Intramolecular competitive addition of vinyl radicals to keto and alkenyl groups in Wieland–Miescher ketones—synthesis of carbocycles and propellanes
01 Jan 1994-Journal of The Chemical Society, Chemical Communications (The Royal Society of Chemistry)-Iss: 1, pp 25-26
TL;DR: Wieland-Miescher ketone analogues are prepared by monoalkylation of cyclohexane-1,3-dione with bromomethylcycloalkenyl bromides followed by annulation with methyl vinyl ketone; they undergo 5-exo-trig competitive intramolecular radical addition to the keto and enone olefins to give angularly rused carbocycles and propellanes, respectively as discussed by the authors.
Abstract: Wieland–Miescher ketone analogues are prepared by monoalkylation of cyclohexane-1,3-dione with bromomethylcycloalkenyl bromides followed by annulation with methyl vinyl ketone; they undergo 5-exo-trig competitive intramolecular radical addition to the keto and enone olefins to give angularly rused carbocycles and propellanes, respectively.
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TL;DR: Substituted propargyl acetates are converted into 4-boryl-2(5H)-furanones upon thermolysis in the presence of an N-heterocyclic carbene borane (NHC-borane) and di-tert-butyl peroxide.
Abstract: Substituted propargyl acetates are converted into 4-boryl-2(5H)-furanones upon thermolysis in the presence of an N-heterocyclic carbene borane (NHC-borane) and di-tert-butyl peroxide. The acetyl methyl group is lost during the reaction as methane. Evidence suggests that the reaction proceeds by a sequence of radical events including: 1) addition of an NHC-boryl radical to the triple bond; 2) cyclization of the resultant β-borylalkenyl radical to the ester carbonyl group; 3) β-scission of the so-formed alkoxy radical to provide the 4-boryl-2(5H)-furanone and a methyl radical; and 4) hydrogen abstraction from the NHC-borane to return the initial NHC-boryl radical and methane.
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References
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TL;DR: In this paper, a free radical initiated ring expansion of haloalkyl β-keto esters is described, and the resulting halide is treated at reflux with tri-n-butyltin hydride.
105 citations
TL;DR: In this article, the authors obtained rate data for cyclopentanol (C=O) 5 formation in a direct-competition experiment, and the value k c=O ≥ 9.6×10 5 s −1 is consistent with that obtained by Beckwith and Hay.
Abstract: Cyclizations of ω-formylalkyl radicals can provide an efficient route to the corresponding cycloalkanols. However, if an ω-vinyl group is present an alternative mode of cyclization exists, and there is competition between cycloalkanol and methyl cycloalkane formation (i.e. (C=O) n versus (C=C) m ). Cyclohexanol formation, (C=O) 6 , usually overwhelms any alternative process, but cyclopentanol and methylcyclopentane processes ((C=O) 5 and (C=C) 5 ) can be competitive. The latter process involves the well-studied 5-hexenyl radical ring closure, and hence by choice of a suitable substrate, where both modes of cyclization are optimal, we have obtained rate data for cyclopentanol (C=O) 5 formation in a direct-competition experiment. The value k c=O ≥9.6×10 5 s −1 is consistent with that obtained by Beckwith and Hay. The study has also helped to define some of the requirements for optimizing the formation of cycloalkanols
78 citations
TL;DR: Suitably constituted aryl and alkyl radicals readily rearrange by 1,2- or 1,4-acyl or cyano migration as discussed by the authors, and they can be represented as follows:
Abstract: Suitably constituted aryl and alkyl radicals readily rearrange by 1,2- or 1,4-acyl or cyano migration.
74 citations
TL;DR: Etude de la cyclisation radicalaire par reaction de (BU) 3 SnH des R-8 iodo-2' ethyl-7 methoxy-6 vinyl-8 perhydro pyranno [3,2d] m-dioxinnes as discussed by the authors.
Abstract: Etude de la cyclisation radicalaire par reaction de (BU) 3 SnH des R-8 iodo-2' ethyl-7 methoxy-6 vinyl-8 perhydro pyranno [3,2-d] m-dioxinnes (R=formylmethyl, cyanomethyl, propargyl): obtention de perhydro pentaleno [6a',1'-4,5] pyranno [3,2-d] m-dioxinnes
71 citations
TL;DR: In this article, the cyclisation radicalaire d'un radical formyl-5 pentyle was used to donner un cyclohexanol semble etre preferee a la cyclisation of a radical hexene-5yle.
Abstract: La cyclisation radicalaire d'un radical formyl-5 pentyle pour donner un cyclohexanol semble etre preferee a la cyclisation d'un radical hexene-5yle
70 citations