The Sn mechanism in aromatic compounds. XXXVIII. Comparative reactivity of 1-Halogeno-2,6-dinitrobenzenes and some other halogenonitrobenzenes

1969 ◽  
Vol 22 (12) ◽  
pp. 2555 ◽  
Author(s):  
MEC Biffin ◽  
J Miller ◽  
R Roper
Keyword(s):  
Nitro Group ◽  
Aromatic Compounds ◽  
Steric Effects ◽  
Reference Standard ◽  
Group Mobility ◽  
Steric Interactions ◽  
Leaving Group ◽  
Typical Range ◽  
Comparative Reactivity

The reactivity of 1-halogeno-2,6-dinitrobenzenes with methanolic methoxide has been studied quantitatively and compared with the results of similar studies of o- and p-halogenonitrobenzenes and 1-halogeno- 2,4-dinitrobenzenes. Adverse steric interactions of the ortho-nitro group are very small in the o-halogenonitro- and 1-halogeno-2,4- dinitrobenzenes. The interactions are substantially larger in the reactions of 1-halogeno-2,6-dinitrobenzenes in displacement of Cl, Br, and I, but not of F, but they are small compared to steric interactions found in many other classes of reactions. ��� Steric effects are observed as a reduction in rates affecting values of the Substituent Rate Factors of the o-nitro group, and affecting also the mobility as a leaving group of Cl, Br, and I, but not of F. However, since Cl is the usual reference standard for leaving group mobility, that of F appears as having an unusually high value. Nevertheless a depression of the mobility of iodine from its typical range is also evident.

Zum stoffwechsel von aromaten, II. über die muconsäurespaltung von einfachen o-diphenolen / on the metabolism of aromatic compounds, ii * the muconic acid scission of simple o-diphenols

1973 ◽  
Vol 28 (11-12) ◽  
pp. 662-674 ◽  
Author(s):  
Günther Schulz ◽  
Erich Hecker
Keyword(s):  
Acetic Acid ◽  
Sulfuric Acid ◽  
Ethyl Acetate ◽  
Peracetic Acid ◽  
Aromatic Compounds ◽  
Time Course ◽  
Protocatechuic Acid ◽  
Uv Light ◽  
Steric Effects ◽  
Muconic Acid

Abstract The preparation of substituted cis,cis-muconic acids by oxidative ring scission of simple o-di-phenols with peracetic acid is investigated. Scission of pyrocatechol (1) to cis,cis-muconic acid (2) gives optimal yields, if acetic acid or ethyl acetate is used as solvent and if the solution is 15-20% with respect to sulfuric acid free peracetic acid comprising a one molar excess of oxidant. Under similar conditions, 3-tosylamino-pyrocatechol yields with peracetic acid the hitherto unknown α-tosylamino-cis,cis-muconic caid (18). 18 may be converted to α-tosylamino-traras,trans-muconic acid (19) by means of iodine, UV light or heating. From protocatechuic acid (4) under similar conditions not β-carboxy-cis,cis-muconic acid (5) is obtained, but rather β-carboxy-mucono-lactone (6 b, γ-carboxymethyl-β-carboxy-Δα-butenolide). As yet, this lactone has been accessible only from an isomer of β-carboxy-cis,cis-muconic acid, the latter being obtainable by enzymatic scission of protocatechuic acid (4). Steric effects are responsible for both, the formation of the free cis,cis-muconic acids 2 and 18 from pyrocatechol (1) and α-tosylamino-pyrocatechol, and the formation of the γ-lactone 6 b instead of β -carboxy-cis,cis-muconic acid by scission of protocatechuic acid (4). The time course of the reactions shows that - compared to pyrocatechol (1) - a 3-tosylamino-group enhances the peracetic acid scission, whereas a 4-carboxygroup as in 4 slows it down

Steric Effects of the Nitro Group on the Uncatalyzed Halogenation of Methylbenzenes

1964 ◽  
Vol 86 (13) ◽  
pp. 2677-2680 ◽  
Author(s):  
Enrico. Baciocchi ◽  
Gabriello. Illuminati
Keyword(s):  
Nitro Group ◽  
Steric Effects

Addition Reactions in the Nitration of Some Polycyclic Aromatic Compounds

1972 ◽  
Vol 50 (20) ◽  
pp. 3367-3372 ◽  
Author(s):  
A. Fischer ◽  
D. R. A. Leonard
Keyword(s):  
Nitric Acid ◽  
Acetic Anhydride ◽  
Nitro Group ◽  
Aromatic Compounds ◽  
Addition Reaction ◽  
Polycyclic Aromatic Compounds ◽  
Addition Reactions ◽  
Polycyclic Aromatic ◽  
Acetyl Nitrate

Reaction of 3-oxo-1,2,3,7,8,9,10,10a-octahydrocyclohepta[de]naphthalene with nitric acid in acetic anhydride gives two stereoisomeric 4-acetoxy-6a-nitro-3-oxo-1,2,3,4,6a,7,8,9,10,10a-decahydrocyclohepta[de]-naphthalenes as well as the expected nitro substitution products. Formation of these adducts from a substrate containing a meta-directing deactivating substituent shows that the 1,4-addition reaction of acetyl nitrate is more general than previously suspected. 1,4-Acetyl nitrate adducts are also formed from tetralin, benzsuberane, 5,6,7,8-tetrahydrocyclohepta[fg]acenaphthene, and 1,2,3,4,7,8,9,10-octahydrodicyclohepta[de,ij]naphthalene. Decomposition of the last two adducts gives in each case a product with the nitro group substituted into the alicyclic ring.

Substitution of Bridgehead Halogens by a Free-Radical Electron-Transfer Mechanism

1996 ◽  
Vol 49 (5) ◽  
pp. 581 ◽  
Author(s):  
MC Harsanyi ◽  
PA Lay ◽  
RK Norris ◽  
PK Witting
Keyword(s):  
Electron Transfer ◽  
Nitro Group ◽  
Intramolecular Electron Transfer ◽  
Substitution Reactions ◽  
Radical Chain ◽  
Electron Transfer Mechanism ◽  
Regioselective Substitution ◽  
Leaving Group ◽  
Aromatic Nitro ◽  
Bridgehead Position

The reactions of 1-bromo-7-nitro- and 1-bromo-6-nitro-1,4-methanonaphthalene (2) and (3), and 9-bromo-2-nitro, 10-bromo-2-nitro-, 9,10-dibromo-2-nitro- and 9,10-diiodo-2-nitro-9,10-ethano-9,10-dihydroanthracene (4)-(7). respectively, with the sodium salt (1) of p-toluenethiol gave substitution products that were shown to be formed by an SRN1 or a related radical chain mechanism. In the relatively slow substitution reactions of the salt (1) with compounds (2)-(5). That contain bromine at bridgehead positions that are either meta- or para-benzylic to an aromatic nitro group, the rates of substitution in the isomers where the leaving group was meta- benzylic to the aromatic nitro group were slightly greater than those for the corresponding para-benzylic isomer. In compounds (6)and (7) the halogens are at bridgehead positions that are either meta- or para-benzylic relative to an aromatic nitro group within the same molecule. In the case of the reaction of the dibromide (6) with the thiolate (1), substitution was slow and occurred more rapidly at the benzylic -bridgehead position meta to the nitro group than at the corresponding para-benzylic position. In contast , the reaction of the diiodide (7) with the thiolate (1) gave substitution products which formed more rapidly than in the corresponding reaction of the dibromide (6) and the regioselectivity was reversed, with substitution occurring more readily at the bridgehead position para-benzylic to the nitro group than at the corresponding meta- benzylic position. The ratio of meta to para substitution products, determined for the reactions of compounds (2)-(6) with the salt (1), were in the range 1.15-2.5:1, while the reaction of (7) with the same nucleophile afforded a meta-to-para ratio of 1:2:3. These ratios contrast not only with each other, but also with the differences in reactivities determined for other nitrobenzylic systems, which are known to undergo SRN1 substitution reactions with the same nucleophile. The differences in first, the regioselectivity of substitution between the bridgehead systems, and secondly, the differences in the observed rates of regioselective substitution are compared with other simple nitrobenzylic halides. These differences are rationalized in terms of the effect of fixing the C-X bond at a bridgehead position to be orthogonal with the plane of the nitroaromatic group; this results in a reduction of the rate constants of intramolecular electron transfer, with significant consequences on the detailed overall mechanism for these reactions.

Simple Synthesis of Dimethyl Nitrobenzhydrylphosphonates and Heteroarylnitroarylacetonitriles via Vicarious Nucleophilic Substitution (VNS) Reaction

Synthesis ◽  
2020 ◽  
Vol 53 (01) ◽  
pp. 175-181
Author(s):  
Mieczysław Mąkosza ◽  
Małgorzata Bechcicka ◽  
Krzysztof Wojciechowski
Keyword(s):  
Nucleophilic Substitution ◽  
Nitro Group ◽  
Nitro Compounds ◽  
Simple Synthesis ◽  
Para Position ◽  
Crucial Step ◽  
Vicarious Nucleophilic Substitution ◽  
Aromatic Nitro Compounds ◽  
Leaving Group ◽  
Aromatic Nitro

Acetals of dimethyl phenyl- and heteroaryl-α-hydroxymethanephosphonates were deprotonated to generate carbanions, which enter the vicarious nucleophilic substitution (VNS) of hydrogen in aromatic nitro compounds to form 4-nitrobenzhydrylphosphonates and α-heteroaryl-4-nitrobenzylphosphonates. Similarly acetals of cyano­hydrins of heteroaromatic aldehydes (furfural and 2-formylthiophene) react to form heteroaryl 4-nitroarylacetonitriles. The anion of the hemiacetal of acetaldehyde is an efficient leaving group in the base-induced β-elimination step – the crucial step in the VNS reaction. The reaction selectively occurred at the para-position to the nitro group.

Acetylation of aromatics over acid zeolites: Seeking a viable alternative to Friedel-Crafts catalysts

2007 ◽  
Vol 79 (11) ◽  
pp. 1833-1838 ◽  
Author(s):  
Matteo Guidotti ◽  
Jean-Marie Coustard ◽  
Patrick Magnoux ◽  
Michel Guisnet
Keyword(s):  
Acetic Anhydride ◽  
Aromatic Compounds ◽  
External Surface ◽  
Active Catalyst ◽  
Steric Effects ◽  
Batch Reactors ◽  
Relevant Role ◽  
Acid Zeolites ◽  
Substrate Reactivity ◽  
Steric Constraints

Three acid zeolites (H-BEA, H-FAU, and H-MWW) were used as catalysts for acetylation in batch reactors with acetic anhydride of five aromatic compounds (benzenic and naphthalenic derivatives). The substrate reactivity is mainly governed by electronic factors (the nature of the substituents and degree of ring activation), but steric effects also play a relevant role when the reaction takes place in a narrow micropore system. In general, H-FAU was the most active catalyst, whereas with H-BEA remarkable steric constraints were observed. H-MWW showed good stability toward deactivation and an interesting activity of the sites located on the external surface.

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