Article

An unprecedented tandem 1,3-dipolar cycloaddition-cheletropic elimination: a facial approach to novel push-pull olefins.

Chemistry Department, Beijing Normal University, Beijing, 100875, China.
Organic & Biomolecular Chemistry (Impact Factor: 3.57). 05/2007; 5(8):1282-6. DOI: 10.1039/b701326d
Source: PubMed

ABSTRACT The interaction of 2-(phenylthiocarbamoyl) imidazolium inner salts with dimethyl acetylenedicarboxylate produced dimethyl 2-(imidazolin-2-ylidene)-3-thioxobutanedioates in moderate to good yields. The process involved a tandem reaction comprising a 1,3-dipolar cycloaddition and an unprecedented cheletropic elimination of the phenyl isonitrile from a 2-phenyliminodihydrothiophene moiety. NMR and X-ray diffraction studies confirmed that the 2-(imidazolin-2-ylidene)-3-thioxobutanedioates are novel push-pull olefins and have potential applications in nonlinear optical materials.

0 Bookmarks
 · 
41 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Reaction of 2-thiocarbamoyl thiazolium salts with dimethyl acetylenedicarboxylate proceeded via a tandem [3+2] cycloaddition and a unprecedented ring transformation to produce functionalized thieno[2,3-b]pyrazine derivatives in good to excellent yields.
    Chemical Communications 01/2008; · 6.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Similarly to NHCs, CAAC(a) and BAC(a) react with CO2 to give the corresponding betaines. Based on the carbonyl stretching frequencies of cis-[RhCl(CO)2(L)] complexes, the order of electron donor ability was predicted to be CAAC(a) approximately BAC(a)>NHCs. When the betaines nu(asym)(CO2) values are used, the apparent ordering is BAC(a)>NHCs approximately CAAC(a) that indicates a limitation for the use of IR spectroscopy in the ranking of ligand sigma-donating ability. Although all carbenes react with carbon disulfide to give the corresponding betaines, a second equivalent of CS2 reacts with the BAC-CS2 leading to a bicyclic thieno[2,3-diamino]-1,3-dithiole-2-thione, which results from a novel ring expansion process. Surprisingly, in contrast to NHCs, CAAC(a) does not react with carbodiimide, whereas BAC(a) exclusively gives a ring expanded product, analogous to that obtained with CS2. The intermediate amidinate can be trapped, using the lithium tetrafluoroborate adduct of BAC(b) as a carbene surrogate.
    Chemistry - An Asian Journal 09/2009; 4(11):1745-50. · 4.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: N-Heterocyclic carbenes (NHCs) form stable zwitterionicadducts with a range of heteroallenes, ketenes, and allenes. Although the first representatives of this class of inner salts were first investigated as far back as the 1960s, they have enjoyed a sustained interest from the chemical community over the years. Depending on the nature of their anionic moiety, NHC betaines display a very broad palette of reactivities and have found applications in various fields of organic synthesis and catalysis. In this Microreview, the synthesis, properties, and reactivity of NHC betaines are surveyed. The NHCs under consideration include ylidenes derived from imidazole, benzimidazole, imidazoline, thiazole, or triazole, and the heteroallenes investigated so far are carbon dioxide, carbon disulfide, isocyanates, isothiocyanates, and their selenium analogues. A historical background is provided for each type of adduct under consideration, but emphasis is placed mainly on developments that have appeared in the literature within the past few years. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
    Berichte der deutschen chemischen Gesellschaft 03/2009; 2009(13):1681 - 1699. · 2.94 Impact Factor