[ C O S I R I B U T I O N FROM THE S O Y E S CIIENICAL LABORATORY,
USIVERSITI' OF
ILLINOIS]
Displacement of Methoxyl Groups in the 6-Mesitoylnaphthalene Series with Grignard Reagents T Z r REYNOLD C Fr~sou\VI> VICTORT T ~ I , L I O ~ In 1,3-dimethoxy-2-naphthyl mesityl ketone the methoxyl group in the 1-position is replaced by the action of Grignard reagents whereas that in the 3-position is unattacked at ordiiiary temperatures. Siniilarly, Grignard reagents attack mesityl 3-methoxy-%naphthyl ketone at the 1-position, the niethoxyl grouii being unt-r:ic'ti\-r.
Replacement of o-methoxyl groups by the hydrocarbon radical of a Grignard reagent has been realized with a number of substituted benzonitriles2 and with hindered ketones of both the benzene and naphthalene3series. In 2,6-dimethoxyphenyl duryl ketone both methoxyl groups were replaced by methyl groups when the ketone was treated with the methyl Crignard reagent.4 'The present work was undertaken to determine whether both methoxyl groups mesityl ketone (1) in 173-dimethoxy-2-naphthyl could likewise be replaced. The possibility of displacement a t the 3-position is of particular interest since that position is generally unreactive. I t has been found that one of the methoxyl groups, 'tssumed to be that in the 1-position, is readily replaced by a benzyl radical under the influence of the benzyl Grignard reagent, the methoxyl group in the 3-position being unaffected Eveti a t temperatures in the neighborhood of 7:)' tlie I-benzyl-3-methoxy-2-naphthyl mesityl ketone (1I is not attacked by benzylmagnesiuni chloride. IVhen "forcing" conditions were used with phenyl magnesium bromide, the 3-niethoxyl group again resisted displacenient. The only reaction 01)served a t this position was cleavage of the ether to produce mesityl 1-I)lienvl-:~-h~-tlrt,\(\ -2-i!;~i)litIn~l A+ tone (111).
I
11
111
Similar results were obtained with mesityl :;inethoxy-%naphthyl ketone (IV). 1Iethylrnagnesiuin iodide was without effect and phenylmagnesium bromide attacked the 1-position, giving the corresponding dihydro compound (V) in a r i Syi yield. I t iq :t striking fact th,it thv aii'ilogour
I \-
1).
1.1
reaction with mesityl 2-naphthyl ketone affor(1s 1 ,t'-dihydro-l-phenyl-2-naphthylmesityl ketone (VI) in a yield of 84yo.5 Evidentlv the reaction is opposed by a niethosyl group in the 3-position. ' 1) hllied Chemical and Dye Corporation Fellow, 1950-1951 1 2 ) 11. Richtzenhain, BPI..,77B, 1 11944); H. Richtzenhaiu a n d I'. Nippus, i b i d , 77B,BfiG (1944); R . C Fuson, R C.;ierrner aiirl ! I 11 Chadwick, J . Org. Chpm , 13, 489 (1948). C 3 ) R. C. F u s o n a n d S. 14. Spcck, THISJ O U R N A L , 64, 244G t l 9 4 2 ) . I.
Experimental 1,3-Dirnethoxy-Z-naphthyl Mesityl Ketone (I) (a) Ethyl 1,3-Dimethoxy-2-naphthoate .--Ethyl 1,3-dihydroxy-2ii:iplitlioate6 (I
