The Stille reaction in the synthesis of the C37-norcarotenoid butenolide pyrrhoxanthin. Scope and limitations.
The sequential Stille cross-coupling reactions of the dihalogenated gamma-alkylidenebutenolide 7 with stannanes 9 and 6 afforded the carbon skeleton of pyrrhoxanthin, a highly functionalized C7'-C8' acetylenic C37-norcarotenoid butenolide. Although the first halogen-selective Stille coupling takes place in 90% yield at ambient temperature, double isomerization of the Z,E- to the E,Z-C7'-C10' enyne, likely induced by the catalyst, accompanyied the bond formation, leading to 9'Z-20 and, ultimately, to 9'Z-pyrrhoxanthin 9'Z-1.
Vaz
Belén
B
Departamento de Química Organica, Facultade de Química, Universidade de Vigo, Lagoas Marcosende, E-36310, Vigo, Spain.
Domínguez
Marta
M
Alvarez
Rosana
R
de Lera
Angel R
AR
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D002338:Carotenoids / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure
C520451:pyrrhoxanthin; D002338:Carotenoids; D002244:Carbon; C004511:butenolide; D015107:4-Butyrolactone