Weygand/Hilgetag Preparative Organic Chemistry

C-C linkage by replacement of hydroxyl by carbon 951

Toluidine is methylated in the ring by methanol and hydrogen chloride under

pressure;

661

aniline can also be alkylated in the ring by alcohols;

662

and so

can indoles by alcohols containing alkoxides at 220° under pressure.

663

In a high-yielding synthesis of indole-3-acetic acids the heterocycle is heated

with potassium glycolate at 250°, e.g.:

66

*

HOCH 2 COOK

and other <%-hydroxy acids react analogously.

664

Indane and tetralin derivatives can be obtained by cyclodehydration of

3-aryl-l-alkanols and 4-aryl-l-alkanols, respectively.

665

Isomerization does not

occur in such reactions; thus 4-phenyl-l-butanol gives tetralin and not 1-

methylindane, and only 1,1-dialkylindanes are formed from the corresponding

tertiary alcohols, e.g.:

CR,OH

however, neither primary nor secondary alcohols of this type cyclize, owing

to polymerization.

An interesting case is the preparation of ionene (l,2,3,4-tetrahydro-l,l,6-tri-

methylnaphthalene).

6 6 6

1,1-rDimethylindane:^665 85% Sulfuric acid (1.2 parts by volume) is added slowly to vigor-
ously stirred 2-methyl-4-phenyl-2-butanol (1 part by volume) at 10°. Reaction appears to
be instantaneous, but for certainty stirring is continued for another hour at room temperature.
Then the mixture is diluted with water (10-15 parts by volume) and distilled. An oil separates
in the distillate and is separated; the aqueous distillate is returned to the distillation flask,
and the mixture is redistilled. The oil is redistilled from aqueous alkali, separated from that
distillate, dried over calcium chloride, and fractionated, giving 1,1-dimethylindane (65%),
b.p. 191°.
The same process has been employed for preparation of 1,1,2-trimethylindane (90%),
b.p. 208°, tetralin (55%), and 1,1,4-trimethyltetralin (86%).^667

2-(l-Cyclohexenyl)benzyl alcohol cyclizes when warmed for a short time

in formic acid, giving a 53% yield of 1,2,3,4-tetrahydrofluorene.

668

(^661) R. W. Cripps and D. H. Hey, /. Chem. Soc, 1943, 14.
(^662) I. J. Rinkes, Rec. Trav. Chim., 62, 557 (1943).
(^663) R. H. Cornforth and R. Robinson, /. Chem. Soc, 1942, 680.
(^664) H. E. Johnson and D.G.Crosby, /. Org. Chem., 28, 1246 (1963); N. A. Preobraz-
henskii, M. E. Maurit, G. I. Bazilevskaya, G. V. Smirnova, M. M. El'manovich, A. I. Va-
lakhanovich, and E. Persiyanova, Zh. Obshch. Khim., 30, 2250 (1960); Chem. Abstr., 55,
9367 (1961).
(^665) M. T. Bogert and D. Davidson, /. Amer. Chem. Soc, 56, 185 (1934).
666
667 M. T. Bogert, D. Davidson, and P. M. Apfelbaum, /. Amer. Chem. Soc, 56,959 (1934).
M. C. Kloetzel, /. Amer. Chem. Soc, 62, 3405 (1940).
(^668) W. E. Parham, C. D. Wright, and D. A. Bolon, /. Amer. Chem. Soc, 83, 1751 (1961).