Preparation of isoxazolin-3-ylacylbenzene
A process is described for preparing isoxazoles of the formula I where the substituents are as defined below: R 1 is hydrogen, C 1 -C 6 -alkyl, R 2 is C 1 -C 6 -alkyl, R 3 , R 4 , R 5 are hydrogen, C 1 -C 6 -alkyl, or R 4 and R 5 together form a bond, R 6 is a heterocyclic ring, n is 0, 1 or 2; which comprises preparing an intermediate of the formula VI where R1, R3, R4 and R5 are as defined above, followed by halogenation, thiomethylation, oxidation and acylation to give compounds of the formula I. Also novel intermediates for preparing the compounds of the formula I and novel processes for preparing the intermediates are described.
1. A process for preparing a compound of formula XV
in which
X is NO 2 or S(O) n R y ,
R x is halogen, carboxyl, carboxamide, N-alkyl-carboxamide, N,N-dialkylcarboxamide, phenyl, C 1 -C 6 -alkyl, C 1 -C 6 -alkoxy or C 1 -C 6 -alkylthio,
R y is C 1 -C 6 -alkyl;
m is 1, 2, 3 or 4, and
n is 2,
or a corresponding aldehyde, nitrile or nitrile oxide, which comprises reacting a compound of the formula XVI
in which X and (R x ) m are as defined above,
with an organic nitrite of the formula R—O—NO, where R is an aliphatic or aromatic radical, in the presence of a base, to obtain the compound of the formula XV,
and optionally converting the oxime group —CH═NOH in formula XV into an aldehyde moiety (—CHO), a nitrile (—CN) or a nitrile oxide (—CHO),
wherein the reaction is carried out at a temperature below −20° C. in the presence of a dipolar aprotic solvent.
2. A process as claimed in claim 1 , wherein the compound of formula XVI is reacted in the presence of DMF.
3. The process of claim 1 , wherein
R x is halogen, carboxyl, carboxamide, N-alkyl-carboxamide, N,N-dialkylcarboxamide, phenyl, C 1 -C 6 -alkyl, C 1 -C 6 -alkoxy or C 1 -C 6 -alkylthio,
wherein a first group R x is bonded to the phenyl ring in ortho position relative to the CH═N—OH moiety and denotes C 1 -C 6 -alkyl, halogen, C 1 -C 6 -alkoxy or C 1 -C 6 -alkylthio;
R y is C 1 -C 6 -alkyl, and
m is 2.