Cl, --I, and --CH.sub.2 CO.sub.2 H and methyl; and the aromatic stannane is a compound represented as (R.sub.y).sub.3 Sn--R.sub.10wherein R.sub.y is either n-butyl or methyl; R.sub.10 is a radical selected from a group consisting of one of the following structures: ##STR7## ##STR8## ##STR9##and (in a broader aspect of the invention) ##STR10##wherein Rx is acyl, especially lower alkanoyl, such as a