Hydroquinonic aldehydes. II.Cardani, Cesare; Grunanger, Paolo.
Gazz. chim. ital. (1955), 85 252-62.
CAN 50:56769 AN 1956:56769
Abstract
cf. C.A. 49, 2357b. In a continued study of disubstituted hydroquinonic aldehydes, the conditions of oxidation were changed so that better yields were obtained. The possibility of applying the Duff reaction directly to hydroquinones instead of to phenols was then studied. p-C6H4(OH)2 (I) does not react in this way, but 1,4,2,5-(HO)2C6H2Me2 (II) and 5,4,2-Me(HO)2C6H2CHMe2 (III) from the corresponding aldehydes. The secondary products isolated from the Duff reaction are phenols, and in the Elbs oxidation of salicylaldehydes are dialdehydes and hydroquinones.
Aq. K2S2O8 (21.3 g. in 800 cc.), added during 4 hrs. (50 cc. each 15 min.) to a mixt. of 9.2 g. KOH in 274 cc. H2O and 100 cc. C5H5N and 8 g. carvacrylaldehyde at 16-18°, the mixt. let stand 18 hrs., acidified (Congo red), filtered, extd. with Et2O, 1/6 vol. of concd. HCl added to the aq. soln., the soln. heated at 70°, let stand, filtered, the residue (1.1 g.) extd. with hot petr. ether, the ext. let stand, the ppt. sublimed in vacuo, the residue from the hot extn. sublimed, and the 2 products combined, gives 0.6 g. 3,6,2,5-Me(Me2CH)(HO)2C6HCHO (IV), m. 184.5-5°. The aq. soln. extd. with Et2O, the ext. dried by Na2SO4, evapd., and the residue extd. with warm H2O, leaves a little IV. C5H5N was used to increase the soly. of the intermediate alk. salt and thus increase the yield. Glycerol (32 cc.) and 9 g. H3BO3 heated 30 min. at 170°, a mixt. of 6.4 g. II and 6.4 g. (CH2)4N6 (V) added slowly (keeping the temp. not over 160°), the mixt. cooled to 110°, 7.7 cc. concd. H2SO4 in 26 cc. H2O added, the mixt. extd. with Et2O, the ext. evapd., and the residue purified by C6H6, give 0.8 g. 2,5,3,6-Me2(HO)2C6HCHO (VI), m. 139-41°. Alc. VI (0.2 g. in 10 cc.) and 0.15 g. o-C6H4(NH2)2 refluxed 4 hrs., let stand, and the ppt. purified by EtOH, give the Schiff base, C15H16O2N2, orange-yellow, m. 210°. III (3.5 g.) and 3.5 g. V made to react in the same way with 4.9 g. H3BO3 and 17 g. glycerol, the mixt. acidified with dil. H2SO4, the ppt.
(9.2 g.) dissolved in Et2O, the soln. percolated through a column of active Al2O3, and the 1st fraction evapd., give 1.2 g. 2,5,3,6-Me(Me2CH)(HO)2C6HCHO m. 180-1°. Elution with Et2O, and then Et2O-MeOH, gives a product with lower m.p., probably a mixt. of 2 isomeric aldehydes, which could not be sepd. even by repeated sublimation or crystn. from C6H6. o-Allylphenol (8 g.) and 8 g. V, added slowly to 40 cc. glycerol and 11.2 g. H3BO3 at 150-60°, the mixt. heated 15 min. longer at 150-60° and cooled to 110° 9.6 cc. concd. H2SO4 + 32 cc. H2O added slowly, the mixt. steam distd., the distd. oil extd. with Et2O, and the ext. dried and evapd., give 1.05 g. 2.3-HO(CH2:CHCH2)C6H3CHO (VII), yellowish oil, b2 90°. Further steam distn. gives a small amt. of an impure compd. (VIII), m. 71-3°.
Following the procedure of Renz (C.A. 41, 4128h), oxidation of VII by alk. K2S2O8, decompn. of the ester by heating with an acid, cooling, and purification of the ppt. by H2O, gives 3,2,5-CH2: CHCH2(HO)2C6H2CHO (IX), yellow, m. 120-1°. IX (0.2 g.) in glacial AcOH and 0.4 g. PhHNHNH2 let stand 2 hrs., poured into ice-water, and the ppt. purified by C6H6, give the phenylhydrazone, C10H16O2N2, m. 116-17°; in EtOH with FeCl3 it gives intense violet solns., which are decolorized by reducing agents. In dil. aq. alkalies, IX slowly oxidizes to a violet product. IX (0.1 g.) and 0.15 g. 2,4-(O2N)2C6H4NHNH2 in MeOH contg. a little HCl, heated briefly, and the product purified by EtOH, give the dinitrophenylhydrazone, C16H14O6N4, red, m. 258-9° (decompn.). The white product obtained in the prepn. of 3,6,2-Me2(HO)C6H2CHO from the steam distillate (cf. C.A. 49, 2357b), purified by MeOH, gives 2,5,4,6-Me2(OHC)2C6HOH, m. 159°; phenylhydrazone, yellow, m. 209-10° (decompn.). VIII, purified by hexane, gives 2,4,6-CH2:CHCH2(OHC)2C6H2OH (X), m. 75-6°. With excess alc. PhHNNH2, X gives, after purification by glacial AcOH, the bis(phenylhydrazone), C23H22ON, yellow, m. 208-10° (decompn.).
With p-O2NC6H4NHNH2 in glacial AcOH, X gives, after purification by aq. C5H5N, the bis(p-nitrophenylhydrazone), C23H20O5N6, intense red, decomp. 275-80°. Prolonging the steam distn. or extg. with Et2O the nonvolatile residue in the prepn. of 2,5,6-Me(Me2CH)(HO)C6H2CHO, and crystg. the product from EtOH, gives 5,2,4,6-Me(Me2CH)(OHC)2C6HOH, m. 79°. With excess alc. PhNHNH2, and purification by glacial AcOH, it gives the bis(phenylhydrazone), C24H26ON4, yellow, m. 197-8° (decompn.).
The prepn. of 2,5,3,6-Me(Me2CH)(HO)2C6HCHO (XI) already described (cf. loc. cit.) was modified. After having acidified with concd. HCl and heated the soln. at 70°, the ppt. was sepd. to obtain XI. The aq. mother liquor, extd. with Et2O, the ext. evapd., the residue fractionally crystd. from boiling water to remove XI, the mother liquor satd. with (NH4)2SO4 or extd. with Et2O, and the recovered product purified by sublimation, gives thymohydroquinone (XII), m. 143°. The yield is 0.2 g. per 8 g. thymolaldehyde. The ppt. formed by satg. with (NH4)2SO4 the mother liquor in the prepn. of IV, sublimed and crystd. from H2O, gives XII. In the prepn. of IX, the filtrate from the removal of IX, extd. with Et2O, and the ext. evapd., gives a mixt. of IX and another compd.; the latter, sepd. by H2O (IX is insol.), the soln. satd. with (NH4)2SO4, extd. with Et2O, the ext. evapd., and the residue purified by C6H6, gives allylhydroquinone, m. 93°.
Applied to I, the Duff reaction does not give an appreciable yield of 2,5-(HO)2C6H4CHO, but some unaltered I and a large amt. of resin.
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