Sonogashira-Type Reactions with 5-Chloro-1-phenyl-1H-pyrazole-4-carbaldehydes: A Straightforward Approach to Pyrazolo[4,3-c]pyridines

作者：Vilkauskaite Gyte; Sackus Algirdas^*; Holzer Wolfgang

来源：European Journal of Organic Chemistry, 2011, (26): 5123-5133.

DOI：10.1002/ejoc.201100626

• Nitrogen heterocycles
• C-C coupling
• Palladium
• Cyclization

The easily obtainable 5-chloro-1-phenyl-1H-pyrazole-4-carbaldehydes 2 were used as precursors in Sonogashira-type cross-coupling reactions with various alkynes to provide the corresponding 5-alkynyl-1H-pyrazole-4-carbaldehydes 3. Treatment of these with tert-butylamine with microwave assistance afforded the corresponding 1-phenylpyrazolo[4,3-c]pyridines 4. The oximes 5 - derived from the aldehydes 3 - were transformed into the corresponding 1-phenylpyrazolo[4,3-c]pyridine 5-oxides 6 through silver-triflate-catalysed regioselective cyclisation. Ring closure of the oximes 5 in the presence of iodine in ethanol gave the 7-iodo-1-phenylpyrazolo[4,3-c]pyridine 5-oxides 7. Detailed NMR spectroscopic investigations were undertaken with all obtained products.

• 出版日期2011-9