sg3524,sg3526 are not intended to be used as pure sine wave, but can be used as modified sine wave. Sine wave purity depends upon the filter output. You can refer to this... http://www.ee.nmt.edu/~erives/382_10/FR_NotPl.pdf
If you tried to convert the output square wave to sine wave with a filter, you would likely be unhappy with the result. Instead of converting the square wave to sine wave, it's better you use sinusoidal pulse-width modulation to drive a MOSFET bridge and then filter that output with LC filter. You can get pure sine wave through this.