A new catalytic cross-coupling approach for the synthesis of protected aryl and heteroaryl amidines.
[reaction: see text] A new method for the synthesis of protected benzamidines is described. The commercially available 1,3-bis(tert-butoxycarbonyl)-2-methyl-2-thiopseudourea guanidylation reagent, after SEM-protection, functions as an amidine-forming cross-coupling partner under Liebeskind-Srogl conditions. In the presence of copper(I) thiophenecarboxylate (CuTC), the palladium-catalyzed cross-coupling of the SEM-protected thiopseudourea reagent with boronic acids affords fully protected benzamidines in good to excellent yield (40-91%).
Kusturin
Carrie L
CL
Chemistry and Process Technology, Pharmacia Corporation, 800 North Lindbergh, St. Louis, Missouri, USA.
Liebeskind
Lanny S
LS
Neumann
William L
WL