4-Chloro-2-hydroxyphenylboronic acid pinacol ester is a building block which has seen use in the preparation of 5,6,7,8-tetrahydro[1]benzothieno[2,3-b]pyridin-3-ylacetic acid derivs. for treatment of HIV infection, and in the preparation of disubstituted pyridazine analogs useful in the treatment of SMN deficiency related diseases.