Illustrating the Utility of X-ray Crystallography for Structure Elucidation through a Tandem Aldol Condensation/Diels–Alder Reaction Sequence

2015 ◽  
Vol 92 (8) ◽  
pp. 1381-1384 ◽  
Author(s):  
Giang T. Hoang ◽  
Tomohiro Kubo ◽  
Victor G. Young ◽  
Jacob A. Kautzky ◽  
Jane E. Wissinger
Keyword(s):  
Structure Elucidation ◽  
Aldol Condensation ◽  
Alder Reaction ◽  
Diels Alder ◽  
Reaction Sequence ◽  
X Ray ◽  
X Ray Crystallography ◽  
Diels Alder Reaction

Syntheses of Angucyclinones Related to Ochromycinone. III. An 11-Hydroxy Isomer and Some Reduced Analogues

1999 ◽  
Vol 52 (2) ◽  
pp. 129 ◽  
Author(s):  
Tomas Rozek ◽  
Tomas Rozek ◽  
Dennis K. Taylor ◽  
Dennis K. Taylor ◽  
Edward R. T. Tiekink ◽  
...  
Keyword(s):  
Hydroxy Group ◽  
Alder Reaction ◽  
Diels Alder ◽  
X Ray ◽  
X Ray Crystallography ◽  
Diels Alder Reaction ◽  
Stereo Selectivity ◽  
Hydrolysis Of ◽  
Alder Adduct

The boron triacetate assisted Diels Alder reaction between racemic 5,5-dimethyl-3-vinylcyclohex- 2-enyl acetate and 5-hydroxynaphthoquinone yields the racemic 11-hydroxy-3,3-dimethyl-7,12-dioxo- 1,2,3,4,6,6a,7,12,12a,12b-decahydrobenzo[a]anthracen-1-yl acetate as the sole stereoisomer by regio- and stereo-selective cis endo addition. Aromatization of the Diels Alder adduct followed by hydrolysis of the acetate and oxidation of the resultant 1-hydroxy group gives the target angucyclinone, 11-hydroxy-3,3-dimethyl-1,2,3,4,7,12-hexahydrobenzo[a]anthracene-1,7,12-trione, in an overall yield of 37% from 5-hydroxynaphthoquinone. The regio- and stereo-selectivity of the Diels Alder addition is confirmed by a combination of 13C n.m.r. spectroscopy and X-ray crystallography.

scholarly journals Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome

2014 ◽  
Vol 10 ◽  
pp. 848-857 ◽  
Author(s):  
Amitabh Jha ◽  
Ting-Yi Chou ◽  
Zainab ALJaroudi ◽  
Bobby D Ellis ◽  
T Stanley Cameron
Keyword(s):  
Molecular Modelling ◽  
Alder Reaction ◽  
Diels Alder ◽  
Probable Mechanism ◽  
Steric Effects ◽  
X Ray ◽  
X Ray Crystallography ◽  
Diels Alder Reaction ◽  
Steric Hinderance ◽  
Mechanism Of The Reaction

The synthesis of 5-substituted 6,6a-dihydroisoindolo[2,1-a]quinolin-11(5H)-ones via [4 + 2] imino-Diels–Alder cyclization from N-aryl-3-hydroxyisoindolinones and N-vinyl lactams under Lewis acid-catalysed anhydrous conditions is reported. Reactions of N-(2-substituted-aryl)-3-hydroxyisoindolinones with N-vinylpyrrolidone under identical conditions resulted in the formation of 2-(2-substitued-aryl)-3-(2-(2-oxopyrrolidin-1-yl)vinyl)isoindolin-1-one analogues indicating steric hinderance as the cause of deviation. The probable mechanism of the reaction based on the results from X-ray crystallography and molecular modelling is discussed.

scholarly journals Synthesis of the [11]Cyclacene Framework by Repetitive Diels–Alder Cycloadditions

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 3047
Author(s):  
John B. Bauer ◽  
Fatima Diab ◽  
Cäcilia Maichle-Mössmer ◽  
Hartmut Schubert ◽  
Holger F. Bettinger
Keyword(s):  
Building Block ◽  
Building Blocks ◽  
Alder Reaction ◽  
Diels Alder ◽  
X Ray ◽  
X Ray Crystallography ◽  
Diels Alder Reaction ◽  
Synthetic Intermediate

The Diels–Alder cycloaddition between bisdienes and bisdienophile incorporating the 7-oxa-bicyclo[2.2.1]heptane unit are well known to show high diastereoselectivity that can be exploited for the synthesis of molecular belts. The related bisdiene 5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octene is a valuable building block for the synthesis of photoprecursors for acenes, but it has not been employed for the synthesis of molecular belts. The present work investigates by computational means the Diels–Alder reaction between these bisdiene building blocks with syn-1,4,5,8-tetrahydro-1,4:5,8-diepoxyanthracene, which shows that the diastereoselectivity of the Diels–Alder reaction of the etheno-bridged bisdiene is lower than that of the epoxy-bridged bisdiene. The reaction of the etheno-bridged bisdiene and syn-1,4,5,8-tetrahydro-1,4:5,8-diepoxyanthracene in 2:1 ratio yields two diastereomers that differ in the orientation of the oxa and etheno bridges based on NMR and X-ray crystallography. The all-syn diastereomer can be transformed into a molecular belt by inter- and intramolecular Diels–Alder reactions with a bifunctional building block. The molecular belt could function as a synthetic intermediate en route to a [11]cyclacene photoprecursor.

The synthesis of homoisotwistanes by the tandem wessely oxidation - diels-alder reaction sequence

1991 ◽  
Vol 32 (35) ◽  
pp. 4439-4442 ◽  
Author(s):  
N.K. Bhamare ◽  
Thierry Granger ◽  
C.R. John ◽  
Peter Yates
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Reaction Sequence ◽  
Diels Alder Reaction

scholarly journals Two-Carbon Ring Enlargement of Five-, Six-, and Seven-Membered 1-Aza-2-vinylcycloalk-2-enes with Dimethyl Acetylenedicarboxylate and Subsequent Thermal Isomerization Reactions

2006 ◽  
Vol 61 (4) ◽  
pp. 385-395 ◽  
Author(s):  
Gerhard Maas ◽  
Robert Reinhard ◽  
Hans-Georg Herz
Keyword(s):  
Elevated Temperatures ◽  
Alder Reaction ◽  
Thermal Isomerization ◽  
Diels Alder ◽  
Dimethyl Acetylenedicarboxylate ◽  
X Ray ◽  
Ring Enlargement ◽  
Diels Alder Reaction ◽  
Carbon Ring ◽  
Electrocyclic Reaction

2-Aminodienes, in which the enamine function is incorporated in a five-, six-, or seven-membered ring, react with dimethyl acetylenedicarboxylate in a sequence of [2+2] cycloaddition and electrocyclic ring-opening to form the two-carbon ring expanded unsaturated heterocycles, i.e., 3,4- dicarboxylate substituted 6,7-dihydro-1H-azepines 3, 8 and 21, 1,6,7,8-tetrahydroazocines 22, and 6,7,8,9-tetrahydro-1H-azonines 13. Similarly, 2-[(2-thienyl)ethynyl]-4,5,6,7-tetrahydro-1H-azepine 9 is converted into 2-[(2-thienyl)ethynyl]-6,7,8,9-1H-azonine-3,4-dicarboxylate 10 which was characterized by X-ray structure determination. The eight- and nine-membered azaheterocycles 22 and 13, which have not been isolated, undergo thermal isomerization at elevated temperatures. Thus, ring contraction by a 6π-electrocyclic reaction takes place for N-methyl substituted azonine 13, while the N-allyl moiety of azocines 22 engages in an intramolecular Diels-Alder reaction or a 1,7- electrocyclization reaction

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