GRIGNARD REAGENTS WITH
April, 1951 [CONTRIBUTION
FROM THE
(Y,
&UNSATURATED ETHERS
DEPARTMENT OF CHEMISTRY, TENNESSEE AGRICULTURAL AND
INDUSTRIAL
1663 STATE COLLEGE]
The Reaction of Grignard Reagents with a,p-Unsaturated Ethers BY CARLM. HILL,ROBERT A. WALKERAND MARYE. HILL Theoretical considerations of the electron displacement tendencies in cu,&unsaturated ethers indicate a possibility of reaction with Grignard reagents, a s indicated in I. The formation of a Grignard complex with the ether oxygen would render the electron deficiency on the alpha carbon more acute, thus favoring an alpha-gamma migration of the aryl group of the Grignard with its electron pair a s shown in the scheme CCHZ CHa R:C:O:Et
+ R'-MgX
[
+
+(I)
I/
+ EtO-MgX
+R-C-R'
R-C-OEt Rk:'gXl
(11)
Woods and Tucker's2 have reported that phenyl- with phenyl bromide would be the obvious source magnesium bromide reacts with the ethyl enol of biphenyl, treatment of l-phenyl-l-ethoxyethylethers of dimedone and dihydroresorcinol to yield ene with p-anisylmagnesium bromide gave p-meth5,5-dimethyl-3-phenyI-A2-cyclohexenone and 3- oxybiphenyl (50%), along with 1-p-anisyl-1-phenylethylene (22%). This must mean that the phenyl phenyl- A2-cyclohexenone,respectively. Ethers of the type of a-ethoxystyrene together group of the unsaturated ether and the p-anisyl with aryl Grignard reagents were selected as react- group of the Grignard interacted. The amount of ants. Results of this investigation have clearly biphenyl obtained from the Grignard reagent was shown that the reaction predicted by the above small as compared to the quantity isolated after the mechanism does occur. In addition to the antici- same number of moles of Grignard reacted with the unsaturated ether. Furthermore, when l-p-tolylpated product (11),a second product (111),R-R', 1-ethoxyethylene reacted with p-anisylmagnesium was isolated from the reaction mixture. When 1-phenyl-1-ethoxyethylene was allowed to bromide, only unchanged a,P-unsaturated ether react with phenylmagnesium bromide, the princi- (6%) and 1-p-anisyl-1-9-tolylethylene (63%) were pal products isolated were biphenyl (21%), unre- isolated. acted cu,P-unsaturated ether, (50%), and 1,l-diExperimental phenylethylene (88%). Similar results were obSynthesis of a,p-Unsaturated Ethers.-The c~,p-unserved from the reaction of l-phenyl-l-ethoxy-l-bu- saturated ethers employed in this investigation were tene, 1-phenyl-1-ethoxy-1-heptene and 2-methyl-1- synthesized by the procedure reported by Lauer and Spielphenyl-1-ethoxypropene with phenylmagnesium man.8 The intermediate bromo ethers are new compounds. properties are given in Table I. bromide. The ethylenic derivatives were those Their The unsaturated ethers used in this study have not been predicted by the above mechanism.and designated previously described in the literature. Table I1 shows the as (11). Although coupling of Grignard reagent properties and analytical data for these ethers. TABLE I PHYSICAL CONSTANTS AND ANALYTICAL DATAFOR BROMO ETHERS R
I
BrCH2CH-O-CzHs
Yield,
%
B.P., 4c. Mm. 125-127 10 131-132 15
Formula
-Br,a Calcd.
CnHlsOBr CIIHISOBr
32.88 32.88
%--
--MRD--
Found
d 2nd
n%
Calcd.
Found
33.12 32.56
1.2490 1.2561
1.5298 1.5332
58.81 58.81
60.08 60.65
61.47 H 68 79-81 12 C6H120Br2 61.47 CsHj 67 73-75 61 52 CHI 8 CsHlnOBrz 61.47 CHI H 59 114-116 52.91 52.73 18 CsH1aOBrz n-CjH11 Analyzed by modified Stepanow method: THISJOURNAL, 31, 49 (1939).
1.5429 1 5480 1 4060
1.4700 1.4730 1.4790
17 OB 47.08 60.94
47 02 47.53 60.93
R=
P-CHIC~" m-CH3C6H4
60 63
K' \
I
