Carbamoylimidazolium and thiocarbamoylimidazolium salts: novel reagents for the synthesis of ureas, thioureas, carbamates, thiocarbamates and amides
作者:Justyna A. Grzyb、Ming Shen、Chiaki Yoshina-Ishii、W. Chi、R.Stanley Brown、Robert A. Batey
DOI:10.1016/j.tet.2005.05.056
日期:2005.7
Carbamoylimidazolium salts act as efficient N,N-disubstituted carbamoylating reagents. These salts are readily prepared by the sequential treatment of secondary amines with N,N′-carbonyldiimidazole (CDI) and iodomethane. The carbamoylimidazolium salts are more efficient carbamoyl transfer reagents than the intermediate carbamoylimidazoles, as a result of the ‘imidazolium’ effect. Kinetic studies on
2-Hydroxy-3- (2'-piperidyl) quinolizidine (5), an intermediate for the synthesis of (±) -leontiformidine (1a), was converted into (±) -sparteine (7) by a three-step procedure of oxidation, Mannich reaction and deoxygenation.
Studies toward Labeling Cytisine with [<sup>11</sup>C]Phosgene: Rapid Synthesis of a δ-Lactam Involving a New Chemoselective Lithiation−Annulation Method
receptors, with [11C]phosgene, the rapid synthesis of a lactam model of our target has been studied. The key step of the δ-lactam formation is a new chemoselective lithiation−annulation method, under high dilution, of a suitable piperidinylcarbamoyl chloride. This precursor was obtained from (2-hydroxyethyl)piperidine in a linear synthetic sequence involving a Corey−Fuchs olefination of the corresponding
Synthesis and transformations of sulfur-substituted indolizidines and quinolizidines
作者:Shang-Shing P. Chou、Chung-Wen Ho
DOI:10.1016/j.tetlet.2005.09.191
日期:2005.12
underwent [4+2] cycloaddition reactions with p-toluenesulfonyl isocyanate to give tetrahydropyridinones 3a–b. Through N-detosylation of 3a–b and subsequent intramolecular cyclization, indolizidine 5a and quinolizidine 5b were synthesized. Useful functional group transformations of compounds 5a–b were also investigated.