Tributyl(1-ethoxyvinyl)stannane
[CAS 97674-02-7]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organotin
• Name: Tributyl(1-ethoxyvinyl)stannane
• Synonyms: 1-Ethoxyvinyltributyltin
• Molecular Formula: C₁₆H₃₄OSn
• Molecular Weight: 361.15
• CAS Registry Number: 97674-02-7
• EC Number: 641-308-0
• SMILES: CCCC[Sn](CCCC)(CCCC)C(=C)OCC

Properties

• Density: 1.069 g/mL (Expl.)
• Boiling point: 319.2 °C 760 mmHg (Calc.)^*, 379.1 - 380.9 °C (Expl.)
• Flash point: 160.3±28.4 °C (Calc.)^*, 113 °C (Expl.)
• Refraction index: 1.476 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS06;GHS07;GHS08;GHS09 Danger
• Risk Statements: H301-H312-H315-H319-H372-H400-H410
• Safety Statements: P260-P264-P264+P265-P270-P273-P280-P301+P316-P302+P352-P305+P351+P338-P317-P319-P321-P330-P332+P317-P337+P317-P362+P364-P391-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	3	H301
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Acute toxicity	Acute Tox.	4	H312
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Acute toxicity	Acute Tox.	2	H330

chemBlink Chemical Story

Tributyl(1-ethoxyvinyl)stannane, CAS 97674-02-7, is an organotin reagent used primarily in palladium-catalyzed cross-coupling reactions. Its molecular formula is C₁₆H₃₄OSn and its molecular weight is approximately 361.16. Structurally, the molecule contains three butyl groups attached to tin together with a 1-ethoxyvinyl group.

Its most useful feature is not the tributylstannyl portion itself.

The important cargo is the 1-ethoxyvinyl group.

Under Stille cross-coupling conditions, this fragment can be transferred from tin to an aromatic or heteroaromatic carbon bearing a suitable leaving group such as bromine, iodine, or, under appropriately optimized catalytic conditions, chlorine.

The result is an aryl or heteroaryl enol ether.

That product can then undergo acidic hydrolysis.

And something very useful happens:

Ar-C(OEt)=CH₂

becomes

Ar-COCH₃

In other words, the 1-ethoxyvinyl group becomes an acetyl group.

This makes Tributyl(1-ethoxyvinyl)stannane a convenient synthetic equivalent for installing a methyl ketone at a position that originally carried a halogen.

The strategy is especially valuable because direct introduction of an acetyl group onto a complicated heteroaromatic framework is not always straightforward.

Instead, chemists can use the predictable carbon-carbon bond-forming behavior of a palladium-catalyzed Stille reaction.

First transfer the masked carbonyl fragment.

Then reveal the ketone.

A published medicinal-chemistry example makes this sequence very clear. In work on potent and selective prostaglandin D₂ receptor antagonists, a brominated heteroaromatic intermediate was subjected to Stille coupling with 1-ethoxyvinyltributyltin. Hydrolysis of the resulting enol ether converted the position originally bearing bromine into a methyl ketone.

The transformation can be viewed simply as:

Ar-Br

→

Ar-C(OEt)=CH₂

→

Ar-COCH₃

The carbon-carbon bond is created in the first step.

The carbonyl is revealed in the second.

This two-stage logic is one of the reasons the reagent appears repeatedly in medicinal chemistry and total synthesis.

A more recent patent example shows the same idea on a complex fused heterocycle. A brominated pyrroloquinazolinone was coupled with Tributyl(1-ethoxyvinyl)stannane using a palladium catalyst to give the corresponding 1-ethoxyvinyl intermediate. Treatment with hydrochloric acid then produced the acetyl derivative.

The chemistry is remarkably modular.

The aromatic or heteroaromatic framework can be highly complicated.

As long as a suitable halogen or related coupling handle is present, the reagent can potentially deliver the same small two-carbon fragment.

The tin portion plays a temporary role.

During the catalytic cycle, the organic fragment attached to tin is transferred to palladium and then coupled to the electrophilic partner. The tributylstannyl portion does not belong in the final target molecule.

This creates an interesting contrast inside the reagent.

The 1-ethoxyvinyl fragment is there to become part of the product.

The organotin portion is there to make the transfer possible.

After coupling, the tin-containing residue must be separated from the desired material.

This is also one of the practical disadvantages of Stille chemistry.

Organotin compounds and tin-containing byproducts raise toxicity, waste-handling, and purification concerns. For this reason, synthetic chemists often prefer alternative coupling methods when they provide comparable results.

Nevertheless, Stille coupling remains valuable in situations where its functional-group tolerance and reliable carbon-fragment transfer solve difficult synthetic problems.

The 1-ethoxyvinyl version is particularly useful because it does something more subtle than simply install a vinyl group.

It installs a vinyl ether that is deliberately temporary.

The ethoxy group is not intended to survive.

Acidic hydrolysis converts the enol ether into a ketone, transforming what initially looks like an alkene into a carbonyl-containing product.

This is an example of functional-group masking.

The chemist wants an acetyl group.

But the fragment that behaves conveniently in the coupling reaction is not an acetyl group.

It is a 1-ethoxyvinyl group.

The molecule is therefore transferred in one chemical identity and revealed later in another.

This strategy appears in many areas of synthesis.

Published examples include kinase-inhibitor research, heteroaromatic medicinal chemistry, natural-product synthesis, and the construction of specialized photochemical protecting groups.

In each case, the molecular surroundings may be different, but the logic remains recognizable:

couple the 1-ethoxyvinyl fragment,

then hydrolyze it to the methyl ketone.

The chemistry also demonstrates why synthetic equivalents are so important.

A synthetic equivalent is not necessarily structurally identical to the group ultimately desired.

Instead, it is a reagent that behaves in a useful way during construction and can later be transformed into the required functionality.

Tributyl(1-ethoxyvinyl)stannane is a particularly clear example.

On paper, it is an organotin vinyl ether.

In a synthetic plan, it can function as a hidden acetyl group.

The reagent therefore tells a broader story about molecular construction.

Sometimes the best way to install a functional group is not to install it directly.

First install something that can survive the reaction you need.

Then change its identity afterward.

References

1. PubChem. Stannane, tributyl(1-ethoxyethenyl)-, CID 619414. CAS 97674-02-7. Molecular formula C₁₆H₃₄OSn; molecular weight 361.2.

2. Littke, A. F.; Schwarz, L.; Fu, G. C. (2002). "Pd/P(t-Bu)₃: A Mild and General Catalyst for Stille Reactions of Aryl Chlorides and Aryl Bromides." Journal of the American Chemical Society, 124.

3. Sturino, C. F. et al. (2007). "Discovery of a Potent and Selective Prostaglandin D₂ Receptor Antagonist." Journal of Medicinal Chemistry. Conversion of a brominated intermediate into a methyl ketone by Stille coupling with 1-ethoxyvinyltributyltin followed by hydrolysis.

4. US 11,059,784 B2. Oxime ether compounds. Conversion of aryl bromides to ketones through coupling with Tributyl(1-ethoxyvinyl)stannane followed by acidic hydrolysis.

5. Published medicinal-chemistry and natural-product syntheses employing 1-ethoxyvinyltributyltin as a masked acetyl-group equivalent.