in ethanol; toluene according to: M. Boualam et al., Appl. Organomet. Chem. 4 (1990) 335; addn. of diorganotin oxide to soln. (toluene/ethanol 4:1) of 3-amino-4-methylbenzoic acid (molar ratio 2:1), refluxing (4 h), azeotrop distn.; evapn. (red. pressure), recrystn. (chloroform/petroleum ether);