Ritter-type iodo(iii)amidation of unactivated alkynes for the stereoselective synthesis of multisubstituted enamides.

The Ritter reaction, Brønsted- or Lewis acid-mediated amidation of alkene or alcohol with nitrile via a carbocation, represents a classical method for the synthesis of tertiary amides. Although analogous reactions through a vinyl cation or a species alike may offer a route to enamide, an important synthetic building block as well as a common functionality in bioactive compounds, such transformations remain largely elusive. Herein, we report a Ritter-type trans-difunctionalization of alkynes with a trivalent iodine electrophile and nitrile, which affords ß-iodanyl enamides in moderate to good yields. Mediated by benziodoxole triflate (BXT), the reaction proves applicable to a variety of internal alkynes as well as to various alkyl- and arylnitriles. The benziodoxole group in the product serves as a versatile handle for further transformations, thus allowing for the preparation of various tri- and tetrasubstituted enamides that are not readily accessible by other means.

Metal Free Access to Polysubstituted Pyrimidines via Nitrile Activation and [2+2+2] Cycloaddition.

Tf2 O mediated intermolecular / intramolecular [2+2+2] cycloaddition between alkynes and nitriles has been developed for efficient construction of polysubstituted pyrimidines and bicyclopyrimidines. In presence of Tf2 O, aza-allene species were generated in situ through nitrile activation and subsequently participated in the [2+2+2] cycloaddition, which was fully supported by deuteration experiments. The reaction had good substrate extensibility with moderate to excellent yield including trimethylsilylalkynes. The method was utilized as a synthetic tool in the preparation of a luminescent metal complex.

Fluorobenziodoxole-BF3 Reagent for Iodo(III)etherification of Alkynes in Ethereal Solvent.

A combination of fluorobenziodoxole (FBX) and BF3 ⋅ OEt2 in cyclopentyl methyl ether promotes regio- and stereoselective addition of benziodoxole and methoxy groups to alkynes. This difunctionalization reaction tolerates a variety of functionalized internal and terminal alkynes to afford trans-ß-alkoxyvinylbenziodoxoles, which represent versatile precursors to stereochemically well-defined multisubstituted vinyl ethers. The reaction is proposed to involve cleavage of the I-F bond of FBX by BF3 , followed by electrophilic activation of the alkyne by the resulting cationic IIII species that triggers the nucleophilic addition of the ethereal oxygen.

Stereoselective Access to Highly Substituted Vinyl Ethers via trans-Difunctionalization of Alkynes with Alcohols and Iodine(III) Electrophile.

A method for the regio- and stereoselective synthesis of highly substituted vinyl ethers via trans-1,2-difunctionalization of alkynes with a cyclic λ3-iodane electrophile (benziodoxole triflate) and alcohols is reported. The reaction tolerates a variety of internal and terminal alkynes as well as various alcohols, affording ß-λ3-iodanyl vinyl ethers in good yields with high regio- and stereoselectivities. The benziodoxole moiety of the products can be used as a versatile linchpin for the synthesis of structurally diverse vinyl ethers that are difficult to access by other means.

The coordination chemistry of phosphinidene sulfides. Synthesis and catalytic properties of Pd4 and Pt4 clusters.

7-Phosphanorbornene sulfides were used as [RP = S] precursors. The reaction of these precursors with [M(PPh3)4] (M = Pd, Pt) yields star-like M4 clusters in which the central core is coated by three RP = S units acting as 4-electron µ2-P, η2-P = S ligands. The Pd cluster displays both stability and catalytic activity in the Suzuki-Miyaura reaction. DFT analysis suggests that a mononuclear [η2-RP = S]Pd(PPh3) complex is involved in the formation of the Pd4 clusters.