1911 Encyclopædia Britannica/Coumarones

COUMARONES or Benzofurfuranes, organic compounds containing the ring system C₆H₄ $<$ CH
O $\eqslantgtr$ CH. This ring system may be synthesized in many different ways, the chief methods employed being as follows: by the action of hot alcoholic potash on σ-bromcoumarin (R. Fittig, Ann., 1883, 216, p. 162),

C₆H₄ $<$ CH:C·Br
C·CO $\to$ C₆H₄ $<$ CH
O $\eqslantgtr$ C·COOH $\to$ C₆H₄ $<$ CH
O $\eqslantgtr$ CH;

from sodium salts of phenols and α-chloracetoacetic ester (A. Hantzsch, Ber., 1886, 19, p. 1292),

C₆H₄ $<$ H
O
Na $\to$ COCH₃
Cl·CH·COOR $\to$ C₆H₄ $<$ C·COCH₃
O $\eqslantgtr$ C·COOR;

or from ortho-oxyaldehydes by condensation with ketones (S. Kostanecki and J. Tambor, Ber., 1896, 29, p. 237), or with chloracetic acid (A. Rossing, Ber., 1884, 17, p. 3000),

C₆H₄ $<$ OH
CHO ${\xrightarrow {\mathsf {CH_{3}CO\cdot C_{6}H_{5}}}}$ C₆H₄ $<$ OH
CH
:CH·COC₆H₅ ${\xrightarrow {2\ {\mathsf {Br}}}}$ C₆H₄ $<$ OH
CH
Br·CHBr·COC₆H₅ ${\xrightarrow {\mathsf {KHO}}}$ C₆H₄ $<$ O
CH $\geqslant$ C·COC₆H₅,

C₆H₄ $<$ OH
CHO ${\xrightarrow {{\mathsf {Cl}}\cdot {\mathsf {CH_{2}}}\cdot {\mathsf {COOH}}}}$ C₆H₄ $<$ CHO
O·CH₂
·COOH ${\xrightarrow {\mathsf {CH_{3}COONa}}}$ C₆H₄ $<$ CH
O $\eqslantgtr$ C·COOH.

The parent substance coumarone, C₈H₆O, is also obtained by heating ω-chlor-ortho-oxystyrol with concentrated potash solution (G. Komppa, Ber., 1893, 26. p. 2971),

C₆H₄ $<$ CH
OH:CHCl
${\xrightarrow {\mathsf {KOH}}}$ C₆H₄ $<$ CH
O $\eqslantgtr$ CH.

It is a colourless liquid which boils at 171-172° C. and is readily volatile in steam, but is insoluble in water and in potash solution. Concentrated acids convert it into a resin. When heated with sodium and absolute alcohol, it is converted into hydrocoumarone, C₈H₈O, and ethyl phenol.