You Think You Know Sigmatropic Rearrangement? Watch This First! - Synthesis Studio Ep. 04

Описание: Welcome back to Synthesis Studio with Chemicator! In this episode, we dive deep into one of the hardest rearrangement questions in organic chemistry — a sigmatropic shift that seems to violate orbital symmetry rules!

We explore the tropilidene skeleton, a 7-membered ring with conjugated π-bonds, and examine how temperature-induced pyrolysis leads to a peculiar methyl migration. This reaction involves complex 1,5-sigmatropic rearrangements, HOMO-LUMO orbital interactions, and even a dynamic “walking” mechanism of the cyclopropane ring.

You’ll learn:

What is a sigmatropic rearrangement?

The differences between 1,3-, 1,5-, and 1,7-migrations

Why this pericyclic reaction defies traditional stereochemical expectations

How orbital symmetry rules apply — and how this case breaks them

The role of Woodward–Hoffmann rules in understanding pericyclic processes

A fascinating look at suprafacial vs antarafacial shifts

What makes this reaction a true example of a "walk rearrangement"

This video is perfect for:

Students preparing for organic chemistry exams

Chemistry educators looking for advanced reaction mechanisms

Anyone curious about the most challenging rearrangement mechanisms ever published!
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Attributions:
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References:
Source of the questions: Evans, D. A.; Myers, A. G. Advanced Organic Chemistry Lecture Notes, Problem Sets And Exams [ Chem 206 & 215] ( Harvard, 2003, 2006, 2007).

The Stereochemistry of Sigmatropic Rearrangements. Tests of the Predictive Power of Orbital Symmetry Rules. https://doi.org/10.1021/ar50005a004

Origin of the Preference for the Orbital Symmetry Forbidden Stereochemistry of the 1,5 Sigmatropic Shift of Substituted Norcaradienes. https://doi.org/10.1021/ja9840192

Skeletal rearrangements of the methyl-7,7-dicyanonorcaradienes. https://doi.org/10.1021/ja00992a022
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Time Code:
00:00 - Intro
00:19 - Tropilidene Skeleton
01:06 - Introduction to Sigmatropic Rearrangements
01:35 - Butene & Cyclohexadiene Migration
02:42 - Mechanism Breakdown | π-Electrons & Nonatriene Intermediate
04:28 - What is a Walk Rearrangement?
05:45 - Orbital Theory in Rearrangements
06:23 - Suprafacial vs Antarafacial
07:52 - Unexpected Inversion