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On the mechanism of the reduction of 1‐phenyl‐3‐(4‐pyridinylmethylene)‐2‐oxindole with sodium borohydride in methanol
Author(s) -
Pierce Michael E.,
Huhn George F.,
Jensen James H.,
Sigvardson Ken W.,
Islam Qamrul,
Xing Yide
Publication year - 1994
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570310103
Subject(s) - chemistry , sodium borohydride , methanol , oxindole , yield (engineering) , diastereomer , adduct , reduction (mathematics) , medicinal chemistry , ring (chemistry) , indole test , organic chemistry , combinatorial chemistry , catalysis , materials science , geometry , mathematics , metallurgy
Abstract Sodium borohydride reduction of 1‐phenyl‐3‐(4‐pyridinylmethylene)‐2‐oxindole 1 in methanol gives a high yield of the oxindole 2 , a precursor to linopirdine. The reduction is accelerated by methanol and the major by‐products during this reduction are the diastereomeric Michael adducts between 1 and 2 and the overreduced products, 9 and 11 . Surprisingly, indole 9 is not derived from further reduction of 2 but is formed concurrently, whereas the ring opened product 11 is the unexpected reduction product derived from 2 .