Benzo-type heterocyclic compounds

Benzo-type heterocyclic compounds can be prepared by this method. There have been many examples of this type of reaction using various metals, as shown in Eq. 2.54 [7qJ. 

Many benzo-fused heterocycles are obtained by elaboration of substituted benzenes, especially useful for benzobis- 1,3-types. The strategy of photocyclization of 1,2-diheterocyclic substituted ethenes is a versatile approach to angular fused systems, and, while it has some limitations, it may yet be further exploited for systems with more than one heteroatom per heterocyclic ring. Otherwise a linking of diheterocycles by a two-carbon bridge is necessary. For compounds with indole moieties the Fischer approach is often successful. 

A number of polymers containing a heterocyclic group have been prepared using the Reissert alkylation sequence.92 94 Thus, for example, the reaction of the isoquinoline Reissert anion (26) with polyfvinylbenzyl chloride) and sodium hydride gave 36, which on hydrolysis with base gave 37.92,93 A similar condensation takes place with quinoline, phenanthridine, and benzo-[/Jquinoline Reissert compounds.94 The Reissert anion 26 has also been alkylated with a mixture of m- and p-vinylbenzyl chloride and the product polymerized to a polymer of type 37.93 Copolymerization has also been studied.93... 

Volume 29 consists of six contributions. Three of these deal with specific groups of compounds and update previous contributions in this publication on the same type of compounds. Thus, R. K. Smalley, who writes on The Chemistry of Indoxazenes and Anthranils 1966-1979, updates the article by Wunsch and Boulton published in 1967 in Volume 8. Raymond Bonnett and Stephanie A. North, writing on The Chemistry of the Isoindoles, update the contribution by White and Mann, published in Volume 10, in 1969, and Richard M. Scrowston, with his review entitled, Recent Advances in the Chemistry of Benzo[fe]-thiophenes, updates that by himself and Iddon in Volume II, published in 1970. The chemistry of Furoxans and Benzofuroxans is covered by A. Gasco and A. J. Boulton. This and the subject of Mononuclear Heterocyclic Rearrangements reviewed by Michele Ruccia, Nicolb Vivona, and Domenico Spinelli, are both topics close to the hearts of the Editors of this volume. Finally, Yasumitsu Tamura and Masazumi Ikeda have summarized Advances in the Chemistry of Heteroaromatic N-Imines and N-Aminoazonium Salts. Although this subject was reviewed as recently as 1974, in Volume 17 of Advances, its growth since then has been so dramatic that this further review is very timely. 

Synthesis.—In following the practice adopted in Elderfield s treatises on heterocyclic compounds the syntheses of benzothiazoles and benzo-thiazolines are again classified according to the nature of the fragments from which the ring system is built up. The letters designating the type of synthesis correspond to previous usage as closely as practicable. 

The fusion of a furan (thiophene, selenophene) nucleus (2) with a six-membered heterocyclic ring gives rise to two types of heterocycles (e.g. 1, 3). Whereas the former ones are derivatives of benzo[Z>]furans (thiophenes, selenophenes) (Chapters 3.10-3.16) the latter class of compound are derived from benzo[c]furans (78H(9)865, 80AHC(26)135, 81MI31700) (thiophenes, selenophenes). There are three main reasons for the interest in these compounds. Firstly, the overwhelming majority of compounds discussed in this chapter belong to a class of bicyclic heterocycles which arise from the fusion of a ir-excessive nucleus... 

The heterocyclization of peri-aminonaphthoyl compounds allows the preparation of three main types of benzo[crf]indole series, namely, bases 113, benzo[crf]indolium salts 114, and benzo[crf)indole-2-ones 115. Because closure to the nitrogen heterocycle is so facile, peri-amino-substituted naphthaldehydes and naphthyl ketones, even under conditions of their formation, are converted into benzo[crf]indoles 113. Those unsubstituted in position 2, as well as 2-alkyl-substituted benzo[cd]indoles 113 (R = H, Aik), have not been isolated because of their easy oxidation by air. 

Several saturated parent systems shown in Scheme 1, especially (2), (4) and (7), have been incorporated into spiro compounds or have been fused with a variety of non-aromatic carbocyclic or heterocyclic rings. Unsaturated compounds with an endocyclic carbon-carbon double bond, formally possible in all systems with three adjacent heteroatoms, are only known in very few cases (e.g. cyclic sulfites and sulfates of enediols) or in the form of benzo or other condensed systems (mainly cyclic sulfites and sulfates of aromatic 1,2-dihydroxy compounds). For details concerning the various types of derivatives, see Section 4.33.4.2. 

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