422
hlARY ANN MORGAN AND EARLE
Anal. Calcd. for C16H2404: C, 68.57; H, 8.57. Found: C, 68.32; H, 8.64. Reaction of &Pinene with Methylenemalonic Ester.-+Pinene (8.3 g., 0.06 mole) and methylenemalonic esterla (10.3 g., 0.06 mole) were refluxed in xylene (200 ml.) under an atmosphere of nitrogen for 111 hr. The solvent was reand the residue dismoved under vacuum (60' 120 ".)) tilled in an oil-jacketed'flask'to give diethyl nopylmalonate, yield 9.5 g. (51%), b.p. 128' (0.2 mm.), n% 1.4668, [m]"D -20.52'. Anal. Calcd. for C18H?BOI: C, 70.13; H , 9.15. Found: C, 69.89: H , 9.35. Diethyl Nopylma1onate.-Diethylmalonate (24 g . ) was added t o a solution of sodium (5.6 g . ) in absolute ethanol (400 ml.). A solution containing nopyl tosylate (49.8 g.) and absolute ethanol (100 ml.) was added dropwise over 1 hr. to the stirred reaction mixture held a t its boiling point. Heating and stirring were continued for 48 hr., and the cooled mixture was poured into water (2 1.) and extracted with ether (500 ml.). The ether solution was dried over magnesium sulfate, filtered and fractionally distilled to give (13) G. B. Bachman and H. A . Tanner, J . Ovg. Chem., 4 , 493 (1939).
[CONTRIBUTION FROM
THE
\'AN
Vol, 70
HEYNINGEN
diethyl nopylmalonate, yield 14 g. (387,), b.p. 127' (0.2 ".), n Z 5 D 1.4678, !cY]'~D -21.5'. Anal. Calcd. for ClsH2804:C, 70.13; 11, 9.15. l ~ u u n t l : C. 69.97: H , 9.21. All the physical properties of this substance, including its infrared spectrum, were indistinguishable from those for the material obtained directly from @-pineneand methylenemalonic ester. Reaction of 10-Pinen-2-ylsuccinic Anhydride (11) with Methanol.-The anhydride (1 9.) was refluxed with anhydrous methanol (30 ml.) for 16 hr. The excess methanol was removed under partial vacuum and the oily residue was held a t 70" a t a pressure of 0.05 mm. for 3 hr. A value of 275 was obtained as neutral equivalent (calcd. for half acid-ester, 266). This residue showed no anhydride bands in the infrared but exhibited strong absorption a t 5.8 (ester) and 5.9 1.1 (carboxylic acid). Following distillation of the oily residue (b.p. 155" (0.08 mm.)), the product exhibited strong anhydride bands a t 5.43 a n d 5.63 p in addition t o those for the ester (5.8 W ) and carboxylic acid (5.9 p ) . The undistilled crude half-ester reacted rapidly with diazomethane in ether to form dimethj 1 10-pincn-2-ylsuccinate (11'). h7EW YORX, AT. Y .
LILLYRESEARCH LABORATORIES]
2H-Pyran-3,5 (4H,6H)-Diones BY MARYANNEMORGAN' AND EARLEVAN HEYNINGEN RECEIVED AUGUST13, 1956
A synthesis is reported for the previously undescribed 2H-pyran-3,5(4H,GH)-diones.
I n contrast to the many syntheses of 4,5-dihydro2H-pyran-2,6(3H)-diones (I) appearing in the literature, there is no report of the synthesis of the isomeric 2H-pyran-3,5-(4H,6H)-diones (11). Gulland and Farrar2 do mention their interest in compounds of this type as possible chemotherapeutic agents; they had prepared some substituted cyclotelluropentane - 3,5 - diones which had exhibited marked activity and the pyran-3,5-diones are their oxygen analogs. There is, however, no subsequent report of their preparation by these authors.
hexyne (IV, R = H, R' = C3H6)the solvent used was methanol, and transesterification occurred during the reaction to give as a product an inseparable mixture of methyl and ethyl esters. Since the alkoxy1 group is lost in the ring closure, this mixture was as useful as a pure ester. The hydration of 3-carbethoxymethoxy-3-methyl-I-butyne(IV, SCHEXEI
I11
R\C
