Metal-catalyzed carbon-sulfur bond formation.

Stereocontrol in the synthesis of acyclic systems: applications to natural product synthesis

Enantio‐ and Diastereoselective Construction of α,α‐Disubstituted α‐Amino Acids for the Synthesis of Biologically Active Compounds

The hydrothiolation of unsaturated carbon-carbon bonds is a practical and atom-economical approach for the incorporation of sulfur into organic frameworks. In recent years, we have witnessed the development of a range of transition-metal-based catalytic systems for the control of the regio- and stereoselectivity. In this Minireview we highlight the mechanistic background behind this transformation so as to help the design of more specific and active organometallic hydrothiolation catalysts.

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The emergence of transition-metal-mediated hydrothiolation of unsaturated carbon-carbon bonds: a mechanistic outlook.

Synthetic control leading to chiral compounds

3-Acylthiazolidine-2-thiones, easily prepared from carboxylic acids and readily available thiazolidine-2-thione, were reduced to the corresponding aldehydes either with diisobutylaluminum hydride in toluene at −78–−40 °C in 70–90% yields or with lithium tri-t-butoxyaluminum hydride in tetrahydrofuran at −20-0 °C in 80–90% yields. The present method appears to be applicable to the synthesis of aldehydes from both aromatic and aliphatic derivatives having chloro, bromo, nitro, and noncojugated double bond, except for the reduction of α,β-unsaturated derivatives with lithium tri-t-butoxyaluminum hydride and of cyano derivative with diisobutylaluminum hydride. Completion of the reduction is indicated by disappearance of the original yellow color of the reaction mixture.

The Partial Reduction of Carboxylic Acids to Aldehydes via 3-Acylthiazolidine-2-thiones with Diisobutylaluminum Hydride and with Lithium Tri-t-butoxyaluminum Hydride

It was found that, in the presence of Lewis acid such as TiCl4, AlCl3, SnCl4, ZnCl2, and BF3·O(C2H5)2, enol acetate reacts with various acetals and benzaldehyde to afford the corresponding aldol-type addition products in good yields.

Reaction of enol acetate with acetal and carbonyl compound in the presence of lewis acid

It was established that, in the presence of TiCl4, α,β-unsaturated carbonyl compounds react with ethanethiol at room temperature to afford the addition products, 3-ethylthiocarbonyl compounds, in good yields.

ADDITION REACTION OF THIOL TO OLEFIN BY THE USE OF TiCl4

A new synthesis for the preparation of (±)-pestalotin (1) and (±)-epipestalotin (1′) was successfully accomplished by utilizing the following two reactions : The partial reduction of 2-benzyloxyhexanoic acid (3) to 2-benzyloxyhexanal (6) via corresponding 3-acylthiazolidine-2-thione 5, and the TiCl4-promoted reaction of the aldehyde 6 with diketene.

New synthesis of (±)-pestalotin and (±)-epipestalotin

An enanticcontrolled synthesis of (+)-9-deacetyl-9-(hydroxymethyl) -4-demethoxydaunomycinone has been achieved via asymmetric introduction of the 9-hydroxyl group as a key step by catalytic Sharpless epoxidation.

Toshio Izawa

Papers

The Partial Reduction of Carboxylic Acids to Aldehydes via 3-Acylthiazolidine-2-thiones with Diisobutylaluminum Hydride and with Lithium Tri-t-butoxyaluminum Hydride

Reaction of enol acetate with acetal and carbonyl compound in the presence of lewis acid

ADDITION REACTION OF THIOL TO OLEFIN BY THE USE OF TiCl4

New synthesis of (±)-pestalotin and (±)-epipestalotin

A novel enantiocontrolled synthesis of (+)-9-deacetyl-9-(hydroxymethyl)-4-demethoxydaunomycinone.