Question

How will you synthesis the following compounds using alkene metathesis?

Short answer

To synthesize a desired compound using alkene metathesis, follow these steps: 1. Identify the target compound with clear carbon-carbon double bonds. 2. Select suitable starting materials with reactive carbon-carbon double bonds. 3. Choose an appropriate metathesis catalyst, e.g., Grubbs catalysts or Schrock catalysts. 4. React the starting materials with the catalyst under appropriate reaction conditions. 5. Isolate the desired product using purification techniques such as column chromatography or distillation. 6. Verify the product's structure using NMR, IR spectroscopy, or mass spectrometry.

Step-by-step solution

Identify the target compound

Determine the desired compound to be synthesized using alkene metathesis. The structure of this compound should be defined with clear carbon-carbon double bonds. This compound will be the product of the olefin metathesis reaction.

Select suitable starting materials

Identify the appropriate starting materials, which are alkenes that can undergo metathesis to form the desired compound. The starting materials should have reactive carbon-carbon double bonds, which will participate in the metathesis reaction. Consider the connectivity of these double bonds and how they can be rearranged to form the target compound.

Choose appropriate metathesis catalyst

Select a suitable metal catalyst for the alkene metathesis reaction. Common catalysts used in this reaction are Grubbs catalysts, Schrock catalysts, and Hoveyda-Grubbs catalysts. The catalyst choice depends on the starting materials, desired product, and reaction conditions.

React starting materials with the catalyst

Combine the starting materials and the chosen catalyst in the reaction vessel under appropriate reaction conditions, such as temperature and solvent. The metal catalyst coordinates with the carbon-carbon double bond, forming a metal-carbene intermediate, which then undergoes a series of bond-forming and bond-breaking processes to create the desired product.

Isolate the desired product

After the reaction has proceeded to completion, separate the product from the unreacted starting materials, catalyst, and any byproducts. This can be achieved using various purification techniques such as column chromatography, crystallization, or distillation, depending on the specific compound and reaction conditions.

Verify the product's structure

Use analytical techniques such as nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, and mass spectrometry to confirm that the desired compound has been synthesized correctly, and its structure matches the target compound. Now you can apply these steps to synthesize any desired compound using alkene metathesis. Choose appropriate starting materials and catalysts, perform the reaction, and isolate and verify the product.

Key concepts

Grubbs Catalyst

The Grubbs Catalyst is a key player in the world of chemistry, especially when it comes to reactions involving double bonds. This special catalyst, named after chemist Robert H. Grubbs, is often used in olefin metathesis reactions. It primarily involves the rearrangement of carbon-carbon double bonds.

The Grubbs Catalyst is known for its versatility in dealing with a wide range of olefins. It contains a ruthenium metal center, which plays an important role in facilitating the reaction. This metal center interacts with double bonds in the substrate molecules, promoting the metathesis reaction by forming a metal-carbene complex.

• It is tolerant to many functional groups
• It's stable under a variety of conditions
• Has a long shelf life compared to other similar catalysts

When using the Grubbs Catalyst, you generally have to consider factors like the type of olefins, the reaction conditions, and the specific catalyst generation (as there are different types of Grubbs Catalyst) to optimize the reaction yield and selectivity.

Olefin Metathesis Reaction

Olefin Metathesis is a beautiful and innovative chemical reaction used primarily in the synthesis of complex organic compounds. At its core, this reaction involves the redistribution of alkene fragments by breaking and reforming carbon-carbon double bonds. This makes olefin metathesis a crucial tool in organic synthesis.

The reaction mechanism involves the formation of a metal-carbene intermediate and the subsequent exchange of alkylidene groups. Thanks to catalysts like the Grubbs Catalyst, this process is greatly simplified and occurs under relatively mild conditions. Some benefits of olefin metathesis include:

• Efficiency: Often occurs with high atom economy, meaning waste is minimized
• Versatility: Can be used for ring-closing metathesis, ring-opening metathesis, cross metathesis, and more
• Precision: Offers chemists control over the selectivity and outcomes of complex molecule formation

This reaction is highly valuable, not only in laboratories for research but also on an industrial scale for producing polymers and pharmaceuticals.

Organometallic Catalysis

Organometallic catalysis involves the use of a metal that is bonded to a carbon-containing ligand to speed up chemical reactions, especially those involving organic compounds. This field is paramount in modern chemistry due to its wide range of applications.

A prominent example of organometallic catalysis is seen in olefin metathesis reactions. Here, metals such as ruthenium, molybdenum, and tungsten act as catalysts. Here's why organometallic catalysis is so impactful:

• It offers a platform for reactions that are both efficient and selective
• Catalytic reactions often proceed with fewer side products
• Organometallic complexes are tunable by altering the ligands around the metal

Compounds like the Grubbs Catalyst are part of this larger framework of organometallic catalysis, demonstrating how these catalysts can make difficult reactions more accessible, thereby opening new pathways for chemical synthesis.