PHOSPHONIC ACIDS AND ESTERS .20. PREPARATION AND RING-OPENING REACTIONS OF ALPHA,BETA-EPOXYALKYLPHOSPHONATES AND BETA,GAMMA-EPOXYALKYLPHOSPHONATES . PROTON MAGNETIC RESONANCE SPECTRA OF VICINALLY SUBSTITUTED ETHYL- AND PROPYLPHOSPHONATES

Diethyl (3a) and dimethyl (3b) α,β-epoxyethylphosphonates have been prepared by the epoxidation of the corresponding vinylphosphonates with t-butyl hydroperoxide in the presence of a basic catalyst. These epoxides fail to undergo thermal or acid-catalyzed rearrangements in contrast to the behavior of their β-substituted analogs. Both 3 and diethyl β,γ-epoxypropylphosphonate (4) undergo conventional hydrations, alcoholyses, and aminolyses to give α,β-disubstituted ethyl- and β,γ-disubstituted propylphosphonates, respectively. In every case, the products are formed by attack of nucleophile at the terminal carbon of the epoxide and isomerically pure products are formed. Attempted sodium borohydride reductions and Grignard reactions with 3 and 4 failed. The structures of 3 and 4 and their transformation products were established by proton magnetic resonance spectroscopy. Certain aspects of these spectra, namely, geminal β-proton nonequivalence in XCH2¯ CHY-P systems and three- (P-C-O-H) and four- (P-O-C-C-H, P-C-C-C-H) bond spin-spin couplings, are discussed. © 1969, American Chemical Society. All rights reserved.