) basis set of reactions of Li and Na fluoride and chloride with allyl halides and 4-halo-2-pentenes. Solvation is considered by a combination of coordination of dimethyl ether to the lithium and sodium cations and “dielectric solvation” with a polarized continuum model.

39 citations

Journal ArticleDOI
TL;DR: This paper describes the synthesis of several optically pure 4- and 5-substituted lactones obtained via whole cell-catalyzed Baeyer-Villiger oxidations of highly enantiomerically enriched 3-alkyl cyclic ketones.
Abstract: Optically pure or highly enantiomerically enriched 4- and 5-substituted lactones are rather difficult to obtain. Chemical or enzymatic syntheses alone are not particularly successful. A combination of chemical catalysis and biocatalysis, however, provides a convenient route to a variety of these useful chiral compounds. In this paper we describe the synthesis of several optically pure 4- and 5-substituted lactones obtained via whole cell-catalyzed Baeyer−Villiger oxidations of highly enantiomerically enriched 3-alkyl cyclic ketones. Such chiral ketones are readily accessed by recently developed copper-catalyzed asymmetric conjugate reductions of the corresponding enones. A very high proximal regioselectivity and complete chirality transfer was obtained by employing biological Baeyer−Villiger oxidations, using recombinant E. coli strains that overexpress cyclopentanone monooxygenase (CPMO). A comparative study showed that CPMO gives superior results to those obtained with cyclohexanone monooxygenase (CHMO)...

37 citations

Journal ArticleDOI
TL;DR: In this paper, a type of capto-dative olefin, dicyanoketene acetal, was introduced to be a novel type of π-acid catalyst for the monothioacetalization of acetals as well as the corresponding α,β-unsaturated systems.

17 citations

Journal ArticleDOI
TL;DR: In this paper, a curious effect of the substituent at the enolic α carbon was uncovered, in which α substituents is forced to twist into a conformation blocking the proton donor from its side, thus reversing the stereochemistry of protonation.
Abstract: Kinetic control of the stereoselectivity of protonation of enolates and other strongly delocalized anionic species is involved in a large number of organic reactions. Protonation occurring from the less hindered side of the, e.g., enolic system affords the less stable of two diastereomers. However, one apparent discrepancy has been in the synthesis of prostaglandins. The present research deals with the source of this behavior. A curious effect of the substituent at the enolic α carbon was uncovered. In certain instances an α substituent is forced to twist into a conformation blocking the proton donor from its side, thus reversing the stereochemistry of protonation. In the course of this research, a number of five-ring enols of varying structure were investigated. Finally, the ketonization reaction course has been studied theoretically.

10 citations

Journal ArticleDOI
TL;DR: In the presence of TMSOTf in tetrahydrofuran at −78 °C, 3-alkoxy-2-alkenylenesulfonium salts which undergo facile nucleophilic substitution reactions with lithium thioalkoxides and trialkyltin alkoxides to yield α,β-unsaturated O,S-acetals and mixed acetals as discussed by the authors.

9 citations