MPDOC esters

Porter reported the first decarboxylative azidation of thiohydroxamates (Barton PTOC esters). Moderate to good yields of the desired azides were obtained together with the S-pyridyl derivatives resulting from the direct trapping of the radical by the Barton ester. Interestingly, these reactions proved to be diastereoselective as demonstrated by the first example depicted in Scheme 8.12. The formation of the 5-pyridyl derivatives (Barton rearrangement) limits severely the scope of this process. The use of a new type of thio-hydroxamate esters (MPDOC esters) allows to overcome this difficulty (Scheme 8.26). These esters are more stable than the classical Barton esters and less prone to rearrange... 

Scheme 6.30 Decarboxylative radical azidation using PTOC, MPDOC or MMODC esters...

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