Conversion of Pyridine N-Oxides to Tetrazolopyridines

Abstract

An efficient and convenient procedure for the conversion of pyridine N-oxides to tetrazolopyridines by treatment with 4-toluene sulfonyl chloride and sodium azide in toluene at elevated temperature is described.

Regioselective Chlorination of Quinoline N‐Oxides and Isoquinoline N‐Oxides Using PPh3/Cl3CCN

“…As shown in Scheme , compound 4 , which has pharmaceutically important activity as a corticotropin releasing factor (CRF) receptor antagonist, is readily synthesized via Suzuki cross‐coupling with 2‐chloroquinoline 16. Additionally, tetrazolo[1,5‐ a ]quinoline ( 5 ), an appealing ligand in coordination chemistry and important pharmaceutical agent,17 is readily generated by treating aryl chloride 2a with NaN 3 in DMF 18. Notably, a compound library of N‐heterocyclic chlorides, accessible by this efficient chlorinating protocol, would be very useful in efforts to develop molecules with potential applications in pharmaceutical and coordination chemistry.…”

Nitrene–Nitrene Rearrangement under Thermal, Photochemical, and Electron‐Impact Conditions: The 2‐Azidopyridines/Tetrazolo[1,5‐a]pyridines

“…1(3)-15 N-Labeled tetrazolo[1,5-a]pyridine 9 (48 atom-% 15 N) was prepared from 2-bromopyridine and end-labeled potassium azide, K 15 NNN. [11] In the mass spectrometer, loss of nitrogen from the molecular ion formally generates 2-pyridylnitrene ([M - 14 The interconverting pyridylnitrene ions 10 and 12 and/or the dienylnitrene ions 4 ·+ can account for this. Ions of glutacononitriles 5 ·+ could conceivably be formed by an H-shift in the dienylnitrene ions 4 ·+ , but the formation of 5 ·+ can be ruled out, because the mass spectra of glutacononitriles exhibit prominent ions at m/z 52 due to loss of CH 2 CN (α-cleavage), which are not seen in the 2-pyridylnitrene spectra.…”

“…Analogous mass spectra have also been obtained with an AEI MS902 instrument using an all-glass inlet system at 50-100°C, and for 1T also with a Varian MAT CH7 instrument. Identical spectra were obtained by using [11] and methyltetrazolo[1,5-a]pyridines [14] were prepared as described previously.…”

Recent Progress in Non‐Catalytic C–H Functionalization of Heterocyclic N‐Oxides

“…In addition to the amination/amidation procedures described above should be noted as a method for the synthesis of tetrazolopyridines. [51] Treatment of pyridine N-oxides with tosyl chloride and sodium azide in toluene proceeds as a usual cinesubstitution forming 2-azidopyridines, which exist in form of tetrazolopyridines (Scheme 27). The reaction proceeded with complete C2-regioselectivity for the 2-and 6-positions adjacent to the pyridine nitrogen.…”