Aromatic compounds nonbenzenoid

This procedure illustrates formylation by N,N-dimethylamino-methoxymethylium methyl sulfate, a compound which can be produced readily by reaction of easily available materials. 6-(Dimethylamino)fulvene is a useful intermediate for the synthesis of various f used-ring nonbenzenoid aromatic compounds. 

Heilbronner, E. Nonbenzenoid aromatic compounds (ed. D. Ginsburg). New York Interscience Publishers 1959. 

Of course, in reality new chemical substances are not synthesized at random with no purpose in mind—the numbers that have still not been created are too staggering for a random approach. By one estimate,1 as many as 10200 molecules could exist that have the general size and chemical character of typical medicines. Instead, chemists create new substances with the aim that their properties will be scientifically important or useful for practical purposes. As part of basic science, chemists have created new substances to test theories. For example, the molecule benzene has the special property of aromaticity, which in this context refers to special stability related to the electronic structure of a molecule. Significant effort has gone into creating new nonbenzenoid aromatic compounds to test the generality of theories about aromaticity. These experiments helped stimulate the application of quantum mechanical theory to the prediction of molecular energies. 

Tropones, tropolones, and tropylium salts have been known since the early 1950s. Today, they are counted among the most important classes of nonbenzenoid aromatic compounds. 

There are several compounds that possess some measure of aromatic character typical of benzene, but do not possess a benzenoid ring. Appropriately, they have (4n + 2) it electrons and are classified as nonbenzenoid aromatic compounds (see Section 21-9). An example is azulene, which is isomeric with naphthalene and has a five- and a seven-membered ring fused through adjacent carbons ... 

The tropolones make up a very interesting class of nonbenzenoid aromatic compound that was discovered first in several quite different kinds of natural products. As one example, the substance called /3-thujaplicin or hinokitiol has been isolated from the oil of the Formosan cedar and is 4-isopropyltropolone ... 

The rhodizonate dianion C60g (Fig. 20.4.19) is a member of a series of planar monocyclic oxocarbon dianions C 0 (n = 3, deltate n = 4, squarate n = 5, croconate n = 6 rhodizonate) which have been recognized as nonbenzenoid aromatic compounds. However, this six-membered ring species... 

B-69MI42100 M. Ohtaand H. Kato in Nonbenzenoid Aromatic Compounds , ed. J. P. Snyder ... 

Lloyd, D. Carbocyclic nonbenzenoid aromatic compounds, p. 55. Amsterdam Elsevier Publ. Comp. 1966. 

Bis-Wittig reaction. Synthesis of nonbenzenoid aromatic compounds by the bis-Wittig reaction has been reviewed. ... 

Compounds that possess some measure of aromatic character typical of benzene, but are themselves not benzene rings, are known as nonbenzenoid aromatic compounds,... 

Tropylium bromide is a nonbenzenoid aromatic compound. It is aromatic because of delocalization of 6(4n +2, n = 1) TT electrons about seven carbon atoms. Also, the repulsion between the electrons within the ring is low because of their electrostatic interaction with the positive charge. 

E. Heibronner, Nonbenzenoid Aromatic Compound (D. Ginsburg, ed.), Wiley/ Interscience, New York, 264 (1959). 

Naphthalene, phenanthrene, and anthracene are examples of benzenoid aromatic compounds. On the other hand, the cyclopentadienyl anion, the cycloheptatrienyl cation, l6-dimethyldihydropyrene, and the aromatic annulenes (except for [6]annulene) are classihed as nonbenzenoid aromatic compounds. 

Nonbenzenoid aromatic compound (Section 14.8B) An aromatic compound, such as azulene, that does not contain benzene rings. 

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