The vilsmeier reaction in the synthesis of 3‐substituted [1]benzopyrano[4,3‐ b ]pyridin‐5‐ones. An unusual pyridine ring closure
1995; Wiley; Volume: 32; Issue: 2 Linguagem: Inglês
10.1002/jhet.5570320221
ISSN1943-5193
AutoresDieter Heber, Ivo C. Ivanov, Stoyan K. Karagiosov,
Tópico(s)Synthesis and biological activity
ResumoAbstract Starting from 4‐chlorocoumarin‐3‐carbaldehyde (1) and Wittig phosphoranes 2a‐d the title compounds 6a‐c have been synthesized via a four‐step sequence. The intermediate 4‐alkylamino‐3‐vinylcoumarins 5a‐k have been prepared by the reaction of 4‐chloro‐3‐vinylcoumarins 3a‐d with primary amines 4a‐h . The coumarin derivatives 5 (except 5k ) underwent an unusual pyridine ring closure under Vilsmeier conditions to form the benzopyrano[4,3‐ b ]pyridines 6 . When the aminoaldehydes 7 were treated with the Wittig reagent 2b the fused N ‐alkyl‐2 (1 H ) ‐pyridinones 8 have been obtained as expected.
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