この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました。3,5-Disubstituted p-coumaryl alcohols (3-methoxy-5-iodo-, 3,5-diiodo-, 3-methoxy-5-nitro-, 3,5-dinitro-, 3,5-dimethoxy- and 3,5-dimethyl-p-coumaryl alcohols) were synthesized and dehydrogenated to their dimeric compounds with ferric chloride in dioxane (nonpolar solvent) and acetone-water (polar solvent), respectively. Yields of the β-ethers were, for example, 85 % (sinapyl alcohol) and 86 % (3, 5-diiodo-p-coumaryl alcohol) in dioxane, and 11% (the former) and 80 % (the latter) in acetone-water, respectively. These results suggest that the most effective factor in the radical coupling of these alcohols is the electronic effects of the substituent groups, but not the steric hindrance. Syringylglycerol-β-sinapyl ether was obtained in a high yield from sinapyl alcohol when dioxane was used as a solvent

HIGUCHI, Takayoshi

TAKEUCHI, Hideo

TANAHASHI, Mitsuhiko

Kyoto University Research Information Repository

Title Dehydrogenative Polymerization of 3,5-Disubstituted p-Coumaryl AlcoholsAuthor(s)TANAHASHI, Mitsuhiko; TAKEUCHI, Hideo; HIGUCHI,TakayoshiCitationWood research : bulletin of the Wood Research Institute KyotoUniversity (1976), 61: 44-53Issue Date1976-10-30URL http://hdl.handle.net/2433/53378RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityDehydrogenative Polymerization of 3,5-Disubstitutedp-Coumaryl Alcohols*Mitsuhiko TANAHASHI**, Hideo TAKEUCHI**and Takayoshi HIGUCHI* *Abstract--3, 5-Disubstituted p-coumaryl alcohols (3-methoxy-5-iodo-, 3, 5-diiodo-,3-methoxy-5-nitro-, 3, 5-dinitro-, 3, 5-dimethoxy- and 3, 5-dimethyl-p-coumaryl alcohols)were synthesized and dehydrogenated to their dimeric compounds with ferric chloride indioxane (nonpolar solvent) and acetone-water (polar solvent), respectively. Yields of the,B-ethers were, for example, 85 % (sinapyl alcohol) and 86 % (3,5-diiodo-p-coumaryl alcohol)in dioxane, and 27 % (the former) and 80 % (the latter) in acetone-water, respectively.These results suggest that the most effective factor in the radical coupling of these alcoholsis the electronic effects of the substituent groups, but not the steric hindrance. Syringylglycerol-,B-sinapyl ether was obtained in a high yield from sinapyl alcohol when dioxane was used asa solvent.IntroductionFREUDENBERGl) reported that a mixture of coniferyl and sinapyl alcohols inequal amounts is dehydrogenated to a polymer similar to angiosperm lignin, butsinapyl alcohol alone does not form a lignin-like polymer but yields mainly syrin-garesinol. From these results, FREUDENBERG doubted the occurrence of syringyllignin in nature. However, FERGUS and GORING2) proposed on the basis of spectralanalysis of lignin in cell walls with a UV microscope that birch lignin deposited inthe secondary layers of wood fibers and parenchyma cell walls is composed of mostlysyringyl component. Furthermore YAMASAKI, HATA and HIGUCHI3,4) recently foundthat a considerable amount of DHP was formed from sinapyl alcohol alone withperoxidase and H 20 2 in water.In the "Zulauf" method, dehydrogenative dimerization of coniferyl and p-coumaryl alcohols with peroxidase and H 20 2 in water gave 54 % and 48 % ofphenylcoumaranes, 19 % and 20 96 of arylglycerol-,B-aryl ethers, and 27 % and 32 %of resinols, respectively5). However the dehydrogenation of sinapyl alcohol givesonly a limited number of products because 5-position of the aromatic ring of sinapylalcohol is unavailable for coupling, and ,B-,B-coupling is the almost exclusive dehydro-genation reaction which gives syringaresinol in 80 to 90 % yields in the same Zulaufcondition. The difference of the radical coupling reactions between coniferyl and* Presented partly at the 20th Symposium on Lignin Chemistry, Nagoya, Oct. 1975.** Division of Lignin Chemistry.-- 44 --TANAHASHI, TAKEUCHI, HIGUCHI: DHP of 3, 5-Disubstitutedp-Coumaryl Alcoholssinapyl alcohols has been so far ascribed by FREUDENBERG to the steric hindranceof two methoxyl groups of sinapyl alcohol, which was believed to give no syringyl-glycerol-j3-sinapyl ether.However, racemization rate of optically active o-substituted biphenyls6) andthe van der Waals radius of the substituted groups are concerned, the methoxylgroup belongs to a class of relatively smaller bulkiness. Since syringylglycerol-j3-syringylglycerol ether was isolated as a degradation product of Yachidamo(Fraxinus mandshurica) lignin8), j3-0-4 coupling is considered to be formed evenbetween two molecules of sinapyl alcohol. Therefore, in the present investigation,5-position of coniferyl alcohol and 3- and 5-positions of p-coumaryl alcohol weresubstituted by iodine, nitro or methyl groups which are more bulky than methoxylgroup, and their reactivities in dehydrogenations were compared to that of sinapylalcohol.ExperiInentalSynthesis of 3, 5-disubstituted p-coumaryl alcoholsSinapyl) coniferyl and p-coumaryl alcohols were synthesized by the methods ofFREUDENBERG9) .5-Iodo vanillin and 3) 5-diiodo p-hydroxybenzaldekyde were synthesized from vanillinand p-hydroxybenzaldehyde by the method of ERDTMAN10).5-Nitro vanillin was synthesized from vanillin by the method of ACERBO,SCHUBERT and NORDll).3) 5-Dinitro p-hydroxybenzaldehyde was synthesized by nitration of p-cresol accord-ing to the reference 11 and subsequent oxidation of 3, 5-dinitro p-cresol withanhydrous cromie acid by the method of LIEBERMAN and CONNOR12) •o3,5-Dinitro p-cresolNMR (CDCh) 0: 2.44 (3H,s), 8.13 (2H,s), 11.19 (lH, broad).03, 5-Dinitro p-hydroxybenzaldehydeNMR (CDCh) 0: 8.80 (2H,s), 10.01 (IH,s).3, 5-Dimethyl p-kydroxybenzaldehyde was synthesized from 2, 6-dimethylphenylaccording to the method of SMITH13 .NMR (CDCh) 0: 2.22 (6H,s), 5.78 (lH, broad), 7.53 (2H,s), 9.78 (lH,s).3) 5-Disubstituted ethyl p-coumarates were synthesized from the correspondingaldehydes according to the method of FREUDENBERG9).o 5-Iodo ethyl ferulateNMR (CDCh) 0: 1.20 (3H, t, J =6), 3.86 (3H, s), 4.11 (2H, q, J =6), 6.33 (lH, d,J=16), 7.16 (lH,d,J=2), 7.57 (lH,d,J=16), 7.59 (lH,d,J=2).o3,5-Diiodo ethyl p-coumarate- 45-WOOD RESEARCH No. 61 (1976)NMR (CD3COCD:3) 0: 1.27 (3H,t,j=7), 4.24 (2H,q,j=7), 6.33 (lH,d,]=16),7.48 (lH,d,]=16), 7.94 (2H,s).5-Nitro ethyl ferulateNMR (CDCh-l--CD30D) 0: 1.17 (3H,t,]=7), 3.79 (3H,s), 4.16 (2H,q,J=7), 6.22(lH,d,J=16), 6.89 (lH,d,.1=2), 7.42 (1H,d,J=2), 7.45 (1H,d,.1=16).() 3, 5-Dinitro ethyl p-coumarateNMR (CDCh+CD30D) 0: 1.33 (3H,t,.1=8), 4.29 (2H,q,J=8), 6.50 (lH,d,.1=15), 7.61 (1H, d, J = 15), 8.44 (2H, s).o3,5-Dimethyl ethyl p-coumarateNMR (CDCh) 0: 1.15 (3H,t,J=7), 2.16 (6H,s), 3.67 (2H,q,J=7), 6.25 (IH,d,J=16), 7.08 (2H,s), 7.53 (lH,d,J=16).5-Iodo coniferyl alcohol, 3, 5-diiodo p-couma~yl alcohol and 3, 5-dimethyl p-coumarylalcohol were synthesized by the same method as in sinapyl alcohol, using anhydrousether as a solvent.5-Iodo coniferyl alcoholNMR (CDCh) 0: 3.78 (3H,s), 4.28 (2H,d,J~=5), 6.20 (lH,d, t,J=-=15, 5),6.44 (lH,d,J=-d5), 6.83 (lH,d,J=c2), 7.29 (IH,d,J=2).03, 5-Diiodo p-coumaryl alcoholNMR (CD3COCD:3) 0: 4.24 (2H, d, J=3), 6.34 (lH, d, t, J = 16, 3), 6.46 (lH, d, J =16), 7.86 (2H, s).() 3, 5-Dimethyl p-coumaryl alcoholNl\1R (CDCh) 0: 2.16 (6H,s), 4.22 (2H,d,J=5), 6.11 (lH,d,t,J=16, 5),6.40 (lH,d, .1= 16), 6.91 (2H. s),5-Nitro conife~yl alcohol and 3, 5-dinitro p-coumaryl alcohol were synthesized by thesame method, using anhydrous THF as a solvent.5-Nitro coniferyl alcoholNMR (CDCh) 0: 3.96 (3H,s), 4.34 (2H,d,J=c4.5), 6.31 (lH,d,t,J=16, 4.5), 6.40(lH, d,.J = 16), 6.91 (2H, s).Dehydrogenation of 3, 5-disubstituted p-coumaryl alcoholsEn:::;ymic dehydrogenalionEach alcohol (I, II, III) was dehydrogenated with peroxidase and HzOz by Zulaufmethod, and the dilignols were extracted with ethyl acetate.De/~ydrogenation b)J FeCl3 in dioxane-water (5: 2)Each alcohol (I ",-,VIII) 100mg was dissolved in 7 ml of dioxane-water (5; 2) and60 mg of FeCh in 0.7 ml of water was added into the solution under stirring.Stirring was continued for one hour, and then the reaction mixture was extractedwith chloroform.Dehydrogenation by FeCl3 in acetone-water (3: 40)46 --TANAHASHl, TAKEUCHl, HraucHl: DHP of 3, 5-Disubstituted p-Coumaryl AlcoholsEach alcohol (I .......VIII) 100 mg was dissolved in 3 m1 of acetone and 40 m1 of waterwas added. FeCh solution (0.7 ml) was added to the solution under stirring andthen the reaction mixture was treated as described above.Analysis of the diligno1s by NMR spectrometryThe reaction products were dissolved in CDCh or CD3COCD3 and analyzedby a R-22 HITACHI high resolution NMR spectrometer (90 MHz) with TMS asinternal standard.Separation and identification of diligno1sThese reaction mixtures were separated by preparative TLC and identified byNMR and Mass spectrometries.o Syringylglycerol-~-sinapyl etherNMR (CDCh) 0: 3.50 (lH, m), 3.6 ....... 3.9 (2H, m), 3.82 (6H, s), 3.84 (6H, s), 4.29(2H, d,] =5), 4.96 (lH, d,] =3), 6.27 (lH, d, t,] = 16, 5), 6.53 (lH, d,] = 16), 6.56(2H,s), 6.63 (2H,s).13C-NMR (CD3CODC3) 0: 56.5 (OCH3), 60.9 (r), 63.1 (r/), 73.6 and 74.2 (a), 88.0(~), 104.8 (arom. 2-C and 6-C), 105.4 (arom. 2/-C and 6/-C), 129.7 (W), 130.8 (a /),132,5 (arom. 1 and l'-C) , 136.2 (arom. 4 and 4/-C), 148.3 (arom. 3 and 5-C), 153.9and 154.1 (arom. 3' and 5' -C).o 5-Iodo-guaiacylglycerol-~-5'-iodo coniferyl etherNMR (CDCh) 0: 2.85 (2H, broad), 3.20 (lH, broad), 3.87 (6H, s), 4.10 (IH, m),4.30 (2H, d,] =4.3), 4.40 (lH, m), 5.09 (lH, d,] =4), 6.24 (lH, d, t,] =6, 4.3), 6.47(lH,d,]=16), 6.89 (IH,d,]=2), 6.96 (lH,d,]=2), 7.26 (lH,d,]=2), 7.39 (lH,d,]=2).o5,5/-Diiodo pinoresinolNMR (CDCh) 0: 2.99 (2H, m), 3.79 (6H, s), 3.7 ....... 3.9 (2H, m), 4.05 ....... 4.30 (2H, m),4.70 (2H,d,]=5), 6.48 (2H, broad s), 6.88 (2H,d,]=2), 7.28 (2H,d,]=2).03, 5-Diiodo p-hydroxyphenylg1ycerol-~-3/,5'-diiodo p-coumaryl ether (tetraacetate)NMR (CDCh+CD30D) 0: 1.84 (3H, s), 2.10 (3H, s), 2.20 (3H, s), 2.38 (3H, s), 3.38(lH,m), 4.31 (2H,m), 4.70 (2H,d,]=5), 5.31 (IH,d,]=5), 6.20 (IH,d,t,]=17,5), 6.44 (IH, d,] = 17), 7.44 (2H, s), 7.92 (2H, s).o3,5,3/,5/-Tetra iodo p-coumaryl resinol (diacetate)NMR (CD3COCD3) 0: 2.38 (6H, s), 3.01 (2H, m), 3.90 (2H, d, d,] =9,4), 4.23 (2H,d, d,] =9, 7), 4.92 (2H, d,] =4), 7.76 (4H, s).o 5-Nitro guaiacy1g1ycero1-~-5/-nitroconiferyl ether (tetra acetate)NMR (CDCh) 0: 1.39 (3H, s), 2.07 (3H, s), 2.10 (3H, s), 2.33 (3H, s), 3.82 (3H, s),3.91 (3H, s), 4. 14 (1 H, d, d, ] = 12, 4), 4.44 (1 H, d, d, ] = 12, 5), 4.70 (2H, d, ] = 5) ,5.05 (lH, m), 6.07 (IH, d,] =6), 6.24 (lH, d, t,] = 16, 5), 6.53 (IH, d,] = 16), 7.34- 47-WOOD RESEARCH No. 61 (1976)(4H, s).03, 5-Dimethyl p-hydroxyphenylglycerol-,B-3/, 51-dimethyl p-coumaryl etherNMR (CDCh) 0: 2.15 (12H, s), 3.67,....,3.95 (2H, m), 4.02,....,4.20 (lH, m), 4.18 (2H,d,]=5), 4.88 (lH,d,]=4), 6.19 (lH,d,t,j=16, 5), 6.44 (1H,d,J=16), 6.92 (2H,s), 6.97 (2H, s).o3,5,3/,5/-Tetra methylp-coumaryl resino1 (diacetate)NMR (CDCh) 0: 2.15 (l2H, s), 3.00 (2H, m), 3.65,....,3.80 (2H, m), 4.05,....,4.20 (2H,m), 4.58 (2H, d, j =4), 6.27 (4H, s).Results and discussionNMR spectra of the dilignols formed from sinapyl alcohol are shown in Fig. 1.According to NAKATSUB04), a-methine protones of the three main dilignols, phenyl-coumarane, ary1g1ycerol-,B-aryl ether and resinol give peaks at 5.50, 4.96 and 4.68,which are not interfered with other peaks. Therefore, the ratio of the amounts ofthese dilignols can be determined by integration of their a-methine peaks. Thismethod was used for the determination of the ratio of dilignols in this paper. Fig. 2shows the peaks of about 6.00 to 4.30 ppm in the NMR spectra of dehydrogena-tion products from the respective alcohols. The peaks of a-methine of phenylcou-marane, .a-ether and resinol appeared at 5.7 to 5.5 ppm, at 5.1 to 4.9 ppm and at4.7 to 4.5 ppm, respectively. The amonts of .a-ether and resinol were calculatedfrom the corresponding peak areas and the result is given in Table 1.p-Coumaryl and coniferyl alcohols gave 38 % and 41 % of .a-ether and 62 %JG'27% 73%80 7.0 60 50 4.0 3.0 2.0 10 oFig. 1. NMR of dehydrogenative dimers of sinapyl alcohol.-- 48-TANAHASHI, TAKEUCHI, HIGUCHI: DHP of 3, 5-Disubstituted p-Coumaryl AlcoholsAcetone - wa ter (3: 40)Coniferyl alcoholDioxane-water (5: 2)Resinolf3-EtherC~Sinapyl alcohol~ 5-Jodo-coniferyl alcohol~4.55.05.53,5-0i-methyl-p-coumaryl alcohol5.5 5.0 4.5NMR spectra of dehydrogenation products with FeCb in each solvent.6.0Fig. 2.and 59 % of resinol, respectively, and the amount of phenylcoumarane was negligible.On the other hand, sinapyl alcohol gave syringaresinol in 91 % yield. A preferen-tial formation of syringaresinol from sinapyl alcohol has been ascribed to a sterichindrance of two methoxyl groups located at 3 and 5 positions of the aromatic ringby FREUDENBERG. If this assumption is correct, resinols should be mainly formedalso from the 3, 5-disubstituted p-coumaryl alcohols with other large substituents.However, 5-iodo coniferyl alcohol and 3, 5-diiodo p-coumaryl alcohol gave E3-ethers inthe yields of 80 % and 86 %, respectively. Steric effects of iodine, nitro and methylgroups are evidently larger than that of methoxyl group (see Table 2, Fig. 3 andFig. 4). Fig. 3, depicted from the data of Table 2, shows the methyl group inmethoxyl at the most remote position from phenoxyl radical, which is considered tobe the most stable position. It is recognizable from Fig. 3 that the methoxyl groupmust not be so large substituent to prevent 13-0-4 coupling for a phenoxyl radical.Fig. 4 shows the level of the bulky effects of the o-substituents determined fromracemization rate of substituted biphenyls. The racemization rate of the biphenylssubstituted with methoxyl group should be faster than those of biphenyls substitutedwith iodine, nitro or methyl group indicating that methoxyl is the least hinderedsubstituent among the four groups. In spite of the least bulky methoxyl substituent,sinapyl alcohol gives syringaresinol in high yields in dehydrogenation in polar solvent.- 49-WOOD RESEARCH No. 61 (1976)Table 1. Ratio of ,,-ethers and resinols formed by dehydrogenation of 3, 5-disubstitutedp-coumaryl alcohols.I-----'-;.---------- --i--~.------"----20***++45Resinol(22)36**152014++42I-1-(46)63----735080***10010055100***100***58,,-Ether(27) 372750(39)64**858086(20) 38** I (32)62**(19) 4~** I (27) :~**______J _I(27)(48)*(54)CoumaraneConiferyl alcoholSinapyl alcohol5-Iodo coniferyl alcohol3, 5-Diiodo p-coumaryl alcohol5-Nitro coniferyl alcohol3, 5-Dinitro p-coumaryl alcohol3, 5-Dimethyl p-coumaryl alcoholI\II----·-----·~--~r-·~·-'----~--------·-----·--~----'---Coniferyl alcoholI Sinapyl alcohol5-Iodo coniferyl alcohol3, 5-Diiodo p-coumaryl alcohol5-Nitro coniferyl alcohol3, 5-Dinitro p-coumaryl alcohol3, 5-Dimethyl p-coumaryl alcoholFeC13 inacetone-water(3: 40)FeC13 indioxane-watel'(5: 2)* The values in parentheses are the ratio of three main dilignols, coumaranes, resinols and,,-ethers. ** The values are the ratio of resinol and ,,-ether in the dimers from which theamount of coumarane was excluded. *** The values are the yields of ,,-ethers and resinolsseparated by preparative TLC. Determination of dilignols from the peak areas of a-methinson NMR spectra was difficult for overlapping of a-methine peaks of resinols and r-hydroxy-methyl peaks of the starting materials.Table 2. Radii of covalent bonds and of van del' Waals.---------!---------------------------I-------------------------Atom I Radius of covalent bond I Radius of van del' Waals____~ .__... l ,._'"__H 0.30 (A)C o. 77N O. 700 0.66I 1. 33CH31. 20 (A)1. 851. 501.402.152.00However, 3, 5-diiodo p-coumaryl alcohol having the most bulky iodine atoms givesa large amount of j3-ether both in polar and nonpolar solvents. These resultssuggest that the most effective factor in these radical couplings may not be a stericeffect but electronic effects.Then, the substituents which have different inductive and electromeric effectsand are more bulky than methoxyl group were chosen and synthesized in the present---- 50 -T ANAHASHI, TAKEucHI, HIGUCHI: DHP of 3, 5-Disubstituted p-Coumaryl AlcoholsRRRRFig. 3. Diagrams of steric hindrance of dual o-substituted phenoxy radicals.Fields of van der Waals of iodine, methyl and nitro groups are fixedbecause of only one single bond (the formers) and the resonanced1r-electrones (the latter). However, methoxyI group has two singlebonds which can rotate around the aromatic C-G bond. Dashed circleshows the nearest position of methoxyl group to the phenoxy radicalbut that position is less possible.X NOz<) ~ >COOHY NOz<) ~ >6'h COOHY:F<CI<Brx OCH3 <CH3 <COOH < NOzIHOOC~ :> ~ ~COOHISTABLE at ROOr'v1 TEMPERATUREI >Br>NOz>CI >COOH>CH3 > OCH 3 >FFig. 4. Bulky effects determined from racemization rate of substituted biphenyls.The order of X or Y shows the facility of racemization of optical activebiphenyl. The more bulky the substituent is, the slower the rate ofracemization is. Iodine is the most bulky substituent among them, andthen 2, 2/-diiodo-4, 4/-dicarboxy biphenyl is known to be stable at theroom temperature. Methoxyl group belongs to a smaller class for thesteric hindrance as indicatedinvestigation. Table 3 shows the HAMMETT substituent constantsW of these groups.In a nonpolar solvent, only I effect acts on the reaction, whereas in a polar solvent,both I and E effects would be effective. Under these supposition dehydrogenationof these alcohols was carried out by using FeCb in a relatively nonpolar solvent(dioxane-water 5: 2) and a polar solvent (acetone-water 3: 40), respectively. When- 51 -WOOD RESEARCH No. 61 (1976)Table 3. Hammett substituent constants (a).Position i Electronic effectSubstituent group --------------------- -1-------------------;-------------- ----------------meta I i para 1+ E I Inductive Electromeric---·--------~··--··_-·-------·-----··---·-·---T--~--------------------------------------··-----··----··---1--····---------···---------"-0.-"----- --------~--.----,-----CH3 -0.08 -0.16 I + I +EOCH;l +0.11 -0.27 i-I +EI +0.35 +0.18 I - I + ENOz -1-0.71 +0.78 I -- I - Enonpolar solvent is used, meta value of HAMMETT substituent constant is effective tothe reaction and in polar solvent, para value should be effective. The results areshown in Table 1 which definitely indicates that the higher the HAMMETT substituentconstant (a-value), the more the ratio of p-ether increase in the same solvent.Moreover, this relation between the ratio of p-ether and a-value was kept in constanteven in the change of the polarity of solvents for the same 3, 5-substitued p-coumarylalcohol. For example, the yields of p-ether from 5-iodo coniferyl alcohol changedfrom 50 % to 80 % when solvent was changed from polar to nonpolar (from apara =-0.27 (OCH3) +0.18 (1) = -0.09 to ameta=O.ll (OCH3) +0.35 (I) = +0.46). In par-ticular, the relation is clearly found in the dehydrogenation of sinapyl alcohol (Fig. 1).When acetone-water (3 : 40) was used as a solvent syringaresinol was formed in a73 % yield of dilignols by a stronger E effect of methoxyl (a para = -0.27), and theresult is approximately same as that carried out with peroxidase-HzOz system. Whenthe polarity of solvent decreased, the amount of resinol decreased and that of p-etherincreased. When dioxane alone was used as solvent, the amount of p-ether reachedto 94 %, because of the only +1 effect of methoxyl group (ameta= +0.11). Fromthese results it is clear that the most effective factor in the mode of dehydrogenativepolymerization of p-coumaryl alcohols is electronic effect.The fact that syringylglycerol-p-sinapyl ether can be formed mainly in non-polar solvent suggests that syringyl lignin is formed in cell wall matrix which maycontrol the electronic effect of methoxyl groups of sinapyl alcohol in protoplasmicmembrane and cell organelles.Acknowledgm.entThis innestigation was supported in part by the Ministry of Educations ScientificFund (No. 176105).ReferencesI) K. FREUDENBERG and A. C. NEISH, Constitutions and biosynthesis of lignin, Springer-Verlag,p. 34-37 (1968).--- 52---T ANAHASHI, TAKEUCHI, HIGUCHI: DHP of 3, 5-Disubstituted p-Cournaryl Alcohols2) B.]. FERGUS and D. A. I. GORING, Ho1zforschung, 24, 113 (1970).3) T. YAMASAKI, K. HATA, and T. HIGUCHI, Mokuzai Gakkaishi, 19, 299 (1973).4) T. YAMASAKI, K. HATA, and T. HIGUCHI, Mokuzai Gakkaishi, in press.5) F. NAKATSUBO and T. HIGUCHI, Wood Research 58, 12 (1975).6) T. SUAMI, Gendai Kagaku Shiriizu, 38, Tokyo Kagaku Dojin p.48 (1968).7) ]. A. DEAN, Lange's Handbook of Chemistry, 3-118 (1973).8) S. OMORI and A. SAKAKIBARA, Mokuzai Gakkaishi, 18, 577 (1972).9) K. FREUDENGERG, Chern. Ber., 85, 1181 (1952).10) H. ERDTMAN, Svensk. Kern. Tid., 47, 223 (1935).11) S. N. ACERBO, W. L. SCHUBERG, and F. F. NORD, ]. Am. Chern. Soc. 82, 735 (1960).12) S. V. LIEBERMAN and R. CONNOR, Org. Syn., CoIl. Vo1l. 2, 441 (1943).13) W. E. SMITH, ]. Org. Chern., 37, 3972 (1972).14) D. H. McDANIAL and H. C. BROWN, ]. Org. Chern., 23, 420 (1958).- 53-

Dehydrogenative Polymerization of 3,5-Disubstituted p-Coumaryl Alcohols

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Dehydrogenative Polymerization of 3,5-Disubstituted p-Coumaryl Alcohols

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