LOUISA. PINCKAND GUIDOE. HILBERT
2014 [CONTRIBUTIC)N FROM THE
Vol. 68
PLANT INDUSTRY, SOILS AND AGRICULTURAL ENGINEERING, AGRICULTURAL RESEARCH A D ~ I S T R A T I O N , S. DEPARTMENT OF AGRICULTURE]
BUREAUOF
u. The Michael Condensation of Fluorene with Unsaturated Compounds BY LOUISA.
~ ' I N C KAND
GUIDOE. HILBERT~
In this study we have found that the above reaction can be more easily obtained in such solvents as pyridine containing a small volume of aqueous sodium hydroxide and in an alcoholic solution of sodium ethylate. Evidence for the structure of tribiphenylene-propane is obtained in the carbon, hydrogen and molecular weight determinations. Since carbon and hydrogen determinations of a hydrocarbon are not crucial factors for establishing composition, other condensations were therefore obtained with organic compounds containing three elements. Condensations were therefore carried out with (1) dibiphenylene-ethylene and 2,7-dibromofluorene1 (2) 2,7,2',7' - tetrabromodibiphenylene - ethylene and fluorene, (3) 2,7,2',7'-tetrabromodibiphenylene-ethylene and 2,7-dibromofluorene and (4) benzalacetophenone and fluorene. It was also found that benzalfluorene, which is considerably less reactive than dibiphenylene-ethylene, readily reacts with fluorene. The most interesting reaction obtained in this study involves the condensation of 2,7,2',7'tetrabromodibiphenylene-ethylenewith fluorene. The anticipated reaction product, 2,7,2',7'-tetrabromotribiphenylene-propane, was not isolated in pure form. On the basis of the analytical data i t appeared that the tetrabromo derivative was contaminated with a less halogenated product. "hen this experiment was repeated, the reaction mixture was heated for a longer period, this time yielding a product containing even less halogen than that occurring in 2,7-dibromotri biphenylenepropane. However, some 2,7-dibromofluorene was isolated from the reaction mixture. This experiment was therefore repeated for the third time using such conditions so as to obtain a complete reaction. Here the products formed were tribiphenylene-propane and 2,7-dibromofluorene. The final experiment clarified the apparent comThis propane derivative was first obtained i n a plexity of the involved reaction mechanisms. reaction of dibiphenylene-ethylene with liquid This last observation definitely indicates that ammonia ai: a temperature of 65' for a period of 2,7,2',7'-tetrabromotribiphenylene-propane disthree weeks.3 Fluorene, one of the reactants, sociates into 2,7-dibromofluorene and the ethylene was formed in a reaction involving the dismuta- derivative which in turn is condensed with a tion of the unstable 1-aminodibiphenylene-ethane fluorene molecule. The complete reaction, therefore, involves three condensations and two dis(1) Present address: Bureau of Agricultural and Industrial Chemismutations as shown by the equations try, U. S. Department of Agriculture, Peoria, Illinois.
Heretofore the Michael condensation involved reactions in which both the acceptor and the addendum required the presence of such labilizing groups as --COOR, -COR, -CN, --CONHz, I n the present -NOz, --SO2R and -CH0.2 study, condensations are reported with certain compounds which do not have any of the labilizing groups cited above. The novel acceptors are dibiphenylene-ethylene, 2,7,2',7'-tetrabromodibiphenylene-ethylene and benzalfluorene. The common reactive grouping in these compounds is the fluorylidene nucleus. I n a previous publication dealing with the reaction of amines with dibiphenylene-ethylene3 i t was inferred that the electronic configuration of the double bond in dibiphenylene-ethylene is more like that of the ethylenic linkage with an adjacent carbonyl group than that of the normal type in ethylene. The addenda used in the present study are fluorene and 2,7-dibromofl~orene.~The lability of the hydrogen in the (9) position of fluorene derivatives has been emphasized in a previous publication!' and conclusive evidence will be presented in this investigation showing the ionization of the fluorene molecule. It has been found that fluorene condenses with dibiphenylene-ethylene in an alkaline medium to form tribiphenylene-propane as shown in the reaction.
i 7-i 7
(2) Connor and McClellan, J . Org. Chem., 8, 570 (1939). (3) Pinck and Hilbert, THISJOURNAL, 67, 2398 (1935). (4) While this work was in progress France, Maitland and Tucker (J. Chem. Soc., 1739 (1937)) reported a Michael condensation of fluorene with mesityl oxide and after our experimental work bad been completed Taylor and Connor ( J . Oug. Chem., 6, 696 (1941)) published a paper aihowing that fluorene and 2,7-dibromofluorene condense with benzalacetophenone, benzal-p-bromoacetophene and with benzalacetone. ( 5 ) Pinck and Hilbert, THISJOURNAL, 68, 377 (1946).
Br
L
Sr
Br ~
I - -
Br
MICHAELCONDENSATION OF FLUORENE WITH UNSATURATED COMPOUNDS
Oct., i94Ei
2015
I n conclusion i t should be noted that all the Michael condensations reported in this paper are made possible through the dissociation of the fluorene molecule into a fluoryl ion and a proton. Furthermore the dismutation of dibiphenylenephenylpropane into benzalfluorene and fluorene probably involves the intermediation of the fluoryl ion. A similar intermediation probably also occurs in the interaction of the tetrabromotribiphenylenepropane with fluorene. Acknowledgment.-We wish t o express our appreciation t o Mrs. M. S. Sherman for carrying out the recorded microanalyses. Experimental
Br
Br
I3 r
Br I
I
Br Br I
vv
Br
Br
'The final reaction is indicated by equation I. The dissociation of the fluoryl nucleus was also observed in the synthesis of dibiphenylenephenylpropane, the compound dissociating into its original components, namely, fluorene and benzalfluorene. It is possible that this effect may be due to the electronegativity of the phenyl group. The structural formula 1-biphenylene-2,4phenylhydrofuran Hz C-
CHCsHs
I ea4 1
C r H s ( 4 /C
