REDUCTION OF 2-ACYL-1,3-INDANDIONE
Sept. 20, 195s [CO\:TRIBUTION FROM
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DBPARTJIENT OF CHEMISTRY, LTTSIVERSITY OF DELAWARE 1
Wolff-Kishner Reduction of 2-Acyl-1,3-indandionesl BY ROBERT A. BRAUNAND WILLIAMA. MOSIIER RECEIVED APRIL 7, 1958 The Wolff-Kishner reduction of 2-acyl-l,3-indandiones has been found to give 1,4-dihydro-3-substituted-indeno[l,2-c] pyrazoles in good yields. Several of the reaction intermediates have been isolated and characterized and the course of the reaction is discussed.
I n a previous report from this Laboratory it was spectral properties of the products. Structure I11 shown that 2-acyl-l,3-indandiones form two types must be considered, as most pyrazoles exhibit of monohydrazones2 which might be expected to tautomerism. However, in particular cases the cyclize to pyrazoles. The present work was under- equilibrium is displaced to afford homogeneous taken to determine whether reduction, cyclization pyrazoles of a fixed imino type.7 Spectral evior both would occur under WoH-Kishner condi- dence suggests that the tautomer of I, 2,4-dihydrotions. Cyclization has been observed in other at- 3-substituted-indeno [1,2-c]pyrazole (111) is absent, tempted Wolff-Kishner reactions where the inter- but we do not have unequivocal proof of this. The mediate hydrazone undergoes some internal con- 1,4 - dihydro - 3 - substituted - indeno [1,2-c]pyrazole densation before it has an opportunity to expe- structure is used in the subsequent discussion withrience normal reduction, although there is no spe- out excluding the possibility of the tautomeric cific reference in the literature to an attempted 2,4-dihydro- structure. The structure of these Wolff-Kishner reduction of any 1,3-indandi0ne.~ materials was further confirmed by the formation of The Wolff-Kishner reduction, by the Huang- the benzenesulfonamide and benzamide of 1,4Minlon in~dification,~ was found to give 1,4-di- dihydro-3-benzylindeno [1,2-c]pyrazole. Only one hydro-3-substituted-indeno [1,2-c]pyrazoles (I) in product was obtained for each of these reactions, good yields. These apparently constitute a new indicating the presence of only one tautomer. [ 1,2-c]pyraclass of compounds, the only similar compound The 1,4-dihydro-3-substituted-indeno [1,2- zoles are white, crystalline solids. Their properknown being 1,4-dihydro-3-carbethoxy-indeno c] pyrazole, prepared in a completely different way.6 ties and analyses are summarized in Table I. The reaction seems to be general for 2-acyl-1,3Each 1,4-dihydro-3-substituted-indeno [1,2-c]pyindandiones. For the few aroyl-l13-indandiones razole was a strong band a t 3.1-3.5 p in its infrared studied no general pattern is observed. Repeated spectrum due to an N-H group involved in interattempts to reduce 2-benzoyl and P-p-rnethoxy- molecular hydrogen bonding of the type benzoyl-l13-indandione resulted in the corresponding 3-aryl-indeno [l12-c]-pyrazol-4( 1H)-one (11). =N. R The Wolff-Kishner reduction of 2-a-naphthoyl‘ -H-x/x=l l13-indnndione proceeded smoothly to the completely reduced lI4-dihydro-3-cr-naphthylindenoR >-I [1,2-c]pyrazole. There are a number of alternative structures that The benzenesulfonamide VI11 and the benzamide must be considered for the 1,4-dihydro-3-substi- have no bands in the 3.1-3.5 p region, showing the tuted-indeno [1,2-c]pyrazoles. Structure IV was absence of the N-H bond. Each new indeno [l,2-c]eliminated by consideration of chemical and pyrazole has a band in the 7.3.tO.1 p region. Elsner and Parker8 studied the infrared spectra of H a series of 1-alkyl and aryl-indanes and indenes, l and found that the indenes had a characteristic band a t 7.18 p which was absent in the indanes. Thus a band in the 7.3 p region indicates that the correct structure is I which contains an indene ring. Compounds 11, V, VI and VI1 have been prepared by the reaction of 2-acyl-1,3-indandiones with hydrazine under appropriate conditions. From the above information it is clear that the attempted WoLff-Kishner reaction proceeds by the following route: a, the formation of a hydrazone a t the extracyclic carbonyl group (except in the case ( 1 ) From the dissertation submitted by Robert A . Braun in partial of 2-diphenylacetyl-l,3-indandionein which the fulfillment of the requirements for the P h . D . degree, University of hydrazone is on the indan ring2); b, cyclization of Delaware. the monohydrazone to a keto-pyrazole 11; c, (2) R . A . Braun and W. A. Mosher, T H I S JOUKNAL, 80, 3013 hydrazone formation a t the remaining cyclic car(1958). ( 3 ) (a) C. Fisher, H. Beyer and K . Zaicker, A n n . , 486, 55 (1931); bonyl; d , decomposition of the hydrazone to give (b) E. D . Bergmann and R. Ikan, THISJOURNAL, 78, 2821 (1956). the 1,4-dihydro-3-substituted-indeno [1,2-c]pyra(4) R. Adams, “Organic Reactions,” Vol. I V , John Wiley and Sons, zole. Inc., New York, N. Y , 1951, p. 378, for a complete review on the
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Wolff-Kishner reaction up t o 1951. ( 5 ) Huang-Minlon, THIS JOURNAL, 68, 2487 (1946). ( 6 ) H. Leuchs and G. Kowalski, Ber., 58B, 2288 (1925).
(7) K. van Auwers, Ann., 508, 51 (1934). (8) I).B. Elsner and K . J . Parker, J . Chem. SOL, 593 (1957).
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