The electrochemical oxidation of trans-cinnamic acid in a mixed aqueous solution of acetic acid and methanol containing potassium hydroxide was studied. The separation of ketones and aldehydes from the neutral materials using Girard reagent P gave benzaldehyde, tolualdehydes, acetophenone, methylacetophenones, propiophenone, phenacyl acetate, and phenacyl alcohol. The mechanism of the anodic reaction of trans-cinnamic acid has been discussed

Oka, Hirotosi

Takeda, Akira

Torii, Sigeru

Okayama University Digital Information Repository

The Anodic Oxidation of trans-Cinnamic Acid. I. The Formation of Ketone and Aldehyde Derivatives

Okayama University Scientific Achievement Repository

MEMOIRS OF THE SCHOOL OF ENGINEERING, OKAYAMA UNIVERSITY, Vol. 3, No.1, SEPTEMBER, 1968The Anodic Oxidation of trans-Cinnamic Acid. I.The Formation of Ketone and Aldehyde Derivatives*Akira T AKEOADepartment of Synthetics ChemistrySigeru TORII and Hirotosi OKA**Department of Industrial Chemistry(Received March 15, 1968)The electrochemical oxidation of trans-cinnamic acid in a mixed aqueoussolution of acetic acid and methanol containing potassium hydroxide wasstudied. The separation of ketones and aldehydes from the neutral materialsusing Girard reagent P gave benzaldehyde, tolualdehydes, acetophenone,methylacetophenones, propiophenone, phenacyl acetate, and phenacyl alcohol.The mechanism of the anodic reaction of trans-cinnamic acid has been dis-cussed.As a manner of our study of the anodic reac-tion, acetic acid has been electrolyzed in thepresence of various organic substrates, chieflyaldehydes, 1),2) ketones, 2),3) acetals, 2) glyci-dates,3) and cyclopropanecarboxylic acids. 4)These attempts provided us with a chance todiscover a new type of anodic methylation ofaldehydes, in which the hydrogen atom at-tached to the carbonyl of aldehyde (1) is re-placed by methyl group giving ketone (2).1),2)CH3COOHR-C-HII1 0AnodicReaction> R-C-CH3IIo 2of the products as is shown in Scheme I, theproduced neutral materials were separated bythe chemical procedure into two groups: oneis the ketone and aldehyde component, theother is the non ketone and aldehyde compo-nent. The constituents of the ketone andaldehyde component were isolated by the frac-tional distillation as is shown in Table III inthe Experimental Section and were identifiedby their retention times of vpc, physical con-stants, formation of derivatives, and compari-son with their authentic samples as are listed inTable IV in the Experimental Section. TheConstituentBenzaldehydeAcetophenonep-Tolualdehydep-MethylacetophenonePhenacyl AcetatePhenacyl Alcohol7.123.203.227.121.00Constituents of the Ketone andAldehyde ComponentTable I6 208 008 3011 3024 1240 40RetentionTime *)min secII' p:~a~;:a*n I(%) I'------c-------c--------! 11.85,In the present paper, the features of the de-compotition of trans-cinnamic acid and of therecombination of generated radicals and ionicfragments in the course of the anodic reactionof acetic acid in aqueous methanol containingpotassium hydroxide were investigated. Re-cently, the electrochemical oxidation of aceticacid in the presence of 3,3-diphenylacrylicacid5) and maleic acid half-esterS) has beenattempted.Results and DiscussionAccording to the manner of the separation* Presented at the 20 th Anneal l'vfeeting of theChemical Society of JaFan, Tokyo, .\pril I, 1967.** Present Address: l\iihonshozi ~,eifu-ryo, 5, 32Okamaehi-minami, Toyonaka-Si*) Hitachi F6-D gas chromatograph, Golay columnZ-45, carrier gas Ne (0.3 Kg/cm2, 60ml/min),Column temp. 140-200°C (1.25° / min), injection300°C. Detector FlO.**) Neutral Materials (10096).107108 A. TAKEDA, S. TORII and H.OKA (Vol. 3,Scheme I Mode of SeparationI Reaction Mixture98-96% I 2-4%(VPC-l) Neutral Portion Acidic PortionGirard P Reagent20-25% 75-80%(see Table 1__, _I_V--')_-'-t _------1 Ketones, Aldehydes II Route 3 (VPC-2) ~Route 1DimedoneRoute 2Methyl EstersNon Ketones, Aldehydes(VPC-3)~ !Naq. NaOHKeto-esterstI~etonesI N l\'aOHat 50°for 36 hri (auto-oxidation)Acidic PartIMethyl Este;s I (VPC-4)Girard IP Reagent, ---iI Methyl EstersI KetonesPh-CO-CH3, MeCaH.COMePh-COCH20Ac etc.Ph.COCH20HPh-COEtetc.(See Table III)Ph-CHO Ph-COOHCHSC6H4CHO CH3CaH.COOHetc.______t~ _I Fractional Distillation -I1~ldehyd~JPh-CHOCH3-CaH.-CHOPh-CH2CHO(VPC-5)II~\cidic p~1-~--t----'1_ M--=thYIEste~~1tI_Ke~~-~_~~r~ .major constituents of the ketone and aldehydecomponent of the anodic reaction of trans-cinnamic acid are summarized in Table I.Koehl suggested5) a mechanism, where theanodic oxidation of 3,3-diphenylacrylic acidcommenced in the usual Kolbe manner,through the unstable intermediates (4,5,6, and7) to give acetylenic compound (8). And, reason-able evidences of the presence of the interme-diates (4,5,6, and 7) are obtained by the isola-tion of 4-phenylcoumarin, l,l-diphenylprop-ene, benzil, benzoin, and benzoin acetate.In the present study, similar considerationmay be possible, since the discharge of trans-cinnamic acid may occur to give radical andcationic intermediates (10, 11, 12, and 13),Ph""C=CH-C008Ph/-e8 Ph""C=CH-COO'Ph/--~3 4, 51 -e8Ph-C::=C-Ph-HEll<--EllPh-C=CH-PhPh""C=CHEll/Ph8 7 61968) Anodic Oxidation of trans.Cinnamic Acid. I. 109Ph-CH=CH-COO::J ---7 Ph~CH=CH-COO·9 / 10Ph--CH=CH' 11tPh-~CH=CHffi13-OH8Ph-CH=CH-OAcAe08Ph-~C=CH2IOAe 15OH8Ph-C-CHa ~­IIo16 1720 21second mechansim involved discharge of thedouble bond of 14 and 15 to give cation-radical intermediates (20 and 21).ttlPh-C=C-PhCfuIC~--~0/ "0I + IPh, C--CH,25-e8------24Ph"'-C- -CH2- OAePhPh~-C:..=C-- Ph(25) which is formed stereoselectively at theelectrode surface. At the first step of this28 29If the discharge of the double bond of thecompounds (14 and 15) occurs at the "anodecage" to form a cation-radical intermediate(22 and 23), the reaction of an acetate ion with22 and 23 would appear likely, for Swarc!j)has estimated the acetoxy radical lifetime tobe onlylO-"--IO-I:J second, and has suggestedthat such radicals react only in their original"cage" and not in the surrounding solution.reaction, the resonance-stabilized radical (24)has been assumed. Tsutsumi and his co-workers8 ) attempted the homolytic alkoxyla-tion of styrene by the anodic oxidation ofalcohols and postulated an unstable radicalintermediate (26) which undergoes discharge atthe anode to give cationic intermediate (27).-e8 ttlPh- CH-CH2-- OR --- Ph~-CH-Clh-OR26 27Contrary to the above assumption, Koehlhypothesized recently that a cation-radicalintermediate (29) derived from the anodicoxidation of acetylene derivative (28) causesthe formation of the corresponding acetoxyderivatives. 5)23b23affi ffiPh- CH-CH-OAc Ph-C- CH~22a O.\e'"...'"¥ffi EBPh--CH-CH - O.\e Ph-- C -CH222b ();\eConcerning the assumption of the formationof a radical intermediate, the electrolytichydroxylation and acetoxylation of aromaticalkenes have been studied by Mango andBonner,7) indicating a mechanism involvingan intermediate cyclic 1,2-acetoxonium ionwhich can combine with acetate ions to formacetates (14 and 15) and with hydroxide ionsto form aldehyde (16) and ketone (17). Thehydrolysis of 14 and 15 takes place easily toafford the carbonyl compounds (16 and 17).In connection with the mechanism of theformation of the electrolytic hydroxylationand acetoxylation derivatives (18 and 19),following two routes may be considered.Ph-C-CH2-0H Ph-C-CH2-0AcII [Io 18 0 19The first involved the addition of an acetoxyradical to the acetoxystrenes (14 and 15) togive radical intermediates (20 and 21). TheOAe110 A. TAKEDA, S. TORII and H. OKA (Vol. 3,o 32-C02Experimental0.2 mole300 ml150 ml120 g16.8 g8-12 V0.7--0.8 (A/cm2)50 hrs4 5 (pH)Every 30 scctrans-Cinnamic AcidH20CH30 HCH3COOHKOHCell VoltageCurrentTimeEnd PointCommutatorTable II Reaction Procedure------ ' ~_-------a mixed solution of trans-cinnamic acid, accticacid, water, methanol, and potassium hydrox-ide was electrolyzed at Pt electrodes for 50 hI'S.at 25-30°, with terminal voltage 8-12 V ata current of 1.7-2-2 A, magnetically stirring,and changing the current direction in every 30sec by means of a commutator. The resultingreaction mixture was diluted with 300 ml ofwater and extracted with ether. The extractswere washed with aqueous saturated sodiumExperitnental SectionApparatus. - The electrochemical cell con-sisted of a cylindrical glass vessel, 7cm long indiameter and 14cm high, fitted with a gas leadpipe, a thermometer, and a magnetic stirrer.The vessel was immersed in a water bath,cooled with circulating cold water. The elec-trodes were two platinum foils (1.2 X 2.0 cm2)spaced about 2mm apart and the current di-rection was changed in every 30 sec by meansof a commutator. The products were analyzedby vpc (Hitachi F6-D gas chromatograph)using Golay column (Z-45).Materials. - Analytical grade trans-cinnamicand acetic acids, methanol, ethanol, and in-organic reagents were used. The commerciallyavailable compounds were used as a reference,but the following reference compounds wereprepared. Phenacyl alcohol, 101 mp 87°, phen-acyl acetate, 11- 102-164° (2 mm), p-methylace-tophenone, 12, 100° (lOmm), propiophenone,13)60-70° (2mm), and a-tolualdehyde, 14) 80° (10mm), were synthesized.Electrolysis of trans-Cinnatnic Acid inan Aqueous Acetic Acid-Methanol-Potas-siutn Hydroxide Solution. - A typical re-action procedure is shown in Table II. Thus,1263115}ORIPh--C--CH2-0RIOAc18 or 1914IORPh- -CH-CH--OAc'" /33 0}",/ ORPh-CH-CH/"O,\cThus, the attack of anodically produced ace-toxy radicals to aromatic alkenes in the dilutesolution may be unlikely. The direct acetoxy-lation of the methyl group of acetophenonemay give the acetate (19). Indeed, the expectedreaction occurred, when the anodic reactionof acetophenone was carried out in the similarreaction condition, but it gave only ca. 0.1 %yield of 19. 3) Thus, this route should be ex-cluded from the principal role of the formationof 19. Ultimately, it seems conceivable thatthe acetoxy derivatives (14 and 15) might beconverted into 18 and 19 via polyhydroxy oracetoxy compounds (30 and 31).Ph--CHO <------- Ph- C COOHBenzaldehyde and acetophenone are keyconstituents of the ketone and aldehyde com-ponent, obtained by the anodic reaction oftrans-cinnamic acid. Most of acetophenoneand its derivatives must be formed by theanodic methylation of benzaldehyde. l' How-ever, as for the formation of benzaldehyde, ourevidence gives no real suggestion. It appearslikely that a keto-acid (32), which may beobtained by the anodic oxidation of the acetate(26), may be subjected to decarboxylation toform benzaldehyde, on one hand, and theanodic oxidation of both the acetolysis prod-ucts of the epoxy intermediates (33) and poly-acetates (30 and 31), followed by the fission ofa, G-carbon bond, may give benzaldehyde, onthe other. An evidence for that was providedby the isolation of keto-acid in a manner des-cribed in Scheme I, whose infrared spectrumis shown in IR Chart I. The latter assumptionis supported by the result of the anodic reac-tion of sodium B-phenylglycidate. 3) The vinylacetates (14 and 15) are also seemed to beprecursors of benzaldehyde..5)1968) Anodic Oxidation of trans-Cinnamic Acid. I. IIITable IV The Isolation and Identification ofthe Constituents------ --- --_.. ----_._---Referencesand aldehyde component are summarized inTable IV. The gas chromatographs of thecomponents described in Scheme I are shownin VPC Charts 1, 2, 3, 4, and 5. The infraredspectrum of the keto-esters (32) is shown in IRChart I.chloride and concentrated in vacuo. The sepa-ration of the products was carried out in themanner as is shown in Scheme I. The resultsof the fractional distillation of the ketone andaldehyde component are indicated in TableIII. The methods of the characterization andidentification of each constituents of the ketoneTable III The Fractional Distillation of a MixedSolution of Ketone and Aldehyde Component01g)*)Fract. B. p. YieldNo. COC/30 mmHg) (g)1 -82 0.52 82-84.5 0.5 1**)3 84.5-85 -0.54 85-87 2 0.55 87-88.5 0.56 88.5-92-0.25- 37 92-94 4\-0.45J8 96-99-0.359 99-103 0.4710 103-109 0.35-1511 109-120 0.35-12 120-122 0.30-13 122-124 0.2014 124- 0.20 615 124- 0.50-16 Residue 1. 70CompoundBenzaldehydeAcetophenonep-TolualdehydePropiophenonePhenacy1AlcoholPhenacylAcetateMethodsFractional Distillation (F. D.)No. 1-4, IR, VPC, 2,4-DNPH (mp. 237"), Formationof Benzoic Acid.F. D. No. 3-6, VPC, 2,4-DNPH (mp. 250°), IRF. D. 1'\0. 6-7, p-ToluicAcid.F. D. No. 7-8, VPCF. D. No. 10-11, IR, VPC,Mp. 87°. 2,4-DNPH (mp.216°), Microanalysis.F. D. No. 12-15, IR, VPC,Bp. 102-4°/2mm., 2,4-DNPH(mp. 186°), Microanalysis.*) The fractional distillation was carried out by theuse of the Taika-Kogyo Model T A-SBI with aspinning band-type distillation apparatus.**) Major constituent: 1 Benzaldehyde, 2 Aceto-phenone, 3 p-Tolualdehyde, 4 Propiophenone,5 Phenacyl Alcohol, 6 Phenacyl Acetate.I) A. TAKEDA, S. TORII, and H. OKA: Tetrahed-ron Letters No 14 (1968) 1781.2) A. TAKEDA, S. TORII, and U. MATSUI: Preprintof the Osaka meeting of the Chemical Societyof Japan, (968); Bull. Chern. Soc. Japan, to cepublished.3) A. TAKEDA, S. TORII, and T. TAKAKI; PreprintI 1 Neutral ComponentI iIILH'I\I ,'·"ILI:llTi ! l' ~,\ 1I ~L JI 'l \I A Jo-/112 A. TAKEDA, S. TORII and H. OKAKetone and AldehydeI~111I15vrC-3 Non Keton e and Aldehyc\I'C Ic5r02t,.. ,,,, '., lli, J"" ,of the Osaka meeting of the Chemical Societyof japan, (1968).4) A. TAKEDA, S. WADA, and Y. MURAKAMI; Pre-print of the Osaka meeting of the Chemical Societyof japan, (1978).5) W. j. KOEHL; j. Org. Chern. 32, (1967) 614.6) Y. SATOH and A. HAGlTANI; Nippon KagakuZasshi (j. Chern. Soc. japan, Pure Chern. Se-ct.) 86, (1965) 237.7) F. D. MANGO and W. A. BONNER: j. Org. Chern.29, (1964) 1367.8) T. INOUE, K. KOYAMA, T. MATSUOKA, and S.TSUTSUMI: Bull. CLem. Soc. Japan 40, (1967)162.9) L. HERK, M. FELD, and M. SWARC: j. Am.Chern. Soc. 83, (961) 2998.10) R. M. COWPER and L. H. DAVIDSON: Org. Syn.II, 480.II) R. G. LiNVILLE and R. C. ELDERFIELD, j. Org.Chern. 6, (1941) 271.12) C. R. ]\OLLER and R. ADA~IS: j. Am. Chern.:Ooc. 46, 1889 (1924).13) W. T. READ: ihd. 44, (1922) 1746.14) j. \Y. VVILLIAMS; ibid 61, (1939) 2248.

The Anodic Oxidation of trans-Cinnamic Acid. I. The Formation of Ketone and Aldehyde Derivatives

Abstract

Similar works

Full text

Available Versions

Okayama University Digital Information Repository

Okayama University Scientific Achievement Repository