Palladium‐catalyzed decarboxylative coupling of α,β‐unsaturated carboxylic acids with aryl tosylates

We report a general method for selective cross‐coupling of α,β‐unsaturated carboxylic acids with aryl tosylates enabled by versatile Pd(II) complexes. This method features the general cross‐coupling of ubiquitous α,β‐unsaturated carboxylic acids by decarboxylation. The transformation is characterized by its operational simplicity, the use of inexpensive, air‐stable Pd(II) catalysts, scalability and wide substrate scope. The reaction proceeds with high trans selectivity to furnish valuable (E)‐1,2‐diarylethenes.     

Vinylarenetricarbonyl complexes of chromium as chain propagation regulators for polymerization of acrylic monomers

The polymerization of methyl methacrylate and butyl acrylate initiated by azo‐bis‐isobutyronitrile in the presence of metal‐containing monomers (p‐methylstyrene‐, stilbene‐ and α‐methylstyrene‐chromiumtricarbonyl) was studied. Kinetic parameters (i.e. the decrease in the autoacceleration during the polymerization of acrylic monomers, its shift towards a high conversion region in the presence of α‐methylstyrenechromiumtricarbonyl, a linear dependence of the molecular weight of a polymethyl methacrylate and the shift of molecular‐weight distribution curves to a high molecular weight region with conversion) demonstrate the influence of vinylarenetricarbonyl complexes of chromium on basic steps of polymerization. It is important to note that the above organometallic compounds enable the controlled synthesis of polymers under temperature conditions (50–70 °C) corresponding to those of the industrial polymer production. Copyright © 2003 John Wiley & Sons, Ltd.     

Cobalt‐Catalyzed Diborylation of 1,1‐disubstituted Vinylarenes: A Practical Route to Branched gem‐Bis(boryl)alkanes

We report the first catalytic diborylation of 1,1‐disubstituted vinylarenes with pinacolborane using a cobalt catalyst generated from bench‐stable Co(acac)₂ and xantphos. A wide range of 1,1‐disubstituted vinylarenes underwent this transformation to produce the corresponding gem‐bis(boryl)alkanes in modest to high yields. This cobalt‐catalyzed reaction can be readily conducted on a gram scale without the use of a dry box and represents a practical and effective approach to prepare a wide range of branched gem‐bis(boryl)alkanes.