Alkyne trans-haloboration using BX3 represents a simple way to make benzoxaborinines while concomitantly installing a functionalizable group (a halide) at the C4-position. As benzoxaborinines are key intermediates used to form broad spectrum -lactamase inhibitors (BLI) this route has potential as useful method to access novel derivatives of important bioactives. This is supported by the good functional group tolerance of this route to form benzoxaborinines, which is complementary to that of previously reported Ni catalyzed method. The ability to incorporate a halide at the C4 position is particularly significant, as the Ni-catalyzed route to form benzoxaborinines cannot tolerate any substitution at this position. Therefore, the haloboration-Negishi cross-coupling protocol to access C4-functionalised benzoxaborinines fills a gap in the current methodologies used to access these compounds. Finally, our understanding of haloboration and electrophilic borylation reactions enabled the extension of this methodology to generate the important (in BLIs) C8-ester functionalized and C3-C4 difunctionalized benzoxaborinines in good yields. The former required the addition of an exogenous chloride donor ([BCl4] -) and indicated a switch in the mechanism to form chlorinated benzoxaborinines from a double haloboration/retro-haloboration process to a concerted trans-haloboration process. Both mechanisms were supported by computational analysis. In summary, this trans-haloboration methodology reported herein represents a useful addition to the synthetic chemists toolbox for accessing bicyclic-boronates that are increasingly recognized as important active pharmaceutical ingredients (including for tackling important challenges such as antibiotic resistance).