Stille reaction

In organic chemistry, the Stille reaction couples a stannane with an aryl, benzyl, vinyl halide or triflate. This reaction has several components that make it a unique and useful synthesis reaction.

History

The Stille Reaction is a recent discovery in ths scope of chemical science. The reaction has only been around sicne 1977. In a survey conducted in 1992, it was reported that Stille Reactions were used in 50% of all cross-coupling reactions reported.

Properties

-Stille Reactions are unique and convenient for they require mild reaction conditions and produce high yields. It is also capable of forming carbon-carbon bonds under neutral conditions. In addition, it is compatible with all functional groups without protection. This is because most stannanes are rather stable in moisture and air, and therefore do not react with most of the fucntional groups This idea is further depicted under the products section. These properties have led to many applications within the organic field, including, but not limited to the synthesis of:

Amphidinolide A

Sanglifehrin A

Callipeltoside A

-In overview:

R₁-X + R₂-M → R₁-R₂ + M-X

R₁ and R₂ have sp2 hybridization as in a phenyl or vinyl substituent
M is often tin but can also be boron, zirconium or zinc
the catalyst is based on palladium

-The addition of silver salts, copper, and lithium chloride can influence Stille Coupling. Several reagents used in industrial synthesis using Stille Reactions can be reviewed under the industrial reagents sub-heading.

Products

The different products from all combinations of halides and stannanes resulting from Stille Reactions are depicted below:

__________Electrophiles __________________Stannanes_________

File:Stille rxn.jpg

The Stille Reaction is also a very useful synthesis for requisit of tin reagents over other organometallic reagents. Again, this makes a pleasing route for the formation of carbon-carbon bonds in nuetral conditions. This is improtant within polymer chemistry and its effects can be observed with the recent emergence of solid- [41-43] and fluorous-phase [44,45] approaches.[1]

Mechanism

Thank you ecompound for producing this proposed mechanism of a Stille Reaction. As you can see from the image below, this reaction is a versatile system. It serves as a terrific reaction for the formation of carbon-carbon bonds. It is important, as well as interesting, to note the broadness of the reaction pathway shown. Although the Stille Reaction is a commonly repeated and useful synthesis reaction, some of the intermediates and exact locations of active sites have been widely debated. Also, the mechanism may change depending upon the different reaction conditions. Therefore, a less detailed, but more accurate mechanism pathway is shown.

File:Stille coupling mechanism.gif

Industrial Reagents

Below are commonly used catalytic reagents by Acros Organics for Stille Coupling reactions in organic synthesis. Most Industrial syntheses utilize aryl chlorides for the selected reagent since it is more abundant and less expensive than alternative iodides, and aryl bromides.

File:Reagent acros.jpg

External links

--Rhetro29 07:19, 6 February 2006 (UTC)

--Joshua R. Allen (UIUC)