Selectivity in Garratt–Braverman Cyclization of Aryl-/Heteroaryl-Substituted Unsymmetrical Bis-Propargyl Systems: Formal Synthesis of 7′-Desmethylkealiiquinone
作者:Joyee Das、Raja Mukherjee、Amit Basak
DOI:10.1021/jo402749d
日期:2014.5.2
various combinations of aryl/heteroaryl substituents at the acetylene termini were synthesized, and their reactivity under basic conditions was studied. Moderate to high (chemo)selectivity was observed, which followed a trend opposite to that reported earlier for the corresponding sufones. The major products obtained in most cases (except with indole) were formed viaparticipation of the heteroaryl ring
A green protocol (compared to the existing methodology) for carrying out Garratt-Braverman cyclization has been developed. The method involves stirring a pre-absorbed bispropargyl sulfone/ether/sulfonamide over basic alumina. The reaction with sulfones was over within 10-15 mm at room temperature whereas for the ether/sulfonamide the reaction took 6-8 h at 130 degrees C. The products, aryl naphthalene derivatives, are obtained by simple filtration through Celite, in excellent yields. (C) 2014 Elsevier Ltd. All rights reserved.