Evidence and isolation of tetrahedral intermediates formed upon the addition of lithium carbenoids to Weinreb amides and N-acylpyrroles
作者:Laura Castoldi、Wolfgang Holzer、Thierry Langer、Vittorio Pace
DOI:10.1039/c7cc05215d
日期:——
The tetrahedralintermediates generated upon the addition of halolithium carbenoids (LiCH2X and LiCHXY) to Weinreb amides have been intercepted and fully characterized as O-TMS heminals. The commercially available N-trimethylsilyl imidazole is the ideal trapping agent whose employment, combined with a straightforward neutral Alox chromatographic purification, enables the isolation of such labile species
Synthese de pyrroles et d'oxazoles par pyrolyse de N-(hydroxy-2′ ethyl) amino-3 propenoate
作者:Catherine Pale-Grosdemange、Josselin Chuche
DOI:10.1016/s0040-4020(01)81018-8
日期:1989.1
pyrolysis of various N-(2′-hydroxyethyl)-3-amino propenoates 1–6 and N-(2′-hydroxy-2′-phenyl ethyl)-3-amino propenoate 7–9 at 390°–420°C leads respectively to formylpyrroles 11–16 and benzoylpyrroles 17–19 and, in some cases, to substituted oxazoles 36–39. The results are best explained by the intermediate formation of dicarbonyl derivative followed either by an intramolecular thermal crotonisation
The reactions of pyrroles with 2-methoxyphenols, which proceeded smoothly at either 0°C or room temperature via the Diels–Alderreactions of in situ generated masked o-benzoquinones are described.