Synthesis of Phenylacetic Acids from Gallic Acid and Its Methyl Ethers

SYNTHESIS OF PHENYLACETIC ACIDS FROM GALLIC ACID AND ITS METHYL ETHERS.

BY TI-IE LATE A. N. ~{ELDRUM AND P. i. PARIKH, Royal Institute of Science, Bombay.

Received December I0, 1934. (Communicated by Dr. T. S. "Wheeler, Ph.D., F.I.C., F.mSt.r., l~I.Lchem.E.) SEVERAl, phenylacetic acids have been synthesised by Meldrum and colla- borators, t through three successive reactions, viz., (i) Condensation of a hydroxy-benzoic acid with chloral, (ii) Reduction of the group CHOHCC13 to CH2CHCI.~ with zinc and acetic acid, and then (iii) Simultaneous hydrolysis and oxidation of CH2CHCI~ to CH~COOH with sulphuric acid. The present work was undertaken to extend this method to the preparation of phenylacetic acids from gallic acid and its methyl ethers. Gallic acid (I) when condensed with chloral in presence of sulphuric acid yielded the 3-4-5-trihydroxy-2-a-trichloromethyl-phthalide (II).2 The acetyl derivative on reduction with zinc and acetic acid gave 3-4-5- triacetyl-2-fi-dicMoroethyl benzoic acid (III), which on treatment with concentrated sulphnric acid yielded 2-3-4-trihydroxy-6-carboxy-l-pheny~- acetic acid (IV). The same reactions were tried with the derivatives of galHc acid, viz., t~imethyl-gallic acid (viii) and syringic acid (XlII). 3-4-5-trimethoxy-2-/3-trichloromethylphthalide (IX) s gave on reduction with acetic acid and zinc, 3-4-5-trimethoxy-2-fl-dichloroethyl benzoic acid (X), which with s~Iphuric acid yielded 2-3-4-trimethoxy-6-carboxy-l-phenylacetic acid (XI). 3-5-dimethoxy-4-hydroxy-2-a-trichloromethylphthalide (XIV) 4 was reduced to 3-5-dimethoxy-6-hydroxy-2-fi-dichloroethyl benzoic acid (XV).

1 Alimchand~ni aad Melclrum, J., 1921, 119, 201 ; Shah and Alimchanclani, ,I. Ind. Chem. Soc., 1931, 8, 261 ; Meldrnm and Kapadia, ,7. Ind. Chem. Soe., 1932, 9, 483. 2 Alimehandani and l~eldrum, J., 119, 206. s Bargelline and Molina, Atti. R..Accad. Zince4., 1912, Y, 21, 11, 146. Alimchandani and Bieldrum. J., 1920, 117, 964. 431 432 A. N. Meldrum and P. H. Parlkh

The reduction product yielded 2-4-dimethoxv-3-hydroxy-6-carboxy-1- pheuylacetic acid (XVI) with sulphuric acid. The reactions have also been used to produce a phenyl bisaeetic acid by further condensing the phenylacetie acid (I V) to (V), subsequent reduction of (V) to (VI) and converting (VI) to 2-3-4-trihydroxy-6-carboxy phenylene 1-5 bisacetic acid (vii) as usual. OH OH OAe ~o ( oli ,io( o,i .oo/N OAc --> -_~ --> CLI2CHC12 \/ \/i l~ccI~ \/ cool:l I COOH 0 C-- 0 (I) (31) (115) 4 OH I:IO /\ oi~i

,~//CII2CI:ICI2 COOI:[ (Ilia) OK OH OH 1f0 /\-oH -+ HO (~0H ---> HO /\-oi-i

ClaCt-Ii ,~( CtI2COOH C12t-ICI~I2 C (//J C!:FI2CO0H COOH COOH O--CO (IV) (v) (vI) OH

ooc~c __~ c~co oH N/ COOI-I (vii) OM-e OCH~ l~eO(~] OMe l:IaC0 -_.> 07: -+ \/ COOFr OC 0 (viii) (IX) Synthesis o/Phe~eylecetic Acids 433 OCH~ 0C1% OCtta H3CO /~ 0 CH~ Ha CO /\-ocK K:~CO --+ \/CI-I2C]~cI2 CI3CItC \/oH._,cooK COOK I COOI-I O--COI, (X) (iT) (XlI) OH OH OH oct-I~ Tr3C0 ~) i IcICC]3 CO OI-I COOH OC--0 (XIII) (XIV) (XV) OIt -> \;-Cl-l~COOl~. I COOH (XVI) Experimental. 3-4-5-t.riace~yl-2-fl-dichloroeg~yI benzoic acid (III).--3-4-5-triacetyl-2-fl- dichloroethyl phthalide (II) was dissolved in #aciaI acetic acid (70 c.c.), zinc dust (10 g.) was added in portions while the mixture was automatically shaken and occasionally heated on the water-bath. The reduction product separated. After about two hours the mass was treated with hot acetic acid and filtered from unchanged zinc. The filtrate was then diluted with water when a white crystalline solid was obtained. This was crystallised from dilute alcohol in feathery concentric needles, m.p. 189 ~ (Found: Equiv. 389- 0 ; C1, 18.26 ; C15 I-I~ Os C12 requires Equiv. 393- 0 ; C1, 18- 07 per cent.). The substance is soluble in alcohol, acetone, benzene, chloroform, moderately so in glacial acetic acid and insoluble in petrol-ether, carbon- disulphide, toluene and water. $-4-5-trihydroxy-2-fl-dichloroethyl benzoic acid (IIIa).--(III) (5 g.)was dissolved in methyl alcohol (30 c.c.). Concentrated sulphuric acid (15 c.c. 98%) was added and the mixture was heated on the water-bath until no smell of methyl acetate was to be observed. The mixture was poured into water and extracted with ether. It crystallised from chloroform in white shining needles, m.p. 131 ~ (Found : C1, 25-19 ; C10 H10 O~C12 requires 25.27 per cent.). 434 A. N. Meldrum and P. H, Parikh

The substance is the methyl-ester. It was hydrolysed with sulphuric acid (60%). Crystallisedfrom a mixture of ace~cone and petrol-ether, in rectangular plates, m.p. 178~ ~ (Pound : CI, 26.46 ; C9 I-IsOs C12 requires, CI, 26.55 per cent.). The substance is sol~able in alcohol, acetone, ether, toluene, acetic acid, water, insoluble in benzene, petrol-ether, chloroform and carbon disulphide. 2-3-4-trihydroxy-6-cerboxy-l-pheny~aeetic acid (IV).--(III)(10g.) was treated with concentrated sulphuric acid when hydrogen chloride was evolved. The temperature of the mixture should not be allowed to rise more than 80 ~ The yellow mixture was then poured on to crushed ice when a solid separated. This was filtered, washed, and finally crystallised in long needles. The substance has no definite m.p. but turns brown at 252 ~ and completely black at 2600-265 ~ (Found : C, 47.21 ; H, 3.48 ; Co Its 07 requires C, 4-7.35, I-I, 3.53 per cent.). The substance is very soluble in alcohol and hot water, insoluble in ether, chloroform~ benzene, toluene and petrol-ether. The ethyl ester crystallised from dilute alcohol in concentric needles, m.p. 2280-229 ~ (Found : C, 54-.80 ; l-t, 5- 6 per cent. ; C13 H~6 O7 requires C, 54.94; H, 5.67 per cent.). The acet_yl derivative was prepared by the acetic anhydride method. It crystallised from absolute alcohol in slender white needles, m.p. 206~ ~ (Fotmd : C, 50.77 ; t-t, 3.96 ; CI~ t-I1~ Ol0 requires C, 50.83 ; I-t, 3.98 per cent.). 2-3-4-trihydroxy-6-a-tric]r phtha.lide J~henylacetic a.cid (V).--(IV) was condensed with chloral in the usual way. The substance crystallised from a mixture of acetone and chloroform in colourless needles. It becomes brown at 242 ~ and black at 275 ~ (Found : C1, 29.69 ; Cll l-Iv O7 C13 requires C1, 29.74 per cent.). It is soluble in alcohol, acetone and acetic acid; insoluble in benzene, petrol-ether, chloroform, toluene, carbon disulphide, ether and water. A cetyl derivative crystallised from toluene in slender needles, m.p. 119%180 ~ (Found : CI, 21.87 ; C17 I-It30i0 C13 requires CI, 22.02 per cent.). 2-3-4-triacetoxv-5-f3-dichloroethyl-6-carboxy-l-phenylacetic acid (VI~).--The acetyl derivative of (V) was reduced with zinc and acetic acid as usual. The product crystallised from acetic acid and chloroform in needles, m.p. 220%222 ~ (Found : C1, 15.63 ; C17 I-I16 O10 C12 requires C1, 15.71 per cent.). The substance is soluble in ethyl and methyl alcohol, acetone, chloroform, acetic acid, benzene and toluene ; insoluble in petrol-ether, ether and water, 2-3-4--trihydroxy-6-carboxy phenylene-1 : 5-bisacetic acid (vii).--(via) was hydrolysed and oxidised with sulphuric acid in the usual way. The product crystallised from acetone in needles, It turns brown at 258 ~ and black at Sy~zX~esis o/P~e~zy&ce~ic Acids 435

290 ~ . (Found: C, 46.02; I-I, 3.43; Cn Hto 09 requires C, 46.16;H, 3.52 per cent.). The acid is soluble in alcohol, acetone, and insoluble in benzene, chloroform, carbon disulphide, toluene, ether and water. AceXyl derivative was crystallised from alcohol in slender colourless needles, m.p. 2390-243 ~ (decomposes). (Found : C, 49.4 ; I-I, 3.96 ; C~THl~Ot~ requires C, 49.51. ; t-!, 3.91 per cent.). 3-~-5-trimefhox~:-2-fi-dichloroet]tvl be~zoic acid (X).--3-4-5-trimethoxy- 2-fl-trichloromethyl phthalide (IX) 5 was reduced with zinc and acetic acid as usual. The product was crystallised from a mixture of acetolle and petrol ether in white rectangular plates, m.p. 124 ~ (Found : Equiv., 307.5; C1, 22.95 ; C12t-I~OsCI~ requires Equiv., 309 ; C1, 22.98 per cent.). It is soluble in alcohol, acetone, benzene, ether, toluene, xylene, carbon tetrachloride, acetic acid, insoluble in petrol ether, chloroform and water. Lead salt insoluble in water. (Found : Pb, 2-~. 92 ; (Cl~H13OaCl~),,,Pb requires Pb, 25.16 per cent.). 2,3-4-trimethoxy-6-carboxy-!@he~,ylacetic acid (XI).--(X) was hydrolysed and oxidised with concentrated sulphuric acid in the usual way. The product was obtained as a pasty mass. This was ground with water and a few drops of methyl aIcohol and then with benzene when it solidified. It crystallised from benzene and acetone in double pyramids, m.p. 149 ~ The substance is soluble in alcohol acetone, chloroform, ether, acetic acid, sparingly soluble in benzene, water and toluene, insoluble in petrol- ether and carbon tetrachloride. The substance crystallises with too1. of benzene of crystallisation. (Found : Equiv., 308- 6 ; C, 58.11 ; I-I, 5.41 ; C1~H1~O7, requires Equiv., 309.2 ; C, 58- 25 ; It, 5.5 per cent.). Methy[ester prepared as ustml m.p. 480-50 ~ B.P. 2200-225 ~ at 23-25 mm. (Found : C, 56.2 ; I-I, 6.15 ; C1~]?I~807 requires C, 56.37 ; I-t, 6-04 per cent.). Ethylester.--B.P. 2250-2.30 ~ at 20 ram. (Found: C, 58.66 ; H, 6.58 ; ClaH2~.O7 requires C, 58.87; I-t, 6.79 per cent.). Calcium sal~ was crystallised from water in prismatic needles with 8H20 of which only 2H20 are removed at 110~ ~ (Found: Ca, 8.78; C12HI207Ca, 8I-I20 requires Ca, 8-85 per cent.). After heating at 110~ ~ to constant weight. (Found Ca, 10.07 ; C12Hl~O7Ca, 6H20 requires Ca 9- 63 per cent.). Lead s~lt crystallises with 3H20 of which 1.tt~O can be removed at 115~ ~ (Found: Pb, 38.5: C12t{1207Pb, 3I-I20 requires Pb, 39.13

5 Loc. c~t. 2 F 436 A. N. Meidrum and P. H. Parikh per cent.). After heating at 115~ ~ to constant weight (Found: Pb, 39.99 ; CmHi207 Pb, 2H20 requires Pb, 40.15 per cent.). The Anhydride was prepared by heating the acid at m.p. It was crystallised from benzene in rectangular pIates m.p. 121 ~ (Found: Equiv., 267.2 ; Ci2Hi~O7 requires Equiv., 270). 2-3-4-trimethoxy-6-a-trichloromethyl phthalide phe~y[acetic acid (XII).--(XI) was condensed with chloral in presence of sulphuric acid. The pasty amass was dissolved in acetic acid which was then diluted with water, The process was repeatedtitl a solid mass was obtained. This was crystaltised from acetone in square plates m.p. 194 ~ (Found : CI, 26.57 ; CI~III30~Cla requires C1, 26.67 per cent.). The substance is soluble in alcohol, acetone, chloroform, ether, acetic acid, toluene and insoluble in petrol-ether and benzene. 3-5-dimet%oxy-4-hydroxv-2-fi-dichloroethyZ benzoic acid (XV).--3 : 5-dimethoxy-4-hydroxy-2-~-trichloroinethyl phthalide (XIV) was reduced by acetic acid and zinc. The product was crystallised from benzene in rectangular plates, m.p. 158 ~ (Found:Equiv., 292.7; CI, 23.93; Ci1I~<~205C12 requires Equiv., 295 ; C1, 24.07 per cent.). The substance is soluble ir~ alcohol, acetone, toluene, ether, acetic acid, chloroform, sparingly soluble in benzene and ilasolable in petrol-ether, carbon tetrachloride and water. (A further yield is obtained by neutralising the mother-liquor with sodium bicarbonate and extracting with ether.) Acetyl derivative crystallised from benzene in needles, m.p. 178~ ~ witla effervescence. (Found : Equiv., 335.8 ; C1, 21- 16 ; CI3t-I14OGC12 requires Equiv., 337.0 ; C1, 21.0~ per cent.). 2- ~-di~ethoxy- 3-hydroxy- 6-carboxy-p helcylacetic acid (XVI) .-- (XV) was hydrolised and oxidised with snlphuric acid. The solid was crystallised from acetone in rectangular plates, m.p. 243 ~ (Found : Equiv., 256.4; C, 51.42; l-I, 4.61; CnI-Ii.207 requires Equiv., 256 ; C, 51.57 ; l-I, 4.71 per cent.). A cetyZ derivative was crystallised from benzene in rectangular plates, m.p. 189~ ~ (Found : Equiv., 295.8 ; Ci3I-Ii{Os requires Equiv., 298.)