A novel approach to inherently chiral calix[4]arenes by direct introduction of a substituent at the meta position

A novel method for the preparation of inherently chiral calix[4]arenes is described by direct introduction of a substituent in para-acetamido substituted calix[4]arenes. Bromination and nitration of mono(acetamido)calix[4]arenes 5, 6 afforded calix[4]arenes 7¿10, in which the substituent was selectively introduced adjacent to the acetamido moiety, in 58¿98% yield. Bromination of bis(acetamido)calix[4]arene 13 gave a mixture from which dibromo- (14) and tribromocalix[4]arene 15 were isolated in 10% and 22% yield, respectively. The structure of 14 was confirmed by single-crystal X-ray structure determination. Nitration of 13 gave 4,16-dinitro- (16) and 4,18-dinitrocalix[4]arene 17 in 53% and 18% yield, respectively.