Rhodium-Catalyzed Enal Transfer with N-Methoxypyridazinium Salts

Area of Science:

• Organic Chemistry
• Synthetic Methodology
• Catalysis

Background:

• Functionalized enals are crucial building blocks in organic synthesis.
• Developing efficient and mild synthetic routes remains a key challenge.
• Existing methods often require harsh conditions or complex reagents.

Purpose of the Study:

• To report a simple, open-flask method for synthesizing functionalized enals.
• To introduce an enal-transfer reaction using water-soluble N-methoxypyridazinium salts.
• To achieve challenging allene- and allyl-functionalized (E)-enals with a gamma-C(sp3) quaternary center.

Main Methods:

• Utilizing water-soluble N-methoxypyridazinium salts for enal-transfer.
• Employing mild aqueous basic conditions.
• Leveraging [2,3]-sigmatropic rearrangement of sulfur-ylides derived from Rh-(E)-enalcarbene intermediates.

Main Results:

• Successful synthesis of various allene- and allyl-functionalized (E)-enals.
• Good to high yields achieved for synthetically challenging products.
• Demonstration of InCl3-catalyzed cascade cyclization to form pyrrolo[1,2-a]quinoline motifs.

Conclusions:

• The developed method offers a simple and efficient route to valuable functionalized enals.
• The reaction proceeds under mild, aqueous conditions, enhancing its practicality.
• The synthesized motifs are valuable intermediates for further chemical transformations.