Brønsted Acid-Promoted Sequential Hydroarylation- Hydroamidation of Arene-Tethered 1-(2-Alkynylphenyl)ureas: Direct Access to 4,4-Spiro-3,4-dihydro-2-(1H)-quinazolinones
A Brønstedacid-promoted approach to 4,4-sipro-3,4-dihydro-2-(1H)-quinazolinones from arene-tethered1-(2-alkynylphenyl)ureas has been developed. The reaction is initiated by intramolecular hydroarylation followed by hydroamidation, assisted by intramolecular proton transfer from the protonated urea moiety. A variety of tethering atoms, including carbon, oxygen, sulfur, and protected nitrogen are compatible
An efficient synthesis of 4-alkyl-2(1H)-quinazolinones has been achieved by cyclization of 1-(2-alkynylphenyl)ureas (2 R-2 = alkyl) in dichloroethane catalyzed by TfOH. In the case of aryl substitution (2 R-2 = aryl), a mixture of quinazolinone tautomers is obtained in dichloroethane with TFA as co-solvent. Chlorination of the resulting mixture affords 4-alkyl-2-chloro-quinazolines as sole products. (C) 2009 Elsevier Ltd. All rights reserved.