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The whole is then left standing for 1 --2 days at O O C . Alkaline alcoholic solutions vacuum sublimation of the residue left after evaporation of the ether from the extract. Compound (2c) is isolated as its picrate, made by boiling the (3-dicarbonyl compound with picric acid in ethanol. COOCrH5 COOH H CHI CHC12 H COOCzHs COOH CH2CI CHO R2 Solvent Alcohol Ether Ether Ether Ether Ether Alcohol [a I fbl [cl Condensing agent NaOCzHS NaOC2Hs NaOC2H5 NaOC2Hs Na NaOC2Hs NaOC2Hs Reaction temp. [ "C -15 -15 0 0 -15 -1 5 0 [a] Obtained from (2gJ by hydrolysis with conc HCI. [bl Obtained from (2ci by refluxing in acetic acid for 1 h with SnCl2. Icl Obtained from ( 2 ; ) via the pyridinium salt, m.p. 223-224ยฐC (decomp.), and the nitrone, m.p. 207 " C (decomp.). are then acidified with alcoholic sulfuric acid, filtered, and concentrated in vacuo. If alcohol-free sodium ethoxide or metallic sodium in ether is used as condensing agent, the reaction mixture is subsequently treated with water, and the pyrone is isolated by acidification, extraction with ether, and __ Yield I %I __ 75 80 40 25 50 45 40 90 M. p. [ "C] 118-119 238 (decomp.
๐ SIMILAR VOLUMES
the reaction leads to ring opening. We have succeeded in preparing (2) by direct reaction of 4-amino-5-dimethoxymethylpyrimidine ( 1 ) I21 with s-triazine. Compound (2) is very sensitive toward water. Its structure has been proved by elemental analysis and by IR and N M R spectroscopy. The N M R sig
Excluding cyclopentadienone as an intermediate in the thermolysis of (3) we feel that the difference in thermolytic fragmentation of 0-and p-benzoquinone can be explained by assuming that primarily a cyclopropanone-type intermediate is formed in the case of p-benzoquinone. Bicyclo-[2.1.0]pent-4-en-2