Chiral aziridination of cyclic α-bromoenones is achieved by the use of the lithium salt of (S S )-(+)-p-toluenesulfinamide, which leads to products with diastereomeric excesses in the range of 30―65% using a simple protocol. A key factor associated with chiral induction is the incorporation of the reacting olefin in a cycle, indicating the importance of conformational restriction in the reacting double
Combined Computational and Experimental Studies of the Mechanism and Scope of the Retro-Nazarov Reaction
作者:Michael Harmata、Peter R. Schreiner、Dong Reyoul Lee、Patrick L. Kirchhoefer
DOI:10.1021/ja048942h
日期:2004.9.1
have a rate-accelerating effect on the retro-Nazarov reactions of these species. The retro-Nazarov reaction of these intermediates is predicted to exhibit significant torquoselectivity when carbon three is substituted with a methoxy and a methyl group. Experimentalstudies show that oxyallylic cations can undergo effective retro-Nazarov reactions when two alkyl and one aryl/vinyl groups are on carbons
Studies Directed toward the Synthesis of the Unusual Antileukemic Diterpene Jatrophatrione. 1. A Solution to the Problem of Chirality Merger during Elaboration of the Entire Carbotricyclic Framework
作者:Leo A. Paquette、Shogo Nakatani、Thomas M. Zydowsky、Scott D. Edmondson、Li-Qiang Sun、Renato Skerlj
DOI:10.1021/jo9825254
日期:1999.4.1
tricyclic nucleus of jatrophatrione (1) is reported. The two key steps involve an oxyanionic Cope rearrangement and a Grob fragmentation. The building blocks required to reach 44 are the bicyclo[3.3.0]octanone 29 and the cyclopentadienyl bromide 35. The former was obtained in 12 steps from methylcyclopentadiene. The route to the latter began with 4,4-dimethylcyclopentenone. The charge-accelerated [3,3]-sigmatropic
Two routes towards (±) quadrone (), via an intramolecularDiels-Alder reaction have been studied. The cycloaddition of failed, probably because of prohibitive strain. In the alternative approach, the key step afforded a mixture of the endo- and exo-adducts and . Both isomers were transformed into Danishefsky's intermediate , which has previously been converted to the title compound .
Enantioselective Double Michael Addition/Cyclization with an Oxygen-Centered Nucleophile as the First Step in a Concise Synthesis of Natural (+)-Asteriscanolide
作者:Leo A. Paquette、Jinsung Tae、Mark P. Arrington、Aladin H. Sadoun
DOI:10.1021/ja994053w
日期:2000.3.1
The total synthesis of (+)-asteriscanolide (1) starting from 2-bromo-4,4-dimethylcyclopentenone has been accomplished. The synthetic route features two key steps. The first step is an unprecedented Michael−Michael reaction sequence that involves a heteronucleophile and proceeds with complete asymmetric induction. The two five-membered rings of the target molecule are thereby generated enantioselectively