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12.5.5.2.2 Method 2: Substitution via Lithiation

DOI: 10.1055/sos-SD-012-00784

Hajos, G.; Riedl, Z.Science of Synthesis, (200212666.

Lithiation of pyrazolo[1,5-a]pyridine (3) takes place at position 7 selectively.[‌213‌] The 7-lithio compound 300 can be quenched with various electrophiles to yield a series of 7-substituted derivatives in excellent yields. Thus, diethyl disulfide gives the 7-ethylsulfanyl compound 301, upon addition of iodomethane the 7-methyl derivative 302 is obtained, 3-(trifluoromethyl)benzaldehyde affords the benzyl alcohol 303, and with chlorotrimethylsilane the 7-trimethylsilyl derivative 304 could be synthesized. These results are illustrated in Scheme 58.

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