Process for preparing substituted pyridines

• US 20020002285A1
• Filed: 06/04/2001
• Published: 01/03/2002
• Est. Priority Date: 06/08/2000
• Status: Active Grant

• Current Assignee: Bayer AG
• Original Assignee: Bayer AG
• Inventors: Lui, Norbert, Schnatterer, Albert, Panskus, Hans
• Granted Patent: US 6,392,050 B2
• Time in Patent Office: Days
• US Class Current: 546/286
• CPC Class Codes: C07D 213/80 in position 3
• CPC Class Codes: C07D 213/803 Processes of preparation

Abstract

The invention relates to a process for preparing substituted pyridines in a simple and cost-effective manner in good yields by reacting substituted 1,4-dihydropyridines with methyl nitrite in the presence of an acid that contains less than 20% by weight of oxidizing components.

Claims

1. A process for preparing a substituted pyridine of formula (i)

2. A process according to claim 1 wherein in the formulas (I) and (II) R¹ and R⁵ are identical and represent straight-chain or branched C₁-C₆-alkyl;

R² and R⁴ are identical and represent COOR⁶ wherein R⁶ is straight-chain or branched C₁-C₆-alkyl; and

R³ represents fluorine- and/or chlorine-substituted phenyl.

4. A process according to claim 1 wherein the methyl nitrite is prepared by reacting an alkali metal nitrite with methanol in the presence of a strong acid and is used in an amount of from 1 to 20 mol of methyl nitrite per mole of 1,4-dihydropyridine of formula (II).

5. A process according to claim 1 wherein the acid is a mineral or carboxylic acid used in an amount of from 0.01 to 2 mols per mole of 1,4-dihydropyridine of formula (II).

6. A process according to claim 1 wherein the 1,4-dihydropyridine of formula (II) is employed in the form of a 1,4-dihydropyridinium salt of a non-oxidizing acid and the acid is not added separately.

7. A process according to claim 1 wherein the temperature is in the range from −

30 to ±

100°

C.

8. A process according to claim 1 wherein the acid is free of oxidizing components.

9. A process according to claims 1, wherein the gaseous hydrogen chloride, aqueous hydrochloric acid, aqueous sulfuric acid or a C₁-C₄-carboxylic acid in substance or as aqueous solution is used as acid.

10. A process according to claims 1, wherein a carboxylic acid is set in in an amount of up to 50 mols per mol of 1,4-dihydropyridine of formula (II).

3. A process according to claim I wherein the substituted 1,4-dihydropyridine starting material is 4-(4-fluorophenyl)-2,6-diisopropyl-3,5-di(methoxycarbonyl)-1,4-dihydropyridine and the substituted pyridine product is 4-(4-fluorophenyl)-2,6-diisopropyl-3,5-di(methoxycarbonyl)-pyridine.