Naphthols, with ammonia

The reaction of naphthols with ammonia and sodium bisulfite is called the Bucherer reaction. Primary amines can be used instead of ammonia, in which case N-substituted naphthylamines are obtained. In addition, primary naphthylamines can be converted to secondary, by a transamination reaction ... 

The proton transfer reaction has been also studied in rare gas matrices, showing some discrepancies with the gas phase (Brucker and Kelley 1989a,b Crepin and Tramer 1991) in 1- and 2-naphthol with ammonia, the AH B — A -HB + transition takes place for AH (NH3) /Ar matrix-embedded clusters with n > 3 (Brucker and Kelley 1989a,b). 

The Bucherer method has completely replaced the older procedure of heating the naphthol with ammonia. This process gave only about a 70 per cent yield at pressures of 50 to 60 atmospheres. The Bucherer reaction was discussed in more detail on page 182. 

Other classes of reactions that have received much attention are proton transfer and electron transfer reactions. These processes can often be initiated by light. This characteristic has made it possible to monitor their time evolution by ultrafast pump-probe techniques. An example is the acid-base reaction of 1-naphthol with ammonia. On the ground electronic surface... 

Amination of y0-naphthol with ammonia in the presence of sodium sulfite is shown below. 

Evidence for this mechanism was the isolation of 12 and the demonstrati on that for P-naphthol treated with ammonia and HSO3, the rate of the reaction depends only on the substrate and on HS03 , indicating that ammonia is not involved in the rate-determining step. If the starting compound is a P-naphthol,... 

Condensation of 1-naphthol and hetaryl- or substituted-berrzaldehydes in the presence of ammonia, and subsequent acidic hydrolysis, gave 2 in moderate yields. Reactions of amino naphthols with eqrrivalent amormts of aldehydes resulted in... 

The first step in either direction consists of addition of NaHSO-, to one of the double bonds of the ring, which gives an enol (or enamine) that tautomerizes to the keto (or imine) form. The conversion of 10 to 11 (or vice versa) is an example of 6-14 (or 6-2). Evidence for this mechanism was the isolation of 10 " and the demonstration that for p-naphthol treated with ammonia and HSOj. the rate of the reaction depends only on the substrate and on HSOi. indicating that ammonia is not involved in the rate-determining step.112 If the starting compound is a (i-naphthol, the intermediate is a 2-keto-4-suIfonic acid compound, so the sulfur of the bisulfite in either case attacks meta to the OH or NH2-m... 

Similar to the reaction of 2-benzopyrylium salts with ammonia (Section III,C,4,a,i), an excess of competing nucleophiles in reactions with secondary amines is undesirable. Thus, the interactions of l-ethyl-3-methyl-substituted salt 183 with 40% aqueous solution of dimethylamine leads to a-naphthol 189 as the major product (79TH1). 

Betaines of type 241 react slowly with ammonia, yielding isoquinolines 255, whereas the interaction with aqueous-alkaline solutions in the presence of alkylation reagents leads to /3-naphthol derivatives 256 [68ACH(57)181]. 

The direct replacement of the hydroxyl group in simple phenols by an amino or substituted amino group requires drastic conditions and the method is not suitable for laboratory preparations. With the polyhydric phenols, and more particularly with the naphthols, such replacements occur more readily. Thus 2-naphthol is converted into 2-naphthylamine by heating with ammoniacal ammonium sulphite solution at 150°C in an autoclave. The reaction (the Bucherer reaction) depends upon the addition of the hydrogen sulphite ion to the keto form of the naphthol and the subsequent reaction with ammonia. 

In a i-l. round-bottom flask is placed a cold solution of 144 g. (1 mole) of /3-naphthol in 200 cc. of 95 per cent alcohol (Note 1). To this solution is added first 212 g. (2 moles) of freshly distilled benzaldehyde (which has been previously freed from acid by shak ing with 5 per cent sodium carbonate solution) and then about 200 cc. of 95 per cent alcohol which has been saturated with ammonia at room temperature. The solution becomes red and warms up spontaneously. The flask is stoppered and allowed to... 

Naphthols as well as naphthylamines are converted to labile intermediate compounds by the action of bisulfite. These intermediates were considered to be sulfurous acid esters of naphthols (Formula I) by Bucherer, the discoverer of the reaction, but Woroshtzow formulated them as addition products of bisulfite with the keto forms of the naphthols (Formula II). These intermediates yield the corresponding naphthylamines with ammonia, and are hydrolyzed to the naphthols by caustic allrali. Thus, it is possible to convert naphthok into naphthylamines (pages 200 and 203), as well as naphthylamines into naphthols. ... 

The naphthylamines may be prepared by reduction of the corresponding nitro compound, but they are readily accessible from naphthois by the Bucherer reaction The naphthol is heated, preferably under pressure in an autoclave, with ammonia and aqueous sodium hydrogen sulfite solution, when an addition-elimination sequence occurs. The detailed mechanism is not completely elucidated, but the Bucherer reaction is restricted to those phenols that show a tendency to tautomerize to the keto form, such as the naphthois and 1,3-dihydroxybenzene (resorcinol). Using 1-naphthol for illustration, the first step is addition of the hydrosulfite across the 3,4-double bond of either the enol or keto tautomer (Scheme 12.9). Nucleophilic attack by ammonia at the carbonyl group... 

This same reaction may be brought about by heating the naphthol with ammonium chloride and sodium hydroxide in an autoclave at 160° for two or three days. This formation of an amino derivative from a hydroxyl derivative by means of ammonia does not usually take place though it is possible to make aniline from phenol in this way. 

The (x-substituted naphthalenes, like substituted benzenes, are ihpst commonly prepared by a sequence of reactions that ultimately goes back to a nitro compound (Sec. 30.8). Preparation of / -substituted naphthalenes, on the other hand, cannot start with the nitro compound, since nitration does not take place in the j3-position. The route to /3-naphthylamine, and through it to the versatile dia-zonium salts, lies through /9-naphthol. /9-Naphthol is made from the /3-sulfonic acid it is converted into /8-naphthylamine when heated under pressure with ammonia and ammonium sulfite (the Bucherer reaction, not useful in the benzene series except in rare cases). 

They are produced technically by two methods, either by direct sulphonation of the naphthylamines or by heating the naphthol-sulphonic acids with ammonia (he., a compound yielding ammonia on heating). 

Bucherer reaction. A procedure for preparation of (i-naphthylamineby heating (i-naphthol with a water solution of ammonium sulfite. A sulfite solution is prepared by saturating concentrated ammonia solution with sulfur dioxide and adding an equal volume of concentrated ammonia solution, (i-naphthol is added and the charge is heated in an autoclave provided with a stirrer or a shaking mechanism. (L. F. Fieser). This reaction is also involved in the preparation of several azo dye intermediates, e.g., Tobias acid. 

Derivation Sulfonation of (i-naphthol with chloro-sulfonic acid in nitrobenzene at OC followed by heating the resulting 1-sulfonic acid with ammonium hydrogen sulfite and ammonia at 145-150C. Purification is by precipitation from dilute solution of the sodium salt. 

The second observation concerns the increase in the hydrogen-bonding interaction of the O—H moiety of the hydroxyarene. Several observations of this effect were reported in the past, for phenol, naphthol and pyrenol derivatives. Perhaps the most direct observation concerns the red shift observed in the IR absorption frequency of the complexed O—H bond. A shift of about 250 cm was observed for O—H- O and O—H- N type bonds of 1 1 complexes of 1-naphthol with water and ammonia when 1-naphthol was electronically excited. This shift translates to an about 0.7 kcalmol" increase in the hydrogen-bonding interaction in the excited state of the photoacid. A similar effect was observed in solution by Weller for the system 1-hydroxypyrene complexed with pyridine in methylcyclohexane. Other observations include phenol and 1- and 2-naphthol complexed with dioxane in isooctane ", and HPTA complexed with dioxane and DMSO in dichloromethane and dichloroethane. In all cases the hydrogen-bonding interactions of the photoacid were found to increase upon electronic excitation by 0.5-3 kcalmol. No proton transfer was observed in these systems. 

To a solution containing not more than 30 pg of Co, add 1 ml of the 1-nitroso-2-naphthol (or 2-nitroso-l-naphthol) solution with stirring, adjust the pH of the solution with ammonia to 4 (or 5 in the case of 2-nitroso-l-naphthol), and allow to stand for 30 min. Transfer the solution to a separating funnel and extract with two portions of CHCI3. Shake the combined extracts with 2 M HCl, followed by two portions of 2 M NaOH, and finally wash with water. Transfer the extract to a 25-ml standard flask, make up to the mark with chloroform, and measure the absorbance of the solution at 415 nm (in the case of 2-nitroso-l-naphthol, at 365 nm), using the solvent as the reference. 

It is also manufactured by heating a-naphthol with an aqueous solution of ammonia and ammonium sulphite at 120°-150° in an antoclave. It possesses a disagreeable fsecal-like odor, sublimes readily, and turns brown in the air. It crystallizes in colorless needles or prisms, melts at 50°, and boils at 300°. Solutions of its salts give a blue precipitate with ferric chloride and other oxidizing agents. 

To remove Ni or Co, the ZnS04 solution is made alkaline with ammonia and filtered through alumina that has been pretreated with an alcoholic solution of, respectively, diacetyldioxime or a-nitroso-/8 -naphthol. 

For fast reactions of the type represented by reaction 13.2, carried out under the conditions stated earlier, micromixing becomes the dominant consideration. However, studies on the effect of micromixing in such reactions are sparse. Some examples are as follows nitration of aromatic componds in general (Schofield, 1980), potassium metal-provoked reactions of aryl halides with amide and acetone enolate ions (Tremelling and Bunnett, 1980X coupling of 1-naphthol with diazotized sulfanilic acid (Bourne et al., 1981, 1985), reactions of o-(3-butenyl)-halobenzenes and 6-bromo-1-hexene with alkali metals in ammonia/terr-butyl alcohol solution (Meijs et al., 1986), and monoacylation of symmetrical diamines (Jacobson et al., 1987). In some fast reactions, hydrogen ions are produced. 

The amination of naphthalene using primary or secondary amines is one type of modification, and the treatment of naphthol with a complex of Lewis acid and ammonia is another modification. The latter was reported before the Bucherer reaction was published. 

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