1,7 sigmatropic rearrangement

Definition

A 1,7 sigmatropic rearrangement is a type of pericyclic reaction where a sigma bond moves between two atoms while a π bond is formed or broken, specifically involving the migration of a substituent from the first to the seventh position on a carbon chain. This rearrangement typically occurs in the presence of heat or light and can be facilitated by specific catalysts. Understanding this reaction is crucial for grasping the broader concepts of molecular rearrangements and reactivity patterns in organic chemistry.

5 Must Know Facts For Your Next Test

1. In a 1,7 sigmatropic rearrangement, the reaction typically involves a compound with at least seven carbons in its chain, where the rearrangement occurs between the first and seventh carbons.
2. This rearrangement can be classified as either [1,7] or [7,1] depending on how you look at the direction of migration, but they are fundamentally linked in terms of mechanism.
3. The reaction is thermally allowed and can also be photochemically induced, providing insights into reaction conditions and energy profiles.
4. The formation of a cyclic transition state during the rearrangement is crucial, as it stabilizes the process and often leads to unique product distributions.
5. Many natural products and synthetic compounds have been synthesized using 1,7 sigmatropic rearrangements due to their ability to create complex molecular architectures efficiently.

Review Questions

• How does the structure of the substrate influence the outcome of a 1,7 sigmatropic rearrangement?
  • The structure of the substrate plays a significant role in determining the efficiency and outcome of a 1,7 sigmatropic rearrangement. Factors such as steric hindrance and electronic effects can influence the stability of the transition state and ultimately affect product distribution. For example, bulky substituents may hinder rearrangement or lead to side reactions, while electron-withdrawing groups can stabilize positive charges formed during the transition state.
• Discuss how 1,7 sigmatropic rearrangements are related to other types of pericyclic reactions and their significance in organic synthesis.
  • 1,7 sigmatropic rearrangements are part of a larger family of pericyclic reactions that also includes electrocyclic reactions and cycloadditions. These reactions share similar mechanisms characterized by concerted bond-breaking and bond-forming processes. Their significance lies in their ability to create complex structures from simpler ones, making them invaluable tools in organic synthesis for constructing diverse molecular architectures efficiently while often proceeding under mild conditions.
• Evaluate the potential applications of 1,7 sigmatropic rearrangements in drug discovery and materials science.
  • 1,7 sigmatropic rearrangements hold considerable potential for applications in drug discovery and materials science due to their ability to construct complex molecular frameworks with precision. In drug discovery, these rearrangements can be used to synthesize bioactive compounds that target specific biological pathways. Additionally, in materials science, they can contribute to developing polymers with tailored properties by facilitating specific structural changes at defined points within polymer chains. Such applications demonstrate how understanding these reactions can lead to innovations across various fields.

Related terms

Pericyclic Reactions: Reactions that occur via a concerted mechanism involving the simultaneous breaking and forming of bonds in a cyclic transition state.

Sigmatropic Rearrangement: A rearrangement involving the migration of a sigma bond along with the movement of π bonds, categorized based on the positions of the atoms involved.

Electrocyclic Reaction: A type of pericyclic reaction where a cyclic compound forms or breaks into another cyclic compound through the rotation of a σ bond.