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1.
An effective method for the synthesis of vinyl thioethers through the conjugate addition of ethanethiol to electron-deficient alkynes promoted by BF3Et2Ohas been developed.Electron-deficient internal alkynes react with ethanethiol in this system to yield mainly Z-isomer of vinyl thioether adducts,while electron-deficient terminal alkynes afford mainly E-isomer of vinyl thioether adducts. 相似文献
2.
Trost BM Frederiksen MU Papillon JP Harrington PE Shin S Shireman BT 《Journal of the American Chemical Society》2005,127(11):3666-3667
Direct asymmetric aldol reactions constitute a powerful methodology for the efficient synthesis of complex natural products. Herein we report the first application of our recently reported dinuclear Zn-catalyzed direct aldol addition of alkynyl ketones to aldehydes in a short and efficient formal asymmetric synthesis of fostriecin, a potent cyctotoxic natural product. This work highlights not only the power of the aldol methodology but also the utility of the akynyl silane aldol adducts, as it is subsequently utilized in a vinyl silane cross-coupling reaction which affords the target molecule in 14 steps for the longest linear sequence in 8.5% overall yield. 相似文献
3.
The cobalt(I)-catalyzed Diels-Alder reaction of nonactivated aryl alkynyl sulfides with acyclic 1,3-dienes generates dihydroaromatic vinyl sulfides under very mild reaction conditions, and these products can be oxidized with mild oxidants to the corresponding diaryl sulfides in good overall yields. The steric and electronic effects of substituents on the aryl, as well as on the alkynyl, moieties of the aryl alkynyl sulfide are discussed. While the cobalt catalyst system is quite efficient in converting alkynyl sulfides to the Diels-Alder adducts, the transformation of the corresponding aryl alkynyl sulfoxides and sulfones under similar mild reaction conditions gave only moderate yields of the desired adducts. 相似文献
4.
The palladium-catalysed coupling of bromofurans with activated alkenes and of furanoyl chlorides with either terminal alkynes or alkynyl stannanes gave good yields of the corresponding vinyl furans and alkynyl ketones. These studies culminated in a short synthesis of the antifungal agent dihydrowyerone. 相似文献
5.
Teresa E. Campano Igor Iriarte Olatz Olaizola Dr. Julen Etxabe Prof. Antonia Mielgo Prof. Iñaki Ganboa Prof. José M. Odriozola Prof. Jesús M. García Prof. Mikel Oiarbide Prof. Claudio Palomo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(17):4390-4397
Various sets of enolizable alkynyl ketones (including methyl ynones with α-aryl, α-alkenyl, and α-alkoxy groups) were able to react smoothly with nitroolefins with the assistance of bifunctional Brønsted base/H-bond catalysts to provide adducts with two consecutive tertiary stereocenters in a highly diastereo- and enantioselective fashion. Further transformation of the obtained adducts into optically active acyclic and polycyclic molecules, including some with intricate carbon skeletons, was also demonstrated. 相似文献
6.
Reductive cyclization of aryl and vinyl iodides tethered to vinylogous acyl triflates (VATs) induces a ring-expanding fragmentation to provide cyclic alkynyl ketones, including strained nine-membered cycloalkynes, in fair to excellent yield. The tandem cyclization/C-C bond-cleavage is initiated under carefully optimized conditions by halogen-metal exchange in the presence of carbonyl and vinyl triflate functionality. A modified protocol for alkylation of 1,3-cyclohexanedione is described for preparing the relevant VAT substrates. 相似文献
7.
Bee C Han SB Hassan A Iida H Krische MJ 《Journal of the American Chemical Society》2008,130(9):2746-2747
We report the first enantioselective reductive aldol couplings of vinyl ketones, which were achieved through the design of a novel monodentate TADDOL-like phosphonite ligand. Specifically, hydrogenation of commercially available methyl vinyl ketone (MVK) or ethyl vinyl ketone (EVK) in the presence of aldehydes 1a-7a using cationic rhodium catalysts modified by chiral TADDOL-like phosphonite ligands AP-I and AP-IV produces aldol adducts 1b-7b and 1c-7c with excellent control of relative and absolute stereochemistry. The absolute stereochemical assignments of the aldol adducts are made in analogy to that determined for the 5-bromophthalimido derivative of aldol adduct 1b and the 2-bromo-5-nitrobenzoate of 3b, which were established by single-crystal X-ray diffraction analysis using the anomalous dispersion method. 相似文献
8.
《Tetrahedron: Asymmetry》1999,10(3):457-471
The scope and limitations of the Pauson–Khand reactions of alkynyl sulfoxides with strained alkenes have been studied. (S)-1-Hexynyl p-tolyl sulfoxide and (S)-2-phenylethynyl p-tolyl sulfoxide afforded β-(p-tolylsulfinyl)enones in moderate yields and low diastereoselectivities. The diastereomeric mixtures were easily separated by column chromatography and the sulfinyl group could be cleaved by a sequence involving reduction to sulfide, carbonyl reduction and enol thioether hydrolysis to afford 1,3-rearranged enantiomerically enriched α-butyl and α-phenyl enones. The absolute configuration of the Pauson–Khand adducts was determined by X-ray diffraction. The decreased enantiomeric excess of the final products uncovered an unprecedented low temperature racemization of the hexacarbonyl dicobalt complexes of alkynyl sulfoxides. 相似文献
9.
A highly chemoselective PPh(3)-catalyzed three-component reaction of an imine, alkyl vinyl ketone, and phthalimide or succinimide is developed. Various highly functional adducts with high diastereoselectivities can be generated via aza-Morita-Baylis-Hillman reactions of aryl-substituted imines and alkyl vinyl ketones followed by Michael additions of imides and then epimerization. 相似文献
10.
The stereochemistry of the addition of the zinc derivative of ether PhCCCH2OMe, to aldehydes and ketones has been studied. In the case of saturated carbonyl compounds, the results can be explained by a mechanism which takes into account the steric effects of the substituents. However, with those which contain phenyl, vinyl or alkynyl groups in the α position, conformational and electronic factors must be considered. 相似文献
11.
Adducts from the radical addition of xanthates to ethyl vinyl sulfide readily undergo elimination of the xanthate group upon thermolysis to give vinylic and/or allylic sulfides, depending on the structure. In the case of α-xanthyl ketones, the adducts are converted into α-keto vinyl carbinols by rearrangement of the sulfoxides derived from the vinylic and allylic sulfides. 相似文献
12.
A novel electrotelluration process is described in which a Michael addition of an alkyl or aryl tellurolate anion occurs onto an activated alkyne with subsequent trapping of a vinyl anion with electrophiles (aldehydes and ketones) other than a proton. This process provides an efficient regio- and stereospecific route to tri- and tetrasubstituted alkenes. Methodologically significant examples of this chemistry were studied in which aryl and alkyl tellurolate anions were added to omega-keto alkynyl esters in a Michael reaction, and the incipient vinyl anions were trapped intramolecularly by the internal aldehydes. The reactive centers were tethered by different lengths of alkyl chains to form highly functionalized five-, six-, seven-, and eight-membered rings in modest to good yields. 相似文献
13.
《Tetrahedron letters》1986,27(3):373-376
A method is described for the synthesis of chiral alkynyl ketones and alkynols via trimethylaluminum-promoted pinacol-type rearrangement where alkynyl groups behave as “the staying group”, followed by stereoselective reduction leading to the latter. 相似文献
14.
Prof. Dr. Barry M. Trost Jacob S. Tracy Tas Yusoontorn Chao-I Joey Hung 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(6):2390-2394
The preparation of acyclic β-fluoro amines bearing tetrasubstituted fluorine stereocenters is described via a direct Zn/ProPhenol-catalyzed Mannich reaction. The reaction utilizes branched vinyl or alkynyl α-fluoro ketones that can be coupled with a range of aryl, heteroaryl, vinyl, or cyclopropyl aldimines in high yield and with excellent diastereo- (up to >20:1) and enantioselectivity (up to 99 %). The use of readily cleaved tert-butoxycarbonyl (Boc) or carboxybenzyl (Cbz) imine protecting groups adds utility to the reaction by allowing for easy access to the free amine products under mild and chemoselective reaction conditions. 相似文献
15.
Barry M. Trost Jacob S. Tracy Tas Yusoontorn Chao‐I Joey Hung 《Angewandte Chemie (International ed. in English)》2020,59(6):2370-2374
The preparation of acyclic β‐fluoro amines bearing tetrasubstituted fluorine stereocenters is described via a direct Zn/ProPhenol‐catalyzed Mannich reaction. The reaction utilizes branched vinyl or alkynyl α‐fluoro ketones that can be coupled with a range of aryl, heteroaryl, vinyl, or cyclopropyl aldimines in high yield and with excellent diastereo‐ (up to >20:1) and enantioselectivity (up to 99 %). The use of readily cleaved tert‐butoxycarbonyl (Boc) or carboxybenzyl (Cbz) imine protecting groups adds utility to the reaction by allowing for easy access to the free amine products under mild and chemoselective reaction conditions. 相似文献
16.
Marie-Claude Bellassoued-Fargeau Pierre Maitte 《Journal of heterocyclic chemistry》1984,21(5):1549-1552
Cycloaddition between α,β-unsaturated ketones and vinyl ethers gave 2-alkoxydihydropyrans. On treatment with hydroxylamine hydrochloride, these adducts afforded the corresponding substituted pyridines in good to moderate yields. By applying this scheme we could obtain benzopyrannopyridines and dihydrobenzoquinolines. Structures have been studied by spectroscopic methods. 相似文献
17.
An overview of studies on hydrogenative reductive aldol addition is presented. By simply hydrogenating enones in the presence of aldehydes at ambient temperature and pressure, aldol adducts are generated under neutral conditions in the absence of any stoichiometric byproducts. Using cationic rhodium complexes modified by tri(2-furyl)phosphine, highly syn-diastereoselective reductive aldol additions of vinyl ketones are achieved. Finally, using novel monodentate TADDOL-like phosphonite ligands, the first highly diastereo- and enantioselective reductive aldol couplings of vinyl ketones were devised. These studies, along with other works from our laboratory, demonstrate that organometallics arising transiently in the course of catalytic hydrogenation offer byproduct-free alternatives to preformed organometallic reagents employed in classical carbonyl addition processes. 相似文献
18.
E. A. Dikusar N. G. Kozlov K. L. Moiseichuk A. P. Yuvchenko 《Russian Journal of Organic Chemistry》2001,37(8):1093-1098
A method was developed for preparation of alkynyl peroxides from terpene and steroid aldehydes and ketones by reaction of lithium peroxyacetylides with the corresponding aldehydes and ketones followed by treating the intermediate lithium alcoholates with acyl chlorides. 相似文献
19.
Syntheses of 2-amino-2,3-dihydrobenzofuran derivatives 3a-g and fully substituted furans 5a-f were achieved starting from the Baylis-Hillman adducts. We prepared 2-amino-2,3-dihydrobenzofurans from the Baylis-Hillman adducts of methyl and ethyl acrylates and fully substituted furans from the Baylis-Hillman adducts of alkyl vinyl ketones. 相似文献
20.
Manzano R Andrés JM Álvarez R Muruzábal MD de Lera ÁR Pedrosa R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(21):5931-5938
A series of chiral thioureas derived from easily available diamines, prepared from α-amino acids, have been tested as catalysts in the enantioselective Michael additions of nitroalkanes to α,β-unsaturated ketones. The best results are obtained with the bifunctional catalyst prepared from L-valine. This thiourea promotes the reaction with high enantioselectivities and chemical yields for aryl/vinyl ketones, but the enantiomeric ratio for alkyl/vinyl derivatives is very modest. The addition of substituted nitromethanes led to the corresponding adducts with excellent enantioselectivity but very poor diastereoselectivity. Evidence for the isomerization of the addition products has been obtained from the reaction of chalcone with [D(3)]nitromethane, which shows that the final addition products epimerize under the reaction conditions. The epimerization explains the low diastereoselectivity observed in the formation of adducts with two adjacent tertiary stereocenters. Density functional studies of the transition structures corresponding to two alternative activation modes of the nitroalkanes and α,β-unsaturated ketones by the bifunctional organocatalyst have been carried out at the B3LYP/3-21G* level. The computations are consistent with a reaction model involving the Michael addition of the thiourea-activated nitronate to the ketone activated by the protonated amine of the organocatalyst. The enantioselectivities predicted by the computations are consistent with the experimental values obtained for aryl- and alkyl-substituted α,β-unsaturated ketones. 相似文献