Ring synthesis 3- bromo

Hegedus also described an efficient synthesis of 4-bromoindoIe (10) and 4-bromo-l-(4-toluenesulfonyl)indole (11) starting from 2-amino-6-nitrotoluene (9) [20]. The synthesis is lengthy but yields are good, and the method involves the Hegedus indole ring synthesis discussed later in this chapter. 

Nucleophilic displacement of chloro groups by fluoride was accomplished under pyrolysis conditions with potassium fluoride the chloro (and bromo) precursors are available by ring-synthesis [78HC(33)1 79CB1529 84MI7]. Halogens next to annular nitrogens are the most easily displaced,... 

Many isothiazole-4-carboxylic acids, esters, amides, and nitriles have been prepared by direct ring synthesis (see Section I), but another widely employed route is the sequence bromo compound, nitrile, amide, or acid (Scheme 37) 70- s-95.107... 

In another example of heterocyclic ring synthesis, pyridinium salts 816 require only Et3N for deprotonation, the resulting ylides 817 add to esters of 2-bromo-2-alkenecarboxylic acids or analogous benzonitriles to give intermediate betaines 818 which, via intramolecular nucleophilic attack, give indolizines 819 (Scheme 174) <1999JOC7618>. 

The ring synthesis of imidazo[l,2-a]pyridines is based on the Chichibabin route to indolizines (Section 25.1.2), but using 2-aminopyridines instead of 2-alkylpyridines. The initial reaction with the halo-ketone is regioselective for the ring nitrogen, so isomerically pure products are obtained. 2-Oxoimidazo[l,2-a]pyridines are the products when an o-bromo-ester is used instead of a ketone. 

A-4-Thiazoline-2-ones and ring substituted derivatives are usually prepared by the general ring-closure methods described in Chapter II. Some special methods where the thiazole ring is already formed have been used, however. An original synthesis of 4- 2-carboxyphenyl)-A-4-thiazoline-2-one (18) starting from 2-thiocyanato-2-halophenyl-l-3-indandione (19) has been proposed (Scheme 8) (20, 21). Reaction of bicyclic quaternary salts (20) may provide 3-substituted A-4-thiazoline-2-one derivatives (21) (Scheme 9) (22). Sykes et al. (23) report the formation of A-4-thiazoline-2-ones (24) by treatment ef 2-bromo (22) or 2-dimethylaminothiazole (23) quaternary salts with base (Scheme 10). 

Azepine, 5-bromo- 1-ethoxycarbonyl-X-ray crystallography, 7, 520 1 //-Azepine, 5-cyano-4,5-dihydro-rearrangement, 7, 512 1 //-Azepine, 3-cyclopropyl-2-diethylamino-synthesis, 7, 536 1//-azepine, 2,6-dicyano-ring contractions, 7, 506 1//-Azepine, 2,3-dihydro-synthesis, 7, 42 1 //-Azepine, 2,5-dihydro-valence tautomerism, 7, 506 1 //-Azepine, 2,7-dihydro-rearrangement, 7, 507 1//-Azepine, 4,5-dihydro-... 

H-Azepine, 2-allyloxytetrahydro-Claisen rearrangement, 7, 508 3H-Azepine, 2-amino-acylation, 7, 511 effect of acidification, 7, 510 nucleophilic displacement reactions, 7, 514 synthesis, 7, 533, 535 3H-Azepine, 2-amino-7-bromo-synthesis, 7, 529 3H-Azepine, 2-anilino-ring inversion, 7, 495-499 structure, 7, 533... 

Azetidine, 7V-bromo-, 7, 240 Azetidine, AT-r-butyl- N NMR, 7, 11 Azetidine, AT-t-butyl-3-chloro-transannular nucleophilic attack, 7, 25 Azetidine, 3-chloro-isomerization, 7, 42 Azetidine, AT-chloro-, 7, 240 dehydrohalogenation, 7, 275 Azetidine, 7V-chloro-2-methyl-inversion, 7, 7 Azetidine, 3-halo-synthesis, 7, 246 Azetidine, AT-halo-synthesis, 7, 246 Azetidine, AT-hydroxy-synthesis, 7, 271 Azetidine, 2-imino-stability, 7, 256 Azetidine, 2-methoxy-synthesis, 7, 246 Azetidine, 2-methyl-circular dichroism, 7, 239 optical rotatory dispersion, 7, 239 Azetidine, AT-nitroso-deoxygenation, 7, 241 oxidation, 7, 240 synthesis, 7, 246 Azetidine, thioacyl-ring expansion, 7, 241 Azetidine-4-carboxylic acid, 2-oxo-oxidative decarboxylation, 7, 251 Azetidine-2-carboxylic acids absolute configuration, 7, 239 azetidin-2-ones from, 7, 263 synthesis, 7, 246... 

Benzoselenolo[2,3-ii]benzoselenophenes synthesis, 4, 116, 1078 Benzoselenolopyrylium cations oxidative ring contraction, 4, 969 [l]Benzoselenolo[3,4-ii][l,2,3]selenadiazoles synthesis, 6, 354 Benzo[h]selenophene, 2-acetyl-synthesis, 4, 966 Benzo[h]selenophene, 2-bromo-acylation, 4, 948... 

Chromone, 2-amino-3-chloro-synthesis, 3, 713 diacetate, 3, 714 Chromone, 3-aroyl-photochemistry, 3, 695 Chromone, 2-benzhydryl-3-benzoyl-photoenolization, 3, 695 Chromone, 3-benzoyl-2-benzyl-photoenolization, 3, 695 Chromone, 3-benzoyl-2-methyl-synthesis, 3, 823 Chromone, 2-benzyl-in photochromic processes, 1, 387 Chromone, 3-benzyl-photolysis, 3, 695 Chromone, 3-bromo-synthesis, 3, 828 Chromone, 3-bromoacetyl-ring opening, 3, 713 Chromone, 3-bromo-2-methyl-reactions... 

Pyrazolino[2,3-c][l,2,3]triazoles, 5, 702 Pyrazolium hydroxide, l,2-dimethyl-3,5-diphenylanhydro-4-hydroxy-IR spectra, 5, 201 Pyrazolium salts dequatemization, 5, 269 H NMR, 5, 185 hydrogen exchange at ring carbon, 5, 245 mesoionic compounds, 5, 171 nitrodebromination, 5, 237 reactivity, 5, 217 reduction, 5, 68, 243 synthesis, 5, 156 UV spectra, 5, 199 Pyrazolium salts, amino-reactions, 5, 262 Pyrazolium salts, bromo-nucleophilic displacements, 5, 266 Pyrazolium salts, 1,2-dimethyl-deuteration, 5, 175, 245 hydrogen exchange, 5, 71 acid-catalyzed, 5, 239 reactions... 

In general, imines are too reactive to be used to protect carbonyl groups. In a synthesis of juncusol, however, a bromo- and an iodocyclobexylbnine of two identical aromatic aldehydes were coupled by an Ullmann coupling reaction modified by Ziegler. The imines were cleaved by acidic hydrolysis (aq. oxalic acid, THE, 20°, 1 h, 95% yield). Imines of aromatic aldehydes have also been prepared to protect the aldehyde during ring metalation with. -BuLi. ... 

This method has been applied to a large-scale preparation of 6-bromoindole, which reacts with various arylboronic acids via the Suzuki reaction to afford 6-aryhndoles fEq. 10.50. 6-Bromo-5-methoxyindole for use in the synthesis of marine bromoindole " and 5-amino-7-ethoxycarbonyhndole for use in synthesis of l//-pyrrolo[3,2-g quina2ohne ring system fEq. 10.51 " have been prepared from the appropriate o-nitrotoluene. 

An elegant extension of these intramolecular acylnitrene-induced ring expansions has been used for the synthesis of cyclopent[h]azepines.2 2-Haloindan-l-yl azidoformates 14 (X = Cl, Br), when subjected to pyrolysis at 300 °C in a hot tube packed with calcium oxide and copper turnings, produce cyclopent[6]azepine (15), as a dark turquoise oil, in excellent yield. Lesser yields (30 and 50%, respectively) of the 4-bromo and 3-methoxy derivatives can be similarly obtained. 

In the synthesis of the bromo derivative 12 from diepoxide 11, an interesting epoxide ring-opening-ring-closure reaction is involved.5... 

The Gabriel-Cromwell aziridine synthesis involves nucleophilic addition of a formal nitrene equivalent to a 2-haloacrylate or similar reagent [29]. Thus, there is an initial Michael addition, followed by protonation and 3-exo-tet ring-closure. Asymmetric variants of the reaction have been reported. N-(2-Bromo)acryloyl camphor-sultam, for example, reacts with a range of amines to give N-substituted (azir-idinyl)acylsultams (Scheme 4.23) [30]. 

The Suzuki reaction97 allows tire coupling of two aromatic rings by reaction of an arylboronic compound with a iodo or bromo aryl derivative. The tetrakis (U iphenylphosphine) Pd is the catalyst working in the basic medium. This reaction was recently used98 in aqueous media for the preparation of different isomers of diphenyldicarboxylic acids (Fig. 5.21) but also for the synthesis of soluble rodlike polyimides99 by coupling the 3,6-diphenyl- V, V,-bis(4-bromo-... 

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