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Efficient Approaches for the Synthesis of Substituted Thiazolo[3,2‐ a ]‐benzimidazole‐Phosphonates and ‐Phosphinic Diamide Derivatives
Author(s) -
Abdou Wafaa M.,
Shaddy Abeer A.,
Khidre Maha D.
Publication year - 2016
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201601310
Subject(s) - chemistry , phosphonate , moiety , benzimidazole , reagent , intramolecular force , yield (engineering) , medicinal chemistry , alkyl , stereochemistry , michael reaction , tris , organic chemistry , catalysis , biochemistry , materials science , metallurgy
Phosphrylation of E ‐3‐(dimethylamino)‐1‐(3‐methylbenzo[ d ]‐thiazolo[3,2‐ a ]imidazol‐2‐yl)‐prop‐2‐en‐1‐one ( 1 ) and 1‐(3‐methylbenzo[ d ]thiazolo[3,2‐ a ]imidazol‐2‐yl)ethanone ( 12 ) was studied in detail. The enaminone ( 1 ) reacted with trialkyl phosphites, dialkylphosphonates, and tris(dialkylamino)‐phosphines to afford the corresponding ( E/Z ) thiazolobenzimidazol‐3‐oxoprop‐1‐enyl‐phosphonate and phosphonic diamides. The reactions proceeded via phospha‐Michael (P‐Michael) addition reaction, followed by extrusion of HNMe 2 moiety and intramolecular migration of the phosphono‐alkyl group. Only the major E ‐isomer of the respective oxopropenyl phosphonates was isolated by fractional crystallization (∼ 65% yield) in a pure form whereas the two isomers were chromatography separated and identified in the second case of the respective phosphonic diamide mixtures. The trans ‐configuration is also confirmed by nuclear Overhauser effect (N O E) experiments. On the other hand, substituted thiazolobenzimidazole‐ α ‐hydroxyphosphonate‐ and α ‐hydroxyphosphinic diamide derivatives were produced from the reaction of the 2‐acetyl thiazolo[3,2‐ a ]benzimidazole ( 12 ) with the same P( III ) reagents via Abramov 1, 2‐addition reaction.