Stoichiometric Auxiliary Ligands for Metals and Main Group Elements: Ligands for Tin and Stannanes☆

Methodologies Limiting or Avoiding Contamination by Organotin Residues in Organic Synthesis

“…Despite the versatility of organotin reagents and their possible use in asymmetric synthesis, 44 their applications have been strongly hampered by the difficulty to remove organotin residues from final products combined with the high toxicity of some of them. 45−51 Thus, Me 3 SnX or Et 3 SnX are highly toxic for animals and humans as underlined by the disaster encountered with the pharmaceutical preparation "Stalinon", 52 while most of them, like tributyltin derivatives, are moderately toxic (LD 50 generally over 150 mg/kg) despite their impact on environment as algaecides or molluscicides.…”

“…Despite the versatility of organotin reagents and their possible use in asymmetric synthesis, their applications have been strongly hampered by the difficulty to remove organotin residues from final products combined with the high toxicity of some of them. − Thus, Me 3 SnX or Et 3 SnX are highly toxic for animals and humans as underlined by the disaster encountered with the pharmaceutical preparation “Stalinon”, while most of them, like tributyltin derivatives, are moderately toxic (LD 50 generally over 150 mg/kg) despite their impact on environment as algaecides or molluscicides. − Some others such as dioctyltindithioglycolates or other dioctyltin esters are nearly nontoxic compounds (in terms of acute toxicity) and have been used in food or pharmaceuticals wrapping materials . As a general trend, the toxicity decreases upon size increase of the alkyl groups (Me 3 SnX ∼ Et 3 SnX ≫ Bu 3 SnX ≫ Octyl 3 SnX) and upon decrease of the number of alkyl groups (R 4 Sn ∼ R 3 SnX > R 2 SnX 2 > RSnX 3 ) .…”