Naphthol ring

This is a member of an interesting class of compounds which are chiral, without actually containing a defined chiral centre. They are chiral because their mirror images are non-superimposable. In the case of this molecule, there is no rotation about the bond between the two naphthol rings because of the steric interaction between the two hydroxyl groups, d and T forms can be isolated and are perfectly stable (Optical purity determination by H NMR, D. R Reynolds, J. C. Hollerton and S. A. Richards, in Analytical Applications of Spectroscopy, edited by C. S. Creaser and A. M. C. Davies, 1988, p346). 

Carboxonium-carbenium dications have also been proposed in the reactions of aryl ethers, phenols, and naphthols, with superacids. When 2-naphthol is reacted with an excess of AICI3 (3 equivalents) and cyclohexane, the product of ionic hydrogenation is observed in 59% yield (eq 15).24 This conversion is thought to occur by double protonation of the 2-naphthol ring to give the dication 48, which is capable of abstracting hydride from cyclohexane. Similar intermediates are formed by the reactions of HF-SbFs with naphthyl ethers (eq 16).25... 

The case of diketonc 66 is more difficult to interpret, as this substrate undergoes a Mannich reaction initially on the acetyl group at position 4 of the 1-naphthol ring and is then further aminomethylated at the acetyl group in position 2. ... 

Naphthol ring from acetylenehomophthalic anhydrides via intramolecular diene synthesis... 

Molisch s test A general test for carbohydrates. The carbohydrate is dissolved in water, alcoholic 1-naphthol added, and concentrated sulphuric acid poured down the side of the tube. A deep violet ring is formed at the junction of the liquids. A modification, the rapid furfural test , is used to distinguish between glucose and fructose. A mixture of the sugar, 1-naphthol, and concentrated hydrochloric acid is boiled. With fructose and saccharides containing fructose a violet colour is produced immediately the solution boils. With glucose the appearance of the colour is slower. 

Both 2- and 3-nitrothiophenes are reduced by tin and hydrochloric acid to the corresponding aminothiophenes. In contrast to anilines, the free bases are very unstable their salts and acyl derivatives, however, are stable. 2-Aminothiophene can be diazotized and the resulting diazonium salt coupled with /3- naphthol. The chemical instability of aminothiophenes compared with aniline is illustrated by the ring opening of 2-amino-3-ethoxycar-bonylthiophenes (157) with ethanolic sodium ethoxide to give cyanothiolenones (158) <75JPR861). 

According to Section 4.02.3.1.8 substituents removed from the pyrazole ring by two or more saturated carbon atoms and substituents on the benzene ring of indazoles are similar in reactivity to the corresponding aromatic derivatives. For instance, chloromethyl-pyrazoles are comparable to benzyl chlorides and 5-hydroxyindazoles to /3-naphthols in their reactivity. 

Two different all-aromatic crowns have been reported ". In 1975, de Jong, Siegel and Cram reported the synthesis of a tri-binaphthyl system in which each oxygen was bound to a naphthalene ring, but aliphatic bridges were used to join the binaphthyl units. Relatives of this compound are discussed further in Sect. 3.13. The synthesis of this molecule (Structure 17, below) was not simple, but was relatively straightforward. An interesting feature of it was the use of ethyl chloroacetate followed by LAH reduction to attach ethyleneoxy units to the naphthol unit. 

Reaction of epichlorohydrin with I-naphthol affords the glycidic ether (61). Opening of the oxirane ring with isopropyl-iimine gives racemic propranolol (62) the only 3-blocker... 

Hydrogenation of 2-naphthol can proceed at either ring with the general tendency to reduce the unsubstituted ring preferentially. The ratio R of... 

The 2a,7b-dihydrocyclobuta[7>]benzofuran structure, obtained by addition of activated acetylenes to benzofurans (see Houben-Weyl, Vol.E6b, p 148), isomerizes thermally to a 1-benz-oxepin182 184 185 which reacts further to 1-naphthol derivatives at higher temperature182,185 (see Section 1.2 ). Under photochemical conditions, the 1-benzoxepins undergo ring contraction to the starting material.182 184... 

Benzo-l,2,3-triazin-4-ones with the general structure 6.54 (X = O, S, or H2) are obtained by diazotization of the appropriate aniline derivatives 6.53 (Scheme 6-38). In polar aprotic solvents (e. g., nitrobenzene) the reverse reaction takes place to give the diazonium ion (for an example see Kullick, 1966). Diazotization of 1,8-diamino-naphthalene yields l-i/-naphthol[l,8-cfe]triazine (6.55 Tavs et al., 1967). In concentrated HC1 the triazine ring is opened again. 

It can also be mentioned that polyphosphazenes substituted with aromatic groups, such as phenols or naphthols, can form inter- and intra- molecular excimers by coupling reaction of the planar aromatic rings of the substituents under illumination [467-471,473,725]. These species disappear as soon as the light is switched off. 

Electron-rich rings are reduced more eas ily so that E-naphthol (20) can be reduced to ketone (21) in base. ... 

---