Method for preparation of potassium 5-lodo-2-carboxybenzene sulfonate
The invention discloses a method for the preparation of potassium 5-iodo-2-carboxybenzene sulfonate by diazotization of 5-amino-2-carboxybenzene sulfonate and subsequent reaction with KI.
1. A method for the preparation of compound of formula (3),
the method comprises two steps STEP1 and STEP2,
in STEP1 compound of formula (2)
is reacted in a reaction REAC1 with KNO 2 in the presence of HCl providing the diazonium salt of compound of formula (2); and
in STEP2 the diazonium salt of compound of formula (2) is reacted in a reaction REAC2 with KI providing compound of formula (3).
2. The method according to claim 1 , wherein
REAC1 is done in aqueous medium.
3. The method according to claim 1 , wherein
the reaction time TIME2 of REAC2 is from 2 to 10 h.
4. The method according to claim 3 , wherein
TIME2 comprises a time TIMEMIX2 for mixing of the reaction mixture obtained from REAC1 with KI and a time TIMESTIRR2 for stirring after said mixing;
TIMEMIX2 is from 15 min to 2 h.
5. The method according to claim 4 , wherein
the mixing during TIMEMIX2 is done at a temperature TEMPMIX2,
the stirring during TIMESTIRR2 is done at a temperature TEMPSTIRR2,
the stirring during TIMESTIRR2 is done with an increase of TEMPSTIRR2 during TIMESTIRR2, starting from lower temperature and going to higher temperature,
said lower temperature being from −10 to below 15° C.;
said higher temperature being from 15 to 70° C.; and
the mixing during TIMEMIX2 is done at said lower temperature.
6. The method according to claim 1 , wherein
REAC1 and/or REAC2 can be done in the presence of small amounts of xylene, small amounts are molar amounts of xylene of from 0.01 to 2 eq of the molar amount of compound of formula (2).
7. The method according to claim 1 , wherein
REAC1 or REAC2 or both are done consecutively without isolation of the diazonium salt of compound of formula (2).
8. The method according to claim 1 , wherein
compound of formula (2) is prepared by a reduction of compound of formula (1).
9. The method according to claim 8 , wherein
the reduction is done with H 2 , Fe, Zn, Sn, hydrazine or NaBH 4 .
10. The method according to claim 8 , wherein
the reduction is done with H 2 .
11. The method according to claim 10 , wherein
the reduction is done in the presence of a catalyst CAT, and CAT is Pd/C.
12. The method according to claim 10 , wherein
the reduction is done in water as solvent.
13. The method according to claim 8 , wherein
the reduction is done in the presence of small amounts of xylene, small amounts are molar amounts of from 0.01 to 2 eq of the molar amount of compound of formula (1).