Scientia Sinica

50 SCIENTIA SINICA Vol. V

O CF 7 —OC2H,s (CHe)s O=C aN C(COOC;H;). O OX L | | cE aa _ ae a Har = SSHe LN/\_ 7 Cl OCH; OCH, CH Vv He \CH:—C—0C.Hs HPO, ( 1. KOH PSE 2. HCI SS Veeco: eS 100% | at 3. —CO, UNI NOL > OCH, °CHs VI CH, CH, JON VN CH, CH,—COOH CH CH,—COOH | Cc H CH aN z aN? | ¥ “c—coou ——__——> | ) “cH—CooH | CH, Pd—C | (CH LS eo LNA OCH: 55, OCH: Fy, VII VIII

In continuing the work on the synthesis of estrone, the same series of reactions was employed in the preparation of the unsaturated dibasic acid (VII), except that in some steps the experimental conditions used were somewhat modified. From steps (V) to (VI), Bachmann and coworkers used 100% orthophosphoric acid as cyclization agent which was only suitable for small batches of 2.5 g of the keto malonic ester in each run. In our experiment, two other cyclization agents were used: (1) anhydrous hydrofluoric acid, and (2) concentrated sulfuric acid. Under different conditions, both of these cyclizing agents could smoothly convert the keto malonic ester (V) into the unsaturated triester (VI). By using these two cyclizing agents, not only larger runs could be made but also the yields were much higher than that obtained by Bachmann and coworkers!.

With acetic acid purified over chromium trioxide as solvent, the unsaturated dibasic acid (VII) was hydrogenated in the presence of 5% palladium-