Photo-induced ATC reactions of RI, CO, and amines to produce amides, were examined using ionic liquids, such as [bmim]PF6 and [bmim]NTf2, as reaction media in the presence of a catalytic amount of a Pd–carbene complex. When the primary alkyl iodide was used, the yield of the amide was lowered due to competing SN2 reactions between RI and amines, whereas the reaction of the tertiary alkyl iodides was dependent on the structure of the substrates. ATC reactions of a wide variety of secondary RI proceeded smoothly when ionic liquids were used as reaction media. The Pd-catalyst and ionic liquid could also be recycled.
Acylated oxime ethers have been prepared by a three-component coupling reaction using alkyl allyl sulfone precursors, carbon monoxide, and phenylsulfonyl oxime ether derivatives under tin-free radical reaction conditions.
Ab initio calculations using the 6-311G**, cc-pVDZ, and (valence) double-ζ pseudopotential (DZP) basis sets, with (MP2, QCISD, CCSD(T)) and without (HF) the inclusion of electron correlation, and density functional (BHandHLYP, B3LYP) calculations predict that the transition states for the reaction of acetyl radical with several alkyl halides adopt an almost collinear arrangement of attacking and leaving radicals at the halogen atom. Energy barriers (ΔE‡) for these halogen transfer reactions of between 89.2 (chlorine transfer from methyl group) and 25.3 kJ mol–1 (iodine transfer from tert-butyl group) are calculated at the BHandHLYP/DZP level of theory. While the difference in forward and reverse energy barriers for iodine transfer to acetyl radical is predicted to be 15.1 kJ mol–1 for primary alkyl iodide, these values are calculated to be 6.7 and –4.2 kJ mol–1 for secondary and tertiary alkyl iodide respectively. These data are in good agreement with available experimental data in that atom transfer radical carbonylation reactions are sluggish with primary alkyl iodides, but proceed smoothly with secondary and tertiary alkyl iodides. These calculations also predict that bromine transfer reactions involving acyl radical are also feasible at moderately high temperature.
Straightforward access to 2-alkyl-substituted 1,3-diketones is provided by a regioselective addition of aldehydes to enones catalyzed by the ruthenium hydride catalyst [RuHCl(CO)(PPh3)3] (see scheme). The reaction involves a hydrometalation of the enone to form a metal enolate, a cross-aldol reaction to form an alkoxymetal species, and a subsequent β-metal hydride elimination.
Substitution at nitrogen by α,β-unsaturated acyl radicals took place accompanied by elimination of an α-phenethyl radical. This reaction led to the development of a new carbonylative annulation method for five- to seven-membered ring lactams.
Ruthenium catalyzes a carbonylative [3+2+1] cycloaddition, using silylacetylenes, α,β-unsaturated ketones, and CO as the starting materials, providing the new method for the synthesis of tetrasubstituted α-pyrones. In this reaction, the carbonyl group and α-carbon of vinyl ketones are incorporated as a three-atom assembling unit.