Preparation of Lithium 5-Lithiomethyl-3-methylpyrazole-1-carboxylate and its Reaction with #alpha#-Oxoketene Dithioacetals: A New General Method for Substituted and Annelated Pyrazolo[1,5-a]pyridines

摘要

5-Methylpyrazole derivative 1 is metallated at the C-5 methyl carbon atom to form lithium 5-lithiomethyl-3-methylpyrazole-1-carboxylate 3 which on reaction with #alpha#-oxoketene dithioacetals 4a-d, 12a-c and 15a-b yields substituted and annelated pyrazolo[1,5-a]pyridines 7a-d, 13a-c and 16a-b.