A Fischer-Type Ruthenium Carbene Complex as a Metathesis Catalyst for the Synthesis of Enol Ethers

Area of Science:

• Organometallic Chemistry
• Organic Synthesis
• Catalysis

Background:

• Ruthenium-based catalysts are crucial in olefin metathesis.
• Ring-opening cross metathesis (ROCM) offers a pathway to functionalized dienes.

Purpose of the Study:

• To investigate the efficacy of Grubbs G-I/G-II catalysts in ROCM reactions.
• To characterize the products and reaction conditions for ROCM of strained cyclic alkenes.

Main Methods:

• Utilized Grubbs G-I or G-II catalysts to form ruthenium ethoxy carbene complexes.
• Performed ROCM on strained cyclic alkenes, including norbornene and cyclopropenes.
• Analyzed reaction kinetics and substrate scope, including the effect of neighboring groups.

Main Results:

• ROCM efficiently produced dienes with an ethoxy substituent; no polymeric products were observed.
• The reaction tolerated various functional groups, including amines, imides, esters, and halides.
• Reaction rates (t50) varied significantly based on alkene strain and nucleophilicity, with anchimeric assistance dramatically increasing reactivity.

Conclusions:

• Grubbs catalysts facilitate selective ROCM of strained alkenes, yielding valuable diene products.
• Reaction efficiency is tunable via substrate structure, particularly through neighboring group participation.
• The developed method offers a controlled route to functionalized dienes under mild conditions.