New approach toward the synthesis of deuterated pyrazolo[1,5-a]pyridines and 1,2,4-triazolo[1,5-a]pyridines

• Aleksey Yu. Vorob’ev,
• Vyacheslav I. Supranovich,
• Gennady I. Borodkin and
• Vyacheslav G. Shubin

Beilstein J. Org. Chem. 2017, 13, 800–805, doi:10.3762/bjoc.13.80

• and a high degree of deuterium incorporation were achieved. The procedure was applied for several 4-R-1-aminopyridinium cations (R = H, Me, OMe). Keywords: deuteration; 1,3-dipolar cycloaddition; pyrazolo[1,5-a]pyridine; 1,2,4-triazolo[1,5-a]pyridine; Introduction Isotopically labeled compounds find

• years deuteration became also an efficient tool in drug design [6]. Pyrazolo[1,5-a]pyridine and 1,2,4-triazolo[1,5-a]pyridine scaffolds attracted significant attention to the medicinal chemistry community during the past decade. For example, pyrazolo[1,5-a]pyridine derivatives were used in the design of

• dimethyl acetylenedicarboxylate (2a, DMAD) in MeCN D-labeled pyrazolo[1,5-a]pyridine 3 was obtained in 70% yield (Table 1). The deuteration at room temperature even for 24 h led to a significantly lower degree of deuteration (DD, 20%). Salt 1b gave the corresponding 5-CD3-7-D-pyrazolopyridine 5 along with