• 10.1039/B912364D
  • Chemical Communications
  • Volume
  • January 2009
  • pp 6267

Best method to make various 2-phenylpyridine derivatives

Details


Review :-

1) Synthesized all compounds from Table 1 (1-8) and Table 2 (1-13). I was able to achieve higher yields than the ones reported in this paper by doubling the catalyst concentration.

2) I used excess i.e 3 mol % Palladium acetate than the reported 1.5 mol % for complete conversion of starting material. The other reaction conditions like base, time and temperature were as per the paper. My purification steps were little different as I used gradient eluent system via Teledyne combiflash purification instrument than the regular flash system used in this paper.

Observations :-

1) Scale up :- The reaction provides similar yields when scaled to 10 times the initial concentration of starting material.

2) Base :- I obeserved that the reaction does not go to completion in some other bases like K3PO4,5H2O and KOH.  This creates a problem in purification as in some cases the starting material 2-bromopyrdine and the corresponding product have same retention factor in various Hexane/Ethyl acetate eluent systems.

3) Solvent :- The reaction does not require 4 ml of solvent. It works very well even in 2 ml of solvent. Ethlene glycol can be used as a substitute for 50 % isopropanol.

4) Table 1 ( 5 and 7 ) required overnight sirring for complete conversion of starting material.

5) Excess 1.5 Eq. of boronic acid is not necessary. The reaction goes to completion even with 1 Eq. of boronic acid. The depends on the purity and stability of various boronic acids used in this paper.



Comments

Need some clarification about the modifications

Arnab Bhattacharya
(13)
PhD, Inorganic & Computational Chemistry, Tripura University, 4yrs

I have a few questions regarding the modified procedure.

1. Is it really needed to double the catalyst concentration? You have not mentioned the effect of that on the yields. Some of the reactions like entry 5, 7 in Table 1 are yilding 72 & 79% respectively according to the paper. In table 2, the entry 3 & 9 are only yielding 35 & 24% respectively which is very low. Is there any significant increase in those yields by doubling the catalyst concentration?

2. What advantage did you get by using the combiflash purification instrument than the regular flash system used in this paper.

3. Does the use of bases K3PO4.5H2O and KOH always impede the reaction? Or this observation is about only specific cases? Please mark those entries in their respective Tables, for clarity.

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