Propargylic alcohols hydrostannation

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))."... 

Dihydro-l,2-oxastannole 204 undergoes a similar exchange with phenylboron dichloride to afford 2,5-dihydro-1,2-oxaborole 205 <20040M5088>. This synthesis is particularly convenient since the tin compound can be easily prepared by the hydrostannation of propargyl alcohol (Scheme 28) <1973SRI1>. 

Allenyltins are conveniently prepared from the terminal alkynes which have a suitable leaving group. An example is shown in equation 19. A two-step one-pot procedure for the synthesis of allene by hydrostannation of alkynes has recently been reported starting from propargylic alcohols a hydrostannation and subsequent deoxystannylation generates the allenes 6 as shown in equation 20. A chiral version of this procedure has also been described in the paper. 

Hydrostannation of AU nols. Dibutyl(trifluoromethan-sulfoxy)stannane was first introduced as a reagent for hydrostannation of alkynols other than propargyUc alcohols. The authors had previously descrihed the use of Bu2SnHCl for the Iree radical hydrostannation of propargylic alcohols (eq 1 ). A key controlling element in this methodology was coordination of the tin center to the oxygen atom, which allows for suppression of isomerization of the Z- to i -vinylstannane (eq 2). ... 

When the alkyne moiety of a propargyl alcohol is internal rather than terminal, the nature of the flanking substituent can influence the regiochemistry of the hydrostannation when Bu2SnHCl is... 

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