Functionalization of Methane Initiated by Cp*W(NO)(CH2CMe3)(η3-CH2CHCMe2)

Phenyl Sulfones: A Route to a Diverse Family of Trisubstituted Cyclohexenes from Three Independent Nucleophilic Additions

A novel process is described for the synthesis of di- and trisubstituted cyclohexenes from an arene. These compounds are prepared from three independent nucleophilic addition reactions to a phenyl sulfone (PhSO₂R; R = Me, Ph, and NC₄H₈) dihapto-coordinated to the tungsten complex {WTp(NO)(PMe₃)}(Tp = trispyrazolylborate). Such a coordination renders the dearomatized aryl ring susceptible to protonation at a carbon ortho to the sulfone group. The resulting arenium species readily reacts with the first nucleophile to form a dihapto-coordinated sulfonylated diene complex. This complex can again be protonated, and the subsequent nucleophilic addition forms a trisubstituted cyclohexene species bearing a sulfonyl group at an allylic position. Loss of the sulfinate anion forms a π-allyl species, to which a third nucleophile can be added. The trisubstituted cyclohexene can then be oxidatively decomplexed, either before or after substitution of the sulfonyl group. Nucleophiles employed include masked enolates, cyanide, amines, amides, and hydride, with all three additions occurring to the same face of the ring, anti to the metal. Of the 12 novel functionalized cyclohexenes prepared as examples of this methodology, nine compounds meet five independent criteria for evaluating drug likeliness. Structural assignments are supported with nine crystal structures, density functional theory studies, and full 2D NMR analysis.

Synthesis and structure of a pyridine-stabilized silanone molybdenum complex and its reactions with PMe3 and acetone

The synthesis, structure and reactivity of a pyridine-stabilized silanone molybdenum complex are described.

Propene complexes of molybdenum and tungsten stabilized by intramolecular coordination of the 1-(quinol-8-yl)indenyl ligand

Synthesis, reactivity and properties of unusually stable propene complexes of molybdenum and tungsten are reported.

Room temperature olefination of methane with titanium-carbon multiple bonds

C–H activation of methane followed by dehydrocoupling at room temperature led ultimately to the formation of the olefin H₂C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH^tBu via the addition of redox-active ligands (L) such as thioxanthone or 2,2′-bipyridine (bipy) to (PNP)Ti Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH^tBu(CH₃) (1).

C–H activation of methane followed by dehydrocoupling at room temperature led ultimately to the formation of the olefin H₂C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH^tBu via the addition of redox-active ligands (L) such as thioxanthone or 2,2′-bipyridine (bipy) to (PNP)Ti Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH^tBu(CH₃) (1). Using both of these exogenous ligand systems, we could trap the titanium fragment via an insertion reaction with these two substrates to afford species of the type (PNP)Ti(L)(LH). A combination of computational and isotopic labeling studies reveals that the L ligand promotes the C–C bond forming step by migration of the methyl moiety in 1 to the α-alkylidene carbon by producing a Ti(iii) species (PNP)Ti{CH(CH₃)^tBu}(L). In the case of L = thioxanthone, β-hydrogen abstraction gives an olefin, whereas with 2,2′-bipyridine β-hydride elimination and migratory insertion lead to (PNP)Ti(L)(LH). These redox-active ligands play two important roles: (i) they accept an electron from the Ti-alkylidene fragment to allow the methyl to approach the alkylidene and (ii) they serve as traps of a hydrogen atom resulting from olefin elimination. These systems represent the first homogeneous models that can activate methane and selectively dehydrocouple it with a carbene to produce an olefin at room temperature.