scholarly journals A versatile Diels–Alder approach to functionalized hydroanthraquinones

2020 ◽  
Vol 7 (11) ◽  
pp. 200626
Author(s):  
Janina Beck ◽  
Olaf Fuhr ◽  
Martin Nieger ◽  
Stefan Bräse
Keyword(s):  
Natural Product ◽  
Alder Reaction ◽  
Diels Alder ◽  
Coupling Reactions ◽  
Ring Systems ◽  
Mild Conditions ◽  
Diels Alder Reaction ◽  
High Yields

The synthesis of highly substituted hydroanthraquinone derivatives with up to three stereogenic centres via a Diels–Alder reaction, starting from easily accessible 2-substituted naphthoquinones, is described. The [4+2]-cycloaddition is applicable for a broad range of substrates, runs under mild conditions and results in high yields. The highly regioselective outcome of the reactions is enabled by a benzoyl substituent at C2 of the dienophiles. The obtained hydroanthraquinones can be further modified and represent ideal substrates for follow-up intramolecular coupling reactions to create unique bicyclo[3.3.1] or -[3.2.2]nonane ring systems which are important natural product skeletons.

scholarly journals Convenient Synthesis of Functionalized Unsymmetrical Vinyl Disulfides and Their Inverse Electron-Demand Hetero-Diels-Alder Reaction

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1342
Author(s):  
Bartosz Jędrzejewski ◽  
Mateusz Musiejuk ◽  
Justyna Doroszuk ◽  
Dariusz Witt
Keyword(s):  
Functional Groups ◽  
Alder Reaction ◽  
Diels Alder ◽  
Inverse Electron Demand ◽  
Mild Conditions ◽  
Diels Alder Reaction ◽  
Convenient Synthesis ◽  
High Yields ◽  
Electron Demand

The simple, convenient, and efficient methods for the preparation of unsymmetrical vinyl disulfides with additional functional groups under mild conditions with moderate to high yields were designed. The developed methods include the reaction of S-vinyl phosphorodithioate with thiotosylates or S-vinyl thiotosylate with thiols. The designed methods allow for the synthesis of unsymmetrical vinyl disulfides with additional functionalities such as hydroxy, carboxy, protected amino, or ester groups. Vinyl disulfides reacted with the generated transient o-iminothioquinones in an inverse electron-demand [4+2] cycloaddition to produce benzo[b][1,4]thiazine derivatives.

Masked Bisketenes as Diels–Alder Dienes

2020 ◽  
Author(s):  
Isuru Dissanayake ◽  
Jacob Hart ◽  
Emma Becroft ◽  
Christopher Sumby ◽  
Christopher Newton
Keyword(s):  
Natural Product ◽  
Ring Opening ◽  
Alder Reaction ◽  
Diels Alder ◽  
Natural Product Synthesis ◽  
One Pot ◽  
Neuroprotective Agent ◽  
Mild Conditions ◽  
Diels Alder Reaction

<div> <div> <div> <p>2,5-Bis(<i>tert</i>-butyldimethylsilyloxy)furans are established as masked vicinal bisketenes for application as dienes in the Diels–Alder reaction. Cycloaddition with olefinic dienophiles, under exceptionally mild conditions, enables convergent access to highly substituted <i>para</i>-hydroquinones in unprotected form via a one-pot Diels–Alder/ring-opening/tautomerization sequence. The synthesis of <i>para</i>-benzoquinones from acetylenic dienophiles, including benzynes, is also demonstrated, and 2,5-bis(<i>tert</i>-butyldimethylsilyloxy)pyrroles are established as competent dienes for the synthesis of <i>para</i>-iminoquinones. Application in natural product synthesis enables gram-scale access to the neuroprotective agent (±)-indanostatin. </p> </div> </div> </div>

Bisketene Equivalents as Diels–Alder Dienes

2020 ◽  
Author(s):  
Isuru Dissanayake ◽  
Jacob Hart ◽  
Emma Becroft ◽  
Christopher Sumby ◽  
Christopher Newton
Keyword(s):  
Natural Product ◽  
Ring Opening ◽  
Alder Reaction ◽  
Diels Alder ◽  
Natural Product Synthesis ◽  
One Pot ◽  
Neuroprotective Agent ◽  
Mild Conditions ◽  
Diels Alder Reaction

<div> <div> <div> <p>2,5-Bis(<i>tert</i>-butyldimethylsilyloxy)furans are established as vicinal bisketene equivalents for application as dienes in the Diels–Alder reaction. Cycloaddition with olefinic dienophiles, under exceptionally mild conditions, enables convergent access to highly substituted <i>para</i>-hydroquinones in unprotected form via a one-pot Diels–Alder/ring-opening/tautomerization sequence. The synthesis of <i>para</i>-benzoquinones from acetylenic dienophiles, including benzynes, is also demonstrated, and 2,5-bis(<i>tert</i>-butyldimethylsilyloxy)pyrroles are established as competent dienes for the synthesis of <i>para</i>-iminoquinones. Application in natural product synthesis enables gram-scale access to the neuroprotective agent (±)-indanostatin.</p> </div> </div> </div>

Synthese neuer Pyridin-C-nukleoside der 2 ,3 -Didesoxyribose durch „inverse“ [4+2]-Cycloaddition Synthesis of Novel Pyridine-C-nucleosides of 2,3-Dideoxyribose by „Inverse“ [4+2]-Cycloaddition

1997 ◽  
Vol 52 (7) ◽  
pp. 851-858 ◽  
Author(s):  
Gunther Seitz ◽  
Johanna Siegl
Keyword(s):  
Cycloaddition Reaction ◽  
Alder Reaction ◽  
Diels Alder ◽  
The Novel ◽  
Protecting Group ◽  
Enol Ethers ◽  
Inverse Electron Demand ◽  
Diels Alder Reaction ◽  
Cyclic Ketene Acetals

The anomeric imido esters 5 and 6, appropriate precursors for C-nucleoside synthesis, were prepared and utilized as heterodienophiles in a Diels-Alder reaction with inverse electron demand to yield the novel, protected 1.2.4-triazine C-nucleosides 8 and 9. They could be deprotected by treatment with 70% trifluoroacetic acid to furnish the free C-nucleosides 10 and 11. The triazine „aglycon“ of 8 contains an electron deficient diazadiene system, highly activated to react with various electron rich dienophiles such as enamines, enol ethers and several cyclic ketene acetals in an „inverse“ [4+2]-cycloaddition reaction. The Diels-Alder adducts spontaneously eliminate N2 and after follow-up reactions the O-TBDPS protected pyridine-C-nucleosides 13, 15, 17,19, 21 and 23 are formed. Removal of the protecting group by treatment with CF3CO2H /H2O leads to the corresponding 2’,3’-dideoxy-β-D-ribofuranosyl- pyridines.

scholarly journals Studies on the transannular Diels–Alder reaction of 15-membered macrocyclic trienes containing a trans-trans diene. Part I: Synthesis and isomerization of various model cyclopentadecatrienes

1995 ◽  
Vol 73 (10) ◽  
pp. 1675-1694 ◽  
Author(s):  
Dennis G. Hall ◽  
Renate Müller ◽  
Pierre Deslongchamps
Keyword(s):  
Aqueous Media ◽  
Alder Reaction ◽  
Membered Ring ◽  
Diels Alder ◽  
Coupling Reactions ◽  
Diels Alder Reaction ◽  
Trans Diene

The transannular Diels–Alder reaction of 15-membered macrocyclic trienes with a trans-trans-cis (TTC) olefin geometry can lead to A.B.C.[6.6.7] tricyclic products of trans-syn-trans (TST) and cis-syn-cis (CSC) stereochemistry whereas the TTT isomers can produce the trans-anti-cis (TAC) and cis-anti-trans (CAT) tricycles. In order to study the influence of the position (pro-6.6 or pro-6.7) and the nature (alkyl, alkoxymethyl, or formyl) of the dienophile substituent, a set of 10 model cyclopentadecatrienes was prepared. The synthesis of appropriately functionalized trisubstituted dienophile and diene synthons, as well as their coupling reactions affording acyclic precursors, is described in this paper (first in a series of two). A mild and efficient macrocyclization protocol yielded the required methyl- or alkoxymethyl-substituted cyclic substrates. Further transformations led to the formyl-substituted ones. In particular, the TTT macrocycles containing an enal as a dienophile could be completely isomerized to the corresponding TTC thermodynamic isomers in acidic aqueous media. Keywords: transannular, Diels–Alder, 15-membered ring, A.B.C.[6.6.7] tricycles, diterpene.

Asymmetric Synthesis of 3,3′-Piperidinoyl Spirooxindoles and Discovery of Stereospecific Cycloadducts as Novel Hedgehog Pathway Modulators

Synthesis ◽  
2020 ◽  
Vol 52 (21) ◽  
pp. 3140-3152
Author(s):  
Kamal Kumar ◽  
Mohammad Rehan ◽  
Jana Flegel ◽  
Franziska Heitkamp ◽  
Jorgelina L. Pergomet ◽  
...  
Keyword(s):  
Transition Metal ◽  
Small Molecules ◽  
Asymmetric Synthesis ◽  
Natural Product ◽  
Transition Metal Complexes ◽  
Alder Reaction ◽  
Diels Alder ◽  
Hedgehog Pathway ◽  
Diels Alder Reaction ◽  
Efficient Access

An enantioselective hetero-Diels–Alder reaction of alkylidene­ oxindoles and 2-aza-3-silyloxy-1,3-butadienes, catalyzed by divalent transition metal complexes with N,N′-dioxide ligands offered an efficient access to natural-product-based 3,3′-piperidinoyl spiroox­indole class of small molecules. exo-Cycloadducts formed via stereospecific cycloaddition with Z-olefin displayed potent activity in modulation of hedgehog pathway.

Synthesis and Application of Tetrafluoroethylene (CF2CF2)-Containing Acetylene Derivatives

Synthesis ◽  
2020 ◽  
Vol 52 (13) ◽  
pp. 1947-1958
Author(s):  
Tsutomu Konno ◽  
Gen Egashira ◽  
Chihiro Kajimoto ◽  
Takuto Kataoka ◽  
Shigeyuki Yamada
Keyword(s):  
Coupling Reaction ◽  
Cross Coupling ◽  
Alder Reaction ◽  
Diels Alder ◽  
Benzene Derivatives ◽  
Diels Alder Reaction ◽  
Cross Coupling Reaction ◽  
Oxidative Aromatization ◽  
High Yields ◽  
Acetylene Derivatives

On treating 1,3,4-tribromo-1,1,2,2-tetrafluorobutane, readily prepared from commercially available 4-bromo-3,3,4,4-tetrafluorobut-1-ene, with 3.3 equivalents of LHMDS at 0 °C in THF, the corresponding lithium acetylide could be prepared quantitatively. The acetylide reacted well with various aldehydes, ketones, or chlorosilanes to give the corresponding acetylene derivatives in high yields. It was also found that various iodoarenes could participate in the cross-coupling reaction with the zinc acetylide, readily prepared from the lithium acetylide and ZnCl2·TMEDA complex, in the presence of Pd(PPh3)4 to bring about the adducts in high yields. Thus-obtained acetylene derivatives underwent smooth Diels–Alder reaction with various 1,3-dienes to afford the corresponding 1,4- or 1,3-cyclohexadiene derivatives. In addition, it was revealed that the oxidative aromatization of the resulting cyclohexadiene derivatives with DDQ took place very smoothly, providing the multi-substituted benzene derivatives having a tetrafluoro­ethylene group.

scholarly journals The Total Synthesis of (–)-Scabrolide a

2020 ◽  
Author(s):  
Nicholas Hafeman ◽  
Steven A. Loskot ◽  
Chris Reimann ◽  
Beau P. Pritchett ◽  
Scott C. Virgil ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Natural Product ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

The first total synthesis of the norcembranoid diterpenoid scabrolide A is disclosed. The route begins with the synthesis of two chiral pool-derived fragments, which undergo a convergent coupling to expediently introduce all 19 carbon atoms of the natural product. An intramolecular Diels–Alder reaction and an enone-olefin cycloaddition/fragmentation sequence are then employed to construct the fused [5–6–7] linear carbocyclic core of the molecule and to complete the total synthesis.

Copper(i)/TF-BiphamPhos catalyzed asymmetric nitroso Diels–Alder reaction

2017 ◽  
Vol 53 (10) ◽  
pp. 1657-1659 ◽  
Author(s):  
Jun Li ◽  
Hai-Yan Tao ◽  
Chun-Jiang Wang
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Highly Efficient ◽  
Diels Alder Reaction ◽  
Cyclic Dienes ◽  
High Yields

A highly efficient enantioselective nitroso Diels–Alder reaction of 6-methyl-2-nitroso pyridine with various 1,3-dienes was successfully developed using a copper(i)/(S)–TF-BiphamPhos complex as the catalyst. For most of the cyclic dienes, the cycloadducts were obtained in high yields with excellent regio-, and stereoselectivities. Acyclic 2-silyloxy-1,3-diene also worked well in the reaction.

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