Cycloaddition Reactions of a Nitrogen-Substituted Oxyallyl Cation with Cyclopentadiene and Substituted Furans. Reaction Conditions, Diastereoselectivity, Regioselectivity, and Transition State Modeling

1996 ◽  
Vol 61 (4) ◽  
pp. 1478-1486 ◽  
Author(s):  
Michael A. Walters ◽  
Helene R. Arcand
Keyword(s):  
Transition State ◽  
Cycloaddition Reactions ◽  
Reaction Conditions ◽  
Substituted Furans ◽  
Oxyallyl Cation

Cycloaddition reactions. Addition of dimethyl acetylenedicarboxylate to 1-dimethylaminoindene

1970 ◽  
Vol 48 (11) ◽  
pp. 1633-1638 ◽  
Author(s):  
Terrence W. Doyle
Keyword(s):  
Ring Opening ◽  
Cycloaddition Reactions ◽  
Dimethyl Acetylenedicarboxylate ◽  
Reaction Conditions

The cycloaddition of 1-dimethylaminoindene (2) to dimethyl acetylenedicarboxylate to form a fused cyclobutene system 3 is discussed. Compound 3 underwent two modes of ring opening to yield either the indene–maleate system 4 or the benzocycloheptatriene system 5 depending on reaction conditions. The synthesis of a number of multifunctional benzotropones from 5 is discussed.

Gold-catalyzed generation of vinylthionium ions and the development of an organocatalytic, asymmetric (4+3)-cycloaddition reaction

2017 ◽  
Author(s):  
◽  
Michael Topinka
Keyword(s):  
Amino Alcohol ◽  
Good Yield ◽  
Lewis Acids ◽  
Cycloaddition Reaction ◽  
Unsaturated Ester ◽  
Cycloaddition Reactions ◽  
University Of Missouri ◽  
Considerable Problem ◽  
The University ◽  
Substituted Furans

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] An allylic benzoate ester was prepared and used as a progenitor of vinylthionium ions for (4+3)-cycloaddition reactions. The chemistry was limited to 2-substituted and 2,5-disubstituted furans. In the case of 2-substituted furans, only Friedel-Crafts alkylation products were procured. In the case of 2,5-disubstituted furans, (4+3)-cycloaddition products were furnished in good yield. A catalytic, asymmetric variant using 2,5-dialkylfurans and chiral acids to procure cycloaddition products was unsuccessful. There was an opportunity to overcome the Friedel-Crafts alkylation problem that arose in a gold-catalyzed cycloaddition project. A sulfur-substituted unsaturated ester and alcohol were prepared, but silyl migration was a considerable problem upon activation by various agents. The problem of silyl migration was circumvented, but the target aldehyde was unreactive toward dienes in the presence of various Lewis acids. In further pursuit of an asymmetric (4+3)-cycloaddition reaction, 2-substituted furans were reacted with 2-tosyloxycyclopentanone in the presence of K2HPO4/H2O in perfluorobenzene as solvent and 30 mol% of an amino alcohol catalyst developed by David MacMillan. Enantioselectivities were modest for 2-alkylfurans and excellent for 2-arylchalcogenofurans (90% ee). 3-Substituted furans also work in this process.

scholarly journals Enantioselective 1,3-Dipolar Cycloaddition Reaction of Nitrones with α-(Acyloxy)acroleins Catalyzed by Dipeptide-Derived Chiral Tri- or Diammonium Salts

Synlett ◽  
2019 ◽  
Vol 30 (15) ◽  
pp. 1835-1839 ◽  
Author(s):  
Chihiro Kidou ◽  
Haruki Mizoguchi ◽  
Tatsuo Nehira ◽  
Akira Sakakura
Keyword(s):  
Cycloaddition Reaction ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
Reaction Conditions

Organoammonium salts of dipeptide-derived chiral triamines or diamines with TfOH catalyzed the enantioselective 1,3-dipolar cycloaddition reactions of α-acyloxyacroleins with nitrones to give the corresponding adducts in good yields (up to 96%) and with high diastereo- and enantioselectivities (up to 89% ee). Although α-(p-methoxybenzoyloxy)acrolein is rather unstable under the reaction conditions, α-(3-pyrroline-1-carbonyloxy)acrolein is stable enough to be smoothly converted into the corresponding adducts with the aid of the chiral organoammonium salt catalysts.

scholarly journals Ultrasound-promoted organocatalytic enamine–azide [3 + 2] cycloaddition reactions for the synthesis of ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones

2017 ◽  
Vol 13 ◽  
pp. 694-702 ◽  
Author(s):  
Gabriel P Costa ◽  
Natália Seus ◽  
Juliano A Roehrs ◽  
Raquel G Jacob ◽  
Ricardo F Schumacher ◽  
...  
Keyword(s):  
Reaction Times ◽  
Cycloaddition Reactions ◽  
Reaction Conditions ◽  
Keto Esters ◽  
Efficient Access ◽  
High Yields ◽  
Short Times

The use of sonochemistry is described in the organocatalytic enamine–azide [3 + 2] cycloaddition between 1,3-diketones and aryl azidophenyl selenides. These sonochemically promoted reactions were found to be amenable to a range of 1,3-diketones or aryl azidophenyl selenides, providing an efficient access to new ((arylselanyl)phenyl-1H-1,2,3-triazol-4-yl)ketones in good to excellent yields and short reaction times. In addition, this protocol was extended to β-keto esters, β-keto amides and α-cyano ketones. Selanyltriazoyl carboxylates, carboxamides and carbonitriles were synthesized in high yields at short times of reaction under very mild reaction conditions.

Palladium-catalyzed one-pot cycloaddition reactions of thioureas with 3H-indol-3-ones generated in situ from 2-alkynyl arylazides: rapid and efficient access to imidazoloindolines

2020 ◽  
Vol 7 (21) ◽  
pp. 3480-3485
Author(s):  
Ping Li ◽  
Boyu Zhu ◽  
Yao Xu ◽  
Zhiqiang Zhou ◽  
Guiwen Hu ◽  
...  
Keyword(s):  
Cycloaddition Reactions ◽  
Reaction Conditions ◽  
One Pot ◽  
One Pot Synthesis ◽  
Efficient Access ◽  
Palladium Catalyzed

An efficient palladium-catalyzed one-pot synthesis of imidazoloindolines from 2-alkynyl arylazides under mild reaction conditions has been described.

REACTIONS OF SUGAR CHLOROSULFATES: VII. SOME CONFORMATIONAL ASPECTS

1966 ◽  
Vol 44 (13) ◽  
pp. 1483-1491 ◽  
Author(s):  
A. G. Cottrell ◽  
E. Buncel ◽  
J. K. N. Jones
Keyword(s):  
Transition State ◽  
Sulfuryl Chloride ◽  
Reaction Conditions ◽  
Steric Interactions

The reaction of sulfuryl chloride with several 1,6-anhydro-hexosans has yielded crystalline, fully chlorosulfated derivatives. Replacement of the chlorosulfate moieties by chlorodeoxy groups could not be achieved under the reaction conditions employed. This non-reactivity is discussed in terms of steric interactions in the transition state for substitution.An examination of some chloro-substituted sugar chlorosulfates confirmed that an axial chlorodeoxy group in a glycopyranoside deactivates a neighboring equatorial chlorosulfate group and thus prevents further chlorodeoxy groups being introduced into such positions. Methyl α-D-altropyranoside, methyl α-L-rhamnopyranoside, methyl α-D-lyxopyranoside, L-rhamnose, and D-lyxose were reacted with sulfuryl chloride. The resulting products were those expected if these sugars reacted primarily in the C1 conformation.

Effect of cyclodextrin on elimination reactions

1999 ◽  
Vol 77 (5-6) ◽  
pp. 860-867 ◽  
Author(s):  
Luis Viola ◽  
Rita H de Rossi
Keyword(s):  
Inclusion Complex ◽  
Transition State ◽  
Rate Constant ◽  
Reaction Rate ◽  
Basic Solution ◽  
Substitution Product ◽  
Reaction Conditions ◽  
Pure Solvent ◽  
Elimination Reactions

The reaction of 1-bromo-2-X-2-(Y-phenyl) ethane derivatives (1: X = Y = H; 2: X = Ph, Y = H; 3: X = H, Y = 4-Ac; 4: X = H, Y = 3-NO2; 5: X = H, Y = 4-NO2; 6: X = H, Y = 3-Me; 7: X = H, Y = 4-Me) in basic solution was studied, and in most cases, only the elimination product is formed. Only (2-bromo-1-phenylethyl)benzene, 2, yielded significant substitution product, and this yield decreased with the concentration of HO-. Addition of cyclodextrin (β-CD) diminished (about half for 0.02 M cyclodextrin concentration) the reaction rate of all substrates but 4 and 5. In the latter two cases, the rate rises. The observed rate-constant value at 0.5 M NaOH is 6.78 × 10-4 s-1 (at 40°C) and 1.80 × 10-3 s-1 (at 25°C) for 4 and 5, respectively. Under the same reaction conditions but with 0.01 M β-CD, the corresponding rates were 7.70 × 10-4 s-1 and 5.20 × 10-3 s-1. The elimination yield for 2 increased from 64 to 98% when the β-CD changed from zero to 0.02 M at 0.5 M NaHO. Also, there was an increase in the relative elimination products of 20-40% for compounds 6 and 7. The Hammet ρ values were 1.3 and 2.3 for the reaction in pure solvent and in the presence of β-cyclodextrin, indicating an increase in the negative character of the transition state for the reactions in the latter conditions. The results are interpreted in terms of the formation of an inclusion complex whose structure depends on the substrate.Key words: cyclodextrin, elimination reactions, inhibition, catalysis.

Synthesis of functionalized hexahydro-, octahydro-, and decahydro-1H-phenalenes via Diels–Alder reactions of 1-methylene-4a-methoxycarbonyl-1,2,3,4,4a,5,6,7-octahydronaphthalene and related dienes

1993 ◽  
Vol 71 (9) ◽  
pp. 1463-1483 ◽  
Author(s):  
Edward Piers ◽  
Richard W. Friesen ◽  
Paul Kao ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Maleic Anhydride ◽  
Transition State ◽  
Methyl Acrylate ◽  
Diels Alder ◽  
Cycloaddition Reactions ◽  
Methoxycarbonyl Group ◽  
The Face ◽  
Group Reaction ◽  
Bicyclic Dienes

The results of a study of Diels–Alder reactions of the bicyclic dienes 6–8 with a variety of dienophiles are reported. Although 6 and 7 undergo cycloaddition reactions smoothly and efficiently, thermal Diels–Alder reactions of 8 are generally sluggish or, under the conditions investigated, do not proceed at all. Additions of tetracyanoethylene (TCNE) to 6–8 are highly face-selective, with preferential attack of the dienophile on the side of the dienes opposite to the angular methoxycarbonyl group. Reaction of 7 with maleic anhydride (MAN) is completely face-selective and proceeds preferentially via an endo transition state. Diels–Alder reactions of 6 and 7 with methyl acrylate (MAC) and nitroethylene (NE) are entirely regioselective, but the face-selectivities, which vary from ~2:1 to ~3:1, are rather low. The use of this chemistry as a method for the synthesis of functionalized, stereochemically defined, perhydro-1H-phenalenes is demonstrated.

scholarly journals New insights into the mechanism of Schiff base synthesis from aromatic amines in the absence of acid catalyst or polar solvents

2019 ◽  
Author(s):  
Pedro J Silva
Keyword(s):  
Transition State ◽  
Aromatic Amines ◽  
Density Functional ◽  
Large Scale ◽  
Reaction Pathway ◽  
Acid Catalyst ◽  
Functional Study ◽  
Computational Studies ◽  
Reaction Conditions ◽  
Polar Solvents

Extensive computational studies of the imine synthesis from amines and aldehydes in water have shown that the large-scale structure of water is needed to afford appropriate charge delocalisation and enable sufficient transition state stabilisation. These insights cannot, however, be applied to the understanding of the reaction pathway in apolar solvents due their inability to form extensive hidrogen-bonding networks. In this work, we perform the first computational studies of this reaction in apolar conditions. This density-functional study of the reaction of benzaldehyde with four closely related aromatic amines (aniline, o-toluidine, m-toluidine and p-toluidine) shows that an additional molecule of amine may provide enough stabilization of the first transition state even in the absence of a hydrogen bonding network. Our computations also show that the second reaction step cannot take place unless an extra proton is added to the system but, crucially, that reaction rate is so high that even picomolar amounts of protonated base are enough to achieve realistic rates. Additional computations show that those minute amounts of protonated base may be obtained under reaction conditions without the addition of extraneous acid through the auto-protolysis of the amines themselves. To our knowledge, this is the first report of a role for the auto-protolysis of anilines in their extensive reactional repertoire.

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