Process for preparing substituted 2-nitrobiphenyls

A process for preparing a compound of formula (I)

• wherein
• R1, R2, R3, R4 and R5 are independently of each other selected from hydrogen;
• halogen;
• cyano;
• hydroxyl;
• C1-C6-alkyl, wherein the alkyl group may carry 1, 2 or 3 substituents R6;
• C1-C6-haloalkyl;
• C3-C10-cycloalkyl which may carry 1, 2, 3 or 4 C1-C4-alkyl substituents;
• C3-C10-halocycloalkyl;
• C1-C6-alkoxy;
• C1-C6-haloalkoxy;
• C1-C6-alkylthio;
• C1-C6-haloalkylthio;
• aryl;
• aryl-C1-C4-alkyl;
• wherein aryl in the two last-mentioned radicals may carry 1, 2, 3 or 4 substituents selected from the group consisting of halogen, C1-C4-alkyl, C1-C4-haloalkyl and a radical R6;
• amino;
• C1-C4- alkylamino;
• and di-(C1-C4-alkyl)-amino;
• each R6 is independently selected from the group consisting of C3-C10-cycloalkyl which may carry 1, 2, 3 or 4 C1-C4-alkyl substituents;
• C3-C10-halocycloalkyl;
• C1-C4-alkoxy;
• C1-C4-haloalkoxy;
• amino;
• C1-C4-alkylamino;
• di-(C1-C4-alkyl)-amino;
• carboxyl;
• hydroxyl;
• SH and aryl;
• each R7 is independently selected from the group consisting of C1-C4-alkyl, OR8, amino, C1-C4-alkylamino, di-(C1-C4-alkyl)-amino and halogen;
• wherein
• R8 is selected from the group consisting of hydrogen, C1-C4-alkyl, a protecting group, and aryl, wherein aryl may carry 1, 2, 3 or 4 substituents selected from the group consisting of halogen, C1-C4-alkyl, C1-C4-haloalkyl and a radical R6;
• and
• a is 0, 1 or 2;
• comprising reacting a compound of formula (II)
• wherein a′ is 0, 1 or 2 and X is a halogen atom,
• wherein when a′ is 2, the two substituent(s) R7 are not bound to the same carbon atom, and wherein when a′ is 1 or 2, the substituent(s) R7 is/are not bound to the carbon atom carrying the phenyl substituent;
• with a base wherein HX is eliminated from compound II in a dehydrohalogenation reaction,
• and aromatizing the resulting product;
• wherein aromatization is accomplished by carrying out the dehydrohalogenation reaction under air atmosphere and/or by keeping the reaction mixture at air atmosphere after the completion of the dehydrohalogenation;
• or by sparkling air or oxygen through the reaction mixture during the dehydrohalogenation reaction and/or after its completion;
• or by oxidizing the product of the dehydrohalogenation reaction with an oxidizing agent.