Nickel-catalyzed synthesis of benzocoumarins: application to the total synthesis of arnottin I.
The ring-opening addition of methyl 2,3-dimethoxy-6-iodobenzoate to oxabenzonorbornadienes followed by cyclization in the presence of NiBr2(dppe) and Zn metal powder in acetonitrile at 80 degrees C to give the corresponding benzocoumarin derivatives is described. This methodology was then applied to the synthesis of natural product arnottin I, first isolated from Xanthoxylum arnottianum Maxim, using protecting group chemistry. After deprotection and subsequent ring closure, arnottin I was obtained in 21% overall yield after six steps starting from catechol.
Madan
Sachin
S
Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
Cheng
Chien-Hong
CH
D002384:Catalysis; D003374:Coumarins / Q000138:chemical synthesis*; D003500:Cyclization; D007463:Iodobenzoates / Q000737:chemistry; D009532:Nickel / Q000737:chemistry*; D009636:Norbornanes / Q000737:chemistry
D003374:Coumarins; D007463:Iodobenzoates; D009636:Norbornanes; C414400:arnottin I; D009532:Nickel