Syntheses,Structures, Reactivity, and Catalytic Applicationsof Enantiopure Rhenium-Containing P‑Stereogenic PhosphoniumSalts, Phosphines, Phosphine Boranes, and Phosphine Oxides

Easily accessed enantiopure (η⁵-C₅H₅)Re(NO)(PPh₃)(CH₃) is treated with Ph₃C⁺ PF₆^– (−78 °C) to generate the methylidene cation [(η⁵-C₅H₅)Re(NO)(PPh₃)(=CH₂)]⁺ and then racemic chiral secondary phosphines PHXX′ (<b>4</b>; X/X′ = <b>a</b>, <i>t</i>Bu/Ph; <b>b</b>, Cy/Ph; <b>c</b>, <i>t</i>Bu/Cy; <b>d</b>, CH₃/Ph; <b>e</b>, 2-furyl/Ph; <b>f</b>, α-naph/Ph; <b>g</b>, β-naph/Ph) to give the phosphonium salts (<i>S</i>_Re<i>R</i>_P)- and (<i>S</i>_Re<i>S</i>_P)-[(η⁵-C₅H₅)Re(NO)(PPh₃)(CH₂PHXX’)]⁺ PF₆^– (<b>2</b>·H⁺) as mixtures of Re, P-diastereomers that are usually separable (<b>a</b>,<b>b</b>,<b>c</b>,<b>f</b>,<b>g</b>). Treatment of <b>2a</b>-<b>g</b>·H⁺ with <i>t</i>BuOK generates the phosphines <b>2a</b>-<b>g</b>, which are variously isolated (<b>2f</b>,<b>g</b>), treated with BH₃·S(CH₃)₂ to give <b>2a</b>-<b>e</b>·BH₃, or oxidized (O₂ or PhIO) to give <b>2a</b>-<b>c</b>·O. Oxidations are also effected with <b>2a</b>,<b>c</b> that has been generated from <b>2a</b>,<b>c</b>·BH₃ and pyrrolidine. For the diastereomerically pure complexes in the <b>a</b>-<b>c</b> series, configurations have been assigned crystallographically, and the Ph₃P–Re–CH₂–P−X conformations were analyzed in detail. In an unusual but precedented phenomenon, the diastereomers of <b>2a</b>·H⁺ PF₆^– cocrystallize. <b>2f</b>,<b>g</b> catalyze highly enantioselective intramolecular Morita–Baylis–Hillman cyclizations of R(CO)CHCHCH₂CH₂CHO (RPh, S<i>i</i>Pr), and (<i>S</i>_Re<i>S</i>_P)-<b>2b</b> (2.4 mol %) and [Pd(allyl)Cl]₂ (1.2 mol % based upon “Pd atoms”) give a catalyst for the allylic alkylation of racemic 3-(acetoxy)cyclohexene that furthermore effects a kinetic resolution of the educt (<i>s</i> = 15.0).