1-Trimethylgermyl-1-alkynes easily prepared by deprotonation of terminal alkynes with n-butyllithium in ether at low temperature readily undergoes hydroboration with dichloroborane-dimehyl sulfide complex in n-pentane at zero degrees for 2 h in the presence of boron trichloride. The supernatant pentane layer was separated under nitrogen atmosphere. It was then treated with 1,3-propane diol at zero degrees and stirred for an hour. The resulting alpha trimethylgermyl -1- alkenylboronate esters are subjected to Suzuki coupling in the presence of potassium carbonate , Dimethylformamide , tetrakis(triphenylphosphine)palladium, and p-methoxyphenyl magnesium bromide and the reaction mixture is refluxed for 3 h. After workup, the corresponding (Z)-trisubstituted alkenes containing trimethylgermyl and p-methoxyphenyl moieties are isolated in 72%-82% yields. The compounds are purified by column chromatography over alumina  and the structures are confirmed by spectral data (PMR and CMR).

Highly diastereoselective synthesis of (Z)-trisubstituted alkenes containing 1-trimethylgermyl and 1-p-methoxyphenyl moieties via organoboranes

ACS Spring 2022

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