A Process for the Production of Trichloropurine.
Year: 1897

page_text: Date of Application, 16th June, 1897-Accepted, 24th July, 1897
COMPLETE SPECIFICATION.
A Process for the Production of Trichloropurine.
I, BENJAMIN WILLCOX, of 47 Lincoln's Inn Fields, in the County of London, Patent
Agent, do hereby declare the nature of this Invention (which has been communicated
to me from C. F. Boehringer & Soehne, of Waldhof, near Mannheim, in the Empire
of Germany) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
According to the process described in the Provisional Specification of the Application
for Letters Patent No. 3957 of the 13th February 1897 both the oxygen atoms of
uric acid which are situated in the alloxan ring, undergo elimination by the agency
of phosphorus oxychloride; in this manner 2: 6-dichloro-8 oxypurine is produced,
having the followingconstitutional formula :—
This substance is most conveniently isolated when pure dichloroxypurine is used as
the initial material.
The most suitable method of preparing trichloropurine is as follows:-
One part of finely powdered 2: 6-dichloro-8-oxypurine is heated with 70 parts
by weight of phosphorus oxychloride in closed vessels for 4 hours at 1500-
1550 Centigrade the mass being agitated frequently during the process. At the end of
the operation a clear and pale yellow liquid is obtained, and this is evaporated in vacuo
in order to completely remove the phosphorus oxychloride. The amorphous residue
becomes crystalline when agitated with cold water; the colourless product is then
filtered, and washed with cold water.
For complete purification, the crude trichloropurine is extracted with five times its
weight of ether, and the residue, which remains after removing the ether, is boiled
with sixty parts by weight of water, when foreign substances remain behind in a
solid mass.

page_text: On allowing the aqueous solution to cool, trichloropurine separates in slender
colourless leaflets, in quantity representing 65 per cent. of the dichloroxypurine
employed. The air-dried substance has the formula C,HN,CI, + 5 H₂O.
The water of crystallisation is completely eliminated at 110° Centigrade. The
anhydrous substance when quickly heated begins to sinter at 180° Centigrade, and
melts at 1840-1880 Centigrade with effervescence.
'
The anhydrous product dissolves in about seventy parts of boiling water, and is
readily soluble in warın ether, alcohol, acetone, and chloroform. It dissolves in dilute
alkalies with equal readiness and is precipitated from these solutions by mineral
acids.
Trichoropurine dissolves readily in warm, dilute ammonia, and the solution on
cooling deposits the ammonium derivative in long needles, collected together in
spherical aggregates.
In preparing trichloropurine it is unnecessary to employ autoclaves, it being
sufficient to heat dichloroxypurine with phosphorus oxychloride in a reflux apparatus,
in order to obtain a clear solution, it is necessary to boil for say from 50 to
60 hours.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed I declare that what I
claim is
The production of trichloropurine by heating 2: 6-dichloro-8-oxypurine with
phosphorus oxychloride.