Propargylic ethers, hydrostannation

Chlorodi- -butyltin hydride (Bu2SnClH) promotes regio- and stereo-selective hydrostannation of propargylic ethers without any additives or catalysts to give /3-(Z) adduct as single isomer (Equation (34)). Effective coordination of ether oxygen to tin moiety determines the selectivity.100,101... 

Most attention to date has been paid to the hydrostannation of propargyl alcohols and ethers where interaction of the Lewis-basic oxygen enhances the regio- and stereoselectivity and gives high yields of the Z-/3-adducts (e.g., Equations (20) and (21)), whereas hydrostannation with Bu3SnH gives only the Z-cr-adducts. 

In the case using Mo(CO)3(ButNC)3 as a catalyst, propargylic alcohols and ethers undergo highly regioselective a-hydrostannation regardless of their substitution pattern (Equation (33))."... 

Hydrostannation. Enestannanes from acetylene derivs. An equimolar amount of NaBH4 in ethanol added dropwise to tri-n-butyl-tin chloride in abs. ethanol, stirred 10 min. at 25°, propargyl 2-tetrahydropyranyl ether added, and refluxed 3.5 hrs. -> trans-3-tri-rt-butylstannyl-2 -propenyl 2-tetrahydropyranyl ether. 

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