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Tetracyclic phenothiazines. VI . Attempted pummerer cyclization of 10‐(2‐Keto‐3‐methylsulfinylpropyl)phenothiazine
Author(s) -
Vishwakarma L. C.,
Martin A. R.
Publication year - 1982
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.5570190118
Subject(s) - phenothiazine , chemistry , pummerer rearrangement , carbanion , yield (engineering) , condensation , medicinal chemistry , catalysis , organic chemistry , medicine , acetic anhydride , physics , pharmacology , thermodynamics , materials science , metallurgy
The title compound ( 3 ), a β‐ketosulfoxide prepared by a Claisen‐type condensation of ethyl 2‐(10‐phenothiazino)acetate ( 4 ) with dimsyl carbanion, was subjected to a variety of catalysts in attempts to achieve a Pummerer cyclization to 1,2‐dihydro‐3‐methylthio‐2‐oxo‐3 H ‐pyrido[3,2,1‐ kl ]phenothiazine ( 2 ). Although the Pummerer rearrangement product, 10‐(2‐oxo‐3‐hydroxy‐3‐methylthiopropyl)phenothiazine ( 5 ), could be obtained in excellent yield under mild conditions, neither it nor the β‐ketosulfoxide could be successfully cyclized under any of the conditions attempted. Instead, phenothiazine, 2‐hyroxy‐3‐(10‐phenothiazinyl)‐2‐propen‐1‐al ( 7 ), 3‐(10‐phenothiazinyl)‐1,1‐di(methylthio)propan‐2‐one ( 8 ), 3‐(10‐phenothiazinyl)‐1‐methylthiopropan‐2‐one ( 9 ) and 10‐phenothiazinylformamide ( 10 ) were variously obtained.