M a y 3, l%j?
COhlMUNIC.ITIOh'S TO THE
ether, a small amount of the propenyl ether, and a trace amount of the thiol resulting from cleavage (rather than rearrangement) of the thiophenyl ethers. JVe have identified this substance as 2 methyl-2 , 3-dihydrothi~naphthene~ (I I I) by means of both synthetic and analytical procedures. The identification of (111) is based on this evidence: Oxidation with :307c HzOs gives a sulfone (IILd.), 1n.p. 116.3-1 17.5' (calcd. for CYH1002S: C , 59.4; H , z.3. Found: C, 59.60; H, 5.51). The n.m.r. spectrum is in full agreement with the suggested structure showing (in deuteriochloroform) a sharp methyl proton doublet centered on 'T = S.54, approximately 24 poorly resolved peaks grouped around
T
=
\ 6.6 (-C-H
/
\
and CH? protons
/
in the sulfone ring), and a group of sharp lines in the region of 'T = 2.5 protons). Furthermore, the n.m.r. spectrum is very similar but not superimposable (TCH, = 8.62) on that of the isomeric (VIA) which we prepared according to path C, proceeding through (VIII) and (VI) as previously described.lo5" The sulfones, (IIIX) and (VIA), also differ decidedly in physical properties and in the important fingerprint region of their infrared spectra. The fact that the propenyl thiophenyl ether (V) is quantitatively recovered from reaction conditions which can effect the conversion of (I) to (111) is a good indication that (V) is not an intermediate or a precursor of (111). The absence of any Claisen thiol product (11) suggests that the ring closure reaction proceeds very rapidly under the conditions of formation of (11). The formation of 2-methylcoumaran as a minor product Gf rearrangement of the oxyether' obviously occurs much less easily. The amine medium might also be expected to greatly facilitate the prototropic shift which competitively (and, to all intents and purposes, irreversibly) removes allyl thiophenyl ether from the reaction with formation of (V). Since the amount of (V) formed is significantly reduced from what was formerly experienced* (under conditions which do not produce (111)), we can perceive the full magnitude of the "catalytic effect" induced by the use of these high boiling amines. This is t o say that while the accelerating influence of dimethylaniline solvent on the rate of rearrangement of the oxyether is negligible12s13i t can serve as an indispensable medium for bringing about rearrangement of (I), which under (other) nornial Claisen conditions is merely tautomerized. I t is not clear, as yet, whether the influence of certain amines can be correlated with empirical solvent parameters such as Kosower's14 "Z" value or others which have been shown t o be applicable in (9) This was once mistakenly assumed b y H u r d and Greengards to be t h e side product of t h e reaction conditions which have been shown4 t o lead t o ( V ) Both in our experience and in ref. ( 4 ) (111) never has been identified previously as a product of t h e pyrolysis uf allyl thiophenyl ether. (10) E. G G LVerner, Rec. Trot'. C h i n . , 68, 509 (1949) (11) F. G Bordwell and W , H LIcKelIin. J . A m C h r m S o c . , 73, 2231 (1951). (12) J . I; Kincaid and 11. : : Tarbell, i b i d . , 61, 3085 (1939). (13) I ) S Tarbell and J. I:. Kincaid, i b i d . , 68, 728 (1940).
EDITOR
li35
the Diels-Alder reaction'j or to catalytic activity of the type recently identified for the Diels-Alder by other The close similarity of the Claisen, the Diels-Alder and a host of others now classified as four-center reactions often has been pointed oUt.18 We are presently studying such relationships in terms of the rate response to changes in reaction medium and temperature, as well as photochemical catalysis. Acknowledgment.-\Ye are obliged to Mr. Francis Scalzi and IZIr. R. \V.Body for some very timely assistance and discussions. (I,?) J. A. Berson, Z. Hamlet a n d XI'. A . Mueller, i b i d . , 84, 297 (196.'). (16) P Yates and P. E a t o n , i b i d . , 82, 4436 (1960) ( 1 7 ) G. I. F r a y and R. Robinson, ibid.. 83, 240 (1961). (18) See, for example, E. S. Gould, "Mechanism and Structure in Organic Chemistry," Henry Holt and Co., Xew 170rk. S .Y., 19.59, p. 646.
DEPARTMEKT OF CHEMISTRY Il.4ROLD KTVART USIVERSITYOF DELATVARE KETARK,DELAWARE C. M. HACKETT RECEIVED FEBRUARY 28, 1962
A CONVENIENT SYNTHESIS OF 3,s-CYCLOHEPTADIENONE
Sir: Cycloheptadienorles and alkoxy- and acyloxpcycloheptatrienes have proved to be valuable intermediates for the synthesis of tropone and tropolories.',? Here, we wish to report the synthesis of 3,3-cycloheptadienone (IV) by a method which is not only operationally simple but which also may be useful for the synthesis of other unconjugated cycloalkadienones. 3,3-Cycloheptadienone has been prepared previously by Rleinwald, et u I . , ~ by the base degradation of tropinone niethiodide. Reaction of I-ethoxycyclohexene (I), prepared from cyclohexanone uia the diethyl ketal,4 with dichlorocarbene5 gave 1-ethoxy-7.7-dichloronorcarane (11),b.p. 644i4.5' (1.0 mni.), in 87'; yield (found: C, 51.86; H , (i.99). Rearrangement of this material in hot quinoline resulted in the elimination of both atoms of chlorine and the formation of l-ethoxy-l,3,3-cycloheptatriene(111),e b.p. 5233' (4.0 mm.) in 3770 yield;, ; : : A: O.lS, (i.30, i.00, T.23, 7.42, 7.69, 7.89, 8.31, 8.39, S.93, T.3, 12.40, and 14L17p; 290 mp (3,S40),2 207 mp (1T,030),(calcd: C, i 9 . 3 i ; H, S.SS; found: C, 79.23; H, S.23). Hydrolysis of 111 with a very small quantity of hydrochloric acid in methanol-water produced 3,j-cycloheptadiecone (IT.'), b.p. 43.5-43' (4.G mm.), in 9lYc yield.
A$zoH
(1) E. E. van Tamelen and G . T. Hildahl, J . Ai!i C h e m SOL 7 8 , 4405 (193,) ( 2 ) 0 . L. Chapman and P. Fitton, zbid., 83, 100: ( 1 9 l i l ) (3) J. hleinwald, S. L. Emerman, S . C. Yang and G Bnchi, i b d 77, 4401 (1955). (4) A. Johannissian and E . Akunian, Bull. t < n h 'ita1 , I
