Synthesis of (±)-epiisopodophyllotoxin

1983 ◽  
Vol 61 (3) ◽  
pp. 573-575 ◽  
Author(s):  
Margaret B. Glinski ◽  
Tony Durst
Keyword(s):  
Title Compound ◽  
Dimethyl Fumarate ◽  
Dimethyl Acetal ◽  
Alder Reaction ◽  
Diels Alder ◽  
Carbon Skeleton ◽  
Diels Alder Reaction ◽  
Alder Adduct

The synthesis of (±)-epiisopodophyllotoxin commencing with 6-bromopiperonal dimethyl acetal is described. The carbon skeleton of isoepipodophyllotoxin was assembled via a Diels–Alder reaction between the hydroxyquinodimethane generated photochemically from 6-(3′,4′,5′-trimethoxybenzyl)-piperonal, obtained from the bromoacetal above, and dimethyl fumarate. This Diels–Alder adduct was converted in five steps into the title compound. The overall yield for the seven steps was 15%.

scholarly journals Crystal structures and conformations of two Diels–Alder adduct derivatives: 1,8-bis(thiophen-2-yl)-14-oxatetracyclo[6.5.1.02,7.09,13]tetradeca-2(7),3,5-trien-10-one and 1,8-diphenyl-14-oxatetracyclo[6.5.1.02,7.09,13] tetradeca-2,4,6-trien-10-one

2015 ◽  
Vol 71 (2) ◽  
pp. 213-216
Author(s):  
S. Gopinath ◽  
P. Narayanan ◽  
K. Sethusankar ◽  
Meganathan Nandakumar ◽  
Arasambattu K. Mohanakrishnan
Keyword(s):  
Crystal Packing ◽  
Rotation Axis ◽  
Alder Reaction ◽  
Ring System ◽  
Diels Alder ◽  
Compound I ◽  
Diels Alder Reaction ◽  
Phenyl Rings ◽  
Axis Parallel ◽  
Alder Adduct

The title compounds, C21H16O2S2(I) and C25H20O2(II), are products of a tandem `pincer' Diels–Alder reaction consisting of [2 + 2] cycloadditions between benzo[c]furan and cyclopentanone. Each comprises a fused tetracyclic ring system containing two five-membered rings (inenvelopeconformations with the O atom as the flap) and six-membered rings (inboatconformations). In addition, two thiophene rings in (I) and two phenyl rings in (II) are attached to the tetracyclic ring system. The cyclopentanone ring adopts atwistedconformation in (I) and anenvelopeconformation in (II). In (I), the thiophene rings are positionally disordered over two sets of sites, with occupancy ratios of 0.901 (2):0.099 (2) and 0.666 (2):0.334 (2). In (II), the oxygen atom of the cyclopentanone ring is rotationally disordered over two sites with an occupancy ratio of 0.579 (4):0.421 (4). The molecular structure of (I) is stabilized by an intramolecular C—H...O hydrogen bond, which generates anS(7) ring motif. In the crystal, the molecules are linkedviaweak C—H...O hydrogen bonds, which generateR22(16) ring motifs in (I) andC(8) chains in (II). In both structures, the crystal packing also features C—H...π interactions. The crystal studied of compound (I) was twinned by non-merohedry. The twin component is related by the twin law [−1 0 0 −0.101 1 −0.484 0 0 −1] operated by a twofold rotation axis parallel to thebaxis. The structure of (I) was refined with a twin scale factor of 0.275 (2).

scholarly journals Hetero Diels-Alder adduct formation between nitrosobenzene and tetra-methyl purpurogallin and its retro-Diels-Alder reaction

2001 ◽  
Vol 12 (4) ◽  
Author(s):  
Daniela Gamenara ◽  
Eduardo Días ◽  
Néstor Tancred ◽  
Horacio Heinzen ◽  
Patrick Moyna ◽  
...  
Keyword(s):  
Alder Reaction ◽  
Adduct Formation ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Alder Adduct

Diastereoselectivity and asymmetric induction in the Diels–Alder reaction of o-quinodimethanes

1986 ◽  
Vol 64 (4) ◽  
pp. 720-725 ◽  
Author(s):  
James L. Charlton
Keyword(s):  
Maleic Anhydride ◽  
Methyl Acrylate ◽  
Dimethyl Fumarate ◽  
Alder Reaction ◽  
Diels Alder ◽  
Asymmetric Induction ◽  
Diels Alder Reaction ◽  
The Absolute ◽  
Alkoxy Groups

The extent of asymmetric induction in the bimolecular Diels–Alder reactions of chiral o-quinodimethanes with dimethyl fumarate, methyl acrylate, and maleic anhydride has been studied. o-Quinodimethanes with chiral α-alkoxy groups were prepared from 1-alkoxy-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4a–f or 1-alkoxy-3-phenyl-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4g–h by thermolysis. These alkoxybenzosulfones were prepared from the corresponding hydroxybenzosulfones 8 and 1-phenylethanol, 2-phenyl-1-propanol, 4-phenyl-2-butanol, 1-phenyl-2-propanol, 3,3-dimethyl-2-butanol, or 1-cyclo-hexylethanol. The 1-phenylethoxy substituent yielded the largest asymmetric induction. The absolute configurations of the major cycloadducts of methyl acrylate with the o-quinodimethanes generated from 1-(R- 1-phenylethoxy)- and 1-(S-1-phenylethoxy)-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4i and 4j have been determined to be 1S,2S-1-(R-1-phenylethoxy)- and 1R,2R-1-(S-1-phenylethoxy)-2-carbomethoxy-1,2,3,4-tetrahydronaphthalene 11i and 11j, respectively. The proposition that a chiral alkoxy substituent can block one face of the o-quinodimethane towards addition of a dienophile is discussed.

Diels–Alder reaction of tetraarylcyclopentadienones with benzo[b]thiophene S,S-dioxides: an unprecedented de-oxygenation vs. sulfur dioxide extrusion

2020 ◽  
Vol 56 (97) ◽  
pp. 15317-15320
Author(s):  
Palani Manikandan ◽  
Jayachandran Karunakaran ◽  
Elumalai Varathan ◽  
Georg Schreckenbach ◽  
Arasambattu K Mohanakrishnan
Keyword(s):  
Sulfur Dioxide ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Alder Adduct

The Diels–Alder adduct, dihydrodibenzothiophene S,S-dioxides underwent aromatization either through de-oxygenation or extrusion of sulfur dioxide to furnish substituted dibenzothiophenes or benzenes.

C-Nucleosides and related compounds. VIII. Synthesis of 5-(4′β-hydroxymethyl-2′β,3′α-dihydroxycyclopent-1′β-yl)-6-azauracil

1976 ◽  
Vol 54 (18) ◽  
pp. 2925-2934 ◽  
Author(s):  
G. Just ◽  
R. Ouellet
Keyword(s):  
Double Bond ◽  
Title Compound ◽  
Sodium Methoxide ◽  
Alder Reaction ◽  
Oxidative Cleavage ◽  
Diels Alder ◽  
Keto Ester ◽  
Diels Alder Reaction ◽  
Related Compounds

Starting from the Diels–Alder reaction of trans-β-bromoacrylic acid with cyclopentadiene, a synthesis of the substituted bicycloheptene 8 is described. The stereochemistry of the substituents is clearly defined. Oxidative cleavage of the double bond in the compound 8c afforded an acid keto ester 10 that was treated with thiosemicarbazide. Treatment of the resulting thiosemicarbazone 11 with sodium methoxide gave a 3-thioxo-1,2,4-triazine-5-one compound that was converted into the title compound.

A reactive lactonic dienophile – 3-carbethoxy-5,5-dimethyl-2(5H)-furanone. Application to the synthesis of a monoterpenoid lactone

1982 ◽  
Vol 60 (7) ◽  
pp. 921-925 ◽  
Author(s):  
Hsing-Jang Liu ◽  
Eric N. C. Browne ◽  
Purushottam R. Pednekar
Keyword(s):  
Title Compound ◽  
Room Temperature ◽  
Alder Reaction ◽  
Diels Alder ◽  
Stannic Chloride ◽  
Lithium Iodide ◽  
Diels Alder Reaction ◽  
Reaction Region ◽  
Unsaturated Lactones

In contrast to the low dienophilicity generally observed for α,β-unsaturated lactones, the title compound 2 is shown to be a reactive dienophile. Under stannic chloride catalysis, it undergoes Diels–Alder reaction region- and stereoselectively with a variety of dienes at room temperature. The synthesis of (±)-o-mentha-1,3-dien-1→8-olide (20) has been achieved by a two-step sequence using lactone ester 2. Addition of 2 to 1-acetoxy-1,3-butadiene afforded epimeric acetoxy lactones 12 and 13 which were converted to the monoterpenoid lactone 20 by treatment with lithium iodide dihydrate in collidine.

Syntheses of Angucyclinones Related to Ochromycinone

1998 ◽  
Vol 51 (6) ◽  
pp. 515 ◽  
Author(s):  
Tomas Rozek ◽  
Wit Janowski ◽  
John M. Hevko ◽  
Edward R. T. Tiekink ◽  
Suresh Dua ◽  
...  
Keyword(s):  
Structural Study ◽  
Alder Reaction ◽  
Diels Alder ◽  
Dimethyl Acetylenedicarboxylate ◽  
X Ray ◽  
Diels Alder Reaction ◽  
Synthetic Approaches ◽  
Alder Adduct

Two synthetic approaches have been investigated for the syntheses of model angucyclinones related to ochromycinone. The first involves a Diels–Alder/Friedel–Crafts strategy in which the Diels–Alder adduct formed between dimethyl acetylenedicarboxylate and 3-ethenyl-5,5-dimethylcyclohex-2-en-1- one was converted into 6,6-dimethyl-8-oxo-5,6,7,8-tetrahydronaphthalene-1,2-dicarboxylic anhydride, which was then reacted with benzene in a Friedel–Crafts reaction. Acid-catalysed cyclization of the Friedel–Crafts products gave 3,3-dimethyl-3,4-dihydrobenz[a]anthracene-1,7,12(2H)-trione (3) in poor yield. Angucyclinones related to (3) are formed (in 40–50% overall yield) by aromatization of the adduct formed between the appropriate 1,4-naphthoquinone and 3-[(E)-2-methoxyethenyl]- 5,5-dimethylcyclohex-2-en-1-one (this dienone reacts with itself by a Diels–Alder process to yield an adduct which decomposes to 3,3,8,8-tetramethyl-3,4,7,8-tetrahydroanthracene-1,6(2H,5H)-dione). When the substituted 1,4-naphthoquinone is unsymmetrical, a boron triacetate assisted Diels–Alder reaction gives a single regioisomer (e.g. X-ray investigations indicate that 8-hydroxy-3,3-dimethyl-3,4-dihydrobenz[a]anthracene-1,7,12(2H)-trione is the product from 5-hydroxy-1,4-naphthoquinone). An X-ray structural study of the Diels–Alder adduct in the above reaction confirms the operation of an endo cyclization.

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