Nitrosation, Barton esters

Girard, P., Guillot, N., Motherwell, W. B., Hay-Motherwell, R. S., Potier, P. The reaction of thionitrites with Barton esters a convenient free radical chain reaction for decarboxylative nitrosation. Tetrahedron 1999, 55, 3573-3584. 

Another related reaction is the Barton reaction, by which a methyl group in the 0 position to an OH group can be oxidized to a CHO group. The alcohol is first converted to the nitrite ester. Photolysis of the nitrite results in conversion of the nitrite group to the OH group and nitrosation of the methyl group. Hydrolysis of the oxime tautomer gives the aldehyde, for example,... 

A related reaction is the Barton reaction. In this case, a methyl group that is 5 to a hydroxyl group is oxidised into an aldehyde functionality. The hydroxyl group is first converted into a nitrite ester by the action of nitrosyl chloride, NOC1, and after exposure to light the 8-methyl group undergoes nitrosation. Write down the pathway for these steps. 

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