Related Experiment Video
Updated: Jul 20, 2026
07:28
Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
Catalytic Ni/Cr-mediated macrocyclization without use of high-dilution techniques
1Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA.
Journal of the American Chemical Society
|November 3, 2005
Summary
Catalytic nickel/chromium-mediated macrocyclization of halichondrin precursors was achieved efficiently. This user-friendly method avoids high-dilution conditions, offering scalability and cost-effectiveness.
Area of Science:
- Organic Chemistry
- Catalysis
- Synthetic Methodology
Background:
- Macrocyclic compounds are crucial in medicinal chemistry.
- Efficient synthesis of complex macrocycles like halichondrins remains a challenge.
- Existing methods often require harsh conditions or specialized techniques.
Purpose of the Study:
- To demonstrate the feasibility of catalytic Ni/Cr-mediated macrocyclization.
- To develop a user-friendly and scalable synthetic route for halichondrin precursors.
- To explore cost-effective catalytic approaches in complex molecule synthesis.
Main Methods:
- Utilized catalytic amounts (5 mol %) of Nickel (Ni) and Chromium (Cr) catalysts.
- Applied the method to two distinct substrates from the halichondrin area.
- Macrocyclization reactions were performed without high-dilution techniques.
Main Results:
- Successfully achieved macrocyclization for both halichondrin-related substrates.
- The catalytic Ni/Cr system proved effective under mild conditions.
- Demonstrated the absence of need for high-dilution, simplifying the process.
Conclusions:
- Catalytic Ni/Cr-mediated macrocyclization is a feasible and efficient strategy.
- The developed method offers user-friendliness, easy workup, scalability, and cost-effectiveness.
- Reagents are readily available, enhancing the practicality of this synthetic approach.
Related Concept Videos
02:50Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
01:16Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
01:17Ziegler–Natta Chain-Growth Polymerization: Overview
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular...
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).