Synthesis of cyclic aminomethylphosphonates and aminomethyl‐arylphosphinic acids by an efficient microwave‐mediated phospha‐mannich approach

Microwave‐assisted condensation of 1,3,‐2‐dioxaphosphinane 2‐oxide ( 1 ), paraformaldehyde and secondary amines including 5‐ and 6‐membered N‐heterocycles at 55°C gave cyclic aminomethylphosphonates ( 2 ), whereas an analogous reaction involving dibenzo[c.e][1,2]oxaphosphinane 2‐oxide ( 3 ) resulted in the corresponding aminomethyl‐2‐(2′‐hydroxybiphenyl)phosphinic acids ( 4 ) as a consequence of a hydrolytic ring opening following the condensation. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:207–210, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20387