demorol
(Hive Bee)
02-21-03 12:26
No 410518
      Oxidation of benzylic alcohols
(Rated as: excellent)
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Oxidation and Bromodehydroxymethylation of Benzylic Alcohols using NaBrO3/NaHSO3 Reagent (Bull. Korean. Chem. Soc. 2002, Vol. 23, pp 1667)

General procedure

To a stirred solution of alcohol (5 mmol) in aqueous acetonitrile (30mL, 1:1 by volume) was added NaBrO3 (1.51g, 10 mmol) and NaHSO3 (1.04g, 10 mmol). Reactions were continuously monitired by TLC and stirred at room temperature for the time indicated in Table 1. The reaction mixture was quenched with aqueous sodium thiosulfate and extracted with ether (3 30mL). The combined organic layers were washed with aqueous Na2CO3, water, dried over MgSO4, filtered and concetrated in vacuo. The residue was chromatographed on a silica gel column and eluted with hexane-EtOAc (10:1) to give aldehyde or aryl bromide (Table 1). The combined aqueous layer was acidified with 10% HCl to pH 2 and extracted with EtOAc (2 50mL). The organic layers were washed with water, dried and evaporated to afford the products.



I'm dreaming of the white crystals.
 
 
 
 
    Aurelius
(Hive Addict)
02-21-03 13:44
No 410536
      Great  Bookmark   

Great! so, what is the product?  the aldehyde or the halide?  (i can't see the pic)  how do you influence the formation of one or the other? 
 
 
 
 
    zorohydride
(Stranger)
02-22-03 07:24
No 410759
      Pyridinium Chlorochromate  Bookmark   

I have used the above mentioned reagent with great ease to effect oxidation of benzyl alcohols to the corrsponding ketone. It requires a little clean up and DCM is the preferred solvent for reaction. Sigma-Aldrich has lots of good info RE:the reagent. Here is an enclosed link to a different site:http://www.csbsju.edu/chemistry/OrganicChemPages/cps4.html