Nonclassical Pschorr and Sandmeyer reactions in pyrazole series

The diazonium salt derived from 4-amino-N,1,3-trimethyl-N-(3-methyl-1-phenyl-IH-pyrazol-5-yl)-1H-pyrazol e-5-carboxamide (14) was reacted with a mixture of CuSO4 and NaCl, with ascorbic acid as an initiator to afford the planar derivative 4,6-dihydro-1,4,6,8-tetramethyl-3-phenyldipyrazolo[3,4-b:4',3'-d]pyridin -5(3H)one (16) and its unexpected isomer 4,6-dihydro-3,4,6,8-tetramethyl-l-phenyldipyrazolo[4,3-b:4',3'-d]pyridin -5(1H)-one (17), as well as the epimers (3S,4S)- (or (3S,4R)-) and (3S,4R)- (or (3S,4S)-) 4-chloro-2,4-dihydro1',3',5,5'-tetramethyl-2-phenylspiro[pyrazole-3,4'(1 H)-pyrrolo[3,4-pyrazol]-6'(5'H)-one (18a and b, respectively). Epimers 18a and b were converted under basic conditions to 4'-chloro-N,1,3,3'-tetramethyl-l'-phenyl[4,5'-bi-1H-pyrazole]-5-carboxam ide (19). The structures of isomers 16 and 17 determined by single-crystal Xray analysis are also reported. Linear dichroism (LD) measurements for the above isomers suggest that 17 intercalates into DNA, and 17 exhibited antiproliferation activity against human NCI-H460 pulmonary carcinoma cells.