DIETMAR SEYFERTH, DEANE. WELCH,AND
1100
stirring for about 15 min., the olefin mixture was added in one portion. The solution remained blue after the addition of the olefin mixture and the undissolved lithium eventually caked into a silvery ball, from which blue streamers emerged as it was agitated around the flask. After 2 h r . the reaction mixture was poured slowly into ice-water and the resulting top layer was separated. The hydrocarbon layer was washed once with icewater and dried over potassium carbonate. This sample was used for the vapor phase chromatographic analysis. T h e following analysis was obtained using a UCon polar column. Cyclopentene reduction
Cyclohexene reduction
Cyclopentene 5,5.0$, CJ-clopentane 46 0%
Cyclohexene 87 2Vo C~-clohesane 12 8r-h
Other Pairs of Olefins .--Using the experimental procedure described above. the observations summarized in Table Y were made. Several competitive and individual reduction experiments were performed in ethylamine which yielded isomeric olefinic products along with the expected reduction products. The effect
JAMES
K. HEEREN
of adding alcohol t o the system was also studied. The esperiments were all performed according to the previous typical procedure and the results of these esperirnents are presented in Table V I . Typical Reduction Procedure in Liquid Ammonia ( 1-Hexene Reduction) .-In a 500-m1., three-necked flask equipped with an ammonia inlet, a Dry Ice condenser, and a dropping funnel were placed 250 ml. of liquid ammonia, and 1-hesene (15 g., 0.18 mole) n-as added. T o this solution was added a portion of the lithium (2.,5 g . , 0.36 mole), upon which a blue color immediately developed. .\ portion of methanol (total added, 23 g . , 0.72 mole) was added dropaise until the bluecoloration was discharged. This process was repeated until all the lithium and the methanol was added. The ammonia was allowed t o evaporate partially and the residual ammonia was decomposed by the addition of ice. The top layer was separated and dried over potassium Carbonate; weight 5 . 7 g. (41r: 1. This was analyzed b y vapor phase cliromatography. The following analysis was obtained using a tricresyl phosphate column: n-hexane, 17.0('2; 1-hesene, 83.0";. The results of other esperiments performed in the ammonia medium are recorded in Table V I I . S o isomeric products were detected in any of the runs performed in this medium.
TABLE VI
TABLE
Reduction.
53
Olefin or olefin paira
/iXorbornene 42.2 1-Hexene ( T C P ) 1 1 . 9 cis- and trans-2-hexene 33 8 ICyclohexene Sone ... \l-Hexene ( T C P or U ) 3 9 . 0 cis- and tiam-2-hexene 3 6 . 0 1-Hexene ( T C P or V) 35 0 cis- and trans-2-hexene 20.0 1-Hexene' 31 0 S o n e detected 12-Methyl-1-pentene 3 6 . 7 2-Methyl-2-pentene 16 7 (Cyclohexene ( T C P ) 2 4 . . 1-Hesene ( U ) 42 6 cis- and trans-2-hexene 1 1 . 9 3,3-Dimethyl-l-butene (S) 13 ) CycIopentenec 6.0 . . (Cyclohexene 5.8 a All runs were performed with ethylamine as the solvent and the proton source, except where noted. Lithium was used to effect about 50Yc reduction in the competition experiment, and the stoichiometric amount of metal was utilized in the noncompetition runs. 6 The olefin was added with an equimolar amount of t-butyl alcohol. The olefins were added with an equimolar amount of t-butyl alcohol to the lithium in ethylamine.
[CONTRIBUTIOT FROM
THE
1-11 Reduction, Vo
Olefin or olefin pair
Isomer and (7c isomerization
1'
Vol. 86
1-Hexene ( T C P ) 17.0 Meth?-lenec?-clohexene" ( U ) 80 0 Sorborneneh ( T C P ) 5 1-Hesene' (U) 49.0 13 1 ,3,3-Dimetliyl-1-butene ( S) f l-Hesened 22.0 '(Sorbornene (TCP) 2 a Treated successively with two stoichiometric amounts of lithium followed bl- ethanol addition after each portion t o discharge the color. Following the typical procedure for 1hexene except that 3 equivalents of metal were utilized with methanol as the proton source. Using equimolar quantities of olefins and lithium and ethanol as the proton source. Equimolar amounts of olefins and lithium utilized, with methanol as the proton source.
Acknowledgment.-The authors are indebted to the University of Vermont (NSFInstitutional Grant) and to the National Science Foundation (NSF G-19490) for financial support which made this research possible.
DEPARTMENT OF CHEMISTRY, MASSACHUSETTS INSTITUTE OF TECHSOLOGY, CAMBRIDGE 39, MASS.]
The Reaction of Triphenylphosphine Oxide with Alkyllithium and Grignard Reagents] BY DIETMAR S E Y F E R T HD,E~A ~ NE. ~ V E L C H.4ND , ~ ~JAMES K . H E E R E N ~ ~ RECEIVED CCTOBER 10, 1963 The reaction of RCH2Li in ether or of RCH2MgBr in refluxing tetrahydrofuran with triphenylphosphine oxide results in formation of benzene and (CeHb)*P(O)CH(K)M(M = Li and IvlgBr, respectively). Some characteristic reactions of such diphenylphosphinylalkyl organometallic reagents are described. The mechanism of formation of these reagents from triphenylphosphine oside is shown to involve a very rapid exchange step, ( CsH5)3P0 RCH2M ( CsHj)2P( O)CH2K C6HLM,followed bl- a slower ( b u t still rapid) metalation reaction, (C6H6)2P( 0)CHzR C6H5M+ C6H6 (CsHa)yP(O)CH(II)hI, Tvlien L I is lithium. Both exchange and metalation steps are slower when hl is MgBr.
+
-
+
++
Our recent work3 on the mechanism of the reaction of organolithium reagents with phosphonium salts, in which phosphorus bears a full positive charge, prompted further investigations of the action of organolithium reagents on tertiary phosphine oxides, in which phosphorus bears a partial positive charge. Of particular interest to us were those reactions which conceivably might proceed uia transient pentasubstituted phosphorus intermediates. We report here (1) ( a ) Presented in part a t the Symposium, "Current Trends in Organnmetallic Chemistry," Cincinnati, Ohio, June 12-15, 196:3, ( h ) Iirelirninary communication: 11. Seyferth, I1 R Welch, and J K Heeren, J A m ('hrnz S O L ,86, 642 (1963). ( 2 ) ( a ) Alfred P Sloan Research Fellow, ( b j Sational Institutesuf Health Predoctoral Fellow, 1962-1968; (c) Fellow of t h e M I T School lor h d vanced S t u d y , 1961-1962 (3) D. Seyferth, J K Heeren. and W B Hughes, J A m Chein. S o c , 8 4 . 1764 (1962).
on the reaction of alkyllithium and Grignard reagents with triphenylphosphine oxide (TPPO) . X clue that these particular reactions might be of interest was provided by a synthesis used by m'ittig and Rieber4for tetraphenylphosphonium iodide HX
+ C6HjLi ---+ --+
(C6Hj)3P0
[(CBHL),P]S
It seemed possible that here a P(V) intermediate, (C6H5)4PO-L i f , might be involved. In order to obtain further information concerning this reaction, we treated T P P O with alkyllithium reagents. Addition of 1 molar equivalent of methyllithium to a slurry of T P P O in diethyl ether a t room temperature resulted in formation of a reddish brown, homoge( 4 ) G Wittig and R Rieber, A n n , 663, 187 (1949)
March 20, 1964
TRIPHENYLPHOSPHINE OXIDEWITH ALKYLLITHIUMS
neous solution containing a new organolithium reagent, diphenylphosphinylmethyllithium ( I ) ,and benzene.
+
( C 6 H L ) x P 0 CH,Li
+( C6H5)2P(O ) C H & I
+ C6H6
1101
lated alkylphosphine oxides in olefin synthesis as reported by Horner and co-workers.6 Of primary interest to us in this study was the mechanism of the alkylmetallic-TPPO reactions. Two possibilities were considered : (1) Intramolecular loss of benzene from a P(V) intermediate
A Gilman Color Test I5 on the solution was positive. The yield of benzene always was nearly quantitative. Quenching the reaction mixture with aqueous HBr gave methyldiphenylphosphine oxide in 8476 yield, (CgHj)aPO + RCHzM +( C G H B ) ~ P carbonation resulted in (CcH5)aP(0)CH2COOH(47y0), \ and addition of triphenyltin chloride to the reagent CH2R ? P CH2Sn(CsH5)3 (76%). solution gave ( C ~ H E , )(0) The reaction of ethyllithium and of n-butyllithium with T P P O produced (C6H5)2P(0)CHLiCH3and ( c ~ H5)aP(0)CHLiCaHi,respectively. Reactions of these reagents as well as other reactions of I itself are de( C6H5 c),P(O)CHR scribed in the Experimental section. Such cr-lithioalkyldiphenylphosphine oxides were not new, having been prepared previously by Horner, et u I . , ~ b y metaM lating certain alkyldiphenylphosphine oxides. -1fter a preliminary communication1b describing the initial ( 2 ) An exchange-metalation sequence results of the present study had been submitted for (C6Hj)aPO + RCHiM d ( C6Hj)2P(O)CHnR + G H j M (.I) publication, a much more extensive report appeared (Ce,Hj)?P(O)CHnR + K'M + concerning the preparation of such reagents b y the (CsHj)2P(O)CH(R)M R'H ( B ) treatment of tertiary phosphine oxides containing a t M = Li or M g X , K' = C6Hj or RCHn least one primary alkyl group with organolithium reagents.' These studies demonstrated t h a t such Mechanism 2 involves phenyllithium or phenylreagents undergo reactions typical for organolithium magnesium bromide as an intermediate; mechanism 1 compounds. does not. Therefore experiments were performed to -1 similar reaction was found to occur between inquire into the question of the intermediacy of phenylaliphatic Grignard reagents and T P P O , provided it metallics in these reactions. was carried out in refluxing tetrahydrofuran (THF) The clearer picture was obtained in a study of the solution. methylmagnesium bromide-TPPO reaction. The observed results are in agreement with the exchange(C&)&'O + RCHiMgBr + metalation mechanism. They demonstrate t h a t a t (C6Hj)2P(O)CH(R)MgBr CsH6 room temperature in T H F methylmagnesium broU-ith methyl-, ethyl-, and n-propylmagnesium bromide and T P P O react slowly to give a solution conmides the diphenylphosphinylalkyl Grignard reagent taining methyldiphenylphosphine oxide and phenyland benzene yields were ca. goyo. However, the action magnesium bromide. Table I illustrates this. Thus of benzylmagnesium chloride and isopropylmagnesium after S hr. the benzene produced in i9yc yield after bromide on T P P O gave only low benzene yields. The treatment of the reaction mixture with D 2 0 contained diphenylphosphinylalkyl Grignard reagents derived SSTc monodeuteriobenzene, i.e., SSyOof the benzene from methyl-, ethyl-, and n-propylmagnesium bromide obtained was derived from the reaction of C&&fgBr were characterized by reaction with triphenyltin chlowith D20. A t room temperature the metalation reride to form (C6H5)2P(0) C H (R)Sn(C6H5)a derivatives. action B is extremely slow: only 12y0of the benzene These reactions of aliphatic organolithium and obtained had been produced in the metalation step. Grignard reagents with T P P O represent a very conHowever, the results were quite different when this venient route to organofunctional phosphine oxides. reaction was carried out in refluxing T H F (Table I ) . Such a synthesis based on T P P O is more economical and practical than t h a t based on alkyldiphenylphosTABLE I phine since T P P O is a product of the IVittig THF D20 reaction which usually is discarded when the m'ittig .I S T C D Y O F T H E REACTION (C6Hj)sPO + CH:JVgBr --f 4 reaction is performed on a laboratory scale. I t may be Benzene" CsHsl) in T e m p . , 'C. T i m e , hr. yield, To benzene. % mentioned t h a t most of this work was carried out using T P P O recovered from IVittig reaction residues. I t is 25 0.5 14 S o t detd interesting to note t h a t this recovered T P P O , aia 1 24 S o t detd 25 the reactions reported here, can serve again in the 25 3 56 96 synthesis of olefins, for instance, of 1,l-diphenylethyl25 5 65 S o t detd ene 25 8 79 88
/o-M+
+
+
87 53 00 6 86 22 S o t detd 85 a CeH6 from inetalation reaction B C & n from hydrolysis of C6HjMgBr formed in exchange reaction .I. Reflux Reflux Reflux
2
+
This reaction sequence is based on the use of cr-meta( 5 ) H Gilinan and F Schulze. J A m . C h e m S o ( , 47, 2002 (1925). ( 6 ) L Horner. H Hoffmann, H . G N'ippel. and G Klahre. Chein BP7 . . 92, 21!19 IlY.59) (7) 1 J . Richard a n d C V Banks. J . Orb. Chriii , 28, 123 (1963).
The benzene yield after treatment of the reaction mixture with DaO was nearly 90% after only 2 hr.. and the deuteriobenzene content of the benzene dropped to zero within 6 hr., i e . , the benzene produced in the 6-hr. reaction period resulted from the metalation reaction B which had consumed all of the C6H5\!fgBr formed in reaction A.
1102
DIETMARSEYFERTH. DEANE. WELCH,AND
Confirmation of these results was obtained by studying the metalation of methyldiphenylphosphine oxide b y phenylmagnesium bromide separately. One equivalent of phenylmagnesium bromide was added to a solution of 1 equivalent of methyldiphenylphosphine oxide in T H F . Samples were removed a t successive time intervals and quenched in DzO. Analysis of the benzene showed t h a t after 8 hr. a t room temperature the benzene contained 90% monodeuteriobenzene (10% metalation), and after 4 hr. a t reflux the benzene con tained no monodeuteriobenzene ( 1007c metalation), The intermediacy of phenylmagnesium bromide in the KhlgBr-TPPO reaction also was proved by a positive Gilman Color Test 1118 and carbonation to give benzoic acid. Separate experiments demonstrated that (CsH5)2P(0)CH2MgBrdid not give a positive Gilman Color Test 111. The results obtained in a study of the methyllithiumT P P O and ethyllithium-TPPO reactions were not as clear-cut, since the exchange reaction X and the metalation reaction B could not be separated. However, the evidence compels one to the conclusion t h a t mechanism 2 is operative in these reactions as well. Experiments in which T P P O was allowed to react with ethereal methyllithium and the resulting mixture was quenched after ca. 1 min. with DzO showed t h a t phenyllithium was indeed present in solution. When the ratio of CH3Li to T P P O was 1 : 1 , the benzene formed (97%) in the reaction (C6H6 from reaction B monodeuteriobenzene from the reaction of unconsumed phenyllithium present with DzO) contained 2% monodeuteriobenzene. U-hen the CH3Li,'TPPO ratio was increased to 2 and 3, respectively, the monodeuteriobenzene content of the benzene formed (ca. 90-95%) rose to 9 and 13c:',, respectively. Similar results were obtained in a study of tile ethyllithium-TPPO reaction. When these reagents were used in 1 : 1 molar ratio, quenching of the reaction mi'xture with D20 gave benzene in 07% yield, which contained 14% deuteriobenzene. The same experiment with the C2H5Li' T P P O ratio increased to 2 and 3 gave benzene in ca. !IS?; yield, which now contained 25 and 50yGmonodeuteriobenzene, respectively. In a similar 3: 1 experiment the phenyllithium remaining in solution owing to unsuccessful competition with ethyllithium in reaction B was characterized by its reaction with trimethylchlorosilane to give trimethylphenylsilane in 4'77; yield. The possibility of the metalation reaction B was verified experimentally before the paper b y Richard anti Hanks' appeared. However. generation of alithioalkyldiphenylphosphine oxide reagents from alkyldiphenylphosphine oxide and alkyl- or aryllithium reagents gave yellow to reddish yellow solutions. In contrast, the TPPO-RLi reaction mixtures always gave light-to-deep red solutions. This puzzling color phenomeiion is not understood, but possibly could be due to a minor side reaction in the latter system. The high yields of the (C,&),P(O)CH(R)Li reagents obtained i n those reactions in which RCH2Li;'TPP0 = 1 suggested that here one was dealing with a very rapid exchange step followed by a slower (but still rapid) metalation step. Support for this idea was obtained in the following manner. If this were true, i.?.. if the original lithium reagent is completely consurned before the extent of metalation of the alkyldiphenylphosphine oxide formed in reaction A is significant, then, for example, the reaction of 2 molar equivalents of methyllithium with 1 equivalent of T P P O slioultl lead very rapidly to a solution containing 1 molar equivalent each of CH3Li, CsHjLi, and (c6-
+
f X ) H (;ilman and €1. 1. I'ahlunky. J
A m C h r i n Soc , 63, 839 (1941).
JAMES
K. HEEREN
Vol. 86
Hb)zP(O)CH3. Subsequent to this the two lithium reagents present should compete in the metalation of methyldiphenylphosphine oxide. Thus the final reaction mixture, in terms of unconsumed CHjLi and C,&Li due to this competition, should be the same as t h a t obtained in a separate experiment involving the addition of 1 molar equivalent each of methyllithium and phenyllithium to 1 molar equivalent of methyldiphenylphosphine oxide. These reactions were carried out, and in each case the reaction mixture was quenched with D 2 0 after 1 min. The benzene formed in nearly quantitative yield contained 976 deuteriobenzene in the former case, 10% deuteriobenzene in the latter reaction. The results of similar experiments with methyland ethvllithium are listed in Table 11. rlll support
70 C6HKD in benzene
9 10 10
12 13 11.4
25 25 : j 0+I 49 ".
46 In a separate experiment it was found t h a t the action of ethyllithium alone on ethyldiphenylphosphine oxide gave a low ( 71,) yield of benzene presumably through attack of ethj-llithium on phosphorus. I n order to assess the seriousness of such a side reaction leading to benzene in the competition experiments mentioned above, a solution containing 1 molar equivalent each of ethyllithium and p-tolyllithium was allowed t o react with 1 equivalent of ethyldiphenj-lphosphine oxide. S o benzene was formed. Thus the benzene-producing side reaction is not important in the competition experiments.
I n order for an interpretation of the DrO quenching experiments described above to be meaningful, it was necessary to demonstrate t h a t the metalation reaction B was essentially complete under the conditions of the quenching experiments. This was found to be the case. Thus, treatment of ( C & , ) 2 P ( 0 ) C H 3separately with either methyl- or phenyllithium using the same reaction conditions and reaction times used in the D 2 0 experiments, followed b y quenching with a triphenylC H 8 n ( C6H6)3 tin chloride solution, gave ( C6H5) (0) in cu. SOT0 yield. Using an equimolar mixture of methyl- and phenyllithium, a similar yield (8tjyc)of this tin derivative was obtained, along with methyltriphenyltin ( S 6 7 c ) , benzene (SS%), and a small amount of tetraphenyltin. Similar results were obtained in the experiments with ethyllithium. The question as to whether the exchange reactions occurring between T P P O and KCH2h4gBr and KCH2Lj proceed oia a P(V) intermediate or by direct s N 2 displacement a t phosphorus remains unanswered a t the present time. The TPPO-C6H5Li reaction cited earlier, which leads to a product in which all three phenyl groups of T P P O as well as the phenyl group derived froin the lithium reagent are present, suggests that the former alternative is possible in the systems studied by us: I t is suggested by the experiments described in Table I1 t h a t phenyllithium metalates ethyldiphenylphosphine oxide a t a faster rate than does ethyllithium,
TRIPHENYLPHOSPHINE OXIDEWITH ALKYLLITHIUMS
March 20, 1964
1103
treatments in chloroform with Norit removed most of the color. The filtered solution was treated with 30 ml. of heptane and heated to boiling. When the mixture became cloudy it was left t o stand for 2 days. A white solid precipitated. Three recrystallizations from benzene-heptane and chloroform-heptane gave 3.0 g. (6.5%) of white powdery solid, m.p. 149-152". Its infrared spectrum ( K B r pellet) showed major absorption a t 3050, 1420, 1120, 1100, 1030, 1000, 850, 740, and 700cm.-'. Anal. Calcd. for Ca1Hs7SiPO: C, 78.45; H , 5.74; Si, 5.93. Found: C, 78.34; H , 5.61; Si, 6.03. (CsHs)zP(0,)CH2COOH.-The reagent solution (50 mmoles) was poured quickly onto excess Dry Ice. hfter the mixture had warmed to room temperature, 100 ml. of Rater was added, and the aqueous layer was acidified with concentrated hydrochloric acid. The organic layer was found to contain 42.8 mmoles (85.5YG)of benzene. The aqueous phase was extracted with chloroform, and the chloroform extracts were dried over anhydrous magnesium sulfate. The chloroform solution was conExperimental centrated t o ca. 25 ml. under vacuum. Addition of cyclohexane precipitated a yellow solid, 6.7 g. (51.5%), m . p . 136-143'. General.--dl1 benzene yields were calculated using quantitative Recrystallization from chloroform gave 6.05 g. (46.55T 1, m.p. gas chromatography with toluene as an internal standard. The 142-143", reported15 m.p. 142-144" for carboxymethyldiphenylcolumns used were Dow Corning 710 silicone fluid or General phosphine oxide. Its infrared spectrum ( K B r pellet) showed Electric SE-30 silicone grease on Chromosorb W , with helium as major absorption a t 1710, 1438, 1420, 1280, 1220, 1175, 1145, the carrier gas. Sormal operating conditions were: 80-100' 1130, 1092, 1000, 905, 840, 815, 755, and 695 a n - ' . jacket temperature, 10 p.s.i. He, 70' preheater temperature. Diethyl ether and tetrahydrofuran were purified by distillation Anal. Calcd. for CI4Hl3PO3:C, 64.61; H , 5.03; neut. equiv., from lithium aluminum hydride and stored over sodium wire. 260.22 Found: C, 61.44; H , 4.97; neut. equiv., 260.60. All experiments involving organolithium or Grignard reagents (CsHj)2P(0)CH3.-The reagent solution (50 mmoles) was were carried out in a n atmosphere of prepurified nitrogen. quenched with 25 ml. of 48% aqueous HBr. The organic layer Melting points are uncorrected. Ainalyseswere performed by was found to contain 43.7 mmoles (87.5%) of benzene. The D r . S. M . S a g y , M . I . T . Microchemical Laboratory, and by the aqueous layer was saturated with potassium bromide and exSchwarzkopf Microanalytical Laboratory. tracted with 100 ml. of chloroform. The chloroform extracts Preparation of Starting Materials.-Methyl- and ethyllithium were dried over anhydrous magnesium sulfate and the chloroform were prepared from the corresponding bromide and lithium wire removed under vacuum. The yellow, oily residue crystallized in diethyl ether. n-Butyllithium was prepared from n-butyl on standing. The solid was washed with warm cyclohexane and chloride. Ethyl- and n-butyllithium were prepared a t C Q . 0" dried; 9.0 g. (83.3c7,), m . p . 104-111". Recrystallization from and used immediately thereafter. .Ill solutions were standardbenzene-heptane gave 8.2 g. (76tz) of methyldiphenylphosized b>-the double titration method of Gilman" using 1,2-dibrophine oxide, m.p. 109-111". -1mixture melting point with aumoethane in place of benzyl chloride. thentic methyldiphenylphosphine oxide showed no depression. Triphenylphosphine oxide was obtained from 1Vittig reaction ( C6Hs)nP(0)CHzC(OH)!C~Hj)z.~The reagent solution (50 residues or was prepared by the method of Michaelis and Gleichmmoles) was treated dropwise over ca. 20 miti. with 9.11 g . (50 niann.12 Before use, T P P O (1n.p. 155-157') was dried over mmoles) of benzophenone in 25 1111. of ether. The red color P205 a t 110' (0.5 m m . ) . faded almost immediately and a heavy white solid precipitated. The Reaction of T P P O with Alkyllithium Reagents.-The The mixture then was heated to reflux for 2 hr., cooled, and hydropreparation of ( C6H5)aP(0)CHzSn(CP,HC)I is given as an example lyzed with 357 HCI. The heavy, white precipitate was removed of the general procedure used. by filtration and dried over P?Oj t o give 16.0 g. (81%)of white, Treatment of a suspension of 13.9 g. (50 mmoles) of T P P O in crystalline solid, m.p. 184-186'. Two recrystallizations from 100 nil. of ether with 50 mmoles of methyllithium, followed by benzene gave 14.7 g. (74%) of white crystals, m . p . 192-193', stirring for 2 hr., gave a deep red homogeneous solution.'3 This lit.8 m.p. 192-193", whose infrared spectrum (chloroform solumixture then was treated with 19.25 g. (50 mmoles) of triphenyltion) showed principal absorption a t 3325, 3020, 2995, 1490, tin chloride in 50 ml. of ether and 25 ml. of T H F . A precipitate 1445, 1430, 1160, 1118, 980, and 69Ocm.-'. started to form rapidly after C Q . 10 inin. and stirring was con(C6HC)2P(0)CH2P(S)(C6HC)2.16-The reagent solution (40 tinued for 3 lir. The mixture was filtered and ammonia was mmoles) was treated with 40 mmoles of (CsH6)zPCl (Victor bubbled through the filtrate for 3 hr. ( t o remove unreacted triChemical Works) in 25 ml. of ether. The mixture was heated a t phenyltiti chloride). Another filtration and removal of solvents reflux for 12 hr., then was evaporated a t reduced pressure. The from the filtrate under vacuum gave an oil which could be crysresidue was treated with 0.045 g.-atom of sulfur in hot benzene. tallized froin benzene-heptane to give a white solid; 20.5 g. Evaporation of the benzene left a yellow oil, which was dissolved (76(,:), m . p . 135-141 ". Two additional recrystallizations from in chloroform. T h e chloroform solution was extracted with benzene-heptane gave 17.0 g. (6052) of white solid, m.p. 141water, dried, and evaporated. A pale yellox oil (8.28 g . ) re142', whose infrared spectrum ( K B r pellet) showed principal mained, which began t o crystallize in long needles. The oil and absorption bands at 3020, 1485, 1440, 1430, 1173, 1120, 1075, the needles were crystallized from isopropyl alcohol to give 5.31 g. 1025, 1000, 780, 763, 725, and TOO cm.-'; n.m.r.I4:doublet (2H, (257;) of product, m . p . 213-214' (lit." m.p. 209"). The infrared J = 11.0 c.P.s., I'-CH2-) centered a t 2.38 p.p.m., flanked b y t w o spectrum (CHCla) exhibited maxima a t 3055, 2990, 1590, satellite doublets due to splitting by the tin nucleus (Sn"7 and 1480, 1440, 1360, 1310, 1195, 1155, 1125, 1110, 1000, and 690 Snli9) with J = 58 c.P.s.; complex phenyl absorption a t 7.55 cm.-'. p.p.rn. (10H, C & - P ) ; complex phenyl absorption a t 7.15 Anal. Calcd. for CzjHz20SP2:C, 69.44; H , 5.13. Found: p.p.in. ( l 5 H , CsH5-Sn). C, 69.09; H , 5.33. Anal. Calcd. for C31H27POSn: C, 65.87; H, 4.82; P , 5.48. Found: C, 65.52; H , 1.68; P , 5.68. ( 2 ) Vza T P P O C2HjLi: (C!H5)2P(0)CH(CH1)Sn(CGH5)3: by reaction with triphenyltin chloride, in 81Yc crude yield, m . p . The following other preparative scale reactions were carried out 170-175", pure m.p. 176-177" (from benzene-heptane). T h e to give the products described below. (1) Via T P P O CHILi: ( CsHj)rP(0)CH2Si(C~Hj)S.-The infrared spectrum ( K B r pellet) showed major absorption a t 3040, 1485, 1430, 1190, 1120, 1075, 7 3 5 , and TO0 cm.-'. reagent solution (10 mmoles in 33 ml. of ether) was treated with 10 mmoles of triphenylchlorosilane (Dow Corning Corp.) in 25 A n a l . Calcd. for Cz2HaSPOSn:C, 66.35; H , c5.05; P , 5.34; 1111. of T H F . The color of the reaction mixture faded rapidly to a Sn, 20.60. Found: C, 66.20; H , 4.89; P , 5.27; Sn, 20.88. pale yellow and stirring was continued for 2 days. The solvent (CfiHC)2P(0)CH(CH,)COOH:by reaction with Dry Ice, in was removed under vacuum t o give a yellow, oily residue. Three 49.5y0 crude yield, m.p. 135-139", m.p. 138-140" (from chloroform-hexane). The infrared spectrum ( K B r pellet) showed prin(9) €I Gilman, F W . Moore, and 0. Baine. J . A m C h e m . Soc 63, 2479 cipal absorption a t 1746, 1440, 1295, 1230, 1160, 1117, 845, 720, (1941) and 695 cm.-'; n.m.r.: quartet [3H, J = 17 C.P.S.(1'-C-CHI), (10, G . E . Cuates, "Organometallic Compounds," 2nd E d . , Methuen & J = 8c.p.s. (CH-CH,), a t 1.34 p.p.m.1; quartet with some furC o . , I.td , Imndon, 1960, p. 2 0 . ther splitting ( l H , J = 8 c.P.s., centered a t 3.63 p . p . m . ) ; com(11) li G Jones a n d H . Gilman, "Organic Reactions." Vol. V I , John
a surprising result in view of previous reportsg t h a t the reactivity of organolithium reagents in metalation reactions decreases in the order CzHsLi > C6H6Li > CH3Li. I t may be t h a t in the case of rapid metalations, as in the present experiments, factors other than the basicity of "monomeric" RLi species (dissociated or undissociated) are important. Since the accepted order of reactivity of organolithium reagents was established using relatively unreactive substrates requiring half-life reaction times of several hours, perhaps in rapid metalations in ether the degree of association of the metalating agentlo as well as the reactivity of the substrate become important. Preliminary experiments in these laboratories support this.
+
+
Wile? a n d Sons. I n c , S e w Yurk, N Y . , 1951, pp 338-366 ( 1 2 ) A Michaelis and 1, Gleichmann, BP?, 1 5 , 801 (1882). (13) In a separate experiment this deep red solution was found t o contain 96 5 % of the theoretical benzene yield. ( 1 4 ) Chemical shifts are downfield from tetramethylsilane, determined a t 60 hlc with a Varian Model .4-60 n.m r spectrophotometer
(15) K Issleib and G. Thomas, Chem Bey.. 94, 22-14 (1961)
+
Prepared b y
HCI
[(C6Ha)?P(CH:CO:Ci.Hs)*1Br S a O H --f --f (16) Experiment b y Miss Patricia Selby, B.S. Thesis, hl I T , June. 1463 (17) K Issleib and L Baldauf, Phaum. Zmlraihalle, 99, 329 (1960)
1104
DIETMAR SEYFERTH, DEANE. WELCH,AND
JAMES
K. HEEREN
Vol. 86
plex phenyl absorption a t 7.30-7.90 p.p.m. (lOH, C&-P); singThe mixture was stirred rapidly for 5 min. and then quickly let [ l H a t 11.12 p.p.m. (-COOH)]. quenched with 8.15 g. (75 mmoles) of freshly distilled trimethylchlorosilane (Dow Corning Corp.) in 20 ml. of ether. The color Anal. Calcd. for C I S H I ~ P OC~, :65.69; H , 5.51; neut. equiv., of the reaction mixture faded rapidly to a pale yellow, and a white 274.3. Found: C , 65.61; H , 5.66; neut. equiv.,273.6. solid separated. Bnalysis of the reaction mixture by gas chro(C&)zP(O)C&: by reaction with 487, hydrobromic acid, in matography showed t h a t it contained 15.3 mmoles (815;) of 77.5'34 crude yield, m.p. 117-122°, m.p. 121-122' from benzeneof trimethylphenylsilane (colbenzene and 8.70 mmoles (35TC)l8 heptane. A mixture melting point with authentic material was lected by preparative scale gas chromatography j, Z Z ~ D 1.4878, not depressed. reported15 n z 5 1.4883 ~ for trimethylphenylsilane. The infrared (C&)2P( O)CH(CH3)(O H ) (C,Hj)2 : by reaction with benzospectrum was identical with t h a t of an authentic sample of triphenone, in 84% yield, m.p. 260-262" (from benzene). T h e inmethylphenylsilane.20 The yield of ( CHs)3SiC6Hj was measured frared spectrum (CHC13) showed principal absorption a t 3300, by injecting a 50-ml. sample on a v.p.c. column (30qC Dow 3005, 2990, 1480, 1440, 1430, 1160, 1110, 1020, and 680 cm.-'. Corning 710 silicone fluid on Chromosorb W, jacket a t 19O0, Anal. Calcd. for C2,Hz5P02: C , 78.62; H , 6.11; P , 7.51. 10 p.s.i. helium pressure, preheater a t 240°), measuring the area Found: C , 78.85; H , 6.06; P , 7.48. of the (CH3)3SiC6Hjpeak, adding a known amount of authentic ( 3 ) Vza T P P O n-C4H5Li: (C6Hj)2P(0)CH[Sn(C6H5)3]CH*~ (CH3)3SiCsHj to the mixture, and then measuring the increase in CH2CH3 : by reaction with triphenyltin chloride, m.p. 148-151 the area of the ( C H S ) ~ S ~ peak C ~ Husing ~ a 50-pI. sample. (from ether), in 69Tc yield. The infrared spectrum (CHC13) Determination of Conversions for D20 Quenching Experishowed principal absorption a t 3020,2950, 1480, 1430, 1420, 1175, ments.-These experiments were performed in order to determine 1118, 1100, 1078, 1000, and 690 cm.-'. whether the reaction time and conditions used in the D 2 0 quenching experiments were sufficient to allow the metalation reaction B Anal. Calcd. for C3rHsaPOSn: C, 67.24; H , 5.48; P, 5.10. to go essentially to completion. This was found to be the case in Found: C , 66.91; H , 5.50; P, 4.96. all room temperature experiments. One example is described. D*O Quenching Experiments.-The experiments listed in A suspension of 2.78 g. (10 mmoles) of TPPO in 35 ml. of ether Tables I11 and I V were carried out by rapidly (over ca. 15 sec.) was treated very rapidly with 13.08 ml. of 1.53 V : (20 mmoles) adding the lithium reagent (or mixture of lithium reagents) to a methyllithium in ether. The resulting red solution was stirred suspension of the phosphine oxide in ether. The reaction mixture for 1 min. and quenched with 7.72 g. (20 mmoles) of triphenyltin immediately became homogeneous and turned reddish brown. chloride in 20 ml. of T H F . The color of the reaction mixture The mixture then was stirred vigorously for the designated time, faded rapidly and stirring was continued for 6 hr. Then the mixcooled quickly, and the resulting reddish brown homogeneous ture was treated with 10 ml. of K F solution. The organic phase solution was quenched with fresh D 2 0 . T h e benzene produced was found t o contain 9.1 mmoles (910c) of benzene. T h e mixin these reactions was collected by preparative scale gas chromature was filtered. Drying the residue gave 0.4 g. (0.93 mmole) tography and analyzed by mass spectrometry, using a C E C , of white solid, m . p . 223-227'. -1 mixture melting point with Model 21-130, mass spectrometer. Typical operating conditions authentic tetraphenyltin was not depressed. The filtrate was were 20 p and voltage setting = 250. saturated with KBr and the organic phase decanted. The residue was extracted with chloroform and the extracts were combined and dried over magnesium sulfate. T h e solvent was TABLE I11 removed under vacuum to give a yellow, oily residue. ExtracD2O QUENCHING EXPERIMENTS, TRIPHENYLPHOSPHINE OXIDE tion of the oil with pentane and concentration of the pentane gave an oily residue which crystallized from cold ether; 3.04 g. Time (8.35 mmoles), m.p. 5i-69°.21 A mixture melting point with (min.) authentic methyltriphenyltinZ2was not depressed and their inbeBenfrared spectra were identical. The portion of the oil which was Phosphine oxide RI,i EtiO, T , fore zene, % CaHsD not soluble in pentane was treated with ether. On standing, (mmoles) ml. OC. quench yo in benzene (mmoles) crystals formed; 4.5 g. (SOYc), m.p. 138-141". X mixture melt50 25 1 97 2 (C8Hs)sPO (25) CHI-(25) ing point with authentic (C6H5)2P(0)CH2Sn(C6Hj)3 showed no 25 25 1 90 9 ( C ~ , H S ) ~ P(10) O CHs- (20) depression. X similar experiment, substituting ethyllithium for methyl1 95 12 (CsHa)sPO (25) CHI- (75) 50 25 lithium, gave: benzene (71 %); ethyltriphenyltin23 (2.6 g., 6.87 97 13 mmoles, m.p. 53-55'; a mixture melting point with authentic (CsH5)aPO (25) C2H5- (25) 50 25 1 97 14 C2HjSn(C6H5)317 was not depressed and their infrared spectra 91 13 were superimposable); tetraphenyltin (1.92 mmoles, m . p . 222226", identified by mixture melting point with authentic (CsHa)rI 100 25 (CsHj)3PO (IO) CzHs-(20) 25 25 Sn); and (CsHj)*P(O)CH(CH1)(C6Hj)3(4.5 g., 77%, m.p. 166(c&j),po(25) CzHj- (75) 50 25 5 171'). 49 Preparation of (CsH,)2P(O)CH(R)Sn(C6H5)3 Compounds by 99 50 the Grignard Route .--A solution of n-propylmagnesium bromide [prepared from 1.46 g. (0.06 g.-atom) of magnesium turnings and The reaction mixture was concentrated to an aqueous slurry 6.8 g. (55 mmoles) of n-propyl bromide in 90 ml. of T H F ] was under vacuum and extracted with chloroform. Ethyldiphenyladded to a solution of 13.9 g. (50 mmoles) of T P P O in 40 ml. of phosphine oxide (76Yc),m.p. 120-122', was recovered from the T H F . The mixture was then heated a t reflux for 6 hr., during chloroform extracts. which time the color of the reaction mixture changed from dark green to deep red. The mixture was cooled, treated with 23.2 g. (60 mmoles) of triphenyltin chloride in 60 ml. of T H F , and reTABLE IT fluxing was continued for 20 hr. The resulting light brown soluDzO QUENCHING EXPERIMENTS, ALKYLDIPHENYLPHOSPHINE tion was cooled and hydrolyzed with 20 ml. of saturated aqueous OXIDES ammonium chloride solution. The mixture contained 38 mmoles (767,) of benzene. The organic phase was decanted and the Time residue was washed with 150 ml. of T H F . T h e organic layers were (min ) 70 combined and dried over magnesium sulfate. The mixture was heBen- C6HaD filtered and ammonia was bubbled through the filtrate for 4 hr. Phosphine oxide RLi EtsO, T, fore zene, in hen The solution was then filtered and the filtrate was concentrated (mmoles) (mmoles) ml OC quench Yo zene under vacuum to a colorless, opaque oil which crystallized on standing in ether; 17.9 g. (60%j, m.p. 221-223'. T w o recrystallizations from chloroform-heptane gave 16.5 g. (56%) of
+
F Y"Av,
(18) Separate experiments gave 13 8 mmoles (5.570) a n d 11 8 mmoles (47%) of benzene, 10.4 mmoles (427,) and 11.7 mmoles (477,) of trimethylphenylsilane. (19) A . BygdCn, Z. p h y s i k Chem., 90, 243 (1913). (20) Prepared b y M A Weiner, P h D Thesis, M I T , Dec , 1960 (21) Anal. Calcd. for ClsHlsSn: C , 62 51; H , 4.97. F o u n d : C , 6 2 . 2 7 , H , 5 17 (22) Prepared by t h e reaction (CsHdaSnCl R S f g B r in T H F (CsHs)aSnCHa, m p 60-61' (from ether a t -10'); R H Bullard and W R Robinson. J A m . Chem S O L , 4 9 , 1368 (1927). report m p 61' (CsHbIsSnCIHs, m p 54-.56': SI Lesbre, K . Buisson, 1.G 4 Luijten, and G J bl van der Kerk, Rec. l v a v chim , 1 4 , 10.56 (1955), report m p. 55-66' (23) Anal Calcd. for CnaHnoSn: C . 63.36, H , 5 32 F o u n d : C . 63 6 4 , n, 3 33.
+
+
TPPO 3C2HjLi. Trimethylchlorosilane Quench.--A suspension of 6.95 g. (25 mmoles) of triphenylphosphine oxide in 50 mi. of ether was treated rapidly (over ca. 0.5 min.) with 75 mmoles of ethyllithium. T h e mixture refluxed briefly during the addition and very rapidly became homogeneous and turned reddish brown.
March 20, 1964
1105
ot'tho-SUBSTITUTION OF BENZYLTRIMETHYLAMMONIUM I O N
white, crystalline solid, (csH,)zP(o)CH(c~H~)Sn(csH,)a, m.p. 225-227', whose infrared spectrum ( KBr pellet) shoT5 ed principal absorption a t 3000, 1478, 1418, 1075, 1020,995, 725, and 690 cm.-'. Anal. Calcd. for C S ~ H ~ ~ P C, O S66.80; ~: H , 5.27, P , 5.22. Found: C, 66.49; H , 5.02; P , 5.03. Similar experiments with benzylmagnesium chloride, methylmagnesium bromide, isopropylmagnesium bromide, and ethylmagnesium bromide gave benzene yields of 12, 84, 14, and SIC;$ remectivelv. The intermediates from the methvl and ethv1 whose structures were confirmed by melting point and mixture melting point and by comparison of their infrared spectra with authentic samples prepared by the organolithium route. D 2 0 Quenching Experiments. Grignard Procedure .-A solution of 6.95 g. (25 mmoles) of T P P O in 40 ml. of T H F was treated with 23.2 ml. of 1.08 S (25 mmoles) methylmagnesium bromide in T H F . Samples ( 2 ml.) were removed a t successive time intervals and quenched in DrO (1 ml.). The results are summarized in Table I . Carbonation of the TPPO-CH3MgBr Reaction Mixture.-.% solution of 13.9 g. (50 mmoles) of T P P O in 75 ml. of T H F was treated with 46.3 ml. of 1.08 A' (50 mmoles) methylmagnesium bromide in T H F . The mixture then was stirred for 7 hr. a t room temperaturez4and poured onto a slurry of Dry Ice in T H F . The resulting suspension was left to stand for 15 hr. and then acidified with 1 LV HCI. The entire mixture was then concentrated on a rotary evaporator to an aqueous slurry. The residue was extracted with three 100-ml. portions of ether. The ether solutions were combined, washed with 20 ml. of water, and dried over magnesium sulfate. The mixture was filtered and the ether was removed on a rotary evaporator. Sublimation of the residue a t 6 0 - 8 0 O (0.3 m m . ) gave 2.22 g. ( 3 7 5 ) of white, crystalline solid, m.p. 121-122'. -1mixture melting point with authentic benzoic acid showed no depression. The anilide was prepared and recrystallized from ethanol; m . p . IS-160". % . mixture melting point with the anilide prepared from authentic benzoic acid was not depressed. (24) A Gilman Color Test I11 was positive (deep purple)
[COKTRIBUTIOS FROM
THE
Synthesis of Diphenylethy1ene.-Xn ethereal solution of ( CsH5)2P(0)CH2Li [generated from 13.9 g. (50 mmoles) of T P P O and 50 mmoles of methyllithium in ether] was treated with 9.11 g. ( C O mmoles) of benzophenone in ether. The resulting suspension was heated t o reflux for 3 h r . , cooled, and hydrolyzed with 3y0 HC1. The reaction mixture was filtered and the residue dissolved in 200 ml. of benzene. The benzene solution was dried over magnesium sulfate, filtered, and the filtrate concentrated under vacuum. The crude, white crystalline residue was dried under vacuum over P?Oj, suspended in 150 ml. of reagent toluene, and heated to reflux for 3 hr. with 5.73 g. (51 mmoles) of potassium t-butoxide (MSh Research Corp. ) . Analysis of the reaction mixture by gas chromatography a t 200° with Dow Corning 710 silicone fluid on firebrick showed that it contained 36.4 mmoles (ZL;) of 1,I-diphenylethylene. .I sample was collected which gave m.p. 6 " and ~ z ~l.606.i ~ D ( A n a l . Calcd. for ClaHI2: C, 93.29; H , 6.71. Found: C , 93.29; H , 6.83) and whose infrared spectrum and retention time were identical with t h a t of authentic material. A sample of authentic 1,l-diphenylethylene gave m.p. 6" and n Z 51.60E6. ~ The yield of olefin was measured by the increase in peak area, using the same injection volume, after adding a known amount of diphenylethylene to the reaction mixture. The solid remaining in the reaction mixture was removed bv filtration and dissolved in 25 ml. of 0.1 S S a O H . Careful acidification gave diphenylphosphonic acid in 865 yield, m.p. 188-190°, as a white precipitate. The reported melting point for ( C s H j ) ? P ( 0 ) O His 190-192°.26 The same procedure using (C&Hj)?P(O)CH?MgBr in T H F resulted in formation of l,l-diphenylethylene in 71°C yield. ~
~~~~~
Acknowledgments.--The authors are grateful to the E. S. Army Research Office (Durham) (Grant DA-ARO (D)-31-123-G207)and to the United States Air Force (Contract X F 33(657)-%32, monitored by Materials Central, Aeronautical Systems Division, Vi-right Patterson AF Base, Ohio) for generous support of this work and to A i and T Chemicals, Inc., for gifts of chemicals. ( 2 5 ) G hl Kosolapoff, J A m Chem Soc
6 4 , 2982 (1942)
DEPARTMENT OF CHEMISTRY, DUKEUNIVERSITY, DURHAM, S . C.]
Isolation of Intermediate Alkali Salt in ortho-Substitution Rearrangement of Benzyltrimethylammonium Ion as Benzophenone Adduct BY \
T
7 H~. PUTERBAUGH' ~ ~ ~ ~ XSD~ CHARLES R . HAUSER RECEIVED SEPTEMBER 9, 1963
Although the o-substitution rearrangement of the benzyltrirnethylamrnoniuni ion ( I ) by potassium amide or sodium amide in liquid ammonia occurs very rapidly a t -33", the initially formed benzyl carbanion (1') was isolated a t -80" as its benzophenone adduct 111. That the benzyl carbanion I ' was an intermediate in the rearrangement was shown by its conversion a t -33" to rearranged amine I1 in 87% yield within 3 tnin. Ionization of the benzylic hydrogen and also the o-rearrangement occurred more slowly with lithium amide than with potassium amide or sodium amide. .4dduct I11 underwent thermal conversion to benzhydryl phenyl ketone, and the o-substitution rearrangement with excess potassium amide in liquid ammonia t o give carbinolamine V.
T h e o-substitution rearrangement of benzyltrimethylammonium iodide (I) by-alkali amides in liquid ammonia to form amine I1 has been assumed3 to involve the initial formation of the benzyl carbanion 1', this carbanion would be in equilibrium with the methyl carbanion I" which rapidly undergoes the rearrangement (Scheme *I), In agreement with this theory, intermediate alkali salt I' has now been isolated as its benzophenone adduct 111 in yields of i 1 - i 3 , 70, and 19y0when h i was potassium, sodium, and lithium, respectively. None of the isomeric adduct IV, which might have arisen (1) Supported in p a r t b y Army Research Office ( I l u r h a m ) . ( 2 ) National Science Foundation Science Faculty Fellow, on leave from Thiel College (3) See S W . K a n t o r and C . R . Hauser, J . A m . Chem. SOC.,73, 4122 (19511, F . S . Jones and C. R Hauser, J . Ora. C h e m . 26, 2979 ( 1 9 6 1 ) . (4) I t has not been determined whether t h e conversion of I ' t o I" occurs intramolecularly or intermolecularly. A possible mechanism might involve a six-membered ephemeral ring with a molecule of ammonia.
SCHEME % .
+
M"?
C&HjCH2S(CH3)3I-
M - ++
---+ Ce,HjCHS(CHj)a
1-
llq SHa
I
I'
M+
through condensation of salt'I" with the ketone, was found. (CsHs)2COH
CH2C(OH)(CsHi)2
I11 C ~ H ~ C H S ( C H ~ ) B ICsHaCH?N(CH1 121-
-
IV
f
Isolation of 111 was accomplished by addition of
