Allene chemistry. VIII. Diaddition of thiol compounds to allene

The radical-type diaddition of simple aliphatic and aromatic thiols, thiolacetic acid, dialkyldithiophosphoric (phosphorodithioic) acids, 2-mercaptoethanol, mercaptoacetic acid, 2-mercaptopropionic acid, and their esters to allene was studied. In general, such diadditions were found to be better than known metathetical reactions for the large-scale synthesis of trimethylene bis-sulfide compounds, the products of terminal diaddition. The various types of thiol compounds differ widely in their reactivity towards allene. A comparison of the data for t-butane- and benzene-thiol addition suggests that, in general, the amount of branched diadducts from monoadditions is directly proportional to the hydrogen-donor ability of the thiol, and that the amount of the allylic monoadduct formed is proportional to the stability of the thiyl radical.