Hydrostannylation of Propargylic Alcohols Using Mixed Tin Hydrides

Abstract

The hydrostannylation of a series of alkynols and propargylic ethers with mixed tin hydrides Bu2SnHCl and Bu2SnHBr has been studied. These highly reactive tin hydrides undergo radical chain reactions at low to ambient temperatures (−78 °C to 25 °C). Their higher Lewis acidity (in comparison with the most commonly used hydrostannylation reagent Bu3SnH) leads to much better regio‐ and stereoselectivities irrespective of the size and nature of the substituents in the propargylic position. Hydrostannylation of terminal propargylic alcohols and ethers gives almost solely (> 90 %) the products of anti‐addition; these are stabilized by intramolecular coordination. When non‐terminal propargylic alcohols are used, the isomerisation to the thermodynamically favoured syn‐addition product, which normally takes place in free radical hydrostannylations, can be prevented by choosing appropriate reaction conditions. Hydrostannylation of allyl propargyl ether shows that these reagents are highly chemoselective towards C−C triple bonds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Short communication: Stille coupling reactions of functionalized triorganotin halides

“…6,7 These reactions lead, for example, to allylic alcohols bearing a terminal halodibutylstannyl group. The products show intramolecular coordination of the alcohol oxygen with the tin, 5,8 and, as expected, the products do not undergo Stille couplings under standard conditions (data not shown).…”

“…Again, no Sn-F coupling was observed in all cases, so that we have no clear evidence of replacement of bromine by fluorine on adding TBAF. It is obvious that NMP breaks down the intramolecular coordination in the organotin, 5 and that the largest high-field shift is observed on adding the second equivalent of TBAF in both solvents, whereas the third has little effect. Thus, it can be speculated that two fluorine atoms (and presumably one NMP, compare Tables 2 and 3) are involved in the reaction.…”

“…E-mail: thiele@chemie.uni-leipzig.de Contract/grant sponsor: Fonds der Chemischen Industrie. hydrides of the type Bu 2 SnHX (X = Cl, Br), 5 compounds that have recently exchanged their previous role of laboratory curiosities for one of synthetically valuable reagents, thanks in particular to the work of Shibata and co-workers. 6,7 These reactions lead, for example, to allylic alcohols bearing a terminal halodibutylstannyl group.…”

Synthesis of Tin‐Containing Cyclodextrins as Potential Enzyme Models

“…In spite of this, there are examples in literature of radical hydrostannylation of alkenes17,18 and, specifically, the addition of tin hydride to allyl ethers has been reported previously 4b,19. However, because alkynes are known to be more reactive in radical hydrostannylation than their alkene counterparts,20 these were tried. Indeed, when the corresponding 6 A ‐propargyl ether β‐cyclodextrin derivative 10 was heated to 60 °C in toluene with Me 2 SnClH, in the presence of AIBN, full conversion into cyclodextrin‐supported tin derivatives 17 and 18 was observed (Scheme ).…”

Synthesis of cis-vinyltrimethylstannanes and cis-vinylpinacolboronates in a two-step highly regio and stereoselective process

“…5 To date, only a few methods have been reported to tolerate oxygen functionality in the synthesis of cis-vinylstannanes. Unfortunately, most of these methods suffer from limitations, e.g., high cost, 9 substrate dependence in order to exhibit high (Z)-stereoselectivity, 11,12 and loss of stereochemistry in isolated cases. 7a In the case of cis-vinylboronates, a limited number of synthetic methods are available which have seen varying degrees of utilization.…”