Stoichiometric and catalytic inter- and intramolecular hydroamination of terminal alkynes by frustrated Lewis pairs.

Frustrated Lewis pairs (FLPs) based on sterically encumbered anilines and the Lewis acid B(C6 F5 )3 were found to react with terminal alkynes effecting intermolecular hydroamination affording iminium alkynylborate species of the form [RPhNC(R')Me][R'CCB(C6 F5 )3 ]. In these cases, the reagent ratio of borane, aniline, and alkyne is 1:1:2. These reactions could also be performed in an intramolecular fashion by using anilines with alkynyl substituents effecting cyclization reactions.

Electrophilic phosphonium cations catalyze hydroarylation and hydrothiolation of olefins.

Electrophilic phosphonium cations (EPCs) are efficient main group catalysts for the hydroarylation of olefins under mild conditions, providing a facile route to substituted aniline, bis-arylamine, phenol, furan, thiophene, pyrrole, and indole derivatives. Similarly, EPCs catalyze the hydrothiolation of aryl olefins with thiophenol affording a series of alkyl aryl thioethers. Experimental data support a mechanism for these reactions that involves initial activation of the olefin.

Facile Protocol for Catalytic Frustrated Lewis Pair Hydrogenation and Reductive Deoxygenation of Ketones and Aldehydes.

A series of ketones and aldehydes are reduced in toluene under H2 in the presence of 5 mol % B(C6F5)3 and either cyclodextrin or molecular sieves affording a facile metal-free protocol for reduction to alcohols. Similar treatment of aryl ketones resulted in metal-free deoxygenation yielding aromatic hydrocarbons.

B(C6F5)3 mediated arene hydrogenation/transannulation of para-methoxyanilines.

The stoichiometric reaction of para-methoxyanilines and B(C6F5)3 under H2 results in reduction of the N-bound phenyl ring(s), and subsequent transannular ring closure with elimination of methanol, affording the respective 7-azabicyclo[2.2.1]heptane derivatives.

Enabling catalytic ketone hydrogenation by frustrated Lewis pairs.

Hydrogenation of alkyl and aryl ketones using H2 is catalytically achieved in 18 examples using 5 mol % B(C6F5)3 in an ethereal solvent. In these cases the borane and ether behave as a frustrated Lewis pair to activate H2 and effect the reduction.

Frustrated Lewis pair-mediated C-O or C-H bond activation of ethers.

Protocols for the FLP-mediated transformation of ethers are presented. Distinct reaction pathways involving either C-O or C-H bond activation occur depending on the application of oxophilic B(C6F5)3 or hydridophilic tritylium ions as the Lewis acid.

Frustrated Lewis pair catalyzed hydroamination of terminal alkynes.

Catalytic amounts of the Lewis acid B(C6 F5 )3 enable the hydroamination of terminal alkynes by aryl amines to the corresponding enamines. In accord with the results of stoichiometric reactions, the mechanism of this reaction involves a frustrated Lewis pair (FLP). The hydroamination can be followed by an FLP-catalyzed hydrogenation, resulting in a one-pot stepwise synthesis of amine derivatives.

Tautomerism and metal complexation of 2-acylmethyl-2-oxazolines: a combined synthetic, spectroscopic, crystallographic and theoretical treatment.

A synthetic, structural and theoretical investigation into the solid-state, solution and gas phase structure(s) of six 2-acylmethyl-4,4-dimethyl-2-oxazolines is reported. Four of these materials, viz.α-[(4,5-dihydro-4,4-dimethyl-2-oxazolyl)methylene]benzenemethanol (3a), α-[(4,5-dihydro-4,4-dimethyl-2-oxazolyl)methylene]-(4-nitrobenzene)methanol (3b), 1-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)-3,3-dimethyl-1-buten-2-ol (3d) and (E)-1-phenyl-2-((3aR)-3,3a,8,8a-tetrahydro-2H-indeno[1,2-d]oxazol-2-ylidene)ethanone (3f) have been characterised in the solid-state by single crystal X-ray diffraction studies.

Metal-free aromatic hydrogenation: aniline to cyclohexyl-amine derivatives.

Hydrogenation of the N-bound phenyl rings of amines, imines, and aziridine is achieved in the presence of H(2) and B(C(6)F(5))(3), affording the corresponding N-cyclohexylammonium hydridoborate salts.