121358-75-6Relevant academic research and scientific papers
Pyrazole Chemistry. Part 4. Directed Lithiation of 4-Bromo-1-phenylsulphonylpyrazole: a Convenient Approach to Vicinally Disubstituted Pyrazoles
Heinisch, Gottfried,Holzer, Wolfgang,Pock, Sabine
, p. 1829 - 1834 (2007/10/02)
4-Bromo-1-phenylsulphonylpyrazole (10), obtained from 4-bromopyrazole (5) and benzenesulphonyl chloride, can be metallated regioselectively by phenyl-lithium to give the 5-lithio derivative (15) which upon quenching with appropriate electrophiles leads to the 4-bromo-1-phenylsulphonyl-5-substituted pyrazoles (16)-(23), (25), and (26).Compounds (22), (23), and (25) were found to undergo isomerisation to afford the thermodynamically more stable 4-bromo-1-phenylsulphonyl-3-substituted pyrazoles (11), (24), and (13) under the reaction conditions applied.The phenylsulphonyl protecting group then can be removed readily under alkaline conditions to yield the corresponding 4-bromo-3(5)-substituted 1H-pyrazoles (6), (9), (28), (29), and (30).
PYRAZOLES 3. N-1 PROTECTED 4-SUBSTITUTED PYRAZOLES - SYNTHESIS AND NMR INVESTIGATION
Heinisch, Gottfried,Holzer, Wolfgang
, p. 2443 - 2458 (2007/10/02)
13C-Nmr Data (chemical shifts, substituent chemical shifts (SCS), coupling constants) are reported for 26 1,4-disubstituted pyrazoles, bearing a benzyl, benzoyl or (substituted) benzenesulfonyl protecting group at N-1.The pyrazole derivatives 8a-d were pr
