Unprecedented One-Pot Stereoselective Synthesis of Knoevenagel-Type Derivatives via in situ Condensation of <i>N</i>-Methyleniminium Salts of Ethylenethiourea and Ethyleneurea with Active Methylene Reagents
A facile stereoselective synthesis of Knoevenagel-type compounds 8 and 9 was accomplished through a one-pot two-step procedure. The reaction of ethylenethiourea ( 1) and ethyleneurea ( 2) with benzoyl chloride- N, N-dimethylformamide complex in N, N-dimethylformamide gave the corresponding isolable ternary N-methyleniminium chlorides 3 and 4, along with benzoic acid ( 5) as a byproduct. Hydrolysis