353454-95-2Relevant academic research and scientific papers
Cascade radical synthesis of heteroarenes via iminyl radicals
Bowman,Bridge,Brookes,Cloonan,Leach
, p. 58 - 68 (2007/10/03)
A novel cascade cyclisation protocol has been developed which 'zips up' two rings to form new tetracycles. In the protocol, treatment of vinyl bromides and iodides with hexamethylditin (Me3Sn· yields intermediate vinyl radicals which undergo 5-exo cyclisation onto nitrile groups to yield intermediate iminyl radicals. The iminyl radicals can undergo 6-endo cyclisation (or 5-exo followed by neophyl rearrangement) to yield tetracyclic π-radicals which lose hydrogen (H·) in an H-abstraction step. Methyl radicals, generated from the breakdown of trimethylstannyl radicals (Me3Sn·), are proposed as a possible H-abstractor for this final oxidative step. The protocol has been used to synthesise the tetracyclic rings A-D (tetracycle indolizino[1,2-b]quinolin-9(11H)-one) of the anticancer alkaloids camptothecin, mappicine, nothapodytine B and nothapodytine A. The protocol has also been applied to the synthesis of analogues of camptothecin in which ring A has been replaced by thiophene (8,10-dihydrothieno[2′,3′:5,6]pyrido[2,3-a]indolizin-8-one) and ring D by pyrrole (10H-pyrrolizino[1,2-b]quinoline) and benzene (11H-indeno[1,2-b]quinolin-11-one).
Synthesis of heteroarenes via radical cyclisation onto nitriles
Bowman,Bridge,Cloonan,Leach
, p. 765 - 768 (2007/10/03)
A new protocol for the synthesis of tetracyclic nitrogen heteroarenes using cascade radical cyclisation has been developed. The key steps involve 5-exo vinyl radical cyclisation onto nitriles to yield intermediate iminyl radicals which cyclise onto an arene rings. Rings A-D of the anticancer alkaloids camptothecin, mappicine and nothapodytines A and B have been synthesised using this protocol.
