Process for the interconversion of two separate crystal forms of

Details Process for the interconversion of two separate crystal forms of Process for the interconversion of two separate crystal forms of

1991-05-08

1993-04-13

Ford, John M.

Organic compounds -- part of the class 532-570 series

Organic compounds

Nitrogen attached directly or indirectly to the purine ring...

C07D40112

Patent

active

052024393

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to the interconversion of separate crystal forms of (aminosulfonyl)-pyridinecarboxamides. The compounds of this invention and their agriculturally suitable salts are useful as agricultural chemicals, and in particular, as herbicides which may be selective to corn.
U.S. Pat. No. 4,544,401 and U.S. Pat. No. 4,435,206 disclose herbicidal pyridinesulfonylureas.
U.S. Pat. No. 4,518,776 (Swiss priority Jul. 19, 1982 and EP-A-101,670 (Swiss priority Aug. 23, 1982, published Feb. 29, 1984) disclose, in part, a process for the preparation of the compounds of the invention.
U.S. Pat. No. 4,518,776 generally discloses the compound of the invention.
U.S. Pat. No. 4,521,597 discloses, in part, a process for the preparation of the compound of the invention.


SUMMARY OF THE INVENTION

It has been found that preparation of 2[[(4,6-dimethoxypyrimidine-2-yl)aminocarbonyl]-aminosulfonyl-N-N-dimethyl -3-pyridinecarboxamide (Compound I) results in two separate and distinctly different crystal lattice forms (Compounds Ia and Ib) depending on the conditions of preparation. ##STR1##
The compound of Formula Ia may be prepared as a non-hygroscopic, anhydrous crystalline solid via a non-aqueous reaction sequence. The compound of Formula Ia in this physical state is uniquely stable and does not absorb water upon standing.
The compound of Formula Ib may be prepared via an aqueous reaction sequence. This will result in the separate distinct crystal form of Formula Ib which is now susceptible upon standing to conversion to the compound of Formula II via water of hydration. ##STR2##
Both crystalline forms are interchangeable by either reaction with water or thermally induced water removal and recrystallization. The compounds of Formula Ia are useful as a stable analytical product and as an intermediate to the compound of Formula Ib. The compound of Formula Ib provides a better water dispersible granuler than Compound Ia when formulated as a dry flowable. Therefore, Compound Ib is the compound of choice for such formulations.


DETAILS OF THE INVENTION

Compounds of Formula Ia and Ib can be prepared by the methods described in Equations 1 and 2. ##STR3##
The reaction shown in Equation 1 is carried out by contacting the phenyl carbamate of Formula (3) with the aminoheterocycle of Formula (2) in an inert organic solvent such as dioxane or tetrahydrofuran at temperatures of about -20.degree. to 100.degree. C. for a period of about one-half to twenty-four hours. The product can be isolated by evaporation of the reaction solvent and purified by trituration of the evaporation residue with solvents such as 1-chlorobutane or ethyl ether and filtration, by recrystallization from mixtures of solvents such as 1,2-dichloroethane, 1-chlorobutane and heptane or by chromatography on silica gel. ##STR4##
The reaction of Equation 2 can be carried out by contacting equimolar amounts of the sulfonamide of Formula (4) with a heterocyclic phenyl carbamate of Formula (5) in the presence of an equimolar amount of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), by methods known to one skilled in the art and analogous to those described in South African Patent Application 830441.
The hydrated form of Ib, that is Compound II, may be prepared from either Ia or Ib. Slurrying a solution of Ia in water and an appropriate organic solvent such as ethyl acetate and heating results in the direct conversion to Compound II. Compound II may be converted to Ib via removal of the solvent and water by thermal evaporation of the solvent and water. Compound Ib may then be converted Ia by dissolving in the appropriate organic solvent such as ethyl acetate and allowing it to crystallize under anhydrous conditions. The above sequence is outlined in equation 3. ##STR5##
The following examples further illustrate the process of the invention.


EXAMPLE 1



N,N-Dimethyl-2-[[4,6-dimethoxypyrimidin-2-yl)aminocarbonyl]aminosulfonyl]-3
-pyridinecarboxamide (Ib)
To a suspension of 0.50 g (2.2 mmol) N,N-dimethyl-2-(aminosulfonyl)-3-pyridinecarb

REFERENCES:
patent: 4789393 (1988-12-01), Hanagan

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