The methodology developed by Montchamp and co-workers demonstrated a mild and reliable way to esterify the monosubstituted phosphinic acids.
I repeated the preparation of substrate 3 as the entry 5 in table 1 followed their protocol. The reaction went smoothly to afford 100% conversion based on 31P NMR detection of the crude. The reaction time was much shorter according to my observation (6-hour refluxing in stead of the reported 24-hour) to provide the quantitative transformation. The issue that was not commented in the paper was the strong sol-gel tendency of the orthosilicates, which caused unwanted complication for the work-up process. Methyl phenylphosphinate was not very robust upon treatment with basic sodium bicarbonate aqueous solution. These two factors prompted me to avert the reported work-up procedure. The purification by straightforward distillation offered comparable yield (in my case 80% isolated yield).
The advantages of this method to esterify the monosubstituted phosphinic acids were the quantitative conversion and the mild reaction conditions, which could apply for much wider range of substrates. The reproducibility was good.