NITROGEN-HETEROCYCLES BY PALLADIUM-CATALYZED OXIDATIVE CYCLIZATION-ALKOXYCARBONYLATION OF ACETYLENIC UREAS

Acetylenic ureas readily undergo oxidative cyclization-alkoxycarbonyla tion reactions in the presence of PdI2 (or Pd/C)-KI as catalyst in met hanol under mild conditions (65 degrees C and 24 bar of a 3:1 mixture of CO and air). Cyclization occurs by trans-attack of oxygen or cis-at tack of nitrogen functions on the triple bond, followed by stereospeci fic carbonylation, resulting in E or Z-stereochemistry, respectively. In the case of diacetylenic ureas condensed ring formation occurs. The triple bond can also react stereospecifically with carbon monoxide an d methanol to form a maleic group by cis-attack leading to Z-stereoche mistry. (C) 1998 Elsevier Science S.A. All rights reserved.