TY - JOUR
T1 - Free-Radical Carbonylations
T2 - Then and Now
AU - Ryu, Ilhyong
AU - Sonoda, Noboru
PY - 1996/1/1
Y1 - 1996/1/1
N2 - Although known since the 1950s, free-radical carbonylation has not received much attention until only recently. In the last few years the application of modern free-radical techniques has revealed the high synthetic potential of this reaction as a tool for introducing CO into organic molecules. Clearly now is the time for a renaissance of this chemistry. Under standard conditions (tributyltin hydride/CO) primary, secondary, as well as tertiary alkyl bromides and iodides can be efficiently converted into the corresponding aldehydes. Aromatic and ~,//-unsaturated aldehydes can also be prepared from the parent aromatic and vinylic iodides. If the reaction is carried out in the presence of alkenes containing an electron-with-drawing substituent, the initially formed acyl radical subsequently adds to the alkene, leading to a general method for the synthesis of unsymmetrical ketones. This three-component coupling reaction can be extended successfully to allyltin-mediated reactions. Thus, fl,)'-enones can be prepared from organic halides, CO, and allyltributylstannanes. In a remarkable one-pot procedure alkyl halides can be treated with a mixture of alkene, allyltributylstannane, and carbon monoxide in a four-component coupling reaction that provides//-func-tionalized 6,c-unsaturated ketones by the formation of three new C-C bonds. The reaction of 4-pentenyl radicals with CO leads to acyl radical cyclization, which provides a useful method for the synthesis of cyclopentanones. Certain useful one-electron oxidations can be combined efficiently with free-radical carbonylations. These findings and others discussed in this article clearly demonstrate that free-radical carbonyla-tion can now be considered a practical alternative to transition metal mediated carbonylation.
AB - Although known since the 1950s, free-radical carbonylation has not received much attention until only recently. In the last few years the application of modern free-radical techniques has revealed the high synthetic potential of this reaction as a tool for introducing CO into organic molecules. Clearly now is the time for a renaissance of this chemistry. Under standard conditions (tributyltin hydride/CO) primary, secondary, as well as tertiary alkyl bromides and iodides can be efficiently converted into the corresponding aldehydes. Aromatic and ~,//-unsaturated aldehydes can also be prepared from the parent aromatic and vinylic iodides. If the reaction is carried out in the presence of alkenes containing an electron-with-drawing substituent, the initially formed acyl radical subsequently adds to the alkene, leading to a general method for the synthesis of unsymmetrical ketones. This three-component coupling reaction can be extended successfully to allyltin-mediated reactions. Thus, fl,)'-enones can be prepared from organic halides, CO, and allyltributylstannanes. In a remarkable one-pot procedure alkyl halides can be treated with a mixture of alkene, allyltributylstannane, and carbon monoxide in a four-component coupling reaction that provides//-func-tionalized 6,c-unsaturated ketones by the formation of three new C-C bonds. The reaction of 4-pentenyl radicals with CO leads to acyl radical cyclization, which provides a useful method for the synthesis of cyclopentanones. Certain useful one-electron oxidations can be combined efficiently with free-radical carbonylations. These findings and others discussed in this article clearly demonstrate that free-radical carbonyla-tion can now be considered a practical alternative to transition metal mediated carbonylation.
UR - http://www.scopus.com/inward/record.url?scp=0029790992&partnerID=8YFLogxK
U2 - 10.1002/anie.199610501
DO - 10.1002/anie.199610501
M3 - Article
AN - SCOPUS:0029790992
VL - 35
SP - 1050
EP - 1066
JO - Angewandte Chemie - International Edition
JF - Angewandte Chemie - International Edition
SN - 1433-7851
IS - 10
ER -