Substituted dihydro 3-halo-1h-pyrazole-5-carboxylates and their preparation and use
View Patent ↗This invention relates to a compound of Formula I, a method for its preparation and its use in the preparation of a compound of Formula II wherein R 1 , R 2 , R 3 , X and n are as defined in the disclosure. This invention also discloses preparation of compounds of Formula III wherein R 1 , R 2 , R 6 , R 7 , R 8 and n are as defined in the disclosure. Also disclosed are certain intermediates of Formula 4 for the preparation of compounds of Formula I wherein X is N and R 2 , R 3 and n are as defined in the disclosure.
1. A compound of Formula I
wherein
R 1 is halogen;
each R 2 is independently C 1 -C 4 alkyl, C 2 -C 4 alkenyl, C 2 -C 4 alkynyl, C 3 -C 6 cycloalkyl, C 1 -C 4 haloalkyl, C 2 -C 4 haloalkenyl, C 2 -C 4 haloalkynyl, C 3 -C 6 halocycloalkyl, halogen, CN, NO 2 , C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, C 1 -C 4 alkylthio, C 1 -C 4 alkylsulfinyl, C 1 -C 4 alkylsulfonyl, C 1 -C 4 alkylamino, C 2 -C 8 dialkylamino, C 3 -C 6 cycloalkylamino, C 3 -C 6 (alkyl)cycloalkylamino, C 2 -C 4 alkylcarbonyl, C 2 -C 6 alkoxycarbonyl, C 2 -C 6 alkylaminocarbonyl, C 3 -C 8 dialkylaminocarbonyl or C 3 -C 6 trialkylsilyl;
R 3 is H or C 1 -C 4 alkyl;
X is N or CR 4 ;
R 4 is H or R 2 ; and
n is 0 to 3, provided when X is CH then n is at least 1.
2. A compound of claim 1 wherein n is 1 to 3.
3. A compound of claim 1 wherein R 1 is Cl or Br; each R 2 is independently Cl or Br, and one R 2 is at the 3-position; and X is N.
4. A method for preparing a compound of claim 1 comprising
(1) treating a compound of Formula 4
wherein R 3 is C 1 -C 4 alkyl;
with a halogenating agent to form a compound of Formula I; and when preparing compounds of Formula I wherein R 3 is H
(2) converting the compound formed in (1) to a compound wherein R 3 is H.
5. The method of claim 4 wherein n is 1 to 3.
6. The method of claim 4 wherein R 1 is Cl or Br; each R 2 is independently Cl or Br, and one R 2 is at the 3-position; R 3 is C 1 -C 4 alkyl; and X is N.
7. The method of claim 6 wherein the halogenating agent is a phosphorus oxyhalide or a phosphorus pentahalide.
8. The method of claim 7 wherein step (1) is carried out in the absence of a base using acetonitrile as the solvent.