Abstract
Regio- and stereospecific electrophilic addition reactions of
selenium tetrachloride and selenium tetrabromide to propargyl alcohols
are reported. (Z ,Z )-Bis(β-chlorovinyl)selenium
dichlorides were isolated in high yields, and their reactivity was
dependent on their substitution pattern. Products derived from unsubstituted, α-methyl-,
or α,α-dimethylpropargyl alcohols readily underwent transfer
of chlorine atoms to one of the two double bonds. (Z ,Z )-Bis(β-chlorovinyl)selenium
dichlorides derived from γ-phenyl- or γ-isopropenylpropargyl
alcohols underwent cyclization to form benzoselenophene derivatives;
this was accompanied by the formation of the corresponding dichloro-substituted
allylic alcohols. In contrast, selenium tetrachloride reacts with γ-phenylpropargyl
alcohol exclusively as a chlorinating agent, giving (3-chloroprop-1-yn-1-yl)benzene
quantitatively. Products of regio- and stereospecific electrophilic
addition of selenium tetrabromide are also described. Reaction mechanisms
are proposed.
Key words
electrophilic additions - alkynes - alcohols - selenium - halides
