Chemical Synthesis

A-Phos

Introduction
The Suzuki-Miyaura cross-coupling reaction of heteroaryl halides is of particular interest to the pharmaceutical industry since many biologically active compounds are accessed through this methodology. Currently, a need exists for efficient coupling of boronic acids with five-membered heteroaryl halides or six-membered aryl chlorides bearing heteroatom substituents. With many of these types of substrates, catalyst deactivation is noticed, thus, high catalyst loading is typically required in order to achieve good yields. This is an efficient new process to access biaryls substituted with heteroatoms.

Advantages

  • Air stable catalyst
  • Reaction done in aqueous solution
  • Low catalysis loading
  • Access to biaryls substituted with heteroatoms

 

Representative Applications
Guram and coworkers, from Amgen, reported the synthesis and the activities of a set of new air stable palladium catalysts. These new catalysts are based on bulky dialkylphenylphosphines where the phenyl is substituted at the para position with an amine, an alcohol or trifluoromethyl groups. Utilizing these palladium complexes, Guram et al. evaluated their efficiency for the coupling reaction of heteroatom containing substrates. Excellent yields were obtained with 1 mol% loading of the palladium complex for the coupling of a variety of aryl chloride with aryl boronic acids.

In a typical reaction, 1 mol% of the catalyst is loaded with potassium carbonate and refluxed in aqueous mixture for 12 hours. A variety of pyridine derivative were successfully coupled with bulky, electron donating and electron deficient boronic acids with yields up to 99%.

Potassium carbonate, toluene-water, reflux, 12 h image


Product Yield (%)
A-Phos Product Structure 1 Image 93
A-Phos Product Structure 2 Image 92
A-Phos Product Structure 3 Image 93
A-Phos Product Structure 4 Image 98
A-Phos Product Structure 5 Image 95
A-Phos Product Structure 6 Image 94
A-Phos Product Structure 7 Image 99
A-Phos Product Structure 8 Image 98
A-Phos Product Structure 9 Image 97
A-Phos Product Structure 10 Image 96
A-Phos Product Structure 11 Image 99
References
  1. Guram et al. J. Org. Chem. 2007, 72, 5104.
  2. Guram et al. Org. Lett. 2006, 8, 1787.

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More recently, Guram and co-workers reported the Suzuki coupling of various aryl chloride with aryl boronate esters, offering a greater range of coupling reagents. In this reaction, butanol and water are used as solvents with potassium acetate as a base with 1 mol% loading of the catalyst.


Butanol and water, potassium acetate image

Reference
  1. Guram et al. J. Org. Chem. 2007, 72, 5104.



Product No. Product Name Structure Add to Cart
678740 (A-taPhos)2PdCl2 678740 Structure Image
677264 A-taPhos) 677264 Structure Image
692913 (A-caPhos)2PdCl2 692913 Structure Image
692689 A-caPhos) 692689 Structure Image
692921 (A-tfPhos)2PdCl2 692921 Structure Image

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