1,8-Diazabicyclo[5.4.0]undecene Mediated Transesterification of<i>p</i>-Nitrophenyl Phosphonates: A Novel Route to Phosphono Esters
作者:Dan S. Tawfik、Zelig Eshhar、Alfonso Bentolila、Bernard S. Green
DOI:10.1055/s-1993-25982
日期:——
DBU (1,8-diazabicyclo[5.4.0]undecene) was found to efficiently mediate the transesterification of p-nitrophenyl (PNP) phosphonates by various alcohols. The reactions of bis-PNP phosphonates in the presence of DBU, using both primary and secondary alcohols, phenols and amines, proceed rapidly and with high yield to afford the corresponding monoalkyl/aryl mono-PNP phosphonates as sole products (1, Scheme 2). The resulting monoalkyl/aryl mono-PNP phosphonates can be further reacted with a second alcohol to give the corresponding differently disubstituted phosphonates 3, or selectively hydrolysed to yield the monoalkyl/aryl phosphonic acids 2. We have applied this chemistry to the preparation of a series of phosphono ester transition state analogues 11a-e (Scheme 3) that were used as haptens for raising catalytic antibodies.