Formation of a trans-bicyclo[3.3.0]Octane by tandem anionic cyclization: evidence for the highly stereoselective irreversible nature of 5-hexen-1-yllithium cyclizations
TL;DR: Tandem anionic cyclization of 4-ethenyl-6-hepten-1-yllithium (7), prepared from the corresponding iodide (6 ) by low temperature lithium - iodine exchange, occurs rapidly at room temperature in the presence of TMEDA to give ( trans-3-bicyclo[3.3.0]octyl )methytlithium as discussed by the authors.
About: This article is published in Tetrahedron Letters.The article was published on 1990-01-01. It has received 25 citations till now. The article focuses on the topics: Octane & Iodide.
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TL;DR: The diterpene (+)-epoxydictymene has been synthesized in 20 steps using the asymmetry of (R)-pulegone and several substrate-controlled diastereoselective reactions to prepare the natural product in its natural configuration.
Abstract: The diterpene (+)-epoxydictymene has been synthesized in 20 steps using the asymmetry of (R)-pulegone and several substrate-controlled diastereoselective reactions to prepare the natural product in its natural configuration. Three of the four rings were assembled with two consecutive intramolecular reactions involving dicobalt hexacarbonyl complexes of alkynes: a Lewis acid-promoted Nicholas reaction and a Pauson−Khand reaction. The construction of the strained trans-3-oxabicyclo[3.3.0]octane ring system of the natural product presented a significant challenge. To this end, several radical and anionic cyclizations were studied, the latter leading to (+)-epoxydictymene.
118 citations
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TL;DR: This Perspective covers recent synthetic methods that rely on the photocatalytic generation of aminium radical cations for C─N bond formation, specifically in the context of alkene hydroamination, arene C─H bond amination, and the mesolytic bond cleavage of alkoxyamines.
Abstract: Aminium radical cations have been extensively studied as electrophilic aminating species that readily participate in C─N bond forming processes with alkenes and arenes. However, their utility in synthesis has been limited, as their generation required unstable, reactive starting materials and harsh reaction conditions. Visible-light photoredox catalysis has emerged as a platform for the mild production of aminium radical cations from either unfunctionalized or N-functionalized amines. This Perspective covers recent synthetic methods that rely on the photocatalytic generation of aminium radical cations for C─N bond formation, specifically in the context of alkene hydroamination, arene C─H bond amination, and the mesolytic bond cleavage of alkoxyamines.
69 citations
TL;DR: In this article, the intramolecular cyclization reaction of primary or secondary alkenylzincs leads to a cyclopentylmethylzinc derivatives in a totally regiospecific 5-exo-trig cyclization in the presence of a highly sensitive function.
42 citations
TL;DR: In this article, the sequential cyclization/silylation of 1,5-dienes and 1,6-Dienes was effected under mild reaction conditions using catalytic quantities of Cp2*YMe·THF.
Abstract: The sequential cyclization/silylation of 1,5-dienes and 1,6-dienes was effected under mild reaction conditions using catalytic quantities of Cp2*YMe·THF. The process provides carbobicyclics in high yields and with excellent selectivities. The active catalyst is postulated to be Cp2*YH·THF, which is generated in situ. A variety of alkenyl-substituted cyclopentane and cyclohexane substrates were examined. The high diastereoselectivities apparently originate from a preference for a chairlike transition structure that minimizes unfavorable steric interactions between the bulky Cp* ligands of the catalyst and the preexisting ring of the substrate. Acyclic triene precursors, 4-ethenyl-substituted 1,5-heptadienes and 5-ethenyl-substituted 1,8-nonadienes were also examined. These triene substrates, when exposed to the cyclization/silylation protocol, provide the strained trans-bicyclo[3.3.0]octanes and trans-decalin systems in high yield with excellent diastereoselectivity. The high selectivity is again attribute...
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TL;DR: The Zr-promoted bicyclization of 1,6-and 1,7-dienes can stereoselectively produce trans-zirconabicyclo[3.3.0] octanes and cis-Zircon-conabicycleclo [4.3] nonanes, respectively; these compounds can be readily converted into protonolysis, halogenolysis and carbonylation products as discussed by the authors.
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