RESUMO
Various thiomethyl-substituted N-heterocycles (pyridines, pyrimidines, pyrazines, pyridazines, triazines, benzothiazoles, benzoxazoles, pyrazoles, benzindazoles, quinazolines, etc.) undergo smooth Pd-catalyzed cross-coupling reactions with functionalized aryl-, heteroaryl-, benzylic-, and alkylzinc reagents using Pd(OAc)(2)/S-Phos as the catalytic system mostly at 25 degrees C. No copper salt is required to perform these reactions.
RESUMO
The full functionalization of the pyrazole ring was achieved by successive regioselective metalations using TMPMgCl x LiCl and TMP(2)Mg x 2 LiCl. Trapping with various electrophiles led to trisubstituted pyrazoles. An application to the synthesis of the acaricide Tebufenpyrad is reported.
Assuntos
Compostos Organometálicos/química , Pirazóis/síntese química , Pirazóis/químicaRESUMO
A single Br/Mg exchange of 1,2-dibromocyclopentene with iPrMgCl LiCl provides the corresponding beta-bromocyclopentenylmagnesium reagent, which can then be reacted with various electrophiles (yields: 65-82 %). In the presence of a secondary alkylmagnesium halide and Li2CuCl4 (2 mol %), these 2-bromoalkenylmagnesium compounds undergo bromine substitution and can then further react with electrophiles to give 1,2-difunctionalised cyclopentenes (63-79 %). The mechanism of this process is discussed.