A study of the utility of furan-terminated N-acyliminium ion initiated cyclizations for the synthesis of linearly fused alkaloid precursors (Figure 2) is presented. The outcome of the cyclization event depends on the position of furan tether attachment (2 vs 3), tether length, and furan 5-substituent (R = H, CH(3), Ar). 3-Substituted furans cyclized to form 6- and 7-membered ring containing furans 35-38, 50, and 51 in good to excellent yields. 2-Substituted furans closed to form only 6-membered rings; however, the products obtained were a function of the furan 5-substituent. The 5-H furans 17 and 18 led exclusively to the corresponding furans 21 and 22, while the 5-CH(3)-furans 42 and 43 gave only diketone containing compounds 44 and 45. 5-Arylfurans 66-71 provided mixtures of furan- and diketone-containing products 72-83, with the ratio related to the substitution on the phenyl moiety. A preparation of epilupinine 10 is also discussed.
Furan-Terminated N-Acyliminium Ion Initiated Cyclizations in Alkaloid Synthesis.-The cyclization leads to fused furans and/or diketones depending on the position of furan tether attachment, tether length, and furan 5-substituent. The diketone (VIIIe) can easily be transformed into epilupinineXI). -(TANIS, S. P.; DEATON, M. V.; DIXON, L. A.; MCMILLS, M. C.; RAGGON, J. W.; COLLINS, M. A.; J.
Aus den Epoxiden (I) und den Furylalkyl‐Grignard‐Verbindungen (II) erhält man die Reaktionsprodukte (III), die beim Erhitzen mit Ameisensäure zu den Spirocyclen (IV) in hohen Ausbeuten kondensiert werden.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.