The stereomutation rates between a pair of stable diastereomeric hydroxyphosphoranes (2c-exo and 2c-endo) were measured by monitoring the change in the relative diastereomeric ratios and by ¹⁹F NMR magnetization transfer. Analysis of the data gave averaged kinetic parameters of ΔH≠ = 15.7 kcal mol⁻¹; ΔS ^≠ = −19.3 eu; ΔG^≠₂₉₈ = 21.4 kcal mol⁻¹ for interconversion in toluene-d₈ and ΔH^≠ = 18.9 kcal mol⁻¹; ΔS^≠ = 4.8 eu; ΔG^≠₂₉₈ = 20.4 kcal mol⁻¹ for that in pyridine. These results suggested that the ring-opening of 2c to yield a phosphinate occurred and that the process involving the attack of the hydroxy group of this phosphinate to the phosphorus atom from the side opposite of a carbon atom was the rate-determining step. X-ray crystallographic analysis of their symmetric analog 2b was also carried out. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:491–499, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20712

A diastereomeric pair of monocyclic apical H-phosphoranes (2-exo and 2-exo) has been prepared from a diastereomeric pair of bicyclic equatorial H-spirophosphoranes (1) with tBuLi. The thermal cyclization reaction of each diastereomeric apical H-phosphorane gave rise to different diastereomeric O-equatorial anti-apicophilic phosphoranes (3-exo and 3-endo, respectively) as single products. On the other hand, the oxidation reaction of each of these apical H-phosphoranes was complementary to the thermal reaction, affording the opposite diastereomeric anti-apicophilic phosphorane (3-endo and 3-exo, respectively) as a single product. The pseudorotation of each of these diastereomeric anti-apicophilic phosphoranes (3-exo and 3-endo) gave rise to different diastereomeric O-apical phosphoranes (4-exo and 4-endo, respectively) as single products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)