Protonation of P-Stereogenic Phosphiranes: Phospholane Formation via Ring Opening and C-H Activation.

Protonation of cyclopropanes and aziridines is well-studied, but reactions of phosphiranes with acids are rare and have not been reported to result in ring opening. Treatment of -Mes*PCHCHR (Mes* = 2,4,6-(-Bu)CH, R = Me or Ph, --) or -Mes*PCHCHPh (-) with triflic acid resulted in regiospecific -Markovnikov C-protonation with ring opening and cyclophosphination of a Mes* --Bu group to yield the phospholanium cations [PH(CHCHR)(4,6-(-Bu)-2-CMeCHCH)][OTf] (R = Me or Ph, -), which were deprotonated with NEt to give phospholanes -. Enantioenriched or racemic - both gave racemic .

Configurational Lability at Tetrahedral Phosphorus: syn/anti-Isomerization of a P-Stereogenic Phosphiranium Cation by Intramolecular Epimerization at Phosphorus.

Tetrahedral main-group compounds are normally configurationally stable, but P-epimerization of the chiral phosphiranium cations syn- or anti-[Mes*P(Me)CH CHPh][OTf] (Mes*=2,4,6-(t-Bu) C H ) occurred under mild conditions at 60 °C in CD Cl , resulting in isomerization to give a syn-enriched equilibrium mixture. Ion exchange with excess [NBu ][Δ-TRISPHAT] (Δ-TRISPHAT=Δ-P(o-C Cl O ) ) followed by chromatography on silica removed [NBu ][OTf] and gave mixtures of syn- and anti-[Mes*P(Me)CH CHPh][Δ-TRISPHAT]⋅x[NBu ][Δ-TRISPHAT]. NMR spectroscopy showed that isomerization proceeded with epimerization at P and retention at C.

Bio-Based Cycloalkanes: The Missing Link to High-Performance Sustainable Jet Fuels.

Invited for this month's cover is the group of Ben Harvey at the Naval Air Warfare Center, Weapons Division, China Lake. The image shows several examples of bio-based cycloalkanes that have been developed as next-generation sustainable jet fuels. The Review itself is available at 10.

Bio-Based Cycloalkanes: The Missing Link to High-Performance Sustainable Jet Fuels.

The development of sustainable energy solutions that reduce global carbon emissions, while maintaining high living standards, is one of the grand challenges of the current century. Transportation fuels are critical to economic development, globalization, and the advancement of society. Although ground vehicles and small aircraft are beginning a slow transition toward electric propulsion with energy sourced from solar radiation or wind, the extreme power requirements of jet aircraft require a more concentrated source of energy that is conveniently provided by liquid hydrocarbon fuels.

Inversion of Configuration at the Phosphorus Nucleophile in the Diastereoselective and Enantioselective Synthesis of P-Stereogenic syn-Phosphiranes from Chiral Epoxides.

Nucleophilic substitution results in inversion of configuration at the electrophilic carbon center (S 2) or racemization (S 1). The stereochemistry of the nucleophile is rarely considered, but phosphines, which have a high barrier to pyramidal inversion, attack electrophiles with retention of configuration at P. Surprisingly, cyclization of bifunctional secondary phosphine alkyl tosylates proceeded under mild conditions with inversion of configuration at the nucleophile to yield P-stereogenic syn-phosphiranes.