-lug. 20, 1957
TKIPIIENYLSILYL PHENYL KETONE
was filtered. T h e solid obtained b y removal of t h e benzene was purified according t o the methods utilized in t h e literat u r e references (cf. Table 11). Nitrosation Procedure.-Diethyl malonate, 55.0 g. (0.32 mole), was added dropwise at -40" t o a suspension of 72.0 g. (0.45 mole) of complex in 300 ml. of nitroethane in a 500tnl. flask equipped with a dropping funnel, stirrer and reflux condenser. .After 4,5 minutes the blue-colored mixture was allowed t o warm t o room temperature whereupon a n exothermic reaction occurred which required cooling t o maintain t h e temperature below 35'. When t h e reaction subsided, the mixture was washed with 5V0 sodium carbonate solution and water, dried and distilled. There were obtained: ( a ) diethyl mesoyalate, 11 g. (28$,), b.p. 95-115"
[ C o sI'RIBUTION
FROM THE
4373
(;8 mui.), hydrate m.p. 56"; ( b ) diethyl oximinomalonate, 20 g. (3970), b.p. 170-180" (18 m m . ) . A 90% yield of diethyl mesoxalate was obtained b y Curt i s ~ using '~ gaseous NzO; on diethyl malonate in t h e absence of solvent while CerchezKreported a 50-90% yield of diethyl oximinomalonate using Nz03 and sodium ethoxide. Dimethylaniline, 1.2 g., dissolved in 30 ml. of nitroethane, was added t o a suspension of complex in nitroethane at 0-2'. T h e nitroethane was boiled off after washing with 5% sodium carbonate solution giving 1.5 g. of p-nitrosodimethylaniline, m . p . 84'. (13) R. S. C u r t i s , A m . Chem.
J.,35, 482 (190R)
LAFAYETTE, INDIAXA
DEPARTMENT OF CHEMISTRY, UNIVERSITY OF TOROXTO ]
Triphenylsilyl Phenyl Ketone BY A. G. BROOK RECEIVED APRIL 1, 1957 Triphenylsilyl phenyl ketone, the first reported a-silyl ketone, has been prepared. Although not susceptible t o thermal rearrangement, it is readily decomposed by base t o triphenylsilanol and benzaldehyde. It reacts abnormally with phenylmagnesium bromide and phenyllithium.
The abnormal behavior of substituents (espeThat the ketone is colored is of interest since cially halogen) attached to carbon alpha to a silicon organosilicon compounds are generally colorless, a atom has been referred to as the "a-silicon effect."lt2 fact generally attributed to the failure of silicon to I t is also apparent that functional groups located participate significantly in resonance hybridizaalpha to a silicon atom display unusual reactivity: ti or^.^ In the present case the color is even more the susceptibility of a-silanecarboxylic acids and unusual since the carbon analog, P-benzopinacolone, their esters both to thermal rearrangement and to is colorless. The infrared spectrum of the ketone base-catalyzed decomposition have been reported shows apparently normal absorption for the benzoyl recently from this Laboratory.2 It seemed of in- group a t about 1575 and 1610 cm.-l. The ketone does not rearrange thermally. terest to see whether this enhanced reactivity was present in other a-silylcarbonyl compounds, to When heated to 250", i t was recovered almost which end the ketone, triphenylsilyl phenyl ketone, quantitatively, and when heated to 365", although has been prepared. No a-silyl ketones have pre- some decomposition occurred, no carbon monoxide viously been reported in the literature, although in- was eliminated, and 70% of the material was redirect evidence for the formation of an a-silyl- covered unchanged. However, the compound is aldehyde has been reported. extremely labile in basic medium. If a dilute Triphenylsilyl phenyl ketone was best prepared ethanol solution is treated a t room temperature from triphenylbenzylsilane. Seither permangan- with a few drops of aqueous alkali, the yellow color ate oxidation nor chromic acid oxidation yielded disappears in a few minutes and triphenylsilanol the desired compound, probably because of its in- and benzaldehyde are formed. The same reaction stability, and only triphenylsilanol was isolated. occurs when the compound is chromatographed Treatment with two equivalents of h--bromsuc- on activated alumina, although it may be recovered cinimide led to triphenylsilyl-@,a-dibromobenzyl- by elution from acid-washed alumina. This desilane. This compound was converted readily composition is evidently analogous to the basewith silver acetate in an acetone-ethanol-water catalyzed decomposition of triphenylsilanecarboxymedium to the yellow ketone, m.p. 102-104", in lic acid and its esters. good yield. -1 phenylhydrazone derivative was OH N HOH prepared; attempts to prepare the oxime led to the PhaSiCOPh ---+ PhaSi-CO-Ph formation of triphenylsilanol and benzaldehyde. OH The ketone was also prepared, but in poor yield, Ph3SiOH + P h C H O + OHby treatment of benzoyl chloride with an ethereal suspension of triphenylsilylpotassium : attempts When triphenylsilyl phenyl ketone was treated to prepare it from triphenylsilane and benzoyl with phenylmagnesium bromide, the expected chloride using pyridine, aluminum chloride or boron product of addition to the carbonyl group, trifluoride as catalysts failed, and only tars or starting phenylsilyldiphenylcarbinol, was not isolated. Inmaterials were isolated. stead, the only product isolated was tetraphenyl(1) F. C. n'hitmore a n d L . H. Sommer, THISJ O U R N A L . 68, 481 silane (5%), other than some recovered ketone and (1948). triphenylsilanol, presumably formed by decom(2) A . C. Brook a n d H. Gilman, ibid , 77, 2822, 4827 (1955); position of the ketone when the reaction mixture A . C , Brook a n d R. J. Mauris, ibid., 79, 971 (1937). ___f
( 3 ) I,. H. Sommer, D. L. Bailey, G. M. Goldberg. C. E. Buck, T. S . Bye, F. J. E v a n s a n d F. C. Whitmore, ibid., 76, 1613 (1954).
(4) For a s u m m a t y of pertivent evidence a n d references see H. Gilm a n a n d G. E. Dunn. Cham. R e v s , 52, 77 (1953).
was hydrolyzed. The same product was isolated in 10% yield when phenyllithiuin was used. This product was probably formed by nucleophilic attack on silicon by the organometallic reagent analogously to the reaction described above, although, as will be showii in a forthconling publication, the addition product triphenylsilyldiphenylcarbinol is itself decomposed by phenyllithiuin forming tetraphenylsilane in high yield.
acetic acid for 5 minutes. During this time the yellow coliir of the original solution faded. On cooling white crystals were tlepositcd which oii recrystallization from 1 : 1 benzeneethanol yielded @.a5g. (56';,) of almost colorless crystals, ni .p. 1X - - I 31 ,,?' ,
Attempts t o prepare t h e oxime by treatment of tlie ketone with liydroxylarnine hydrochloride and pyridine iii ethanol--water caused rapid fading of the yellow c~ililr. T h e odor IJf benzaldehyde was noticeable a n d a sni,tll amount of triplieiiylsilario1, m.p. 150-151", was tlle ~ i n l y N product isolated. Ph3SiCOPh PliLi --f Ph-Si-COPh + Attempted Thermal Rearrangement of Triphenylsilyl Phenyl Ketone.--;i 0.5-g. sample of t h e ketoiie was heated in $11 - Li * Ph4Si fragments a small test-tube t o 250' and held a t this temperature for 5 minutes. KO carbon monoxide8 was evolved, hut a faint of benzaldehyde was detected. i\fter cooling tlic From this and related work it seems probable odor yellow solid melted at 100-102", and one recr?-stalliz3tioii that all a-silylcarbonyl compounds will be suscep- from absolute ethanol gavc 0.42 g . (8472) uf ketone whicli tible t o base-catalyzed hydrolysis in which the melted a t 102-103". LVlien a 0.1-g. sample a a s heated a t :1ciS" for 10 niinutcs, silicon-carbonyl bond is broken. no carbon monoxide was evolved, b u t a strong odor of berierved and the color of the liquid darkened. Experimentalj 11 melted a t 88-93', hut oiie recrJ-stallizaTriphenyl-a,a-dibromobenzylsi1ane.-To 4.55g. (0.0138 tion from ethanol yielded 0.07 g. (TO(,,;) of ketone, m.p. 101-102°, identified by mixed meltinx- point with 311 :tu. mole) of triphenylben~ylsilane~ in 50 nil. of carbon tetrathentic specimen. chloride was added 5.3 g. (0.030mole) of X-broniosucciniReaction of Triuhenvlsilvl Phenvl Ketone with Alkali,mide. T h e mixture was refluxed for 18 hr., cooled and 3.05 \Yhen 0.5 g. (0.60137mcAc) of -ieltlrd a total of 0.23 g . ( 8 5 % ) of crude h i T h e combined filtrates xci-e evaporated t o dryness under rezaldehytle phenylh>-drazone, which after recr)-stallization duced pressure a t room temperatiirc t a yield 1.89 g. of velfrom ethanol yielded 0.19 g . (70:;) of pale jdlon- needles, low powder, 1n.p. 90-99". This was twice recrystallized m.p. lc54-l,Xo,which were identified by mised melting point from absolute ethanol t o >-icltl 1.G7 g. (7Syo)of yellow nitli an authentic specimen, m.p. 1.3-157'. I n addition, needles, n1.p. 102-10.3O. 0.03 g. (8yc)of t.riphen!-lsilanol, 1n.p. 130-152', vas LoAnal. Calcd. for C2jHnrOSi: C, 82.4; H , 5.54; Si, latcd. Reaction of Triphenylsilyl Phenyl Ketone with Phenyl7.70. Found: C, 82.7; H, ,5.50; Si, 7.63. magnesium Bromide and Phenyl1ithium.-IVhen 2.0 g. Vthen silver nitrate Tvas used t o remove the bromine, the (0.00,i:i mole) of triphenylsilyl phenyl ketone in 45 nil. of same compound was obtained, b u t considerable decomposiether was treated with 2..5 nil. of 2.163 S phtnylmagnesiuin tion occurred as indicated by the forinatioti of triplieiiylbromide (0.005.5mole) no apparent change occurred until silanol and benzaldehyde (see below). 3. From Triphenylsilylpotassium and Benzoyl Chloride .7 after 1 hr. when :t white precipitate fiimietl. The mixture was stirred for 18 h r . but still gave a positive Color Test I.9 -To a solution of 2.81 g. (0.03 mole) of benzoyl chloride in 50 ml. of d r y ether at 0" was added over an hour a suspen- I t was then hydrolyzed with water and acid. The yellow .ellow oil which evens i m of 0.02 mole of amalgamated triphenylsil~-lpotas.iiurn tallization from benin 100 ml. of ether. T h e green suspension was stirred for 14 ilaue, m.p. 233-235", h r . and then was hydrolyzed with water. Insoluble hesaidentified by mired melting point. T h e residual oil was phenyldisilane, m.p. 353-35
