Intermolecular Metal-Catalyzed C‒C Coupling of Unactivated Alcohols or Aldehydes for Convergent Ketone Construction beyond Premetalated Reagents.

Intermolecular metal-catalyzed C‒C couplings of unactivated primary alcohols or aldehydes to form ketones are catalogued. Reactions are classified on the basis of pronucleophile. Protocols involving premetalated reagents or reactants that incorporate directing groups are not covered.

Asymmetric Ruthenium-Catalyzed Carbonyl Allylations by Gaseous Allene via Hydrogen Auto-Transfer: 1° vs 2° Alcohol Dehydrogenation for Streamlined Polyketide Construction.

Iodide-bound ruthenium-JOSIPHOS complexes catalyze the redox-neutral C-C coupling of primary alcohols - with the gaseous allene (propadiene) to form enantiomerically enriched homoallylic alcohols - with complete atom-efficiency. Using formic acid as reductant, aldehydes - and - participate in reductive C-C coupling with allene to deliver adducts and with comparable levels of asymmetric induction. Deuterium labeling studies corroborate a mechanism in which alcohol dehydrogenation triggers allene hydroruthenation to form transient allylruthenium-aldehyde pairs that participate in carbonyl addition.

Stereo- and Site-Selective Crotylation of Alcohol Proelectrophiles via Ruthenium-Catalyzed Hydrogen Auto-Transfer Mediated by Methylallene and Butadiene.

Iodide-bound ruthenium-JOSIPHOS complexes catalyze the redox-neutral C-C coupling of primary alcohols with methylallene (1,2-butadiene) or 1,3-butadiene to form products of anti-crotylation with good to excellent levels of diastereo- and enantioselectivity. Distinct from other methods, direct crotylation of primary alcohols in the presence of unprotected secondary alcohols is possible, enabling generation of spirastrellolide B (C9-C15) and leucascandrolide A (C9-C15) substructures in significantly fewer steps than previously possible.

Conversion of Primary Alcohols and Butadiene to Branched Ketones via Merged Transfer Hydrogenative Carbonyl Addition-Redox Isomerization Catalyzed by Rhodium.

The first examples of rhodium-catalyzed carbonyl addition via hydrogen autotransfer are described, as illustrated in tandem butadiene-mediated carbonyl addition-redox isomerizations that directly convert primary alcohols to isobutyl ketones. Related reductive coupling-redox isomerizations of aldehyde reactants mediated by sodium formate also are reported. A double-labeling crossover experiment reveals that the rhodium alkoxide obtained upon carbonyl addition enacts redox isomerization without dissociation of rhodium at any intervening stage.

Enantioselective Iridium-Catalyzed Allylation of Nitroalkanes: Entry to β-Stereogenic α-Quaternary Primary Amines.

The first systematic study of simple nitronate nucleophiles in iridium-catalyzed allylic alkylation is described. Using a tol-BINAP-modified π-allyliridium ,-benzoate catalyst, α,α-disubstituted nitronates substitute racemic branched alkyl-substituted allylic acetates, thus providing entry to β-stereogenic α-quaternary primary amines. DFT calculations reveal early transition states that render the reaction less sensitive to steric effects and distinct trans-effects of diastereomeric chiral-at-iridium π-allyl complexes that facilitate formation of congested tertiary-quaternary C-C bonds.

Vinyl Triflate-Aldehyde Reductive Coupling-Redox Isomerization Mediated by Formate: Rhodium-Catalyzed Ketone Synthesis in the Absence of Stoichiometric Metals.

Direct conversion of aldehydes to ketones is achieved via rhodium-catalyzed vinyl triflate-aldehyde reductive coupling-redox isomerization mediated by potassium formate. This method circumvents premetalated C-nucleophiles and discrete redox manipulations typically required to form ketones from aldehydes.

Conversion of Aldehydes to Branched or Linear Ketones via Regiodivergent Rhodium-Catalyzed Vinyl Bromide Reductive Coupling-Redox Isomerization Mediated by Formate.

A regiodivergent catalytic method for direct conversion of aldehydes to branched or linear alkyl ketones is described. Rhodium complexes modified by P BuMe catalyze formate-mediated aldehyde-vinyl bromide reductive coupling-redox isomerization to form branched ketones. Use of the less strongly coordinating ligand, PPh, promotes vinyl- to allylrhodium isomerization en route to linear ketones.

Twist sense control in terminally functionalized -phenylenes.

Many abiotic foldamers are based on achiral repeat units but adopt chiral geometries, especially helices. In these systems, there is no inherent preference for one handedness of the fold; however, it is well-established that the point chirality of substituents can be communicated to the helix. This capability represents a basic level of control over folding that is necessary for applications in molecular recognition and in the assembly of higher-order structures.

Solvent effects on the folding of o-phenylene oligomers.

ortho-Phenylene oligomers fold into compact helical conformations in solution, and have therefore recently emerged as a class of foldamers. Previous work has shown that their folding is controlled by arene-arene stacking interactions parallel to the helical axis. Such interactions might reasonably be expected to be sensitive to solvent, but little is known of solvent effects in this system.