A series of selenothioic acid
S-esters and diselenoic acid esters have been synthesized by the following three types of methods : (1) reactions of terminal acetylenes with
n-butyllithium, selenium and thiols; (2) reactions of selenoic acid
O-methyl esters with aluminum chalcogenolates; (3) reactions of selenothioacetic acid
S-esters with aldehydes and/or allylic bromides in the presence of a base. On the basis of synthetic results, the general trends for the relative stability of the esters have been proposed. Among several types of esters, one of the most simple esters, i.e., selenium and sulfur counterparts of acetic acid esters are the most stable. The introduction of aromatic substituents does not necessarily enhance the stability of the esters. Reactions of the esters toward heavy metal salts, such as nickel chloride, zinc iodide, and cadmium acetate, electron deficient alkynes, and reducing agents provided new synthetic methods of a variety of organoselenium compounds.
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