SmI(2)-promoted radical addition reactions with N-(2-Indolylacyl)oxazolidinones: synthesis of bisindole compounds.
The treatment of N-acyl oxazolidinones of N-benzyl 2-indolecarboxylic acids varying in the substitution pattern of the indole ring with samarium diiodide at -78 degrees C led to the formation of two indole dimer products. The major product isolated in yields from 55 to 59% represents an unsymmetrical dimer arising from 1,4-addition to the 2-indolecarboxylic acid derivative of a possible ketyl-type radical anion intermediate originating from the reduction of the exocyclic carbonyl group of the N-acyl oxazolidinone. The minor dimer, represented by a symmetrical diketone, was produced in yields ranging from 11 to 23%. Even in the presence of an alpha,beta-unsaturated amide, dimerization was the preferred pathway rather than the formation of a gamma-keto amide. Upon treatment with acid, the unsymmetrical indole dimer cyclized to form a diindolequinone. Finally, the N-acyl oxazolidinones of pyrrole-2-carboxylic acid and 3-indolecarboxylic acid preferred in both cases to undergo C-C bond formation with an acrylamide in the presence of SmI2 rather than dimerization.
Lindsay
Karl B
KB
Center for Insoluble Protein Structures, Department of Chemistry and Interdisciplinary Nanoscience Center, University of Aarhus, Langelandsgade 140, 8000 Aarhus C, Denmark.
Ferrando
Francesc
F
Christensen
Kasper L
KL
Overgaard
Jacob
J
Roca
Tomàs
T
Bennasar
M-Lluïsa
ML
Skrydstrup
Troels
T
D020106:Acrylamide / Q000737:chemistry; D019281:Dimerization; D007211:Indoles / Q000737:chemistry; D007454:Iodides / Q000494:pharmacology*; D015394:Molecular Structure; D023303:Oxazolidinones / Q000737:chemistry*; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry; D012493:Samarium / Q000494:pharmacology*
D007211:Indoles; D007454:Iodides; D023303:Oxazolidinones; D020106:Acrylamide; D012493:Samarium; C002986:2-pyrrolecarboxylic acid; C030374:indole; D011392:Proline; C409809:samarium diiodide