1332709-04-2Relevant articles and documents
Tert-Butyl Hydroperoxide and Tetrabutylammonium Iodide-Promoted Free Radical Cyclization of α-Imino-N-arylamides and α-Azido-N-arylamides
Li, Dianjun,Yang, Tonghao,Su, Hailin,Yu, Wei
, p. 2529 - 2539 (2015)
The oxidizing system of tert-butyl hydroperoxide (TBHP) and tetrabutylammonium iodide (TBAI) is capable of generating α-(arylaminocarbonyl)iminyl radicals from ethyl 2-(N-arylcarbamoyl)-2-iminoacetates. These iminyl radicals preferably undergo intramolecular ipso attack on the benzene ring to give azaspirocyclohexadienyl radicals, which are readily captured by molecular oxygen under an oxygen atmosphere to yield azaspirocyclohexadienones. In the absence of oxygen, the reaction affords quinoxalin-2-one products. This oxidizing system is also effective to convert α-aryl-α-azido-N-arylamides to the corresponding iminyl radicals under basic conditions (sodium tert-butoxide, t-BuONa), and the subsequent cyclization of these iminyl radicals results in the formation of azaspirocyclohexadienone products in high yields under an oxygen atmosphere. Plausible mechanisms are proposed to rationalize the experimental results, and factors influencing the reactions are discussed.
Carbon-carbon bond-forming reactions of α-carbonyl carbocations: Exploration of a reversed-polarity equivalent of enolate chemistry
Lai, Ping-Shan,Dubland, Joshua A.,Sarwar, Mohammed G.,Chudzinski, Michael G.,Taylor, Mark S.
supporting information; experimental part, p. 7586 - 7592 (2011/10/12)
Carbon-carbon bond-forming reactions of putative α-carbonyl carbocation intermediates generated by Lewis acid- or silver-promoted ionizations of toluenesulfonate or halide leaving groups are described. This under-exploited mode of reactivity represents an 'umpolung' of conventional enolate chemistry, and enables C-C bond construction in both intra- and intermolecular contexts. Attempts to develop diastereoselective variants of this process using chiral ester and oxazolidinone-based auxiliaries are discussed.
