Organic Syntheses, Coll. Vol. 4, p.919 (1963); Vol. 33, p.94 (1953).
is prepared by adding a solution of 150 g. (0.88 mole) of silver nitrate
in 300 ml. of water to a solution of 70 g. (1.75 moles) of sodium hydroxide
in 300 ml. of water. Continuous shaking during the addition ensures complete reaction and results in a brown semisolid mixture. To this mixture, contained in a 1-l. flask
which is cooled in an ice bath
, is added 47.5 g. (0.425 mole) of 3-thenaldehyde
) in small portions with stirring. The oxidation is complete in about 5 minutes after the last of the aldehyde has been added. The black silver
suspension is removed by suction filtration (Note 1)
and is washed with several portions of hot water. The cold combined filtrate and washings are acidified with concentrated hydrochloric acid
, precipitating 49 g.
of 3-thenoic acid
, which melts at 136–137°
. Concentration of the mother liquors gives another 3–4 g.
of acid, making a total of 52–53 g.
). Recrystallization of this acid from water raises the melting point to 137–138°
dissolves readily in concentrated nitric acid
and may be used over and over in oxidations.
has been prepared in low yield by oxidation of 3-methylthiophene
with potassium permanganate
dilute nitric acid
, chromic acid
, and hydrogen peroxide
and by reductive dechlorination of chloro-3-thenoic acid
Starting with 3-iodothiophene
, which is difficult to obtain, good yields are obtained by the Grignard procedure5
or with cuprous cyanide
and potassium cyanide
in a sealed tube
.6 3-Thenoic acid
has been made also from 3-bromothiophene
by reaction with cuprous cyanide
, followed by hydrolysis,7
and by carbonation of the Grignard reagent from 3-bromothiophene
which is prepared by entrainment with ethyl bromide
Oxidation of the aldehyde was not used earlier because of the difficulty of obtaining the aldehyde, which is now readily available by the Sommelet synthesis from 3-thenyl bromide
. Campaigne and LeSuer9
also used alkaline permanganate as the oxidizing agent, but the yields decreased to 40–60%
. The present procedure gives an over-all yield from 3-methylthiophene
of about 45%
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