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Reactivity of the rings

Electrophilic substitution on position 2 of pyrrolo[l,2]benzoheteropines is the most common example of this type of transformation. Thus, [Pg.54]

Reaction of phenyl-5H,llH-pyrrolo[2,l-c][l,4]benzothiazepine 297 (R = Ph) with paraformaldehyde and 1-methylpiperazine dihydrochloride in methanol occurs on the 2-pyrrole position and affords Mannich product 372 (Equation (41) (1999JMC3334)). [Pg.55]

Analogous dimethylamino derivatives of this ring with different substitution patterns on the thiazepine ring have been reported (1996X7745). [Pg.55]

An example of electrophilic substitution on position C2 of the fused furan has been reported for 8H-furo[3,4-d]dibenz[ 7,/]azepine, which reacts with f-butyl hypochlorite to afford a mono chlorinated furan ring product (1995H431). [Pg.56]

This kind of reactivity is usually limited to substitution on the nitrogen of benzazepine ring and the nitrogen of pyrrole (or indole) fused to the heteropine core. [Pg.57]


The choice of the intermediate depends on the reactivity of the ring. For a pyrazolone (34) rather than 35 is used it is the reverse for rhodanine (Schemes 52 and 53). [Pg.60]

Aryl substituents enhance somewhat the reactivity of the ring atoms, the phenyl substituent being arylated in a proportion of 40 to 60% (396,406, 407). [Pg.110]

Arylamines contain two functional groups the amine group and the aromatic ring they are difunctional compounds The reactivity of the amine group is affected by its aryl substituent and the reactivity of the ring is affected by its amine substituent The same electron delocalization that reduces the basicity and the nucleophilicity of an arylamme nitrogen increases the electron density in the aromatic ring and makes arylamines extremely reactive toward electrophilic aromatic substitution... [Pg.939]

Electrophilic substitution of thiophene occurs largely at the 2-position and the reactivity of the ring is greater than that of benzene. 3-Substituted derivatives are generally prepared by indirect means or through ring cyclization reactions. [Pg.19]

Statements in the hterature on the reactivity of the ring-positions in monocyclic azines are conflicting. Reactivity is said to be greater at the position ortho (or alpha) than at the position para (or gamma) to an azine nitrogen 2-> 4-position in pyridine and pyrimidine and 3-> 5-position in as-triazine. By others, the... [Pg.285]

Alteration of the relative reactivity of the ring-positions of quinoline is expected and observed when cyclic transition states can intervene. Quinoline plus phenylmagnesium bromide (Et20,150°, 3 hr) produces the 2-phenyl derivative (66% yield) phenyllithium gives predominantly the same product along with a little of the 4-phenylation product. Reaction of butyllithium (Et 0, —35°, 15 min) forms 2-butylquinoline directly in 94% yield. 2-Aryl- or 6-methoxy-quinolines give addition at the 2-position with aryllithium re-agents, and reaction there is so favored that appreciable substitution (35%) takes place at the 2-position even in the 4-chloroquinoline 414. Hydride reduction at the 2-position of quinoline predominates. Reaction of amide ion at the 2-position via a cyclic... [Pg.365]

The Friedel-Crafts alkylation reaction does not proceed successfully with aromatic reactants having EWG substituents. Another limitation is that each alkyl group that is introduced increases the reactivity of the ring toward further substitution, so polyalkylation can be a problem. Polyalkylation can be minimized by using the aromatic... [Pg.1015]

The outer rings of the anthraquinone molecule (52) are aromatic in nature and as such are capable of undergoing substitution reactions. The reactivity of the rings towards substitution is determined by the fact that... [Pg.85]

Among the sparse data available on reactivity of the ring systems belonging to this chapter, a condensation reaction, a ring transformation, and a ring closure are discussed in this section. [Pg.897]

Nitration is a very general reaction, and satisfactory conditions can normally be developed for both activated and deactivated aromatic compounds. Because each successive nitro group reduces the reactivity of the ring, it is easy to control conditions to obtain a mononitration product. If polynitration is desired, more vigorous conditions are used. Scheme 11.1 gives some examples of nitration reactions. [Pg.695]

Further examples of the ease of exchange of substituents on carbon by nucleophiles under mild conditions have been reported. The reactivity of the ring towards nucleophiles is increased in triazolium cations and mesoionic derivatives. [Pg.135]

There are no reports concerning reactivity of substituents attached to ring heteroatoms. In fact, most 1,4-(oxa/thia)-2-azoles are unsubstituted at ring heteroatoms and the only data concerning dithia- or oxathiazolidine S,S-dioxides, or N-substituted derivatives is limited to their preparation and to the reactivity of the ring systems. [Pg.527]

Photoelectron and ESR spectroscopy Mass spectrometry Reactivity of the Ring Systems Containing Silicon... [Pg.829]

The 5 ring H s of monosubstituted benzenes, C H G, are not equally reactive. Introduction of E into Cf,HjG rarely gives the statistical distribution of 40% ortho, 40% meta, and 20% para disubstituted benzenes. The ring substituent(s) determine(s) (a) the orientation of E (meta or a mixture of ortho and para) and (b) the reactivity of the ring toward substitution. [Pg.218]

In a fused system there are not six electrons for each ring.8" In naphthalene, if one ring is to have six, the other must have only four. One way to explain the greater reactivity of the ring system of naphthalene compared with benzene is to regard one of the naphthalene rings as aromatic and the other as a butadiene system.81 This effect can become extreme, as in the case of triphenylene.82 For this compound, there are eight canonical forms like A. [Pg.44]


See other pages where Reactivity of the rings is mentioned: [Pg.148]    [Pg.368]    [Pg.391]    [Pg.587]    [Pg.128]    [Pg.50]    [Pg.1004]    [Pg.141]    [Pg.77]    [Pg.87]    [Pg.909]    [Pg.909]    [Pg.909]    [Pg.911]    [Pg.911]    [Pg.912]    [Pg.960]    [Pg.974]    [Pg.54]    [Pg.74]    [Pg.693]    [Pg.607]    [Pg.842]    [Pg.1305]    [Pg.157]    [Pg.600]    [Pg.15]    [Pg.17]    [Pg.22]    [Pg.32]    [Pg.34]   


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Reactivities of the Pyrazole Ring

Reactivity of Rings

Reactivity of Substituents Attached to the Ring Carbon Atoms

Reactivity of Substituents Attached to the Ring Nitrogen Atom

Reactivity of the Diazine Ring

Reactivity of the Indole Ring

Reactivity of the Pyridine Ring

Reactivity of the Pyrrole Ring

Reactivity of the Quinoline and Isoquinoline Ring

SUBSTITUENT EFFECTS ON THE REACTIVITY OF BENZENE RINGS

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