Bull. Soc. Chim. Fr. 1961

[orgsynchem]

Scriabine, I.
Bull. Soc. Chim. Fr. 1961, 1194

Scriabine, Igor
New method of preparation of dihydrocinnamic aldehydes
1961, Номер 6, pages 1194-1198
Dihydrocinnamaldehydes were prepared by condensation of aromatic hydrocarbons with acrolein (I) and its alkyl derivatives, or preferably their diacetates, with TiCl4 and promoters. By this method, alkylbenzenes condensed with α-substituted I (but not crotonaldehyde) and with α-, β-, and α,β- (but not β,β-) substituted I diacetates. The structures of the products were established by phys. properties, derivatives, oxidation with Ag2O to known acids, and oxidation to terephthalic acid. Crude 4-MeC6H4(CH2)2CHO (II) and 4-EtC6H4CH2CHEtCHO (III) were contaminated with the o-substituted isomers. Cumene (IV) (120 mL.), 11 mL. TiCl4, and 0.25 mL. BF3.Et2O was treated slowly with stirring at -10° with 7 g. CH2:CMeCHO (V) in 30 mL. IV, the mixture stirred 10 min. and poured onto 100 g. ice and 20 mL. concentrated HCl, and the organic layer washed with water and neutralized with 5% NaHCO3 to give 30.4% 4-Me2CHC6H4CH2CHMeCHO (VI), b1.5 100°, n17D 1.503; semicarbazone (SC) m. 170°; 2,4-dinitrophenylhydrazone (DNPH) m. 116°. Similarly prepared were (compound, reaction temperature and time (min.), % yield, b.p., and refractive index of product, and m.p. derivatives listed): II, -30°, 20, 30, b1.5 80-1°, n14D 1.5235, SC 169-70°, DNPH 121-2°; 4-MeC6H4CH2CHMeCHO (VII), -10°, 40, 22, b6.5 108-9°, n25D 1.5098, SC 154°; 4-MeC6H4CH2CHEtCHO (VIII), -10°, 80, 19, b2 97-100°, n31D 1.5070, SC 125-6°, DNPH 118-19°; 4-EtC6H4(CH2)2CHO, -30°, 40, 29, b1.2 93°, n25D 1.516, SC 162-3°; 4-EtC6H4CH2CHMeCHO, -10°, 65, 18.5, b0.5 89°, n24.5D 1.511, SC 161-2°; III, -10°, 90, 30, bI 98-9°, n26D 1.5072, SC 82-3°, DNPH 84-8°; 4-Me2CHC6H4(CH2)2CHO (IX), -30°, 100, 38, b0.8 90°, n26D 1.5090, SC 152°; 4-Me2CHC6H4CH2CHEtCHO (X), -10°, 80, 36, b1.2 105°, n28.5D 1.5010, DNPH 98-9°; 4-sec-BuC6H4(CH2)2CHO, -30°, 66, 33, b0.6 100-4°, n26D 1.510, SC 112-13°; 4-sec-BuC6H4CH2CHMeCHO, -10°, 65, 7.5, b1 119°, -, SC 142-4°; 4-tert-BuC6H4(CH2)2CHO, -30°, 27, 19, b2.5 112-14°, -, SC 159-60°; 4-tert-BuC6H4CH2CHMeCHO, -10°, 120, 17, b1 102-4°, n25.5D 1.507, SC 160-1°; 2,5-Me(Me2CH)C6H3(CH2)2CHO, -30°, 45, 16, b0.5 92.5°, n27D 1.514, SC 145°. Ac2O (250 mL.) and 2.5 g. anhydrous ZnCl2 was treated with stirring during 1 h. at -3 to 0° with 91 g. V and the mixture stirred 1 h., treated with 2.5 g. anhydrous NaOAc in 15 mL. HOAc and a trace of hydroquinone, and distilled under N to give 98% CH2:CMeCH(OAc)2 (XI), b10 84.5-5°, d15 1.056, n24D 1.4270. Similarly prepared were (the last 5 required 6-7 h. at 20-5°): 78% CH2:CHCH(OAc)2, b20 85-6°, n24D 1.421; 85% CH2:CEtCH(OAc)2, b6 76.5-7°, n23D 1.4275, d25 1.027; 93% MeCH:CHCH(OAc)2, b10 92-3°, n25D 1.4270; 81.5% CH2:C(CHMe2)CH(OAc)2, b4 73°, n27D 1.4257, d25 1.003; 77% EtCH:CMeCH(OAc)2, b1.2 86-7°, n25D 1.437; 80% Me2C:CHCH(OAc)2, b10 98-9°, n20D 1.4350; 75% CH2:CH(CH2)2CH(OAc)2, b0.3 63-4°, n26D 1.4264. To 600 mL. IV, 120 mL. TiCl4, and 2.5 mL. BF3.Et2O at -10° was added during 100 min. 172 g. XI in 150 mL. IV and the mixture stirred 40 min. and worked up as in the preparation of VI above to give 71.5% 4-Me2CHC6H4CH2CH:CHOAc (XII), b10 161-2°, n25D 1.5007, d25 0.9813. Saponification of XII with excess K2CO3 in aqueous MeOH gave 98% VI. Enol acetates of aldehydes unsubstituted in the α-position were hydrolyzed with H2SO4 in aqueous alc. Thus prepared with the appropriate diacetates were (aldehyde, temperature and time (min.) of condensation reaction, % yield, b.p., and refractive index of the enol acetate, % yield, properties, and m.p. of derivatives of the aldehyde listed): Ph(CH2)2CHO, 8°, 100, 35, b1 85°, n22D 1.5185, 83, b12 101°, n21.5D 1.5190, SC 126.5°; PhCH2CHMeCHO, 6°, 135, 31, b1 90-2°, n24D 1.5140, 86, b6 92°, n29D 1.5087, SC 123-4°, DNPH 119°; PhCH2CHEtCHO, 6°, 120, 36, b0.9 90-2°, n24D 1.5105, 87, b10 104.5°, n26D 1.5063, DNPH 116.5°; PhCH2CH(CHMe2)CHO, 6°, 115, 20, b0.5 96-7°, n28D 1.5060, 88, b10.5 120.5°, n28D 1.5020, DNPH 143-4°; VII, -10°, 120, 86, b1.5 96-7°, n25D 1.5142, 93, -, -; VIII, -10°, 120, 77, b2 125-6°, n28D 1.5090, 91, -, -; 4-MeC6H4CHMeCH2CHO, -10°, 125, 58, b1104-5°, n29D 1.5125, 87, b9 110.5-11.5°, n25D 1.5112, SC 78-81°, DNPH 110-13°; III, -10°, 165, 70, b1.3 113-14°, n32D 1.5075, 92, -, -; IX, -10°, 140, 84, b0.5 98-100°, n24D 1.5160, 69, -, -; X, -10°, 120, 58, b1 120°, n25D 1.5060, 89, -, -; 4-Me2CHC6H4CHMeCH2CHO (XIII), -10°, 140, 36, b0.5 107-10°, -, 76, b0.4 89-91°, SC 131-2°, DNPH 118-20°; 4-Me2CHC6H4CHEtCHMeCHO, -10°, 140, 47, b0.5 114-15°, n24D 1.5100, 79, b0.9 104-5°, DNPH 169-9.5°; 4-MeOC6H4(CH2)2CHO, -10°, 140, 85, b1 113-16°, n25D 1.5245, 84, b1 82-4°, n25D 1.5257, SC 138°, DNPH 136.7°; 4-MeOC6H4CH2CHMeCHO, -10°, 140, 88, b0.5 124-9°, n26D 1.5210, 88, b0.3 90°, n27D 1.5175, SC 157-8°, DNPH 126-8°; 3,4-(MeO)2C6H3CH2CHMeCHO, 0°, 100, 62, b0.5 142-3° (m. 47-9°), -, 85, b0.8 134-5°, n24D 1.5270, SC 187-8°, DNPH 154-5°. III with Ag2O gave 91% oily acid (amide m. 84-6°; p-toluidide m. 94-5°; acid chloride (XIV) b4 104°). XIV with AlCl3 gave 69% 2,6-diethyl-1-indanone, b0.5 94°, n24D 1.5375; SC m. 176-8°; DNPH m. 198-9°. IV, MeCHOH(CH2)2OH, and AlCl3 gave 26% 4-Me2CHC6H4CHMe(CH2)2OH, b0.5 97-9°, n21D 1.5110, which with Cu at 260° and 12 mm. gave XIII, b0.7 90-2°, n20D 1.5065.