Benzo and

No minor tautomers were detected for 2-aminoimidazoles fused with benzo and naphtho rings 54-56 [76AHC(S1), p. 430 84CHEC-I(5)345 96CHEC-II(3)77]. 

C. Seven-Membered Heterocycled So far, only benzo- and dibenzo-fused telluroazepines are known. 

In an investigation into the synthetic utility of the oxyindole 122, a wide variety of benzo- and heterocyclo-fused indexes and carbazoles was prepared, e.g., the indolo[3,2-a]carbazole 123 (Scheme 16). Thus, when 122 was reacted with indo-lylacetonitrile 124 in the presence of a base, followed by heating with phosphoric acid, the indolocarbazole 123 could be isolated in good yield (99T11563). 

Besides a parent ion, the mass spectra of benzo- and dibenzothiepins show the corresponding naphthalene or phenanthrene radical cations as the base peak.2-16 The mass spectra of 1-benzo-thiepin 1-oxides and 1,1-dioxides show the same naphthalene radical cation, formed by loss of sulfur monoxide or sulfur dioxide, respectively.14 In contrast, in the mass spectrum of 2,7-di-terf-butylthiepin peaks resulting from the loss of sulfur are not found.17... 

The broad use of this rearrangement for thiepin synthesis has been demonstrated by its application in the preparation of thermolabile 3-benzo- and 1-benzothiepins. Thus, thermolabile ethyl 3-benzothiepin-2-carboxylate (5) can be generated from the diazo precursor by the action of a palladium catalyst at — 10°C and low temperature ( — 40°C) chromatography.5... 

Genkina et al. (1979, 1981, 1985) investigated azo coupling reactions of indoles with fused benzo and benzothiopheno rings, namely 4,5- and 6,7-benzindole, 4,5,6,7-dibenzindole (12.42), indolo[6,5]-, -[4,5]-, and -[5,4]-benzo[Z ]thiophene (12.43 to 12.45). Arenediazonium ions reacted with all these indole derivatives at the 3-position. 

The two principal categories of compounds studied have been diaryl or aryl alkyl sulphones (not dialkyl sulphones, which are polarographically not reducible) and S-dioxides of certain heterocyclic compounds, such as thiophene (also benzo- and dibenzothiophenes) and phenothiazines. The first named have half-wave potentials in the region of — 2.0 V, the thiophene dioxides near — 1.0 V. Some examples of each category may be given. 

Table 1—3. Rate constants and half-life times t1/2 [min] for hydrolysis of NJJ -carbonylbisazoles and their benzo and thio derivatives in THF/water (40 1 27°C) and IR frequencies V(C=o> in CHC13.

Figure 7 1H and 13C NMR chemical shifts of some benzo- and dibenzocycl[3.2.2]azines. 

Although most of the fundamental studies of cycl[3.2.2]azines were reported in CHEC(1984) (see Section 12.16.6.3 for leading references), there is continuing interest - synthetic, spectroscopic, and theoretical - in these and their benzo- and dibenzo-fused analogues, all of which may be considered as bridged analogues of [10]-, [14]-, and [18]-annulenes, respectively. The same level of theoretical interest continues to apply to those />m -fused systems with a hypervalent sulfur or selenium at the 5 5 ring junction (Section 12.16.6.6). 

Reactions of heterocyclic amines 208 with 2-chloro-3-iodopyridine 209 in the presence of a palladium catalyst provide dipyridoimidazole and its benzo- and aza-analogues 210. The synthesis represents the first tandem double palladium-catalyzed amination reaction (Equation 23) <2004CC2466>. 

Phenolic resins are mainly composed of aromatic esters benzoe and storax were the most common in the Mediterranean [86]. 

Many other nitrogen- and sulfur-containing rings are available from reactions of the Willgerodt-Kindler type. Benzo- and pyridino-fused thia-zoles, for example, are formed from anilines (benzeneamines) and amino-pyridines, respectively.25 Asinger26 has reviewed the scope of these reactions in heterocyclic synthesis. 

Very many fused 1,2,5-thiadiazoles, and some fused 1,2,3-thiadiazoles, have been prepared the two typical reactions are illustrated (Scheme 8). The first is exemplified by the synthesis of numerous benzo- and hetero-fused 1,2,5-thiadiazoles by Carmack and co-workers,68 and by Hartman s group 69 an example of the second is the preparation of l,2,3-thiadiazolo[4,5-d]-pyrimidines.70... 

The introduction of sulfur between two ortho amino groups is the oldest and still the most commonly used route to benzo- and heteroarene-fused 1,2,5-thiadiazoles. The reaction has been extensively reviewed in both CHECK 1984) and CHEG-II(1996). The in situ preparation of Ar-sulfinylanilinc via /3-elimination of chloroform from trichlorometh-anesulfinamides 200 was recently supported by trapping with 1,2-benzenediamine to give the benzothiadiazole 2 in 85% yield (Equation 43) <1997TL487>. 

There are a few communications concerning cycloadditions of nitrile oxides to unsaturated oxa and aza cage systems. Benzo- and mesitonitrile oxides RCNO give, with five substituted 7-oxanorbomenes 106, mixtures of the corresponding exo-adducts 107 and 108 in nearly quantitative yields. No traces of compounds resulting from the endo-face attack was detected (274). Substituents at positions 5 and 6 of 106 render the process highly regioselective. 

Extension of the ring numbers, bioisosteric replacement of the benzene ring, and conversion of the quinolone system to the corresponding quinalizinone system has been a subject of research interest during the past decade. For example, Jordis et al. [38] recently reported the syntheses of a series of linear benzo- or pyrido-ciprofloxacin (lin-benzo- and lin-pyrido-ciprofloxacin)... 

Compounds are generally classified according to their fully unsaturated parent compound (but see below). Thus substituted, partially saturated, and fully saturated derivatives of, for example, pyrrole are all indexed under pyrrole. Benzo and similar derivatives are included under the most unsaturated parent system (e.g., quinoline, thienofuran, etc.). For any given heterocyclic parent only one indicated hydrogen isomer appears in the text, typically the most stable or the lowest numbered form thus all instances of pyran, whether of the 2H- or 4H-form, are indexed under 2H-pyran. The charges and additional valences for any heterocyclic parent structure are not indicated. 

The three-component synthesis of benzo and naphthofuran-2(3H)-ones from the corresponding aromatic alcohol (phenols or naphthols) with aldehydes and CO (5 bar) can be performed under palladium catalysis (Scheme 16) [59,60]. The mechanism involves consecutive Friedel-Crafts-type aromatic alkylation and carbonylation of an intermediate benzylpalla-dium species. The presence of acidic cocatalysts such as TFA and electron-donating substituents in ortho-position (no reaction with benzyl alcohol ) proved beneficial for both reaction steps. 

Photolysis of the zwitterionic pyrido[l,2-h]pyridazines (89) and their 5,6-benzo and 2,3-tetramethylene derivatives afforded 6,7,8,9-tetrahydro-4//-pyrido[l,2-fl]pyrimidin-4-ones (90) and their 8,9-benzo [77H(8)377] and 2,3-tetramethylene derivatives (75JOC2201). Photoinduced ring transformation of 2-phenylpyrido[l,2-fe]pyridazinium-4-olate (73) was investigated in methanol (94T4699). 

Semiempirical and molecular mechanics calculations have been widely used. Thus, conformation of indolo benzazepine 423 (Figure 8) with its conjugated benzo and indole rings has been studied by molecular mechanics (MMX force field). Its planarity was estimated from a calculation of dihedral angle Ti 2 3 4 the value of ca. 22° is due to strain as contributed by azepine ring. This characteristic was further compared to that of the open-chain and six-membered... 

This review is based on Mosby s book cited above and covers the literature through 2009 together with several articles published in 2010. It includes pyrido[l,2-fl]azepines and their hydro products as well as linearly or angularly fused benzo and dibenzo derivatives. Patents are taken into account provided they reveal important aspects of synthesis or application. 

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