Stereochemistry and mechanism of acylation of acetylenes

One-Pot Synthesis of (Z)-β-Halovinyl Ketones via the Cascade of Sonogashira Coupling and Hydrohalogenation

Herein, we report an efficient method for the synthesis of (Z)-β-halovinyl ketones through a one-pot Sonogashira coupling and hydrohalogenation reaction promoted by palladium-copper catalyst and Brønsted acid. The ynone intermediates are generated in situ from readily available acid chlorides and terminal alkynes at room temperature, which are directly converted to (Z)-β-halovinyl ketones by treating with triflic acid. This method avoids the use of an external halogen source and features broad substrate scope, high yield, and good to excellent stereoselectivity.

(E)-Selective Friedel–Crafts acylation of alkynes to β-chlorovinyl ketones: defying isomerizations in batch reactions by flow chemistry approaches

Flow chemistry approaches provide a fast, clean, and stereoselective synthetic route to (E)-β-chlorovinyl ketones, free from inherent (E) → (Z) isomerization.

Intramolecular Vinylation of Aryl Rings by Vinyl Cations

A Lewis acid mediated intramolecular electrophilic vinylation of aryl rings by vinyl cations is reported. This reaction takes advantage of β-hydroxy-α-diazo ketones as vinyl cation precursors and provides good yields of tricyclic 1-indenones that contain a seven-membered ring. Extending the alkane chain that tethers the vinyl cation to the aromatic ring leads to 2-napthol and 2-indenone products.

Iridium-catalyzed addition of aroyl chlorides and aliphatic acid chlorides to terminal alkynes

Iridium complexes show high catalytic activity in intermolecular additions of acid chlorides to terminal alkynes to afford valuable (Z)-β-chloro-α,β-unsaturated ketones. Ligands in the catalytic system play a crucial role in this reaction. An N-heterocyclic carbene (NHC) is an efficient ligand for the addition of aroyl chlorides, while dicyclohexyl(2-methylphenyl)phosphine (PCy(2)(o-Tol)) is indispensable for the reaction of aliphatic acid chlorides. The addition reactions proceed regio- and stereoselectively with suppression of decarbonylation and β-hydrogen elimination, which have been two major intrinsic problems in transition-metal-catalyzed reactions. Stoichiometric reactions of active iridium catalysts with aroyl chlorides and aliphatic acid chlorides are carried out to gain insights into the reaction mechanisms.

Rhodium-complex-catalyzed addition reactions of chloroacetyl chlorides to alkynes

The addition reaction of chloroacetyl chloride derivatives with terminal alkynes was found to be catalyzed by Rh(acac)(CO)(AsPh(3)) to afford (Z)-1,4-dichloro-3-buten-2-one derivatives, which displayed diverse reactivities in synthetic elaboration.

Iron-catalyzed regio- and stereoselective addition of acid chlorides to alkynes

An iron-catalyzed regio- and stereoselective addition of acid chlorides to alkynes has been described. The reaction utilizes an inexpensive iron catalyst system and it is suitable for the formation of a variety of bifunctional molecules. This is an inexpensive, regio-, stereoselective and atom-economical approach to beta-chloro-alpha,beta-unsaturated ketones from simple and readily available starting materials.

Syntheses of hemoprotein models that can be covalently attached onto electrode surfaces by click chemistry

Five alkyne-containing hemoprotein models have been synthesized in a convergent manner. Sonogashira coupling was used to introduce the alkyne functional group on the proximal imidazole before or after being attached on the porphyrin. One model was immobilized onto a gold electrode surface via copper(I)-catalyzed azide-alkyne cycloaddition (Sharpless click chemistry).