Disubstituted 2,5-piperazinediones (12) can be 3,6-dibrominated followed by displacement with sodium 2-mercaptopyridine to furnish sy -1,4-disubstituted 3,6-bis(2/-thiopyridyl)-2,5-piperazinediones (8) in high yield. Precomplexation of these sulfides with silver(I) triflate followed by addition of trimethylsilyl enol ethers leads to chemoselective C-C bond formation, furnishing the homologated piperazinediones 10. The remaining sulfide functionality of 10 is relatively inert to a second substitution. These electrophilic 2,5-piperazinediones provide access to relatively inaccessible, unsymmetrical 2,5-piperazinediones and provide advantages over the corresponding well-known enolate anion approach. Substrates that contain
d,Z-Homoserine was condensed with N-p-methoxybenzylglyciné ethyl ester and alkylated to furnish (2hydroxyethyl)piperazinedione 8. Oxidation to the corresponding aldehyde and condensation with dimethylsulfoxonium methylide provided the epoxide 10. Enolate formation resulted in an intramolecular epoxide opening reaction providing the bicyclo[2.2.2] (11) and bicyclo[3.2.2] (12) dioxopiperazines in a 3:1 ratio. Dehydration of 11 and 12 provided 6,8-bis(p-methoxybenzyl)-2-methylene-6,8-diazabicyclo[2.2.2]octane-5,7-dione (2) and 7,9-bis(p-methoxybenzyl)-7,9-diazabicyclo[3.2.2]non-2-ene-6,8-dione (1), respectively.As part of a program directed at synthesizing and studying unnatural analogues of the natural antibiotic
Die (D‐Dibromierungsprodukte (II) werden zu den Bis‐sulfiden (IV) umgesetzt, aus denen durch Präkomplexierung mit Ag‐triflat und nachfolgende Additionsreaktion mit den Silylenolethern (V) die unsymm. substituierten syn‐Piperazindione (VI), zumeist im Gemisch mit den anti‐Isomeren (VII) [(VIa) und (VIIa) sind ihrerseits jeweils Gemische von 2 Isomeren; Tab.] gebildet werden, d.h. die zweite Sul?dfunktion bleibt bei dieser Reaktion praktisch inert.
ChemInform Abstract Swern-oxidation of the alcohol (Ib), obtained by desilylation of (Ia), gives the aldehyde (II) which reacts with dimethylsulfoxonium methylide (III), yielding the diastereomeric epoxides (IV). Cleavage of the oxirane ring is accompanied by rearrangement, producing the bicyclic dioxopiperazines (V) and (VI) which are dehydrated to give the olefins (VII) or (VIII).
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.