Author
Werner Heilmayer
Bio: Werner Heilmayer is an academic researcher from University of Graz. The author has contributed to research in topics: Cycloaddition & De novo synthesis. The author has an hindex of 6, co-authored 11 publications receiving 170 citations.
Papers
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TL;DR: The most important classes of precursor molecules are 2-diazo-1, 3-diketones, 1,3dioxin-4-ones, 2,3-dihydrofuran-2, 3diones, and beta-ketoacid derivatives as mentioned in this paper.
Abstract: This review describes the methods of generation of alpha-oxoketenes and their use in synthesis. While the ketenes are often generated in situ without direct proof for their existence, methods used for their direct observation are also emphasized. The most important classes of precursor molecules are 2-diazo-1,3-diketones, 1,3-dioxin-4-ones, 2,3-dihydrofuran-2,3-diones, and beta-ketoacid derivatives. Synthetically useful reactions are nucleophilic additions to give carboxylic acid derivatives which can be subjected to further functional group manipulation, [2 + 2] cycloadditions to give four-membered rings, and [2 + 4] cycloaddition chemistry with a wide variety of double-and triple-bonded dienophiles, resulting in numerous six-membered heterocyclic ring systems.
110 citations
TL;DR: In this article, the unusual chiral heterocyclic systems, trioxabicyclo[3.1]nona-3,7-dienes ("bridged bisdioxines"), are incorporated as novel spacer molecules into macrocyclic polyether ring systems of various sizes (8, 9 as well as 11-15) by cyclocondensation reaction of the bisacid chloride 4b or bisesters 6,7 and 10, with several ethylene glycols.
Abstract: The unusual chiral heterocyclic systems, trioxabicyclo[3.3.1]nona-3,7-dienes ("bridged bisdioxines"), are incorporated as novel spacer molecules into macrocyclic polyether ring systems of various sizes (8, 9 as well as 11-15) by cyclocondensation reaction of the bisacid chloride 4b or bisesters 6,7 and 10, with several ethylene glycols. The 2:2 macrocycles 12-14 are obtained in approximately 50:50 mixtures of diastereomers. These conclusions are mainly based on HPLC data presented in Table I as well as X-ray analyses of (1R,5R)-8c (space group Pbca, a =10.163(3) A, b =18.999(4) A, c =36.187(10) A, V =6987(3) A3 , Z =8, d calc =1.218 g cmm 3, 6974 reflections, R =0.0553), meso/rac-11 (space group P1 ¥ , a =10.472(5) A, b=16.390(5) A, c =17.211(5) A, f =98.69(2)°, g =93.04(2)°, n =98.52(2)°, V =2879.3(18) A 3 , Z =2, d calc =1.173 g cm m 3 , 11,162 reflections, R =0.0945) and meso-12 (space group P21/c, a =9.927(2), b =18.166(3), c =17.820(3) A, g =96.590(10)°, V =3192.3(10) A 3 , Z =4, D c =1.109 g cmm 3, ...
15 citations
TL;DR: In this article, a trioxabicyclononon-adienes (trioxabicycleclon-deon) was obtained by addition of nucleophiles to the stable α-oxoketene.
Abstract: Trioxabicyclononadienes 2 and 4, easily obtained by addition of nucleophiles to the stable α-oxoketene 1, are transformed into the corresponding 2,4,6,8-tetraoxaadamantanes 3 and 5 in high yields by acid-catalysed hydrolysis.
12 citations
TL;DR: In this article, primary amino groups of di- or triaminoaryl compounds add a remarkably stable dioxinyl-alpha-oxoketene affording bis- or tris-trioxabicyclo[3.3.1]nona-3,7-dienyl (bridged bisdioxine)] systems which can be converted into the corresponding bis-or tris-[2,4,6,8-tetraoxadamantanes] by acidic hydrolysis.
11 citations
TL;DR: In this paper, the molecular skeleton of 6 was confirmed by an X-ray diffraction analysis with the aid of 17 Olabeling experiments and 17 O-NMR spectroscopy mechanistic pathways including novel rearrangements.
Abstract: The furan-2,3-dione 1 combines with N-sulfinylamines or sulfur diimides to afford the pyrrole-2,3-diones 2, while with N-tosylsulfinylamine the (α-iminobenzyl)furandione 3 is obtained. (α-Iminobenzyl)pyrrolediones 4 are formed in the reaction of 2c with N-tosylsulfinylamine or from 3 with N-tosylsulfur diimides. Diisopropylcarbodiimide and the pyrroledione 2 c or the (iminobenzyl)furandione 3a undergo [4+2] cycloaddition reactions accompanied by novel and surprising rearrangements to furnish the bicyclic compounds 5 and 6, respectively. The molecular skeleton of 6 was confirmed by an X-ray diffraction analysis. With the aid of 17 O-labeling experiments and 17 O-NMR spectroscopy mechanistic pathways including novel rearrangements were made evident
10 citations
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TL;DR: In this paper, a review of synthesis pathways for the preparation of unconventional cellulose derivatives with alternative functional groups and patterns of functionalization is given. But the authors focus on the application of NMR spectroscopy including two-dimensional methods and of chromatographic techniques after specific sample pretreatment as enzymatic and acidic partial or complete depolymerization.
818 citations
TL;DR: The results from DFT calculation on the reaction mechanism suggest that Pd is involved in the [2 + 2] cycloaddition process and affects the diastereoselectivity of the β-lactam products by assisting isomerization of the addition intermediate.
Abstract: The carbonylation of carbenes through catalytic cycles is highly desirable due to the importance of ketene-mediated reactions in organic synthesis In this investigation, a highly efficient and mild catalytic approach toward ketene intermediates has been developed based on Pd-catalyzed carbonylation of diazo compounds with CO When α-diazocarbonyl compounds or N-tosylhydrazone salts are heated in the presence of a palladium catalyst under atmospheric pressure of CO, ketene intermediates are formed in situ, where they undergo further reactions with various nucleophiles such as alcohols, amines, or imines The Pd-catalyzed tandem carbonylation−Staudinger cycloaddition gives β-lactam derivatives in good yields with excellent trans diastereoselectivity The results from DFT calculation on the reaction mechanism suggest that Pd is involved in the [2 + 2] cycloaddition process and affects the diastereoselectivity of the β-lactam products by assisting isomerization of the addition intermediate On the other hand
152 citations
TL;DR: The 1,3-dicarbonyl (1D) compound as mentioned in this paper is an exceptional platform for 1D organic synthesis due to the presence of four contiguous reaction sites, which allows cascades of elemental steps from simple substrates.
Abstract: Modern organic synthesis focuses on the discovery and the development of stereoselective multiple bond-forming transformations allowing the creation of several covalent bonds in a single operation. Hence, the number of steps required to obtain a target molecule is reduced, which nicely addresses the efficiency and economy criteria of ‘green chemistry’. In this context, 1,3-dicarbonyl compounds are exceptional synthetic platforms due to the presence of four contiguous reaction sites. This functional group density allows cascades of elemental steps from simple substrates leading to the selective formation of elaborated molecular architectures displaying a large functional diversity.
148 citations
TL;DR: This review investigates the use of complex ester fragment couplings within natural product total synthesis campaigns and presents and discusses a collection of successful examples from the literature.
133 citations