3- -2-naphthaldehyde,

Decant the ethereal solution from the yellow aldimine stannichloride which has separated, rinse the solid with two 50 ml. portions of ether, and transfer the solid to a 2-5 litre flask fitted for steam distillation and immersed in an oil bath at 110-120°. Pass steam through a trap (compare Fig. 11,40, 1,6) to remove condensed water, then through a superheater heated to 260° (Fig. I, 7, 2), and finally into the mixture (2). Continue the passage of y steam until the aldehyde is completely removed (4-5 litres 8-10 hours). Filter the white soUd at the pump, and dry in the air. The resulting p-naphthaldehyde, m.p. 53-54°, weighs 12 g. It may be further purified by distillation under diminished pressure (Fig. II, 19, ) -, pour the colourless distillate, b.p. 156-158°/15 mm., while hot into a mortar and powder it when cold. The m.p. is 57- 58°, and the recovery is over 90 per cent. 

It has been stated that thiourea (about 20 per cent, of the weight of the palladium - barium sulphate) may also be used as a catalyst poison. 

In a 500 ml. flask, fitted with a reflux condenser, place 53 g. of 1-chloro-methylnaphthalene (Section IV.23), 84 g, of hexamethylenetetramine and 250 ml. of 1 1 acetic acid [CAUTION 1-Chloromethylnaphtha-lene and, to a lesser degree, a-naphthaldehyde have lachrymatory and vesicant properties adequate precautions should therefore be taken to avoid contact with these substances.] Heat the mixture under reflux for 2 hours it becomes homogeneous after about 15 minutes and then an oil commences to separate. Add 100 ml. of concentrated hydrochloric acid and reflux for a further 15 minutes this will hydrolyse any SchifiF s bases which may be formed from amine and aldehyde present and will also convert any amines into the ether-insoluble hydrochlorides. Cool, and extract the mixture with 150 ml. of ether. Wash the ether layer with three 50 ml. portions of water, then cautiously with 50 ml. of 10 per cent, sodium carbonate solution, followed by 50 ml. of water. Dry the ethereal solution with anhydrous magnesium sulphate, remove the ether by distillation on a steam bath, and distil the residue under reduced pressure. Collect the a-naphthaldehyde at 160-162718 mm. the yield is 38 g. 

P-Naphthaldehyde. This preparation illustrates the use of -bromo-succinimide (Section VI.26) in the conversion of the readily available P-methylnaphthalene into 2-bromomethylnaphthalene and of the latter into p-naphthaldehyde by the Sommelet reaction. 

Checked by Nath n L Drake, Harry D Anspon, and R lph Mozingo. 

A 500-cc. three-necked flask, equipped with ground joints, is fitted with a mercury-sealed stirrer (Note 1), a reflux condenser, 

After the air in the reaction flask has been displaced by hydrogen, the flask is heated in an oil bath at 140-150°, the stirrer is started (Note 5), and 1 cc. of alkali is run into the Erlenmeyer flask. The course of the reaction is followed by the rate of hydrogen chloride evolution. The first 5 cc. of alkali should be neutralized in twelve to fifteen minutes, and the reaction should be complete in approximately three hours. About 92 per cent of the theoretical amount of hydrogen chloride (equivalent to 55 cc. of 5 N sodium hydroxide solution) is recovered. The end of the reaction is evidenced by a rather abrupt cessation of hydrogen chloride evolution, and the reaction is discontinued at this point. 

The flask is cooled, 1-2 g. of Norite added with stirring, and the solution filtered with suction through a hardened filter paper (Note 6). The xylene is removed from the nearly colorless filtrate by flash distillation under diminished pressure. For this purpose, a 125-cc. modified Claisen flask is arranged for vacuum distillation, the usual capillary being replaced by a separatory funnel whose stem extends to the bottom of the flask. The 

1 Prepared by the method described in Houben, Die Methoden der organ-ischen Chemie, 3rd Ed Vol II, p 500, Verlag Georg Thieme, Leipzig, 1930, Schmidt, Her 52, 401 (1919) 

Submitted by S. J. Angyal, J. R. Tetaz, and J. G. Wilson. Checked by R. S. Schreiber and Paul E. Marlatt. 

Caution Precautions should be taken to avoid contact with i-chloromethylnaphthalene, which is a lachrymator and a vesicant, and with the aldehyde, which seems to possess the same properties to a lesser degree. 

In a 1-1. flask fitted with a reflux condenser are placed 106 g. (0.6 mole) of 1-chloromethylnaphthalene 1 (Note 1), 168 g. (1.2 moles) of hexamethylenetetramine, 250 ml. of glacial acetic acid, and 250 ml. of water. This mixture is heated under reflux for 2 hours. In about 15 minutes the solution becomes homogeneous, and then an oil starts to separate. After the reflux period, 200 ml. of concentrated hydrochloric acid is added and refluxing is continued for an additional 15 minutes (Note 2). After cooling, the mixture is extracted with 300 ml. of ether the ether layer is washed three times with 100-ml. portions of water, then with 100 ml. of 10% sodium carbonate solution (Note 3), and again with 100 ml. of water. The ether extract is dried with about 15 g. of anhydrous sodium sulfate and filtered, and the ether is removed by distillation. The residual liquid is distilled under reduced pressure, the distillate being collected at 105-107°/0.2 mm. or 160-162°/18 mm. (Note 4). The yield of colorless 1-naphthalde-hyde freezing between 0.0° and 2.5° (Note 5) is 70-77 g. (75-82%). 

The checkers found that crude chloromethylnaphthalene obtained from the preparation in Organic Syntheses 1 could be used with good results. Naphthalene, paraformaldehyde, hydrochloric acid, and phosphoric acid are heated under reflux according to the procedure described. After the crude product is washed with water, 10% potassium carbonate, and water, it is dissolved directly in 500 ml. of glacial acetic acid, diluted with 500 ml. of water, and treated with hexamethylenetetramine by the procedure described above. The over-all yield of almost colorless 1-naphthaldehyde is 162 g., b.p. 162-164°/18 mm. 1.6503 (52% yield based on naphthalene). 

In this variation of the preparation, it is best to use a wide-bore tube as a condenser to remove the unreacted naphthalene. After the naphthalene has been distilled, the wide-bore tube is replaced with an ordinary condenser and the naphthaldehyde is distilled in the usual manner. 

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Although phenylmagnesium bromide and zinc chloride do form an equilibrium mixture of diphenylzinc and magnesium halide, diphenylzinc is not thought to be the actual organometal-lic reagent in this addition reaction. In fact, even at room temperature, the addition reaction of pure diphenylzinc to 2-naphthaldehyde in the presence of 21 is very slow, affording little of the addition product. 

The testing of 2-nitrobenzyltriphenylphosphonium bromide and methyl 4-formylbenzoate and four other aldehydes, 3-benzyloxybenzaldehyde, 2-naphthaldehyde, 5-nitrothiophene-2-carboxaldehyde and 4-[3-dimethylamino)propoxy]benzaldehyde, has been reported [13]. 

The photoreductions of a number of carbonyl compounds with either lowest mr or jiji triplet states in the presence of tributyltinhydride are reported24. The carbonyl compounds include cyclohexanone and acetone which possess nrr lowest-energy triplets, and 2-acetonaphthone, 1-naphthaldehyde and 2-naphthaldehyde which possess lowest-energy mr triplets. In the case of the two njr triplets, a simple mechanism is proposed which involves the abstraction of a hydrogen atom from the tributyltinhydride by the triplet state... 

Many aromatic aldehydes and ketones (e.g. benzophenone, anthrone, 1- and 2-naphthaldehyde) have a low-lying n-n excited state and thus exhibit low fluorescence quantum yields, as explained above. The dominant de-excitation pathway is intersystem crossing (whose efficiency has been found to be close to 1 for benzophenone). 

Chemical/Physical. An aqueous solution containing chlorine dioxide in the dark for 3.5 d at room temperature oxidized 2-methylnaphthalene into the following l-chloro-2-methylnaphtha-lene, 3-chloro-2-methylnaphthalene, l,3-dichloro-2-methylnaphthalene, 3-hydroxymethylnaphtha-lene, 2-naphthaldehyde, 2-naphthoic acid, and 2-methyl-l,4-naphthoquinone (Taymaz et al., 1979). 

Scheme 11 Photoaddition of PhCH2SiMe3 with 2-naphthaldehyde (2-NA) via photoin-duced electron transfer from PhCH2SiMe3 to the singlet excited state of the 2-NA-Mg...

The relative energies of the excited states may be such that intersystem crossing may not be favorable. For example, 3- and 4-pyrene-aldehyde, 2-naphthaldehyde, 9-anthraldehyde, 3-acenaphthaldehyde,... 

Naphthaldehyde [66-99-9] M 156.2, m 59°, b 260°/19mm. Distilled with steam and crystd from water or EtOH. 

This type of catalytic strategy has recently been extended to enantio-selective addition of alkyllithiums to certain prochiral imines (Scheme 18) (35). Relevantly, in the presence of a small amount of a chiral ether ligand, 1-naphthyllithium reacts with a sterically hindered imine of l-fluoro-2-naphthaldehyde (conjugate addition/elimination) to afford a binaphthyl compound in greater than 80% ee. 

Although carbonyl compounds are generally nonfluorescent because of fast intersystem crossing to generate the phosphorescent lowest n,n triplet excited state [187], irradiation of the absorption band due to Mg2+ complex of 1-naphthaldehyde (1-NA) or 2-naphthaldehyde (2-NA) formed in the presence of Mg(C104)2 causes strong fluorescence at 430-440 nm as shown in a general manner (Scheme 22) [188]. 

To a solution of 1.5 g 1,4-dimethoxy-5,6,7,8-tetrahydro-2-naphthaldehyde in 20 g nitromethane there was added 0.14 g anhydrous ammonium acetate and the mixture heated on the steam bath for 50 min. The rate of the reaction was determined by TLC monitoring, on silica gel with CH2C12 as the moving solvent the Rf of the aldehyde was 0.70, and of the product nitrostyrene, 0.95. Removal of the volatiles under vacuum gave a residue that spontaneously crystallized. The fine yellow... 

A typical procedure is that described in Expt 6.119 for the synthesis of 1-naphthaldehyde. The synthesis of p-nitrobenzaldehyde provides an example in which the intermediate crystalline hexamine salt is isolated prior to hydrolysis. 2-Naphthaldehyde is prepared from the bromomethyl compound, the preparation of which illustrates the use of Af-bromosuccinimide for effecting benzylic bromination of 2-methylnaphthalene. 

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