PH-Functional and P-(α-hydroxy)benzyl-2-phenyl-1,3-oxaphospholanes - Synthesis, reactivity and structural aspects

P-Benzyl- and alpha-hydroxybenzyl-1,3-oxaphospholanes were synthesized by a one-step and a two-step acid catalyzed reaction of H2PCH2CH(R)OH (R = H, Me), respectively, with benzaldehyde. The latter is the first example of the access to a P-tertiary from a P-secondary 1,3-oxaphospholane. The compounds are rapidly oxidized by air to the respective phosphine oxides, the P-benzyl compound to a small extent even to the alpha-hydroxybenzylphosphine oxide. Prolonged storage of the PH-compound in the presence of a trace of benzoic acid led to slow partial isomerization and P-H transfer reactions, resulting in a phosphinopropyl benzyl ether and a P,P'-bis(1,3-oxaphospholane), characterized by crystal structural analysis. Similar behavior was observed for a PH-functional 1,3-oxaphosphorinane. The structures of the preferred diastereoisomers of the 1,3-oxaphospholanes were determined by angle-dependent NMR conformation analysis, the structures of four of their P-oxides by XRD of single crystals. (C) 2019 Elsevier Ltd. All rights reserved.