Synthesis of 3-Haloisoxazole Boronic Esters: Novel Heterocyclic Synthetic Intermediates Containing Independently Variable Functionality

The regioselective cycloaddition reaction of nitrile oxides with alkynylboronates has been exploited in the preparation of 3-bromo- and 3-chloroisoxazolyl-4-boronates. The synthetic potential of these intermediates has been explored through a number of cross coupling reactions of the boronic ester unit and some representative reactions of the heteroaryl halide moiety.