Mechanistic study of 7-endo selective radical cyclization of the aryl radical

✍ Scribed by Akio Kamimura; Yuriko Ishihara; Masahiro So; Takahiro Hayashi

• Publisher: Elsevier Science
• Year: 2009
• Tongue: French
• Weight: 329 KB
• Volume: 50
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/j.tetlet.2009.01.132

✦ Synopsis

Mechanistic studies on the novel 7-endo selective radical cyclization were carried out. The reaction afforded three products, 7-endo product, 6-exo product, and reduced product. The distribution of these products was estimated by GC analyses. The 7-endo/6-exo selectivity was almost constant against variation in the concentration of Bu 3 SnH, while the reduction/cyclization ratio was sensitive to the concentration of Bu 3 SnH. The reduction/cyclization ratio was mainly affected by the rotational isomeric ratio of the cyclization precursor. Kinetic analyses indicated that the cyclization process should be irreversible, and the rate constant of 7-endo/6-exo radical cyclization was estimated to be about 3.3 Â 10 8 s À1 at 80 °C.