7-endo selective aryl radical cyclization onto enamides leading to 3-benzazepines: concise construction of a cephalotaxine skeleton.
Bu3SnH-mediated radical cyclizations of 2-(2-bromophenyl)-N-ethenylacetamide gave 6-exo cyclization product 15 as the major product, whereas N-[2-(2-bromophenyl)ethyl]-N-ethenylamides gave almost exclusively 7-endo cyclization products. These results indicated that the position of the carbonyl group on enamide played an important role in deciding the course of the cyclization. The 7-endo selective cyclization was applied to concise construction of a cephalotaxine skeleton.
Taniguchi
Tsuyoshi
T
Division of Pharmaceutical Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan.
Ishita
Atsuko
A
Uchiyama
Masahiko
M
Tamura
Osamu
O
Muraoka
Osamu
O
Tanabe
Genzoh
G
Ishibashi
Hiroyuki
H
D000577:Amides / Q000138:chemical synthesis*; D001552:Benzazepines / Q000138:chemical synthesis*; D003500:Cyclization; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D006248:Harringtonines / Q000138:chemical synthesis / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D000077863:Homoharringtonine; D015394:Molecular Structure
D000577:Amides; D001552:Benzazepines; D005609:Free Radicals; D006248:Harringtonines; D006571:Heterocyclic Compounds; D000077863:Homoharringtonine