Electrophilic cleavage of cyclopropanes. II. Concerning the effect of increasing electron demand upon the product-determining transition state in the reaction of 4-substituted-2-nitrobenzenesulphenyl chlorides and benzenesulphenyl chlorides with tetracyclo[3.2.0.02,7.04,6]heptane (quadricyclene)

1980 ◽  
Vol 58 (10) ◽  
pp. 1014-1020 ◽  
Author(s):  
Pierre L. Beaulieu ◽  
Ann Kabo ◽  
Dennis G. Garratt
Keyword(s):  
Transition State ◽  
Nitro Group ◽  
Phenyl Ring ◽  
Relative Proportion ◽  
Electron Demand

The effect of increasing electron demand upon the product-determining transition state in the reaction of arenesulphenyl chlorides with tetracyclo[3.2.0.02,7.04,6]heptane has been investigated. As the electron donating ability of the remote substituents on the phenyl ring of the sulphenyl chloride is varied from nitro to methoxy the relative proportion of adducts derived from edge-on attack is found to increase relative to that of adducts derived from corner attack. An ortho-nitro group was found to lead to a stabilizing interaction only in the case of 2,4-dinitrobenzenesulphenyl chloride. A mechanism involving the competition between the two conceptual modes of approach is suggested.

scholarly journals Crystal structure of (3E)-3-(2,4-dinitrophenoxymethyl)-4-phenylbut-3-en-2-one

2014 ◽  
Vol 70 (9) ◽  
pp. o1051-o1052 ◽  
Author(s):  
Ignez Caracelli ◽  
Stella H. Maganhi ◽  
Paulo J. S. Moran ◽  
Bruno R. S. de Paula ◽  
Felix N. Delling ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Nitro Group ◽  
Benzene Ring ◽  
Torsion Angle ◽  
Title Compound ◽  
Phenyl Ring ◽  
Aromatic Rings ◽  
Compound C ◽  
The One

In the title compound, C17H14N2O6, the conformation about the C=C double bond [1.345 (2) Å] isE, with the ketone moiety almost coplanar [C—C—C—C torsion angle = 9.5 (2)°] along with the phenyl ring [C—C—C—C = 5.9 (2)°]. The aromatic rings are almost perpendicular to each other [dihedral angle = 86.66 (7)°]. The 4-nitro moiety is approximately coplanar with the benzene ring to which it is attached [O—N—C—C = 4.2 (2)°], whereas the one in theorthoposition is twisted [O—N—C—C = 138.28 (13)°]. The molecules associateviaC—H...O interactions, involving both O atoms from the 2-nitro group, to form a helical supramolecular chain along [010]. Nitro–nitro N...O interactions [2.8461 (19) Å] connect the chains into layers that stack along [001].

Reaction mechanism studies. 5. The mechanism of the diaxial → diequatorial rearrangement of β-chlorothioethers

1968 ◽  
Vol 46 (1) ◽  
pp. 9-13 ◽  
Author(s):  
J. F. King ◽  
K. Abikar
Keyword(s):  
Reaction Mechanism ◽  
Transition State ◽  
Nitro Group ◽  
Ion Pair ◽  
Concerted Mechanism

p-Methoxy- and p-nitro substituted analogues (1b and 1c) of the diaxial β-chlorothioether 2β-chloro-3α-(phenylthio)-5α-cholestane (1a), have been prepared and found to undergo the diaxial → diequatorial rearrangement. The rates of rearrangement of these compounds show the sequence p-methoxy > H > p-nitro. It is concluded that the transition state for the rearrangement is polarized in the sense of a sulfonium chloride (3). The rearrangement of 1a is 1600 times faster in butanol than in decalin (at 110°). There is thus no inherent insensitivity to solvent change in a rearrangement in which there may be a "four-atom arrangement" in the transition state, a conclusion relevant to previous work on the diaxial → diequatorial rearrangement of 1,2-dibromides (1). It was further found that the nitro group slowed the rearrangement (at 110°) more in butanol than in decalin, an observation regarded as consistent with, but not requiring, the incursion of a merged ion-pair, cyclic concerted mechanism.

scholarly journals 7-Nitro-2-phenylimidazo[2,1-b][1,3]benzothiazole

2014 ◽  
Vol 70 (2) ◽  
pp. o143-o144 ◽  
Author(s):  
Alexander S. Bunev ◽  
Elena V. Sukhonosova ◽  
Vladimir E. Statsyuk ◽  
Gennady I. Ostapenko ◽  
Victor N. Khrustalev
Keyword(s):  
Nitro Group ◽  
Phenyl Ring ◽  
Three Dimensional ◽  
Interplanar Distance ◽  
Stacking Interactions ◽  
Π Stacking ◽  
The Mean ◽  
Title Molecule

In the title molecule, C15H9N3O2S, the central imidazo[2,1-b][1,3]benzothiazole heterotricyclic unit is essentially planar (r.m.s. deviation = 0.021 Å). The terminal phenyl ring and nitro group are twisted by 9.06 (1) and 11.02 (4)°, respectively, from the mean plane of the heterotricycle. In the crystal, molecules are linked by π–π stacking interactions into columns along [100]; the interplanar distance between neighboring imidazo[2,1-b][1,3]benzothiazole planes within the columns is 3.370 (2) Å. Furthermore, the columns interact with each other by secondary S...O [2.9922 (10) and 3.1988 (11) Å] interactions, forming a three-dimensional framework.

Concise Total Syntheses of Paullone and Kenpaullone via Cyanide-Catalyzed Intramolecular Imino-Stetter Reaction

Synthesis ◽  
2017 ◽  
Vol 49 (18) ◽  
pp. 4247-4253 ◽  
Author(s):  
Cheol-Hong Cheon ◽  
Sang Lee ◽  
Seong Lee
Keyword(s):  
Nitro Group ◽  
Phenyl Ring ◽  
Amino Group ◽  
Subsequent Reduction ◽  
Stetter Reaction ◽  
Total Syntheses ◽  
Target Molecules ◽  
Acidic Conditions ◽  
Direct Use ◽  
Indole 3 Acetic Acid

Highly concise total syntheses of paullone and kenpaullone were developed. Cyanide-catalyzed intramolecular imino-Stetter reaction of aldimines derived from methyl 2-aminocinnamate derivatives and 2-nitrobenzaldehyde provided 2-(2′-nitrophenyl)indole-3-acetic acid derivatives. Subsequent reduction of the nitro group with zinc under acidic conditions to an amino group followed by spontaneous lactam formation allowed for the total syntheses of paullone and kenpaullone to be completed in two steps starting from commercially available materials. The direct use of a nitro group as the precursor of an amino group present in the phenyl ring at the 2-position in the indole ring significantly streamlined the total syntheses of these target molecules.

scholarly journals Anchimeric Assistance in Hydrogen-Atom Transfer to Bromine

2004 ◽  
Vol 57 (7) ◽  
pp. 651 ◽  
Author(s):  
Anna K. Croft ◽  
Christopher J. Easton
Keyword(s):  
Free Radical ◽  
Hydrogen Atom ◽  
Transition State ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Rate Enhancement ◽  
Anchimeric Assistance ◽  
Electron Donation ◽  
Electron Demand

The free-radical benzylic brominations of series of phenylalanine derivatives and O-phenylalkyl benzoates and N-phenylalkylamides with N-bromosuccinimide exhibit anchimeric assistance by neighbouring ester and amido groups. Rate enhancement occurs through electron donation to the electropositive carbon centre that develops in the transition state of the hydrogen-atom transfer to bromine. The extent of the effect depends on the electron demand at the benzylic position and the electron-donating ability of the neighbouring group.

Studies on the rearrangement of ortho-nitrobenzylidenemalonates and their Analogues to 2-aminobenzoate derivatives

2002 ◽  
Vol 80 (2) ◽  
pp. 192-199 ◽  
Author(s):  
Elzbieta Lewandowska ◽  
Stefan Kinastowski ◽  
Stanislaw F Wnuk
Keyword(s):  
Double Bond ◽  
Nitro Group ◽  
Phenyl Ring ◽  
Nitro Compounds ◽  
Trifluoromethyl Group ◽  
Reverse Polarity ◽  
Michael Reactions ◽  
Carbon Double Bond ◽  
Oxidative Rearrangement ◽  
Aromatic Nitro

Reaction of the diethyl 2-nitro-4-(trifluoromethyl)benzylidenemalonate with diethylamine in alcohols resulted in the reduction of the nitro group and the oxidation of the vinylic carbon attached to the phenyl ring. Simultaneous migration of the malonic fragment gave the appropriate 2-amino-4-(trifluoromethyl)benzoate esters. The presence of at least two nitro groups, or one nitro group and trifluoromethyl group on the phenyl ring, attached to the α-carbon and strongly electron withdrawing substituents at the β-carbon (CO2Et, CN) in ortho-nitrobenzylidene systems is necessary for this reductive–oxidative rearrangement to proceed. Reaction of nitrocinnamates with thiols in the presence of triethylamine in tetrahydrofuran gave Michael addition products with different regioselectivity of addition. Ethyl 2-nitrocinnamate undergoes standard β-addition of thiols to a carbon–carbon double bond. However, 2,4-dinitro- and 2,4,6-trinitrocinnamates undergo α-addition of thiols, indicating that the presence of two nitro groups on the phenyl ring can reverse polarity of the carbon–carbon double bond in cinnamate acceptors.Key words: abnormal Michael reactions, aromatic nitro compounds, benzylidene compounds, rearrangements.

scholarly journals Binding energy and specificity in the catalytic mechanism of yeast aldose reductases

1999 ◽  
Vol 344 (1) ◽  
pp. 101-107 ◽  
Author(s):  
Bernd NIDETZKY ◽  
Peter MAYR ◽  
Philipp HADWIGER ◽  
Arnold E. STüTZ
Keyword(s):  
Hydrogen Bonding ◽  
Transition State ◽  
Catalytic Mechanism ◽  
Relative Proportion ◽  
Binding Constants ◽  
Stabilization Energy ◽  
Binary Complex ◽  
Hydrogen Bonding Interactions ◽  
Transition State Stabilization ◽  
Hydroxy Groups

Derivatives of D-xylose and D-glucose, in which the hydroxy groups at C-5, and C-5 and C-6 were replaced by fluorine, hydrogen and azide, were synthesized and used as substrates of the NAD(P)H-dependent aldehyde reduction catalysed by aldose reductases isolated from the yeasts Candida tenuis, C. intermedia and Cryptococcus flavus. Steady-state kinetic analysis showed that, in comparison with the parent aldoses, the derivatives were reduced with up to 3000-fold increased catalytic efficiencies (kcat/Km), reflecting apparent substrate binding constants (Km) decreased to as little as 1/250 and, for D-glucose derivatives, up to 5.5-fold increased maximum initial rates (kcat). The effects on Km mirror the relative proportion of free aldehyde that is available in aqueous solution for binding to the binary complex enzyme-NAD(P)H. The effects on kcat reflect non-productive binding of the pyranose ring of sugars; this occurs preferentially with the NADPH-dependent enzymes. No transition-state stabilization energy seems to be derived from hydrogen-bonding interactions between enzyme-NAD(P)H and positions C-5 and C-6 of the aldose. In contrast, unfavourable interactions with the C-6 group are used together with non-productive binding to bring about specificity (6-10 kJ/mol) in a series of D-aldoses and to prevent the reaction with poor substrates such as D-glucose. Azide introduced at C-5 or C-6 destabilizes the transition state of reduction of the corresponding hydrogen-substituted aldoses by approx. 4-9 kJ/mol. The total transition state stabilization energy derived from hydrogen bonds between hydroxy groups of the substrate and enzyme-NAD(P)H is similar for all yeast aldose reductases (yALRs), at approx. 12-17 kJ/mol. Three out of four yALRs manage on only hydrophobic enzyme-substrate interactions to achieve optimal kcat, whereas the NAD(P)H-dependent enzyme from C. intermedia requires additional, probably hydrogen-bonding, interactions with the substrate for efficient turnover.

Electrophilic additions to allenes. IV. Concerning the nature of the ortho-nitro group effect in the reaction of arenesulphenyl chlorides with allenes

1980 ◽  
Vol 58 (12) ◽  
pp. 1275-1279 ◽  
Author(s):  
Dennis G. Garratt ◽  
Pierre L. Beaulieu
Keyword(s):  
Transition State ◽  
Nitro Group ◽  
Methylene Chloride ◽  
Group Effect ◽  
Steric Interactions ◽  
Electrophilic Additions ◽  
Type Intermediate

The reactions of twelve arenesulphenyl chlorides, five of which contained an ortho-nitro substituent, with ten 1,3-disubstituted allenes, using methylene chloride as solvent, are described. No evidence for a special ortho-nitro group effect involving a spirosulphurane type intermediate is observed. Variations in the chemoselectivity and configurational-selectivity of the additions are interpreted in terms of steric interactions in the product determining transition state.

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