2005 Terpenes U 0200 Tandem Cyclizations Involving α-Ketenyl Alkyl Radicals. New Syntheses of the Natural Triquinanes Pentalenene and Modhephene. — The precursor (II) for race- mic pentalenene (IV) is successfully prepared by tandem radical cyclization of a ketene alkyl radical derived from selenyl ester (I). In an analogous manner the 3,3,3-propellane ring system (VI) of modhephene (VII) is obtained by a tandem transannulation—cyclization of radical species derived from thioester (V) containing a cyclooctane ring. — (DE BOECK, B.; HARRINGTON-FROST, N. M.; PATTENDEN*, G.; Org. Biomol. Chem. 3 (2005) 2, 340-347; Sch. Chem., Univ. Nottingham, Nottingham NG7 2RD, UK; Eng.) — Klein 23- 197

Tandem Cyclizations Involving α-Ketenyl Alkyl Radicals. New Syntheses of the Natural Triquinanes Pentalenene and Modhephene

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Page 1: Tandem Cyclizations Involving α-Ketenyl Alkyl Radicals. New Syntheses of the Natural Triquinanes Pentalenene and Modhephene

2005

TerpenesU 0200 Tandem Cyclizations Involving α-Ketenyl Alkyl Radicals. New Syntheses of the

Natural Triquinanes Pentalenene and Modhephene. — The precursor (II) for race-mic pentalenene (IV) is successfully prepared by tandem radical cyclization of a ketene alkyl radical derived from selenyl ester (I). In an analogous manner the 3,3,3-propellane ring system (VI) of modhephene (VII) is obtained by a tandem transannulation—cycli-zation of radical species derived from thioester (V) containing a cyclooctane ring. — (DE BOECK, B.; HARRINGTON-FROST, N. M.; PATTENDEN*, G.; Org. Biomol. Chem. 3 (2005) 2, 340-347; Sch. Chem., Univ. Nottingham, Nottingham NG7 2RD, UK; Eng.) — Klein

23- 197