US4031100A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for making 2,6-difluoropyridine
Assignee: Dow Chemical Co
•
Filing: 1976-08-23
•
Granted: 1977-06-21
•
Expires: 1996-08-23
Abstract
Abstract It has been found that practical reaction rates can be attained without resort to the high temperatures previously employed in the preparation of 2,6-difluoropyridine from the corresponding dichloropyridine and KF, if: A. dimethyl sulfoxide is employed as the reaction medium; B. the reaction mixture contains solid KF particles and dissolved tetramethyl ammonium or phosphonium chloride; C. there is present in the reaction mixture less than 0.1 grams of acids, bases or organic hydroxy compounds and less than 1.0 grams of water, per 100 grams of solvent, and D. the reaction mixture is intensely stirred.
Inventors
- 👤 Thomas J. Giacobbe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 08:18
CPC Classifications
C; C07; C07D; C07D213/00; C07D213/02; C07D213/04; C07D213/60; C07D213/61
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
161 words
The improvement in the process of preparing 2,6-difluoropyridine by reacting KF with an alpha-chloropyridine which is 2,6-dichloro- or 2-chloro-6-fluoropyridine, at an elevated temperature in an aprotic, polar solvent, whereby practical rates of conversion are attained without resort to temperatures in excess of about 185°, said improvement comprising: a. providing a mixture of solid KF particles and a solution in dimethyl sulfoxide of 1. said alpha-chloropyridine reactant, and 2. a catalytically effective amount of a catalyst which is (CH 3 ) 4 N +Cl - , (CH 3 ) 4 P +Cl - or both; said mixture containing less than 0.1 gram of acids, bases or organic hydroxy compounds and less than about 1 gram of water, per 100 grams of dimethyl sulfoxide; and b. intensely stirring said mixture and maintaining the temperature thereof within the range of from about 100° to about 185°, the reaction being carried out under an inert atmosphere if a reaction temperature above about 180° is employed.
Claim 2
Dependent Claim
161 words
The improvement in the process of preparing 2,6-difluoropyridine by reacting KF with an alpha-chloropyridine which is 2,6-dichloro- or 2-chloro-6-fluoropyridine, at an elevated temperature in an aprotic, polar solvent, whereby practical rates of conversion are attained without resort to temperatures in excess of about 185°, said improvement comprising: a. providing a mixture of solid KF particles and a solution in dimethyl sulfoxide of 1. said alpha-chloropyridine reactant, and 2. a catalytically effective amount of a catalyst which is (CH 3 ) 4 N +Cl - , (CH 3 ) 4 P +Cl - or both; said mixture containing less than 0.1 gram of acids, bases or organic hydroxy compounds and less than about 1 gram of water, per 100 grams of dimethyl sulfoxide; and b. intensely stirring said mixture and maintaining the temperature thereof within the range of from about 100° to about 185°, the reaction being carried out under an inert atmosphere if a reaction temperature above about 180° is employed.
Claim 3
Dependent Claim
18 words
The process of claim 1 in which the catalyst is (CH 3 ) 4 N +Cl - .
Claim 4
Dependent Claim
15 words
The process of claim 1 in which the reaction temperature is 180° C. or less.
Claim 5
Dependent Claim
22 words
The process of claim 3 in which the reaction temperature is within the range of from about 140° to about 175° C.
Claim 6
Dependent Claim
22 words
The process of claim 3 in which the reaction temperature is within the range of from about 145° to about 170° C.
Claim 7
Dependent Claim
22 words
The process of claim 3 in which the reaction temperature is within the range of from about 150° to about 165° C.
Claim 8
Dependent Claim
29 words
The process of claim 1 in which the amount of water present in the reaction mixture is less than 0.3 wt. percent of the amount of DMSO present therein.
Claim 9
Dependent Claim
27 words
The process of claim 1 in which the reaction is carried out in a baffled vessel and a stirring rate of at least 50 rpm is maintained.
Claim 10
Dependent Claim
27 words
The process of claim 1 in which the reaction is carried out in an unbaffled vessel and a stirring rate of at least 300 rpm is maintained.
Claim 11
Dependent Claim
17 words
The process of claim 9 in which a stirring rate of at least 450 rpm is maintained.
Claim 12
Dependent Claim
41 words
The process of claim 1 in which the reaction temperature is within the range of from about 145° to about 170° C., the reaction is carried out in baffled vessel and a stirring rate of at least 60 rpm is maintained.
Claim 13
Dependent Claim
40 words
The process of claim 1 in which the amount of KF introduced to the reaction mixture is from about 110 to about 125% of the stoichiometric requirement for the conversion to 2,6-difluoropyridine of the alpha-chloropyridine reactants charged to the reaction.
Claim 14
Dependent Claim
11 words
The process of claim 1 in which the alpha-chloropyridine is 2,6-dichloropyridine.
Claim 15
Dependent Claim
24 words
The process of claim 1 in which the reaction temperature is above about 175° and the reaction is carried out under an inert atmosphere.
Claim 16
Dependent Claim
33 words
The process of claim 1 in which the amount of said catalyst introduced to the reaction mixture is from about 0.3 to about 0.6 moles per mole of said alpha-chloropyridine reactants present therein.
Claim 17
Dependent Claim
26 words
The process of claim 1 in which the concentration of said alpha-chloropyridine reactant in said solution is from about 2 to about 3 moles per liter.
Claim 18
Dependent Claim
109 words
The process of claim 11 in which: 1. the catalyst is (CH 3 ) 4 N +Cl - , and the amount of it introduced to the reaction mixture is from about 0.3 to about 0.6 moles per mole of said alpha-chloropyridines present therein, 2. the concentration of said alpha-chloropyridine reactant is from about 2 to about 3 moles per liter, 3. the amount of KF introduced to the reaction mixture is from about 110 to about 125% of the stoichiometric requirement for conversion to 2,6-difluoropyridine of said alpha-chloropyridine, and 4. the reaction mixture contains less than about 0.3 grams or less of water per 100 grams of DMSO.
References Cited (Backward Citations)
US3629424A
Cited
GB1306517A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-06-20 | 1980-12-20 | 1981-06-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-20 | 1984-12-20 | 1985-06-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-20 | 1988-12-20 | 1989-06-21 | $7700.00 | Window Closed / Lapsed |