1-Phenylselenyl-1-alkynes readily prepared from terminal alkynes by reacting with n-butyllithium followed by phenylselenyl bromide, are hydroborated with dichloroborane -dimethyl sulfide complex in the presence of boron trichloride in n-pentane at zero degrees. The n-pentne laye r is isolated and treated with 1,3-propane diol. The resulting (Z)-1-alkenylboronate esters are treated with solid potassium-tert-butoxide followed by treatment with copper (I) bromide at lower temperature the resulting transmetallated product is then treated with 1-bromo-1alkynes at lower temperature. After workup, followed by purification over column chromatography the corresponding 1,3-alkynynes are obtained in 70%-75% isolated yield. The structures are confirmed by PMR spectroscopy.

Highly diastereoselective synthesis (Z)-3-phenylselenyl-1,3 alkenynes via orgnoboranes

ACS Spring Meeting 2021

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