REARRANGEMENT OF ~-ISOPROPYL-~-NAPHTHOIC ACID
April 20, 1959
[CONTRIBUTION FOR T H E
1965
DEPARTMENT OF CHEMISTRY, NORTHWESTERN UNIVERSITY]
peri-Substituted Naphthalenes. 111. Acid-induced Rearrangement of 8-Isopropyl-lnaphthoic Acid’ BY R. L. LETSINGER, W. J. V U L L OAND ~ A. S. HUSSEY RECEIVED OCTOBER 11, 1958 8-Isopropyl-1-naphthoic acid was synthesized from 1,s-naphthalic anhydride. I n sulfuric acid or in liydrugcn fluoride it rearranged with a transfer of hydrogen from the isopropyl group t o the carbonyl group. There was 110 iiidication of a 1,5methyl shift. T h e samea ldal product ( V I I I ) also was obtained by dehydration of l-liydrosy-3,3-dii1iet11yl-1H,3H-naplitl10[l,S-c,d]pyran with sulfuric acid.
In the previous papers3 i t was shown that hemiacetal I rearranged readily in formic acid solution to 8-benzhydryl-1-naphthoic acid (11), which in turn rearranged to ketal I11 in sulfuric acid. Both transformations could be accomplished in one operation by the action of concentrated sulfuric acid on I.
I
?Q HC’
were obtained by addition of IV to two mole eyuivalents of methyllithiurn. H3C
9, o=c c=o
I9,
H3CC
C=O
CH.I
I
H3CCH YOOH
I1
‘C-OH
(It2 1x1
The effect of acid reagents on thc analogous iriethyl compounds, VI1 and VI, is reported in this paper. An investigation of V I was of particular interest since, in view of the rcarrangemerit of 11, it would appear that the molecular geometry of this compound would be very favorable for a 1,5methyl shift. Although many cases of rearrangements involving 1,2-methyl migrations are known, previous work has failed to reveal any unambiguous examples of acid-catalyzed intramolecular methyl migrations that occur between carbon atoms separated by one or more atoms (;.e., 1,3-, 1,4-, 1,5-, ctc. shifts). 1,S-Naphthalic anhydride (IV) was converted to 3,3-dimethyl-l&naphthalide (V), which was reduced to s-isopropyl-1-naphthoic acid. Considerable experimentation was necessary to determine conditions for effecting both of these transformations. Although aryl magnesium halidesyielddiarylnaphthalides on reaction with IV,4we failed to isofrom any of sevlate 3,3-dimethyl-l,S-naphthalide eral reactions involving methylmagnesium iodide and IV. However, yields of V of the order of 25y0 (1) Presented a t t h e 131th Meeting of t h e American Chemical Society, Chicago, Ill., September, 1958. (2) Sinclair Oil Co. H a r v e y Fellow, 19.56-1957; S t a n d a r d Oil C o . of I n d i a n a Fellow, 1957-1958. (3) R. L. Letsinger a n d P. T. Lansbury, THISJ O U R N A L , 81, 935 (1959); P. T. Lansbury a n d R. L. Letsinger. ibid., 81, 9-10(1959). (4) M . S. Kharasch a n d D. R e i n m u t h , “Grignard Reactions of N o n metallic Substances,” Prentice-Hall, Inc., New York, PI’. Y., 1954.
Lactone V provcd to be remarkably unreactive. I t was unchanged by 25% aqueous sodiuni hytlroxide a t 150’ for 40 hours and by concentrated 3111monium hydroxide a t 100’ for 45 hours. I t was likewise unchanged by aqueous hydrogcii iodide and phosphorus (6hours a t reflux) and by zinc amalgam in formic acid and hydrochloric acid (30 hours a t reflux), although 1,s-naphthalide has beeii reduced by thc Clemincrisen proced ~ r e . Saponification ~ could be effected by heating V a t 145’ with excess potassium hydroxide in triethylene glycol for several hours. Reduction of the resulting salt with nickel-aluminum alloy6 yielded 8-isopropyl-1-naphthoicacid. If the reduction was carried out without prior saponification of the lactone, a tetrahydrolactone rather than V I was produced. Acidic reagents Converted S-isopropyl-l-naphthoic acid to a neutral, crystalline solid, VIII. The best yield, 6i%, was obtained when liquid hydrogen fluoride was used as a solvent. Concentrated sulfuric acid was also an effective reagent for this transformation and furnished a 55YGyield of VIII. The conditions which had been found to be most satisfactory for the isomerization of I1 to I11 (the action of stannic chloride on the acid chloride of 11) were less suitable with VI; hydrolysis of the com(5) R. C . Fuson and G. M u n n , i b i d . . 71, 1870 (1940). (6) For a survey of t h e use of nickel-aluminum alloy as a reclucing agent see D. P a p a , E. Schwenk a n d H. Breiger, J. Org. Cheirz., 14, 3titi (194D), a n d previous papers in this series.
1l)(ifi
I
