Photooxygenation synthetic applications

Synthetic applications involving regioselective or diastereoselective photooxygenation ene reactions, as key steps, are very common in the literature and some examples have already been reported in the previous sections. Additionally, the number of natural products... 

Singlet molecular oxygen (lC>2) is a very small electrophilic reagent that can produced by photosensitization and react easily with dienes and alkenes in [4 + or [2 + 2] cycloadditions or ene-reactions. In order to develop synthetic applic tions of photooxygenations, numerous studies have recently been developed wi chiral substrates and especially in the presence of chiral auxiliaries. 

Most reactions reported in this chapter are of Type II involving singlet oxygen in the first electronically excited state ( Ag) and, in particular, photooxygenation of [4+2] and [2+2] type will be illustrated. Excellent books [5,6,8] and reviews [9] cover the extraordinarialy wide literature on the mechanistic and synthetic aspects of these reactions, and in the recent years attention has been given to the stereochemical aspects, especially in view of the application of these reactions in asymmetric synthesis [10]. 

Scheme 6.260 shows an example of the application of photooxygenation in the total synthesis of dysidiolide (539), a cdc25A protein phosphatase inhibitor, involving regioselective oxidation of the furan moiety of 540 in nearly quantitative chemical yield in the last step of the synthetic procedure.1447... 

The photooxygenation of organosilicon compounds is also an interesting subject from the synthetic and application viewpoints. The PET reactions of a polymer system having silyl groups and the organopolysilanes represent an attractive area in their applications." " ... 

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