79629-20-2Relevant academic research and scientific papers
A Broad-Spectrum Synthesis of Tetravinylethylenes
Horvath, Kelsey L.,Newton, Christopher G.,Roper, Kimberley A.,Ward, Jas S.,Sherburn, Michael S.
supporting information, p. 4072 - 4076 (2019/03/22)
The first general synthesis of compounds of the tetravinylethylene (TVE) family is reported. Ramirez-type dibromo-olefination of readily accessible penta-1,4-dien-3-ones generates 3,3-dibromo[3]dendralenes, which undergo twofold Negishi, Suzuki–Miyaura or Mizoroki–Heck reactions with a wide variety of olefinic coupling partners. This route delivers a broad range of unsymmetrically substituted tetravinylethylenes with up to three different alkenyl substituents attached to the central C=C bond. The extensive scope of the approach is demonstrated by the preparation of the first higher order oligo-alkenic through-conjugated/cross-conjugated hybrid compounds. An unsymmetrically substituted TVE is shown to undergo a domino electrocyclization–cycloaddition with high site-selectivity and diastereoselectivity, thereby demonstrating the substantial synthetic potential of substituted TVEs for controlled, rapid structural complexity generation.
Catalytic asymmetric synthesis of spirocyclic azlactones by a double Michael-addition approach
Weber, Manuel,Frey, Wolfgang,Peters, René
supporting information, p. 8342 - 8351 (2013/07/27)
Spirocyclic azlactones are shown to be useful precursors of cyclic quaternary amino acids, such as the constrained cyclohexane analogues of phenylalanine. These compounds are of interest as building blocks for the synthesis of artificial peptide analogues with controlled folds in the peptide backbone. They were prepared in the present study by a step- and atom-economic catalytic asymmetric tandem approach, requiring two steps starting from N-benzoyl glycine and divinylketones. The key of this protocol is the enantioselective formation of the azlactone spirocycles, which involves a PdII-catalyzed double 1,4-addition of an in situ generated azlactone intermediate to the dienone (a formal [5+1] cycloaddition). As the catalyst, a planar chiral ferrocene bispalladacycle was used. Mechanistic studies suggest a monometallic reaction pathway. Although the diastereoselectivity was found to be moderate, the enantioselectivity is usually high for the formation of the azlactone spirocycles, which contain up to three contiguous stereocenters. Spectroscopic studies have shown that the spirocycles often prefer a twist over a chair conformation of the cyclohexanone moiety. A formal [5+1] cycloaddition of divinylketones and an in situ-generated glycine-derived azlactone was catalyzed by a chiral bis-palladacycle and provided highly enantioenriched, spirocyclic, masked amino acid products. The latter were used to synthesize biologically interesting constrained cyclohexane analogues of phenylalanine in just two steps (see scheme). Copyright
Syntheses of 4H-thiopyran-4-one 1,1-dioxides as precursors to sulfone-containing analogues of tetracyanoquinodimethane
Rule,Detty,Kaeding,Sinicropi
, p. 1665 - 1673 (2007/10/02)
Synthetic routes to the unsubstituted 4H-thiopynan-4-one 1,1-dioxide (5a), 2,6-dialkyl-substituted, 2-aryl- or 2-heteroaryl-6-alkyl-substituted, 2,6-diaryl- or diheteroaryl-substituted, and 2-heteroaryl-6-aryl-substituted 4H-thiopyran-4-one 1,1-dioxides 5b-s are described. Sodium hydrosulfide hydrate in buffered aqueous alcohol can be used as a substitute for hydrogen sulfide gas for the introduction of sulfur to methyl acrylate, to 1,5-disubstituted-1,4-pentadien-3-ones 13, or to 1,5-disubstituted-1,4-pentadiyn-3-ones 17. The double dehydrogenation of 2,3,5,6-tetrahydrothiopyran-4-one 1,1-dioxides 13 with iodine-DMSO-sulfuric acid gives thiopyran-4-one 1,1-dioxides 5 in good yield and small amounts of 1,4-pentadien-3-ones 13. 2,3,5,6-Tetrahydrothiopyran-4-one 1,1-dioxide (9) and 5,6-dihydrothiopyran-4-one 1,1-dioxide (12), which lack aryl or heteroaryl substituents, give poor yields of 4H-thiopyran-4-one 1,1-dioxide (5a) with iodine-DMSO-sulfuric acid.
