in bis(2-ethoxyethyl) ether l 5 to the tetracyclic hydrocarbon 14 (C9Hlz, t~~j~1 . 4 9 2 8, v 3067-3055 cm.-l) identical with the product obtained by Wolff-Kishner reduction of the known ketone 15. l6 (15) L. Friedman and H . Shechter, J . Am. Chem. Soc., 81,5512 (1959); 83, 3159 (1961). (16) H. K. Hall, Jr., J . Org. Chem., 25, 42 (1960). We are grateful to Dr. Hall, who kindly furnished a sample of 15 to facilitate identification with material we prepared by independent routes.
Bridged Ring Systems by Anionic Rearrangement
Sir :The propensity of bridged-ring molecules to undergo carbonium ion rearrangements is well appreciated. Recent evidence for the existence of homoenolate ions3 led us to explore the possibility that skeletal rearrangements via such anions might afford direct routes to systems otherwise difficultly obtainable. We now demonstrate the potential usefulness of this approach by applying it to the synthesis of tricycl0[4.2.1.0~~~]nonan-2-one (3). This skeleton along with other bridged systems presented here is of inherent interest in studies of carbonium ions and carbanions.j Treatment of brexan-2-one (1)j with potassium t-butoxide in t-butyl alcohol at 185' for 150 hr. transformed it (ca. 60% yield) into an isomeric ketone, CgH120 (m.p. 118.5-119.5", v 1747CgH120 (m.p. 118.5-119.5", v , 1169CgH120 (m.p. 118.5-119.5", v , and 1022 semicarbazone, C10HljN30, m.p. 159.5-162°).6 The following interconversions established the structure of this isomer as 3. The sodium salt of 5-norborneneendo-2-carboxylic acid (7a)' was converted to its acid chloride (7b) (v 1801 cm.-') with oxalyl chloride and then directly to the liquid diazoketone 7c (v 3062, 2005, and 1633 cm.-') by treatment with diazomethane. Without purification, the diazoketone was heated with copper powder in tetrahydrofuran8 and afforded the tetracyclic ketone 4 (CgHloO, m.p. 90.5-92', v 3045 and 1731 cm.-', X (95% ethanol) 271 mp ( E 50),9 no olefinic protons by n.m.r. ; semicarbazone, Cl0Hl3N30, m.p. 204-205 " ; 2,4-dinitrophenylhydrazone, C15H14N404, m.p. 210-21 1 ').Hydrogenation of 4 with palladium in ethyl acetate cleaved a cyclopropyl bondlo and gave a tricyclic ketone shown to be 5 (CsH120, m.p. 120-
