Mallakpour, Shadpour E

Zolfigol, Mohammad Ali

NOPR

Indian Journal of ChemistryVol. 37B, October 1998, pp. 1001 - 1006Reaction of 4-n-propyl-l ,2,4-triazoline-3,5-dione with someselected dienesShadpour E Mallakpour* & Mohammad Ali ZolfigolOrganic Polymer Chemistry Research Laboratory,College of Chemistry, Isfahan University of Technology,Isfahan, 84356, IR, IranReceived 26 September 1997; accepted 5 January 1998The reaction of 4-n-propyl-l,2,4-triazoline-3,5-dione (PTAD) 1 with anthracene, cyclopentadiene(monomer), 5,5-dimethoxy-l ,2,3,4-tetrachlorocyclopentadiene, hexachlorocyclopentadiene, isoprene,2,6-dichlorostyrene, 1,3-cyclohexadiene, and cis, cis-l,3-cycloheptadiene has been investigated. Thesereactions occur via [4+2] Diels-Alder cycloaddition with the formation of novel heterocycles inquantitative yields. The initial reaction of PTAD with 2,6-dichlorostyrene isa [4+2] Diels-Aldercycloaddition which is followed by an allylic type migration of chloride atom.4-Substituted-l,2,4-triazoline-3,5-diones are themost reactive dienophiles'v'", enophiles6-12 and1 hil 13-15 I . 16 he ectrop I es . n a preVIOUSpaper we avereported a convenient method for the synthesis of4-n-propyl-l,2,4-triazoline-3,5-dione (PT AD) 1 ina high yield and purity. The purpose of thisinvestigation was to examine the reactivity ofPTAD with some selected dienes.N=NOJ-.N~OICH2ICH2ICH3PTAO 1The reaction of PT AD 1 with anthracene 2 wasperformed . in methylene chloride at roomtemperature. Addition of the pink crystals of PTADto a methylene chloride solution of anthracene 2produced a purple colour which after a few min.changed to a light-pink colour and then to a paleyellow after about 60 min. At the end of reaction,the solvent was removed giving a white solidwhich on recrystallization from toluene-hexaneafforded white needles of 3 (Scheme I). Elementalanalysis showed 3 to be a I: I adduct formed by a[4+2] Diels-Alder cycloaddition reaction.The 'H NMR spectrum of 3 showed signals at 81+~~20.05 (t, methyl protons), 1.35 (sextet, methyleneprotons attached to the methyl group), 3.22 (t,methylene protons attached to the nitrogen atom),6.25 (s, bridged C-H protons) and 7.2-7.6 (m,aromatic protons).The monomeric cyclopentadiene 4 underwentreaction with PT AD (Scheme II) when a methylenechloride solution of PT AD was added dropwise toa methylene chloride solution of 4 at -lOoC in 1:1molar ratio. The reaction was extremely fast evenat -10°e. The product 5 was obtained as whitecrystals after purification via recrystallization. Theyield was quantitative and the elemental analysisagreed with I: 1 adduct.The 1H NMR spectrum of 5 showed signals at80.83, 1.58 and 3.33 due to the protons of n-propylgroup. The spectrum also exhibited peaks at 8 1.86(d, one of the protons of the bridgehead CH2), 2.18(d, the other proton of the bridgehead CH2), 5.00(s, bridged protons) and 6.33 (s, olefinic protons).1002 INDIAN J CHEM, SEC.B,OCTOBER 19984: R)=R2=R3=~=Rs=Rt;=HS:R)=R2=R3=R4=Rs=Rt;=H6:R)=R2=OCH3 R3=R4=Rs=Rt;=Cl7:R)=R2=OCH3 R3=R4=Rs=Rt;=Cl8:R)=R2=R3=~=Rs=R6=Cl9:R)=R2=R3=~=Rs=Rt;=ClScheme IIThe IJC NMR (20 MHz) spectrum of 5 showedpeaks at 0 10.50 (C,) 26.71 (Cb), 40.77 (Cc), 48.13(Cd), 64.19 (Ce), 130.53 (Cr) and 159.77 (Cg). Thedownfield shift in the signals of C, and Ce carbonsis due to l3-effect. Similarly the reaction of 5,5-dimethoxy-1,2,3,4-tetrachlorocyclopentadiene 6with PT AD was performed in methylene chlorideat room temperature (l: 1 molar ratio). The reactionwas slow compared to that of cyclopentadiene(monomer) even at room temperature. This can beexplained in terms of frontier molecular orbitalstheory. Replacement of four hydrogen atoms byfour chlorine atoms in cyclopentadiene ring, lowersthe energy level of HOMO in diene 6 and thereforethe energy gap between HOMO of diene 6 andLUMO of dienophile 1 increases causing adecrease in reaction rate.The yield was quantitative and the elementalanalysis agreed with l: 1 adduct 7.The 'H NMR spectrum of 7 showed signals ato 0.88, 1.60 and 3.43 which were assigned to theprotons of n-propyl group. The signals at 0 3.6 and3.8 (each s) were assigned to the protons ofmethoxy groups.The reaction of hexachloro cyclopentadiene 8with PTAD was also carried out in a similar way inmethylene chloride at room temperature (SchemeII). The Diels-Alder cycloaddition in this case wasvery slow compared to that of cyclopentadiene andit required almost 48 hr for completion. In this. case, two more chlorine atoms further lowered theenergy level of HOMO in diene 6 leading to furtherlarge energy differences between HOMO andLUMO, and thus, the rate of reaction decreaseddrastically.The yield of the cycloadduct was quantitativeand the elemental analysis agreed with 1:1 adduct9.The 'H NMR spectrum of 9 showed signals at8 0.93, 1.75 and 3.48 which were assigned to theprotons of n-propyl group.Isoprene 10 underwent reaction with PTAD(Scheme III) when a methylene chloride solution ofPT AD was added dropwise to a methylene chloridesolution of 10. The reaction was extremely fasteven at -10°e. The cycloadduct was purified fromn-hexane. The elemental analysis was in agreementwith 1:1 adduct 11.The 'H NMR spectrum of 11 showed signals ato 0.95, 1.75 and 3.65 (each s, n-propyl groupprotons), 1.86 (s, methyl protons), 4.0 (s,methylene protons), and 4.63 (br s, olefinicprotons).The reaction of 2,6-dichlorostyrene 12 withPTAD was also performed in methylene chloride atroom temperature (Scheme IV). The product wasobtained as white crystals after recrystallizationfrom n-hexane.The elemental analysis was in agreement with1:1 adduct 14. The first step of the reaction is theformation of a reactive intermediate 13 via a [4+2]Diels-Alder reaction. The second step is an allylictype rearrangement of chlorine atom whichrearomatizes the benzene ring. Although thisreactive intermediate 13 can undergo a secondDiels-Alder reaction, but a double Diels-Alderadduct was not isolated.Earlier!' we have investigated the reaction of4-methyl- and 4-phenyl-triazolinediones with 2,6-dichlorostyrene and the structure of resultantadduct was determined by Xvray diffractionanalysis of a single crystal which confirmed themigration of chlorine atom.The 'n NMR of compound 13 showed signalswhich are in agreement with its structure.The reaction of PT AD with 1,3-cyclohexadiene15 was performed in methylene chloride at -lOoC,Scheme IIIMALLAKPOUR et al. : REACTION OF 4-n-PROPYL-I,2,4-TRIAZOLINE-3,5-DIONE WITH DIENES 100312CI CI~I • CI migration~N,A,,-->r,;Oo 'CH2,CH2'CHJScheme IVThe reaction was extremely fast even at lower than-10°C. The completion of the reaction could beeasily determined by the disappearance of the pinkcolour of PTAD. The yield of the cycloadduct wasquantitative and elemental analysis was inagreement with l: 1 adduct 16 (Scheme V).The IH NMR spectrum of 16 showed signalswhich were in agreement with the assignedstructure 16.The 13C NMR (20 MHz) spectrum of 16showed signals at 0 10.61 (Ca), 20.88 (Cb), 2l.73(Cc), 40.55 (Cd), 49.88 (Ce), 129.86 (Cf) and 157.79(Cg). The upfield shift in the signals of C, and C,carbons compared to the corresponding signals incompound 5 is due to I)-effect.The reaction of PTAD with cis,cis-l,3-cycloheptadiene 17 was performed in methylenechloride at refluxing temperature. The reaction wasvery slow and it took a long time for the pinkcolour of PTAD to disappear. From l,3-cyclohexadiene to cis.cis-) ,3-cycloheptadiene thereis a drastic decrease in the reactivity of dienes. Thiscould be attributed to the flexibility of compound17 which does not have rigid cis-configuration,which is required for [4+2] Diels-Alder reaction.Besides 18 it is possible to have another productvia ene reaction which was not isolated (SchemeVI).The IH NMR spectrum of 18 showed signalswhich were in agreement with the assignedstructure 18.cat~.C H"2CI2 f N-.6.0• '/ I (9f ~ N N)rg "c H2o d'C~2b CHa 315 16Scheme V17Scheme VIAlthough PT AD is very reactive dienophi1e itdoes not react with tetramethy1benzene. Thereaction of PTAD with l,2,4,5-tetramethy1benzenewas attempted in methylene chloride at refluxingtemperature for 48 hr, but no reaction wasobserved. Tetramethy1benzene has been reported toreact with benzyne intermediate to give acycloadduct 17 in 41 % yield 17.ConclusionIt is very convenient to synthesize 4-n-propy1-1,2,3-triazoline-2,5-dione in a large quantity withhigh yield and high purity. This compound isextremely reactive dienophile. Its reaction with awide variety of dienes gave novel heterocycliccompounds in quantitative yields. The resultedcycloadducts are very interesting compounds forfurther studies.Experimental SectionGeneral. IR spectra were recorded on aShimadzu 435 IR spectrophotometer using KBrpellets. Vibrational transition frequencies arereported in wave numbers (cm'). Proton nuclearmagnetic resonance eH NMR) spectra wererecorded at 90 MHz on a Varian EM-390instrument. Melting point were taken on aGallenKamp melting point apparatus and areincorrected. Elemental analyses were performed atthe Research Institute of Petroleum Industry,Tehran, I.R. Iran.Reagents were purchased from AldrichChemical Co., Fluka Chemical Co., or Riedel-deHaen AG. Isoprene was donated by Professor A1004 INDIAN J CHEM, SEC.B,OCTOBER 1998Entezami, Department of Organic Chemistry,Faculty of Chemistry, Tabriz University, IR Iran.Reaction of PTAD with anthracene. Into a 100mL round-bottomed flask were placed 0.62g(3.5x10-3 mole) of anthracene and 40 mL ofmethylene chloride. The flask was fitted with amagnetic stirrer. The stirrer was started and 0.50 g(3.5xlO-3 mole) of PTAD crystals was added whena deep-purple colour appeared which later onturned to a light-pink colour. After about 60 min., apale yellow solution was obtained. The solutionwas stirred at room temperature for 4hr. Thesolvent was evaporated under vacuum to give awhite solid, yield l.12g (100%). Recrystallizationfrom toluene-hexane gave white needles, m.p. 179-80°; IR (KBr): 2950 (m), 2850 (w), 1770 (m), 1710(s,br), 1570 (m,br), 1440 (s), 1410 (s), 1380 (w),1345 (w), 1315 (w), 1165 (s), 1090 (w), 1070 (m),1050 (m), 1030 (m), 910 (m,sh), 820 (m,sh), 800(w), 790 (m), 765 (s), 690 (m), 535 (m) ern"; IHNMR (CDCh, TMS): 8 0.50 (t, 3H, J=7.5 Hz),1.35 (s, 2H), 3.22 (t, 2H, J=6.0 Hz), 6.25 (s, 2H),7.2-7.6 (m, 8H); Anal. Calcd for CI9H17N30z:C,71.45; H, 5.73; N, 13.16. Found: C, 71.60; H, 5.40;N,13.IO%.Reaction of PT AD with cyclopentadiene.Freshly distilled cyclopentadiene (0.46 g, 7.Ox10-3mole) and 10 mL of methylene chloride wereplaced into a 50mL round-bottomed flask. Thesolution was cooled to -10° with an ice-salt bathwhile being magnetically stirred. To this was addeda solution of PTAD (1.0 g, 7.0x10-3 mole) in 10mL of methylene chloride all at once when a paleyellow solution was obtained. Methylene chloridewas removed under vacuum to leave 1.46 g (100%)of pale yellow solid which on recrystallizationfrom hexane fraction gave white crystals, m.p. 49°;IR (KBr): 3050 (w), 3020 (m), 2950 (m), 2860 (w),1770 (s), 1710 (s,br), 1590 (w), 1440 (s), 1410(s,br), 1370 (m), 1330 (m), 1280 (w), 1185 (s),1060 (s), 995 (m), 960 (m), 920 (s), 870 (m), 800(m,sh), 780 (s), 740 (s), 660 (w), 610 (m) ern"; IHNMR (CDCI3, TMS): 8 0.83 (t, 3H, J=9.0 "Hz),1.58 (s, 2H), 1.86 (d, 1H, J=9.0 Hz), 2.18 (d, 1H,J=9.0 Hz), 3.33 (t, 2H, J=7.5 Hz), 5.00 (s, 2H),6.33 (s, 2H); Anal. Calcd. For CIOH13N30Z: C,57.96; H, 6.32; N, 20.28. Found: C, 57.90; H, 6.40;N,20.20%.Reaction of PT AD with 5,5-dimethoxy-1,2,3,4-tetrachlorocyclopentadiene. In a 50 mLround-bottomed flask, equipped with a magneticstirrer and a constant-pressure dropping funnel, asolution 'of 1.85 g (7.0xlO-3 mole) of 5,5-dimethoxy-1,2,3,4-"tetrachlorocyclopentiadiene in10 mL of methylene chloride was prepared. To thissolution under stirring a pink solution of 1.00 g(7.0xlO-3 mole) of PTAD in 10 mL of methylenechloride was added dropwise over a period of 2.5hr. The solution developed a deep-purple colourwhich turned to pale yellow. The solvent wasremoved under vacuum to give 2.85 g (100%) ofwhite solid which on recrystallization frommethanol gave white crystals, m.p, 133°; IR (KBr):3500 (w), 3020 (w,sh), 3000 (w,sh), 2950 (m),2820 (w), 1795 (m), 1750 (s,br), 1580 (s), 1445 (s),1400 (s), 1345 (m), 1210 (s), 1180 (s), 1150 (s),1130 (s), 1100 (rn), 1070 (m), 1010 (s), 980 (s),930 (m), 890 (m), 805 (s), 780 (w), 760 (m), 650(w), 540 (m) cm'; IH NMR (CDCI3, TMS): 80.88(t, 3H, J=9.0 Hz), 1.60 (s, 2H), 3.43 (t, 2H, J=7.SHz), 3.6 (s, 3H), 3.8 (s, 3H); Anal. Calcd forC12H13N304Ck C, 35.58; H, 3.23; N, 10.37.Found: C, 3S.50; H, 3.30; N, 10.20%.Reaction of PTAD with hexachlorocyclopen-tadiene. Hexachlorocyclopentadiene (1.94 g,7.0x10-3 mole) and 10 mL of methylene chloridewere placed in a 50 mL round-bottomed flask.Stirring was started and a solution of 1.0 g (7.0xI0-3mole) of PTADS in LO mL of methylene chloridewas added all at once. The solution became deep-purple which turned to pink. After 48 hr a pale-yellow solution was obtained. Methylene chloridewas removed under vacuum to leave 2.94 g (100%)of white solid which on recrystallization from n-hexane gave white needles, m.p. 103-4°; IR (KBr):3500 (w), 2995 (m), 2990 (m), 2850 (m), 1810 (s),1745 (s,br), 1580 (s), 1440 (s), 1400 (s,br), 1360(s), 1340 (s), 1170 (s), 1130 (s), 1100 (s,br), 980(w), 930 (m), 910 (m), 880 (s), 780 (s), 760 (m,sh),720 (s), 690 (m), 630 (w), 530 (m) ern"; IH NMR(CDCh, TMS): 8 0.93 (t, 3H, J=7.5 Hz), l.S7 (s,2H), 3.48 (t,2H, J=6.0 Hz); Anal. Calcd forC12H7N30zCI6: C, 29.02; H, l.70; N, 10.lS. Found:C, 28.50; H, 1.70; N, 10.30%.Reaction of PT AD with isoprene. Into a 100m~ two-necked round-bottomed flask, equippedWIth a magnetic stirrer and a thermometer, 0.72 g(1.13 xl 0-3 mole) of freshly distilled isoprene and30mL of methylene chloride were added. Thesolution was stirred and cooled to -10° with an ice-MALLAKPOUR et al. :REACTION OF 4-n-PROPYL-l,2,4-TRIAZOLINE-3,5-DIONE WITH DIENES 1005salt bath. A solution of 1.6 g (1.13 x l 0'3 mole) ofPT AD in 25mL of methylene chloride was addeddropwise over a period of 30 min. The pink colourof PTAD disappeared as fast as the solution wasadded to give a pale-yellow solution. The solventwas removed under vacuum to give a pale-yellowgummy solid which on recrystallization from n-hexane gave white crystals; 1.80 g (76%), m.p. 34-6°; IR (KBr): 3050 (w), 2950 (s), 2930 (s), 2900(m), 2880 (m), 1765 (s), 1700 (s,br),156G (w),1440 (s,br), 1415 (s), 1390 (m), 1350 (m), 1310(w), 1260 (m,br), 1175 (w), 1070 (m), 1030 (m),940 (w), 890 (w), 765 (m,br), 730 (w) cm'; IHNMR (CDC13, TMS): 0 0.95 (t, ,3H, 1=9.0 Hz),1.75 (s, 2H), 1.86 (s, 3H), 3.65 (t, 2H, 1=9.0 Hz),4.0 (m, 4H), 4.63 (s, 1H); Anal. Calcd forClOHISN302: C, 57.40; H, 7.23; N, 20.10. Found: C,57.30; H, 7.30; N, 20.20%.Reaction of PTAD with 2,6-dichlorostyrene.Into a 50 mL round-bottomed flask were placed0.60 g (3.5x10,3 mole) of 2,6-dichlorostyrene and10 mL methylene chloride. The stirring was startedand a solution of 0.50 g (3.5xlO,3 mole) of PTADin 20 mL of methylene chloride was added all atonce when deep-purple colour appeared. After 9 hra pale-yellow solution was obtained. The solventwas removed under vacuum to leave -a gummysolid which was triturated with ether to yield 1.1 g(100%). Recrystallization from n-hexane gavewhite crystals, m.p. 105°; IR (KBr): 3450 (w),3090 (w), 2950 (m), 2880 (m), 1770 (s,br), 1590(s), 1570 (s), 1460 (s,br), 1420 (s), 1380 (s), 1350(s), 1300 (m), 1270 (m), 1180 (s), 1110 (m), 1065(m), 1005 (m), 950 (w), 920 (m), 780 (s), 750 (s),705 (w), 690 (w), 620 (m,br), 500 (w) ern"; IHNMR (CDCh, TMS): 0 1.03 (t, 3H, 1=7.5 Hz),1.76 (s, 2H), 3.66 (t, 2H, 1=7.5 Hz), 3.84 (dd, IH,11~11.7 Hz, 12=2.1 Hz), 4.70 (dd, IH, 11=11.7 Hz,12=2.1 Hz), 5.66 (t, 1H, 1=2.1 Hz), 7.3 (dd, IH,11=8.4 Hz, 12=unresolved), 7.49 (t, IH, 1=8.4 Hz),8.33 (dd,11 =8.4 Hz, 12=unresolved); Anal. Calcdfor C\3H\3N302Ch:C, 49.70; H, 4.17; N, 13.38.Found: C, 49.30; H, 4.30; N, 13.50%.Reaction of PTAD with 1,3-cyclohexadiene.Into a 25 mL one necked round-bottomed flask,equipped with a magnetic stirrer, 0.187 g (0.22 mL,2.3xl0,3 mole) of 1,3-cyclohexadiene in 5 mL ofmethylene chloride was added. The solution wasstirred by a magnetic stirrer and cooled to -10° withan ice-salt bath. A solution of 0.33 g (2.3xlO,3mole) of PT AD in 10 mL of methylene chloridewas added dropwise. The pinck colour of PT ADdisappeared as fast as the solution was added. Apale-yellow solution was obtained. The solvent wasremoved to give a pale-yellow gummy solid, yield,0.517 g (100%). The gummy solid was sublimedunder vacuum at 60° to give a white solid, whichon recrystallization from hexane fraction gavewhite needles, m.p. 65°; IR (KBr): 3400 (w,br),2950 (m), 2850 (w), 1700 (s,br), 1440 (s), 1418 (s),'1370 (m), 1325 (w), 1235 (w), 1200 (m), 1170 (m),1110 (w), 1060 (m), 1050 (m), 950 (w), 920 (m),890 (w), 870 (w), 850 (m), 820 (w), 760 (s), 730(m), 690 (m), 640 (m), 58Q (m) cm'; IH NMR(CDCh, TMS): 00.86 (t, 3H, J=7.5 Hz), 1.33-1.96(m, 4H, overlapped by doublet), 2.16 (d, 2H, 1=9.0Hz), 3.46 (t, 2H, 1=9.0 Hz), 4.83 (dd, 2H,1=unresolved), 6.46 (dd, 2H, J=3 Hz); Anal Calcdfor CllHISN302: C, 59.70; H, 6.80; N, 19.0. Found:C, 59.90; H, 6.90; N, 19.40%.Reaction of PTAD with cis,-cis-l,3-cycloheptadiene. Freshly distilled cis, cis-1 ,3-cycloheptadiene (0.76 g, 0.87 mL, 7.0x10,3 mole)and 10 mL of methylene chloride were placed in a100 mL round-bottomed flask. The solution wasstirred by a magnetic stirrer and a solution of 1.0 g(7.0xlO,3 mole) of PTAD in 40 mL of methylenechloride was added all once. The solution wasstirred at 'room temperature for 24 hr, and thenrefluxed f~r 12 hr. Solvent was removed and theresultant oil was triturated with ether and theresidue sublimed under vacuum at 90° to give 0.60g (34%) of white crystals, m.p. 107°; IR (KBr):3300 (w), 2900 (s), 2850 (m,sh), 1740 (s), 1680(s,br), 1450 (s), 1420 (s), 1370 (m), 1290 (m,br),1230 (w), 1150 (w), 1050 (m), 970 (m), 890 (w),850 (w), 810 (m), 770 (m), 750 (m), 680 (w), 640(w) em"; IH NMR (CDCh, TMS): 0 0.96 (t, 3H,1=7.5 Hz), 1.2-2.43 (m, 8H), 3.56 (t, 2H, 1=7.5Hz), 4.93 (s, br, 2H), 6.0-6.3 (m, 2H); Anal. Ca1cdfor C12H17N302:C, 61.3; H, 7.3; N, 17.9. Found: C,62.2; H, 7.5; N, 16.50%.AcknowledgementThe partial financial support of this work by theresearch affair, Isfahan University of Technology,Isfahan, IR Iran, is gratefull* acknowledged. Wethank Professor Ali A. Entezami (University ofTabriz) for a gift of isoprene. We also thankMiss Sepideh Khoee' for typing this manuscript.1006 INDIAN J CHEM, SEC.B,OCTOBER 1998References1 Cookson R C, Gilani S S H & Stevens IDS, TetrahedronLett, 1962,615.2 Cookson R C, Gilani S S H & Stevens IDS, J Chem Soc,(C), 1967,1905.3 Gilani S S H & Triggle D J, J Org Chem, 31, 1966,2397.4 Solo A J, Sacher H & Gilani S S H, J Org Chem, 30, 1965,769.5 Sauer J, Angew Chem Int Ed, 6, 1967 16.6 Pirkle W H & Stickler J C, Chem Commun, 1967, 760.7 Stickler J C & Pirkle W H, J Org Chem, 31, 1966, 3444.8 Sauer J & Cehroder B, Angew Chem Int Ed, 4, 1965, 71.9 Hoffman H M R, Angew Chem Int Ed, 8, 1969,556.10 Mallakpour S E & Butler G B, In: Advances in polymersynthesis, edited by B M Culbertson & J E McGrath,Polymer science and technology series, Vol 31 (Plenum:New York), 1985, pp \-25.11 Lai Y C, Mallakpour S E, Butler G B & Palenik G J, J OrgChem, 50, 1985,4378.12 Mallakpour S E, Butler G B, Aghabozorg H & Palenik G J,Macromolecules, 18,1985,342.13 Mallakpour S E & Butler G B, J Polym Sci Polym ChemEd, 25, 1987,2781.14 Mallakpour S E & Butler G B, J Polym Sci Polym ChemEd, 27, 1989, 125.15 Mallakpour S E & Butler G B, J Polym Sci Polym ChemEd, 27, 1989,217.16 Mallakpour S E & Zolfigol M A, J Sci I R Iran, 4, 1993,199.17 Callander D D, Coe P L & Tatlow J C, Chem Commun,1966, 143.

Reaction of 4-n-propyl-1,2,4-triazoline-3,5-dione with some selected dienes

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Reaction of 4-n-propyl-1,2,4-triazoline-3,5-dione with some selected dienes

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