ammonium chloride; zinc in tetrahydrofuran; water appropriate alkyltin chloride is added to THF/H2O mixt. with excess of zinc powder, appropriate allyl bromide is added dropwise under stirring within 5 min, mixt. is stirred for 30 min; extn. (petroleum ether), separated org. layer is washed (aq. NaCl), drying (MgSO4), solvent is removed, distn., mixt. of isomers 3-methyl-1-buten-3-yltributyltin and 2-methyl-2-butenyltributyltin ratio 40:60; total yield 62percent;