Efficient synthesis of spirolactones from cyclic anhydrides via an allylation/alkylation-RCM sequence
摘要:
Starting from cyclic anhydrides the diallyl or dibutenyl lactones were obtained. The ring closing metathesis reaction of these using the Grubbs catalyst provided the corresponding spirolactones in good yields. With diallyl delta-lactone 2h, RCM occurred only in the presence of titanium tetraisopropoxide. (C) 2000 Elsevier Science S.A. All rights reserved.
Starting from cyclic anhydrides the diallyl or dibutenyl lactones were obtained. The ring closing metathesis reaction of these using the Grubbs catalyst provided the corresponding spirolactones in good yields. With diallyl delta-lactone 2h, RCM occurred only in the presence of titanium tetraisopropoxide. (C) 2000 Elsevier Science S.A. All rights reserved.
Diastereoselective ruthenium-catalysed cycloisomerisation of diallyllactones: preparation of exo-methylene spirolactones
Diallyllactones (obtained from cyclic anhydrides via a double allylation reactionpromoted by titaniumtetrachloride) were cycloisomerised using 5 mol% of cyclooctadienyl ruthenium dichloride in ethanol providing the corresponding exomethylene spirolactones in good yields, with moderated to good diastereomeric excess.