| DESCRIPTION |
is a multipurpose activating agent that shows great promise in replacing triflic anhydride, DAST and SF4 in many pharmaceutical, agrochemical and fine chemical processes. The molecule's ready availability, low cost and stability make it very desirable in selective fluorination, cross-coupling reactions, as a blocking agent and as a leaving group for unactivated systems.
Triflic anhydride is presently used in many of these applications, but its high cost rules out many synthetic approaches. Additionally, triflic anhydride reacts readily with water and has an unfavorable toxicity profile. In comparison, PBSF reagent is roughly one-half the cost and typically requires one-half the weight of triflic anhydride, for a per pound cost approximately one-fourth that of triflic anhydride. It is noteworthy that PBSF will not react readily with water, making it a more practical reagent to use. "Low reactivity with water is important because people prefer to work with these reagents in an open environment. "Because even humidity in the air can react with triflic anhydride, you have to take time-consuming precautions to use it." Its reactivity with water also makes storing the anhydride difficult. PBSF reagent, however, can be delivered in one-, five- and 55-gallon containers, and stored without risk of water reacting with the reagent during storage.
The sulfonate esters of PBSF (C4f9SO2OR) are highly-reactive because these sulfonate esters, or nonaflates, have a highly-stabilized negative charge on the CF3CF2CF2CF2SO3 leaving group, similar to triflate, CF3SO3. This provides for a facile reaction, gentle reaction conditions and excellent yields for reactions involving an activation agent, a blocking group or for cross-coupling reactions. The high reactivity, ease of handling and low cost of the nonaflate makes PBSF reagent an ideal choice for industrial scale applications in the synthesis of pharmaceutical, agrochemical and other fine chemicals.
PBSF reagent is also used in selective fluorination to replace DAST or SF4. PBSF reagent is an excellent agent in the conversion of alcohols to fluorides, and provides complete inversion of stereochemistry for maintenance of optical purity. The molecule is successfully replacing DAST and SF4 in these reactions for many of the same reasons it is replacing triflic anhydride: it is a lower cost, highly-stable reagent that can be handled and stored in a convenient manner. DAST and SF4 require special handling. DAST is flammable and SF4 is highly-toxic by inhalation and skin contact, and both react violently with water. PBSF reagent, however, is easier to use based on its low reactivity with water and non-flammable nature.
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