Recent studies in our laboratories have also been aimed at developing regiocontrolled methods for the synthesis of highly functionalized pyrazoles.(6) We have largely opted to target pyrazole boronic acid derivatives because of the associated versatility of the boronate motif.(7) Accordingly, we have conducted several studies on the cycloaddition of sydnones with alkynylboronates for the synthesis of pyrazole boronic esters (Figure 1). The regiochemical outcome of ...
