187
absorptions at - 24.1 ppm, tris(diethy1amino)phosphine oxide, and -57.7 ppm, 111. The integrated proton nmr spectrum showed these materials to be present in the ratio 2 :3. Reaction of pBromoanisole and Lithium Diethylamide in the Presence of Tris(dimethy1amino)phosphine Oxide. Lithium diethylamide, 0.064 mole, was prepared as a suspension in 150 ml of benzene and 48 ml of hexane. Tris(dimethy1amino)phosphine oxide (5.83 g, 0.0325 mole) was added with stirring and this was followed by the slow addition of 6.09 g (0.0325 mole) of pbromoanisole. After 16 hr the mixture was concentrated and treated with 30 ml of
water and 100 ml of ether. The aqueous phase was extracted with 80 ml more of ether. Concentration of the ether gave 9.29 g of liquid which was examined by glpc. Tris(dimethy1amino)phosphine oxide and two other components, presumably p and mmethoxy-N,N-diethylanilines, were present. Quantitative glpc indicated 2.27 g of oxide. The aqueous layer was concentrated and extracted with 75 ml of methylene chloride. Concentration afforded 6.48 g of impure tris(dimethy1amino)phosphine oxide : 54% by glpc; 60% by nmr. The total recovery of oxide was ca. 100%.
A Sulfone a-Elimination Rearrangement and a Related Diazoethane Decomposition Howard E. Zimmerman and John H. Munch Contribution from the Chemistry Department, University of Wisconsin, Madison, Wisconsin 53706. Received July 31, 1967 Abstract: The reaction of 2,2,2-triphenylethyl phenyl sulfone with phenyllithium and phenylsodium was found to give triphenylethylene. In the similar reaction of 2-anisyl-2,2-diphenylethylphenyl sulfone, the statistically corrected anisyl migratory aptitude for this reaction was found to be 0.86. This contrasts with the 1.9 value found for the thermal rearrangement of 2-anisyl-2,2-diphenyldiazoethanein hydrocarbon solvents. The nature of the rearranging divalent species is considered.
T
he research described here concerns a novel aelimination reaction of 2,2,2-triarylethyl phenyl sulfones and a parallel study of the reactions of an analogous diazo compound. Interest in the a-elimination reactions of sulfones was prompted by our finding' of the a-elimination rearrangement of l-chloro-2,2,2triphenylethane (la) by treatment with amylsodium t o give triphenylethylene (2). For this reaction two extreme mechanisms may be considered. In path A (note Scheme I), after proton removal by base, the car-
under consideration. Hellerman* found that this diazoethane ( 6 ) lost nitrogen under a variety of conditions, both thermal and acidic, to give triphenylethylene.
-
+
Ph,C-CH-N=N 6
A -----f
-9)
Ph?C=CHPh 2
banion 3a rearranges, followed by loss of chloride to give the olefin. In path B, the same carbanion loses chloride t o yield a carbene (Sa), which then rearranges t o afford the ethylene 2. In between these extreme possibilities, mechanistic gradations are possible. It seemed possible that 2,2,2-triphenylethyl phenyl sulfone ( l b ) would also produce triphenylethylene by a-elimination with base. The decomposition of 2,2,2triphenyldiazoethane2 ( 6 ) was of interest because of its relationship t o the base-induced a-elimination reaction
Synthesis of Starting Materials. For the study of the sulfone a-elimination, both 2,2,2-triphenylethyl phenyl sulfone (lb) and a p-methoxy-substituted analog were needed. 2-Anisyl-2,2-diphenylethyl phenyl sulfone (IC)was selected for the latter. Both compounds were prepared by the oxidation of the corresponding sulfides (9b and 9c) with peracetic acid. The sulfides, in turn, were obtained from the reaction of a-chlorothioanisole with triphenylmethylsodium (8b) and anisyldiphenylmethylsodium (8c), respectively. These organosodium derivatives were conveniently prepared from the corresponding triarylchloromethanes by treatment with a 0.75% (liquid) sodium amalgam using high-speed stirring. The synthetic scheme is outlined in Scheme 11. The synthesis of 2-anisyl-2,2-diphenyldiazoethane (6c) started with anisyldiphenylacetonitrilej(10). This was reduced with lithium aluminum hydride t o give a 54 % yield of the previously unknown 2-anisyl-2,2diphenylethylamine ( l l ) , mp 92.0-93.5 '. The latter was treated with ethyl chloroformate and triethylamine t o afford ethyl N-(2-anisyl-2,2-diphenylethyl)carbamate (12), mp 74.5-76.0', in 70% yield. Nitrosation of 12 with sodium nitrite in acetic anhydride-acetic acid using
(1) H. E. Zimmerman and F. J. Smentowski, J . Am. Chem. SOC.,79, 5455 (1957). (2) L. Hellerman and R. L. Garner, ibid., 57, 139 (1935).
(3) F. G . Bordwell and B. M. Pitt, ibid., 77, 572 (1955). (4) See H.E. Zimmerman and V . R. Sandel, ibid., 85, 915 (1963), for the general method. ( 5 ) I. Lifschitz and G. Girbes, Ber., 61, 1463 (1928).
Scheme I PhjC-CH?-X la, X=C1
b, X = SOLPh.
-H+
Ph,C-CH-X 3a,X=C1
path B
-x-
Ph,C-CH 5a
b, X = SOzPh
i
Path A i
0. .q
Ph&-CHPh
4
+
Ph2C=CHPh 2
4a, X = C1 b, X = S0,Ph
Zimmerman, Munch
Sulfone a-Elimination Rearrangement
188 Scheme I1
Ph,C-I’h-pR
3. PhSCH2Cl
Ph,$-CH2SPh
-----t
I
xa+
Ph-
8b. R = H c
p-R
9b R=H c R=OCH,
R=OCH
1 C H COO H
Mixtures of the three isomers were conveniently analyzed by integration of the methoxyl proton peaks in the nmr spectrum. Results of the analysis of three synthetic mixtures are given in Table I. The analysis of cis- plus trans-1,2-diphenyl-l-(4-methoxyphenyl)ethylene (2b and 2c) relative t o l,l-diphenyl-2-(4methoxypheny1)ethylene (2a) proved more accurate than analysis of the cis and tram isomers themselves due t o smaller nmr differences between the latter.
Ph2C-CHJSO-Ph
I
Ph-p-R
lb, R = H c, R = OCH,
Table I. Nmr Analyses of Known Mixtures of the Anisyldiphen ylethylenes
-
7-
2b
Actual 2c
9.1 29.0 38.6
35.8 34.7 0
--
Z Founda -2b 2c 2a
-Camp,
the general procedure of White6 led to ethyl N-nitrosoN-(2-anisyl-2,2-diphenylethyl)carbamate (13). Treatment of the nitrosocarbamate 13 with sodium methoxide in ether-methanol led t o the desired 2-anisyl-2,2diphenyldiazoethane (6c). This synthetic sequence is given in Scheme 111.
Mixture
Scheme I11
a-Elimination of 2,2,2-Triphenylethyl Phenyl Sulfone. Treatment of 2,2,2-triphenylethyl phenyl sulfone with phenyllithium or phenylsodiumg yielded triphenylethylene (2). The conversions fell in the range of 15-
-
LiAIH.
Ph-C-Ph-p-OMe
I
Ph2C-CH,NH2
I
CX 10
h’aNO,
Ph-CCH?-NHCOOEt I
EtJ
Ph ‘pOMe 11
-
NO
I
MeO-
Ph,C-CH,-NCOOEt II
“p0Me 13
-
+
1 2 3 0
2a
55.1 36.3 61.4
13.1 28.1 39.3
Ph3C-CHZ-SOd’h lb
+PhLC=CHPh base
6c
R
R’
2
90% depending on reaction conditions; the results are summarized in Table 11. Table 11. Products of the Reaction of 2,2,2-Triphenylethyl Phenyl Sulfone with Phenyllithium and Phenylsodium ~~
II
Synthesis of Anisyldiphenylethylenes and Analysis of Mixtures. In order to be able to evaluate the migratory aptitude of the anisyl group relative to phenyl in reactions of 2-anisyl-2,2-diphenylethylphenyl sulfone (IC) and 2-anisyl-2,2-diphenyldiazoethane (6c), mixtures of the three possible anisyldiphenylethylenes needed to be analyzed.
54.0 38.1 60.7
Probable uncertainty ~ t 2 units. z
Ph?C-CH--h’dV Ph ‘p-OMe
32.9 33.8 0
Base, equiv
Solvent
Temp, “C
PhLi, 5.0 PhLi, 1.2 PhLi, 2.0 PhLi, 2.0 PhLi, 3.0 PhLi, 1.1 PhLi, 1.1 PhNa, 8.0 PhNa, 1.2 PhNa, 1.2
Ether Xylene Benzene THF THF THF THF Benzene-THF Benzene-THF Benzene
Reflux Reflux Reflux Reflux Reflux Reflux 24 48 48 48
Recovered Time, l b , Product hr % 2, Z
18 24 6 4 4 4 4 4 4 4
78n 43a 6V 65 45 63a 49 2OQ 24 27
22a 574 35“ 24 32 37a 54 8011 74 68
a Percentages are normalized to 100%; total weight 105-1 1 4 z of theory due to solvent.
When 2,2,2-triphenylethyl phenyl sulfone (lb) was treated with 2.0 equiv of 4-t-butylphenyllithium in tetrahydrofuran at room temperature for 1 hr, 73% of sulfone l b and 28% of triphenylethylene (2) were 2 a , R-H; R’=OMe;R”=H found. However no t-butylphenyl-containing products b,R=H;R‘=H;R”=OMe were obtained, confirming that the role of phenylc, R=OMe; R’=H; R”=H lithium was only that of a base. This also provides The general method of Hauser’ was used for the evidence for the intramolecularity of the reaction. preparation of 1,1 -diphenyl-2-(4-methoxyphenyl)After heating alone for 24 hr at xylene reflux temperethylene. The other two isomers, cis- and trans-1,2ature, 2,2,2-triphenylethyl phenyl sulfone (lb) could be diphenyl-l-(4-methoxyphenyl)ethylene(2b and 2c, rerecovered in 100% yield, showing that the a-eliminaspectively), were knownSs tion required base and was not thermal. Weaker bases than those listed in Table I were not effective. Thus ( 6 ) E. H. Whirc, J . Am. Chem. Soc., 7 7 , 6008 (1955). (7) P. J. Hamrick, Jr., and C . R. Hauser, J . A m . Chem. SOC.,81, sodamide in liquid ammonia-THF, sodium t-butoxide 2096 (1959).
(9) Note H. E. Zimmerman and B. S . Thyagarnjan, J. Am. Cliem.
(8) D. Y . Curtin, E. E. Harris, and E. I
