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COXMUNICXTIONS TO THE EDITOR
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than are either dialkyl or arylalkyl ketones, both in intermolecular and intramolecular competition experiments. This novel selectivity is in direct contrast with the results of Brown on the rates of sodium borohydride reduction in isopropyl alcohol, where the reactivity of pertinent ketones was I I1 acetone > acetophenone > benzophenone. Indeed, C ,H5 as far as we are aware, the reactivity sequence 0reported below is without precedent in previous studies of nucleophilic addition to carbonyl groups, where aryl substitution generally enhances ground state stability by resonance and further may retard I11 IV nucleophilic attack because of steric effect^.^^^ The structure of compound IV was initially asInitial competitive experiments were carried out signed on the basis of its unusual ultraviolet spec- by allowing equimolar amounts of benzophenone trum [X:m(:" 204 mp ( E G820), 278 ( E GO2), and a second ketone to react with excess I in €296 3671 and the excellent correspondence of pyridine for several hours. For example, after its infrared spectrum with t h a t previously published one hour the product mixture from benzophenone for 3,3-cycloheptadienone.3 The structural assign- and 2-octanone showed only a trace of the former ment was confirmed by the n.m.r. spectrum of the (weak infrared absorption a t 6.1 p), but an 83% c o i n p o ~ n dwhich ,~ showed a strong doublet at 168 recovery of the latter (by vapor phase chromatogand 173 cps. (weight 3.8) withvery weak absorption raphy). Similarly, when benzophenone and 1a t 134, 141, and 202 cps. (weight 0.G). The hy- tetralone were kept with I for three hours, then drogens on the double bonds formed a complex worked up, infrared showed essentially complete multiplet from 313 to 363 cps. (weight 3.G). Fur- consumption of the diaryl ketone and the tetralone ther evidence for the structure of IV was obtained was recovered in 95yo yield as the 2,4-dinitroby its conversion to cycloheptanone 2,A-dinitro- phenylhydrazone. A second series of experiments phenylhydrazone, m.p. and m.m.p. 143-143O, to was conducted on individual ketones, using aliquots 8,3-cycloheptadienyl p-nitrobenzoate, m.p. 81- of the same sample of I. The following ketones Sl.5' (reported Sl.3-82.j0),3 and to its Dielswere completely reduced (by infrared) after three hlder adduct with N-phenylmaleimide, m . p . of hours exposure to excess Is: benzophenone, 4,4'adduct 204--%03° (reported 199-202°)3 by the dichlorobenzophenone, 4chlorobenzophenone, 4,4methods previously d e ~ c r i b e d . ~ dimethylbenzophenone and fluorenone. On the -Application of this method to the synthesis of other hand, after twelve hours, these ketones were other cycloalkadienones and to the synthesis incompletely reduced, using the same ratio of of the isomeric tropolones is under study. reactants as above (yields of product alcohol, as Acknowledgment.-This work was supported by determined by v.p.c.): Zoctanone (G9yc),acetoa grant from the National Science Foundation phenone (337,), 4methoxyacetophenone (29%), (NSF-G1-1458). 3-methoxyacetophenone ( 70yc) and benzyl methyl ketone (58%). (7) T h e n.m.r. spectrum was run a t 56.4 megacyclesjsec. in carbon tetrachloride using tetramethylsilane a s an internal standard. W e It appeared especially desirable to demonstrate are indebted t o Urs. John E. Wertz a n d William Schwabacher for the above selectivity intramolecularly in suitable determining this spectrum for us. DEPARTMENT OF CHEMISTRY WILLIAME. P A R H A M diketones. For this purpose, we have prepared UNIVERSITY OF MIXSESOTA ROBERT \I7,SOEDER 4- ($-benzoyl) -phenyl-2-butanone (11),m.p. 36-37', NISSEAPOLIS 11,h l ~ s r . I
