5365-38-8Relevant academic research and scientific papers
Transannular cyclizations of medium-sized cycloalkynes and cycloalkynones induced by electro- and photochemically generated NO3 radicals
Wille, Uta,Plath, Christian
, p. 111 - 119 (1997)
Transannular radical cyclizations of medium-sized cycloalkynes and cycloalkynones induced by addition of NO3 radicals to the C-C triple bond were studied. In the reaction of NO3? with medium-sized cycloalkynes oxidation of the triple bond to a carbonyl group occurred and formation of cis-fused bicyclic alkanones by transannular cyclization was observed. In the reaction of NO3 radicals with medium-sized cycloalkynones α,β-epoxy ketones were formed in a transannular reaction sequence which can be formally considered as a retro Eschenmoser-Ohloff fragmentation reaction. The scope and limitations of these reactions are presented and reaction mechanisms are proposed. VCH Verlagsgesellschaft mbH, 1997.
Self-terminating radical cyclizations: How are thiyl radicals performing?
Tan, Kristine J.,White, Jonathan M.,Wille, Uta
supporting information; experimental part, p. 4902 - 4911 (2010/11/05)
The performance of thiyl radicals RS' in "self-terminating radical cyclisations" was explored. Using the medium-sized cyclodecyne (1) as model system, the reaction of PhS' generated by photolysis of (PhS)2 was used to study the intermolecular S-radical addition and subsequent intramolecular radical translocations. This reaction resulted in the formation of three stereoisomeric sulfides 17a in very good yield, which all possess the bicyclo[4.4.0]decane framework with either cis and trans ring fusion. The isomeric bicyclo[5.3,0]decane framework was not: formed. Product identification was performed using a combination of techniques, e.g. synthesis of authentic samples, X-ray analysis and computational studies of the potential energy surface, which also revealed valuable insight into the mechanism, of this radical cyclisation cascade. The (PhS)2/PhS' system provides an efficient source for in situ generated thiols, which mediate reduction of the α-thio radical, e.g., 13a→17a. The radical cascade initiated by the addition of BnS', tBuS' or AllylS', respectively, to cycloalkyne 1 was typically terminated also by reduction, even in the absence of an apparent H-donor, and resulted in formation of various bicyclic and monocyclic thioethers. The desired "selftermination", e.g., β-fragmentation of the S-R bond in radical intermediate 12/13 and release of a stabilized radical R', was only observed, as minor reaction, pathway in one particular instance where tBuS' was generated by autoxidation of tBuSH. Computional studies showed that the different stereochemical outcome of the radical cyclizations involving S-radicals, compared to O- or N-centred radicals, could be attributed to the reversibility of the initial intermolecular Sradical addition to the C≡C triple bond in cycloalkyne 1.
