A novel carbonylation method based on free-radical reactions has been developed. Acyl radicals, generated by the addition of alkyl free-radicals to carbon monoxide, have been effectively trapped by tin hydride. Through this sequence, the free-radical formylation of organo halides to the corresponding aldehydes was realized. Carbonylative cyclizations to give cyclopentanones can also be affected starting with 4-pentenyl halides. When an alkene was also present in the reaction system, the trapping of the alkyl free-radical by carbon monoxide to form an acyl free-radical and the subsequent addition of that radical to the alkene took place efficiently to give an unsymmetrical ketone. This sequence represents a unique method for the double alkylation of carbon monoxide β, γ-Unsaturated ketones can be synthesized via a three-component coupling of alkyl iodides, carbon monoxide, and allylstannane. All of these findings have demonstrated that free-radical carbonylation is a useful method for the introduction of carbon monoxide into organic molecules.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Highly efficient thermal radical carboaminoxylations of various olefins by using the novel alkoxyamine A to give adducts of type B are described. It is reported that these radical addition reactions can be performed in a microflow reaction system. As compared to conventional batch reaction setup, significantly higher yields are obtained by running carboaminoxylations using the microflow system under analogous conditions.
This Feature Article summarizes our current efforts to develop new strategies for radical carbonylation, which include electron-transfer carbonylation, site-selective C(sp 3 )–H carbonylation by a photocatalyst and ring-opening carbonylation.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
A carbonylative Mizoroki–Heck reaction using alkyl iodides was achieved with a Pd/photoirradiation system using DBU as a base. In this reaction, alkyl radicals were formed from alkyl iodides via single-electron transfer (SET) and then underwent a sequential addition to CO and alkenes to give β-keto radicals. It is proposed that DBU would abstract a proton α to carbonyl to form radical anions, giving α,β-unsaturated ketones via SET.
Ab initio calculations using the 6-311G**, cc-pVDZ, and (valence) double-zeta 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 (DeltaE(double dagger)) 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.
Aromatic β-keto esters were synthesized via a carbonylative cross-coupling reaction of alkyl iodides and arylboronic acids in the presence of a catalytic amount of Pd catalyst.
Abstract In this Short Review, we discuss radical reactions using 1,2-bis(phenylsulfonyl)ethylene (BPSE), which has drawn significant attention as a versatile building block for (phenylsulfonyl)ethenylation. Regardless of its E or Z form, BPSE exhibits reliable reactivity towards the attack of alkyl and aryl radicals in order to function as a reliable radical C2 synthon. 1 Introduction 2 Use in Radical Chain Reactions 3 Use in Reactions Utilizing an Electron-Transfer Process 4 Use in Radical-Based C–H Alkenylation 5 Conclusion
