RESUMO
Making use of temperature-controlled thiation as a key operation, a simple route to 2-aminothiophenes or thieno[2,3- c]isothiazoles has been newly developed wherein the 2-aminothiophene nucleus was formed through an initial formation of thioamide followed by a 5-exo-dig addition to the tethered alkyne; however, under harsher thermal conditions, excess sulfur-transferring reagents enabled further oxidative thiation to generate the corresponding thieno[2,3- c]isothiazoles.
RESUMO
A new N-hydroxyphthalimide (NHPI)/Co(II)-catalyzed protocol, mechanistically involving a sequence of α-hydrogen abstraction, 5-exo-dig cyclization, oxygen capture, hydrogen transfer, and 1,4-dehydration, has been developed to facilitate aerobic oxidation of aryl-, silyl-, and alkyl-capped alkynyl α-cyano alkanone systems to the corresponding highly functionalized products in an effective manner, thus turning this novel chain reaction, originally occurring spontaneously in low yields, into a practical methodology.
RESUMO
Making use of a tandem free radical cyclization process mediated by Mn(OAc)3 as a key operation, the total synthesis of retrojusticidin B, justicidin E, and helioxanthin has been concisely achieved in four or five steps in an overall yield of 45, 33 and 44%, respectively, from a common starting material 5.
Assuntos
Dioxolanos/síntese química , Lignanas/síntese química , Naftalenos/síntese química , Catálise , Ciclização , Dioxolanos/química , Lignanas/química , Estrutura Molecular , Naftalenos/químicaRESUMO
The radical cascade protocol of the α-cyano α-TMS/aryl-capped alkynyl aryl ketones promoted by tert-butyl hydroperoxide under catalysis with tetrabutylammonium iodide in refluxing benzene has been developed, leading to the construction of a variety of highly functionalized [6,6,5] tricyclic frameworks in an efficient manner.
Assuntos
Alcinos/química , Hidrocarbonetos Iodados/química , Cetonas/química , Compostos de Amônio Quaternário/química , terc-Butil Hidroperóxido/química , Catálise , Técnicas de Química Combinatória , Ciclização , Estrutura Molecular , EstereoisomerismoRESUMO
Novel preparation of tetrasubstituted furans, starting from the Michael acceptors, tributylphosphine, and acyl chlorides, is realized. A broad range of highly functional furans can be efficiently generated in one step at room temperature within 10 min to 21 h in moderate to high yields (60-99%). The reaction was proposed to proceed via intramolecular Wittig-type reactions, using phosphorus ylides as intermediates.