Iron Phosphate Catalyzed Asymmetric Cross-Dehydrogenative Coupling of 2-Naphthols with ß-Ketoesters.

Chiral iron phosphate complexes were successfully exploited for asymmetric cross-dehydrogenative coupling reactions between 2-naphthols and ß-ketoester derivatives. On the basis of kinetic studies, it is suggested that iron monophosphate complexes constitute the active catalysts that induce stereoselectivity during the carbon-carbon bond-formation step.

Enantioselective Oxidative Homocoupling and Cross-Coupling of 2-Naphthols Catalyzed by Chiral Iron Phosphate Complexes.

Novel chiral iron phosphate complexes were prepared as catalysts for asymmetric oxidative coupling reactions. These catalysts were applied for the synthesis of enantio-enriched C1- and C2-symmetric BINOLs, in which the 3 and 3' positions are available for chemical modifications. It was proposed that the reaction takes place via an oxidative radical-anion coupling mechanism. A destructive BINOL racemization that competes with the enantioselective oxidative coupling of 2-naphthols was revealed, thereby offering new insights into this highly important reaction.

Synthetic and Predictive Approach to Unsymmetrical Biphenols by Iron-Catalyzed Chelated Radical-Anion Oxidative Coupling.

An iron-catalyzed oxidative unsymmetrical biphenol coupling in 1,1,1,3,3,3-hexafluoropropan-2-ol that proceeds via a chelated radical-anion coupling mechanism was developed. Based on mechanistic studies, electrochemical methods, and density functional theory calculations, we suggest a general model that enables prediction of the feasibility of cross-coupling for a given pair of phenols.

Significant enhancement in the efficiency and selectivity of iron-catalyzed oxidative cross-coupling of phenols by fluoroalcohols.

Significant enhancement of both the rate and the chemoselectivity of iron-catalyzed oxidative coupling of phenols can be achieved in fluorinated solvents, such as 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), 2,2,2-trifluoroethanol (TFE), and 1-phenyl-2,2,2-trifluoroethanol. The generality of this effect was examined for the cross-coupling of phenols with arenes and polycyclic aromatic hydrocarbons (PAHs) and of phenol with ß-dicarbonyl compounds. The new conditions were utilized in the synthesis of 2'''-dehydroxycalodenin B in only four synthetic steps.

Thiol-promoted selective addition of ketones to aldehydes.

A simple and efficient thiol-mediated addition of ketones to aromatic and aliphatic aldehydes is reported. This thermodynamically controlled Pummerer/aldol reaction, which can tolerate both moisture and protic functional groups, provides a direct entry to syn-ß-thioketones in high chemo- and regioselectivity. Mechanistic studies revealed that selective transformation of the aldehyde to an electrophilic thionium ion species concurrent with the generation of a nucleophilic vinyl sulfide coupling partner from the ketone is imposing cross-coupling over dimerization.

A [Pd]-mediated ω-alkynone cycloisomerization approach for the central tetrahydropyran unit and the synthesis of C(31)-C(48) fragment of aflastatin A.

A concise assembly of the central tetrahydropyran unit of aflastatin A featuring a Pd-mediated alkynone cycloisomerization to provide a glycal and its subsequent stereoselective hydroboration to deliver the requisite stereochemistry at C(33) and C(34) centers is documented.