Sequential Rearrangements

Sequential rearrangements are multistep chemical transformations in which a molecule undergoes two or more structural reorganizations in succession, producing a product with a connectivity different from the starting material. Each rearrangement changes the electronic or geometric environment of the intermediate, enabling the next step through processes such as group migration, ring expansion, bond cleavage, or re-formation. In organic chemistry, these sequences can rapidly build molecular complexity and control the placement of functional groups or stereochemical features. Understanding their mechanisms helps researchers predict reaction pathways, design efficient synthetic strategies, and interpret unexpected products in the preparation of pharmaceuticals, natural products, and other structurally complex compounds.

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JoVE Core - Organic Chemistry

[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement

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2023

The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state. From a molecular orbital perspective, the rearrangement can be viewed as the interaction between the ground state frontier orbitals of the allyl anion and cation. Under thermal conditions, the two π...

[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement

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2023

The Claisen rearrangement is a [3,3] sigmatropic rearrangement of allyl vinyl ethers to unsaturated carbonyl compounds. The rearrangement is a concerted pericyclic reaction proceeding via a chair-like transition state. An aromatic Claisen rearrangement involves the conversion of allyl aryl ethers to an unstable ketone intermediate, which tautomerizes to give ortho-substituted phenols. However, ortho-substituted allyl aryl ethers exclusively yield para-substituted phenols via two sequential...

Preparation of Diols and Pinacol Rearrangement

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2023

Compounds bearing two hydroxyl groups are known as diols. When the hydroxyl groups are located on adjacent carbon atoms, the diols are called vicinal diols or glycols. Under acidic conditions, vicinal diols undergo a specific reaction called pinacol rearrangement. The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion. In the second step, the oxonium ion loses H2O, forming a tertiary carbocation intermediate. In the...

Sequential Games

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2025

Sequential games involve players making decisions one after another, with each player considering the prior decisions of other players before deciding their own strategy. The order of these decisions is crucial, as each decision influences subsequent ones, affecting the overall outcome. Decision trees are valuable tools in illustrating these games, helping visualize each possible decision and its consequences, allowing players to anticipate and plan strategies effectively. Consider two coffee...

Sequential Game: Backward Induction

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2025

Backward induction is a technique for solving sequential games. It involves analyzing the game starting from the end and working backwards to the beginning. This method helps players determine their best strategies by anticipating how others will react at each stage of the game, ultimately leading to the Nash equilibrium. Imagine two beverage companies, FreshFizz and CoolBrew, deciding whether to enter a new market. FreshFizz moves first and must choose to enter or stay out. If FreshFizz...

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