acids. The latter acid ha? been reported by and cyclopentanone) and 1668 crn. -I (strong, conFarmer6 (semicarbazone, 1n.p. 199") but the nia- jugated C=C), Amax 220 and 261 nip ( E 14000 aiid terial employed in the present study was prepared 70),aud tetrahydroparthenin (111, C, 67.11; H, by Arndt-Eistert chain elongation of 3-oxocyclo- 8.26), m.p. 140-144', [a] 78.4, infrared bands a t pentane-1-carboxylic acid.' The infrared spec- 3450 and (in acetonitrile) 1760 (y-lactone) arid 1742 trum of the 2-oxo- derivative possessed bands a t cm.-' (cvclopentanc,iie),A m r x 2771np ( E 71).2 1010 and 1118 cm.-l not shown by the 3-oxo,OIi 011 > isomer and the spectrum of the dihydro irradiation -, r < material was identical with that of the 3-oxo0 1 ( 1 7 ' J b, derivative. Furthermore, the seinicarbazones of -* the dihydro material and the %oxo- isomer melt 1) ) 0 a t 203.0-203.4° and show no depression upon ad0 (I mixture while the same derivative of the 2-oxoI I1 isomer melts a t 192.0-192.4' and upon admixture with either of the foregoing materials shows a I 011 f )I I i m.p. depression. With the placement of the carbonyl group a t C-3, in respect to the acetic 1' 0 acid side-chain, it follows that in the original ir' ,, radiation product the only position for the olc(~ ' Oil 0 .' finic linkage which gives rise to an unsubstituted 0 0 cyclopentenone chromophore is between C-3 a i i d I\ I il C-5, thus forming structure I. That the methylene group is conjugated with tlic The formation of this material is viewed (shown lactone carbonyl is shown by the spectra, the prepabelow) as proceeding via an initial "photo" product a p y r a ~ o l i n e ,a~ comparison of the Cration of of the 3,2,0-bicycloheptadiene type. In line with methyl values of I and 111 and low temperature this postulate of a ketene intermediate, i t is found ozonolysis which resulted in formaldehyde and a that when a-tropolone is irradiated in ethanol, the compound C14H1604 (IV, C, 63.62; H, 5.88). ethyl ester of I is obtained. Lithium aluminum hydride reduction oi parthenin followed by dehydrogenation over palladium c) c) 0 ,- oii Ii 0 charcoal gave artemazulene (V) . This determines ',, . o ( the carbon skeleton and the point of attachment. of --. ' ... / the lactone ring. i.-
+
f
A
I
-5
\:
--,
P.
'!
VI (6) E. H. Fermer, J . Chem. Soc., 123, 3324 (1923). (7) E. Hope, ibid., 892 (1912); kindly supplied by Professor D S. A-oyce. (8) Pv'ational Science Foundation Predoctoral Fellow, 1959-1 960. (9) National Science Foundation Predoctoral Fellow, 1958-1959.
DEPARTMENT OF CHEMISTRY UNIVERSITY OF CALIFORWA BERKELEY 4, CALIFORNIA
\vII,I,IAM ~'ILLIAM
G . DALrBEK
