Dinucleoside phosphorofluoridite

Dinucleoside phosphorofluoridites are readily available (Example 47). The Me3SiCF3 reagent reacts with this type of compounds in the presence of a catalytic amount of CsF (step a) and the trifluoromethylphosphonite formed was oxidized to trifluoromethylphosphonate by TBHP (step b). The method is particularly valuable as it is compatible with a sequential procedure combining the formation of phosphorus-fluorine compounds from pi haryloxy precursors with the reaction leading to P cp groups. Both reactions require the presence of fluorine ions as a substrate or catalyst. 

Phosphorodifluoridite 31 itself proved to be capable of selective condensation with one equivalent of nucleoside to give dinucleoside phosphorofluoridite 34 in excellent yield (8). This is shown in Scheme 15. The phosphorofluoridite 34 undergoes oxidation by air or elemental... 

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