462 RUHEMANN : DIKETODIPHENYLPYRROLIKEL . -Dike t o dip he n y lp yrro lin e and its A izal oyues.Part III.By SIEGFRIED RUHEMANN.THE formation of the diketodiphenylpyrrolines by the action ofethyl phenylpropiolate on the sodium derivatives of aromatic amidesis accompanied by the production of colourless compounds (seeRuhemann, Trans., 1909, 95, 984, 1603). One of these substanceshad been isolated previously (Zoc. cit.) from the product of thereaction of sodiobenzamide with the acetylenic ester, and its formulawas found to be C23E1,03Nz. With regard to its constitution, theview was expressed that this substance was the result of the unionof benzamide with the first formed phenylpropiolylbenzamide, andthat, accordingly, it was represented thus :C6H,*C ( NH°CO*CGH5) :CH*CO-NH°CO*C6H5.A closer investigation, however, did not confirm this view; for thecolourless substance, C23HlS03N2, on boiling with potassiumhydroxide decomposes to yield deoxybenzoin, and with cold con-centrated sulphuric acid breaks up quantitatively into diketodi-phenylpyrroline and benzamide.This behaviour, and the factthat the compound has no basic properties, lead to the conclusionthat it is to be regarded as an additive product of diketo-diphenylpgrroline with benzamide. Its constitution, therefore, isto be exmessed thus. Iand it is therefore 3-benzoylamino-3-hydroxy-2-keto-4 : 5-diphenyl-p yrroline.This result induced me to examine whether the diketopyrrolineforms additive products with other substances, and in this respect,also, resembles isatin.It was found, indeed, that, like the lattercompound (see Baumann, Ber., 1885, 18, 890), the diketopyrrolinereadily unites with phenylmercaptan to yield an additive com-pound, C16~,,02N,C6H6S, which undoubtedly has a constitutionsimilar to the additive product with benzamide, and which readilydecomposes into its constituents, phenylmercaptan and the diketo-pyrroline. With piperidine, the diketopyrroline combines even inthe cold to form the compound C,6H,,02N,C5Hl,N. This is morestable than the former substance, and does not decompose until itssolutions in mineral acids are heated, when the diketopyrrolineseparates. The behaviour of piperidine towards isatin was examineAND ITS ANALOGUES. PART 111. 463by Schotten (Ber., 1891, 24, 1367), who carried out the reaction a tthe temperature of the water-bath, and thus obtained dipiperidyl-isatin,"6H4<--&d5-- C(CH N)2>C().The resemblance between isatin and the diketopyrrolines isfurther indicated by the fact that they give the indopheninereaction.On shaking their solutions in concentrated sulphuricacid with benzene which contains thiophen, the red colour firstchanges to brown, and then gradually turns blue. Like isatin,diketodiphenylpyrroline condenses with phenol in the presence ofconcentrated sulphuric acid, and forms 2-keto-3 : 3-bishydroxy-phenyl-4 : 5-diphenylpyrroline,CPh:yPh(C6H4*0H)2C<~~-N~ 'It may finally be stated that the relation which isatin exhibits tothe diketopyrrolines as well as to the diketo-derivatives of cyclo-pentene extends also to the diketopyrazolines :P ? > C O .N*NROne member of this class of compounds, namely, 4 : 5-diketo-l-phenyl-3-methylpyrazoline, was first prepared by Knorr and Pschorr(Annulen, 1887, 238, 194) ; afterwards Sachs and Barschall (Bey.,1902, 35, 1437; 1903, 36, 1132) obtained diketopyrazolines by theaction of nitrosodimethylaniline on the pyrazolones and subsequenttreatment of the former condensation products with mineral acids.Up to the present, however, no member of this group of diketo-compounds is known in which the iminic hydrogen of the pyrazolinering is intact.I propose to prepare such substances with theview of ascertaining whether they behave towards alkalis like theiranalogues and form blue salts.EXPERIMENTAL.3-Benzo ylamino-3-hydro xy-2-ke t 0-4 : 5-diph enylpyrroline,CPh:QPhCO-NH 'C,H,.CO-NH*C(OH)<On boiling this compound with an excess of concentratedpotassium hydroxide, it decomposes and yields ammonia, deoxy-benzoin, oxalic acid, and benzoic acid, thus:C2,H,;03N2 + 3EHO + H,O =C,H,*CH2*CO0C6H, + (CO2E)z + C,H,*CO,K + 2NH3.The heating was continued until ammonia ceased to be evolved464 RUHEMANN : DIKETODIPHENYLPYRROLINEsteam was then passed through the product of the reaction, whena solid slowly passed over which, after crystallisation from lightpetroleum, melted at 60-61O.This substance was deoxybenzoin :0.1732 gave 0.5440 CO, and 0.0962 H,O.Cl4Rl20 requires C = 85-71 ; H = 6.12 per cent.The remaining alkaline solution was treated with an excess ofdilute sulphuric acid and subjected to steam distillation.Thebenzoic acid which is contained in the distillate was extracted withether, recrystallised from water, and identified by the melting point.The formation of oxalic acid in the reaction was ascertained bythe usual test.The result of the action of potassium hydroxide on the colourlesssubstance C23H18O3NZ indicates that it is an additive product ofdiketodiphenylpyrrolint? with benzamide, and this conclusion issupported by the fact that, with sulphuric acid, the substance breaksnp into these components. On adding the colourless compound tothe concentrated acid, it dissolved, yielding a deep red solut,ion.This, after being kept overnight, was gradually poured into coldwater, and the diketodiphenylpyrroline, which separated, wascrystallised from dilute alcohol.It softens a t 1 8 4 O , and melts a t190-191O (instead of 184O, which was previously given as themelting point) :C=85-66; H=6-17.0.1948 gave 0.5505 CO, and 0.0820 H,O.C1,HllO,N requires C = 77-11 ; H = 4.42 per cent.The benzamide which is contained in ths filtrate from the diketo-pyrroline was extracted with ether, and, on evaporation of theether, remained as a red solid, which, after crystallisation fromwater, melted a t 130O:C=77*07; H=4.67.0.2338 gave 24.2 C.C. N, at 18O and 754 mm. N=11*84.C,HiON requires N = 11-57 per cent.A dditive Product of Dike t odiphen ylpgrroline and Phen ylmercaptan,This additive product is readily .formed on adding phenyl-mercaptan to the diketopyrroline, dissolved in hot alcohol.Thedeep colour of the solution turns light red, and faintly pink platessoon separate. These were washed with ether and dried in avacuum desiccator over sulphuric acid. The substance reddens atabout 140°, and melts a t 1’74-175O:C=73*68; H=4*96.C,,H,,O,NS requires C = 73-53 ; €I = 4.74 ; S= 8-91 per cent.C,,H,,O,N,@,W.0.1760 gave 0.4755 CO, and 0.0785 H,O.0.2240 ,, 0.1476 BaSO,; S=9-05.On adding this compound to cold concentrated sulphuric acidAND ITS ANALOGUES. PART 111. 465heat is developed, the odour of phenylmercaptan is perceptible, anda, deep red solution is produced, which yields a precipitate of diketo-diphenylpyrroline when poured into water.Additive Product of D i k e t o d i p ~ e n y l ~ r r o l i n e and Piperidine,On adding piperidine to the diketopyrroline dissolved in ether,the red colour of the solution changes to yellow, and, after a shorttime, faintly brown, glistening prisms separate, which melt anddecompose a t 180-181O :C16H1102N7C5HllN'0.1632 gave 12.2 C.C.N , at 20° and 749 mm.C2,H,,O2N, requires N = 8.38 per cent.The substance is rather stable towards mineral acids; decom-position into its constituents, the diketopyrroline and piperidine,does not take place until the solutions are heated.N=8.42.2-Keto-3 : 3-Bishyd~oxyphenyl-4 : 5-diphenylpyrroline,Phenol reacts with diketodiphenylpyrroline under the same con-ditions as with isatin (see von Baeyer and Lazarus, Ber., 1885,18, 2641). The diketopyrroline (2 grams) was dissolved in anexcess of phenol, and, gradually, concentrated sulphuric acid wasadded until the red colour of the solution turned deep brown. Thewhole was then poured into water, when a yellow, flocculent solidwas precipitated. This was dissolved in ether, and the solutionmixed with chloroform until it became turbid. In the course ofa few hours, yellow plates separated, which retained their coloureven on boiling the alcoholic solution with animal charcoal. Thesubstance melts a t 220-221O :0.1600 gave 0.4697 CO, and 0.0755 H,O.0.2420 ,, 7.2 C.C. N, at 17O and 747 mm. N=3.39.C,8H,,0,N requires C = 80.19 ; H = 5.01 ; N = 3.34 per cent.This compound is sparingly soluble in chloroform or benzene,moderately so in ether or cold alcohol, but readily so in boilingalcohol. It dissolves in potassium hydroxide, yielding a yellowsolution, from which it is precipitated unchanged on the additionof hydrochloric acid.C =80.06; H=5*24.UNIVERSITY CHEMICAL LABORATORY,CAMBRIDGE