Parikh-Doering conditions

This oxidation presented a serious challenge, because of the tendency of the substrate to suffer dehydration, or oxidative breakage at the benzylic positions. It succeeded under Parikh-Doering conditions, provided that scrupously dry conditions are used, and the reaction of SO3 Py with DMSO precedes the interaction with the diol, in order to avoid the formation of a sulfate ester. Thus, the solution of SO3 Py in DMSO was prepared 5 min in advance of its use. The application of the closely related Albright-Goldman oxidation led to erratic yields, the diol acetate being the main side product. 

The nucleophilic substitution of the pyrimidine 168 by N-benzylglycinol afforded 169, which was then oxidised under Parikh-Doering conditions to give the aldehyde 170. Then 170 underwent cyclization to give hydroxydiazepine 171. When the aldehyde 170 upon treatment with para-toluidine under Pictet-Spengler cyclization reaction conditions afforded the diazepine 172, which was labile and quickly imderwent Smiles rearrangement to afford 173. " ... 

Peptide aldehydes 1 can be synthesized effectively by the oxidation of peptide alcohols 15, which are readily available without racemization by reduction of peptide esters 9 with sodium borohydride-lithium chloride (Scheme 5). The peptide alcohols 15 can be readily oxidized to afford enantiomerically pure aldehydes using Parikh-Doering or Dess-Martin reagents. This route is less popular than the previously described reductive methods due to (1) the sensitivity of the aldehydes to further oxidation, (2) racemization under the reaction conditions, and (3) instability of the products under the reaction conditions. 

This oxidation that proved troublesome under a variety of conditions, like Swern, PCC, Dess-Martin and Parikh-Doering, succeeded under Pfitzner-Moffatt conditions. 

After considerable experimentation, it was found that the Parikh-Doering oxidation provides a good and reproducible yield. Under Swern conditions, yields are erratic with substantial quantities of a product, arising from opening of the epoxide by attack of a chloride ion being formed. PCC did not afford a good yield of alcohol. 

It must be mentioned that sensitive compounds, like alkyl silanes,112 alkyl stannanes113 and vinyl stannanes,114 are not affected under the conditions of the Parikh-Doering oxidation. 

To determine the effect of olefin geometry on reaction rate and stereoselectivity, we prepared the E) isomer E)-2A via Parikh-Doering oxidation [39] of (Z)-2J, concomitant isomerization to ( )-olelin, NaBH reduction, and coupling with (ib)-glycidyl benzyl ether (Scheme 2.1). The tandem reaction of ( )-2.4 under Mn02 oxidation conditions also provided 2.6a (dr >20 1, 87 %), suggesting that the double bond geometry appears to have no effect on the stereoselectivity and conversion of the reaction (Scheme 2.2). 

DNA polymerases, 2, 3 Doering/Parikh conditions SO -pyridine complex, 302... 

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