Substituted Benzoxazolyl 3,4-Dihydropyrimidine (1H)-(Thio)-ones. -The classical Biginelli reaction is extended to the use of N-substituted benzoxazolyl (thio-)semicarbazides as intermediates. -(PANI*, M. S.; ARJUN, M.; SRIDHAR, D.; SRINIVAS, K.; RAVIPRASAD, T.; Chin. Chem. Lett. 20 (2009) 8, 909-912; Dep. Pharm., Kakatiya Univ., Warangal 506 009, India; Eng.) -R. Simon 52-171
An efficient synthesis of benzoxazole‐substituted 3,4‐dihydropyrimidinones (DHPMs) using alumina supported trifluoromethane sulfonic acid as the catalyst for the first time from an aldehyde, β‐keto ester, and benzoxazole‐substituted urea and thiourea under solvent‐free conditions is described. When compared with the classical Biginelli reaction conditions, this new method consistently has the advantage of excellent yields (80–93%) and short reaction time (30–120 minutes) at 120°C temperature. J. Heterocyclic Chem., 46, 119 (2009).
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