Syntheses and applications of vinylstannanes

The development of methods for the synthesis of vinylstannanes is reported. The applications of these useful compounds are highlighted in a variety of total syntheses of natural products.;Trans-1-stannyl-1-alkenes were prepared in high regioselectivity (95:5, trans:gem) from unhindered 1-alkynes by using Pd 2dba3/Cy3PHBF4/i-Pr 2NEt on a wide range of terminal alkynes. This system exhibited higher selectivities and yields for trans-vinylstannanes than the original PPh3-based catalysts that are widely adopted. Contrary to popular belief, it was found that ligands have a dramatic effect on the regioselectivity of palladium-catalyzed hydrostannations of 1-alkynes. Steric and electronic arguments were used to explain the observed regioselectivities. An insect sex pheromone was synthesized using the hydrostannation methodology that was developed. An inseparable 95:5 mixture of trans and geminal vinylstannanes did not pose a problem during the synthesis, as the geminal isomer did not participate in the Stille coupling.;A two-step synthesis of trans-1-stannylbutadiene, as an extension of hydrostannation of terminal alkynes, is reported. A convergent synthesis of a trienic sex pheromone was demonstrated as a convenient route to this class of compounds.;Another extension of hydrostannation chemistry, synthesis of trans-vinyl iodides in excellent selectivities (95:5 to 99:1 trans:gem) in a one-pot procedure from unhindered terminal alkynes, is reported. Purities of trans-vinyl iodides were improved from the hydrostannation regioselectivity of 95:5 to 99:1 by using less than 1 equivalent of iodine to quench the reaction. Two dienyl sex pheromones were synthesized to illustrate the application of this methodology. Also, inseparable 95:5 mixture of trans and geminal vinyl iodides did not pose a problem during the syntheses, as the geminal isomer did not participate in the Sonogashira couplings.;Cyclic and acyclic vinylstannanes were prepared conveniently in a simple one-pot procedure from the corresponding ketones. The scope of ketones was illustrated and the limitations were highlighted. Moderate to high yields of vinylstannanes are reported that compare favourably with other methods. Two cases of unsymmetrical ketones provided the less substituted vinylstannanes. A straight-forward purification procedure was developed for non-polar vinylstannanes that allowed for the separation from Bu3SnH contamination.;Trans-1-stannylbutadiene was able to undergo Diels-Alder reactions with various cyclic, five-membered ring, doubly activated dienophiles. Enantioselective Diels-Alder reaction was obtained in 33% ee by using a Mikami catalyst. The allylstannane from a racemic Diels-Alder reaction was able to undergo allylstannation with an aldehyde and a ketone using SnCl2/MeCN or SnCl4/CH2Cl2 systems to provide gamma-addition products as the major isomers with high diastereoselectivity. A diastereoselective Diels-Alder reaction was effected by using Waldner's chiral dienophile to provide isomeric allylstannanes in a 10:1 ratio; the major product could be purified by flash chromatography. A Diels-Alder/allylstannation sequence was achieved with Waldner's dienophile and trans-1-stannylbutadiene to provide a pure functionalized cyclohexene in 60% yield in a one-pot procedure.