Route to Highly Substituted Pyridines.

Pyridine rings are common structural motifs found in a number of biologically active compounds, including some top-selling pharmaceuticals. We have developed a new approach to access substituted pyridines. The method aims to provide a reliable synthesis of a diverse range of substituted pyridines through a three-step procedure.

The electronic ground state of [Fe(CO)3 (NO)](-) : a spectroscopic and theoretical study.

During the past 10 years iron-catalyzed reactions have become established in the field of organic synthesis. For example, the complex anion [Fe(CO)3 (NO)](-) , which was originally described by Hogsed and Hieber, shows catalytic activity in various organic reactions. This anion is commonly regarded as being isoelectronic with [Fe(CO)4 ](2-) , which, however, shows poor catalytic activity.

Fe-catalyzed allylic C-C-bond activation: vinylcyclopropanes as versatile a1,a3,d5-synthons in traceless allylic substitutions and [3 + 2]-cycloadditions.

The low-valent iron complex Bu(4)N[Fe(CO)(3)(NO)] (TBAFe) catalyzes the allylic C-C-bond activation of electron-poor vinyl cyclopropanes to generate synthetically useful a1,a3,d5-synthons which are prone to undergo multiple consecutive reactions. The versatility of this approach is demonstrated by a traceless allylic substitution and a formal [3 + 2] cycloaddition to give either functionalized acyclic products or densely substituted cyclopentanes and pyrrolidines in high yields and regioselectivities.

Fe-catalyzed multicomponent reactions: the regioselective alkoxy allylation of activated olefins and its application in sequential Fe catalysis.

We present herein a versatile and broadly applicable Fe-catalyzed regioselective alkoxy allylation of activated double bonds. Substituted allylic carbonates are converted into the corresponding σ-enyl Fe complexes by reaction with Bu(4)N[Fe(CO)(3)(NO)] (TBAFe) at 30 °C. The liberated alkoxide adds to an activated double bond with the generation of a C-nucleophile, which is trapped by the σ-enyl Fe complex in a regioselective manner.

Binuclear Fe-complexes as catalysts for the ligand-free regioselective allylic sulfenylation.

Binuclear Fe-complexes that are readily prepared by treating Bu(4)N[Fe(CO)(3)(NO)] with an excess of thiol or from Fe-salts under reductive conditions are potent catalysts for the regioselective allylic sulfenylation. Low catalyst loadings of only 0.25 mol% and reaction temperatures of only 40 °C allow for the coupling of functionalized allylic starting materials with functionalized mercaptans in good yield with full retention of the configuration.