Lithium‐Tellurium Exchange: A New Entry to Organolithium Compounds

Abstract

NMR spectra (in [D],DMF) of natural D and synthetic 4 were essentially identical, particularly in the region representing olefinic protons (6 = 5.6-6.8). This, in turn, proves that the the component D is pure all-trans-fecapentaene-14 (4).We have also established that the CI mass spectra of the natural and the synthetic compounds are identical. These spectra, however, show very little fragmentation, and thus are not sufficiently informative.These investigations enable us for the first time to assign the complete structural formulas to two naturally occurring fecapentaenes. The geometry of the CC double bonds may play a role in the degree of mutagenicity exhibited by both types of fecapentaene~.''.~~ Interestingly, the two identified components, all-trans-fecapentaene-12 (3)[91 and alltrans-fecapentaene-I4 (4)['] belong to the most potent mutagens so far known. Their occurrence in human feces and their accessibility by chemical synthesis raise hopes that they might serve to answer the question whether the fecapentanes are carcinogens.

Hydrotelluration of alkynes: a unique route to Z-vinyl organometallics

“…The tellurium precursors of the Z-vinyllithiums are the vinylbutyltellurides, introduced by us as source of Z-vinyllithiums in 1989, since the initially used Z-vinylaryltellurides 43 give mixtures of vinyl and aryllithiums as demonstrated by us in our original report 44 (Scheme 14).…”

One‐Pot Synthesis of Pyridyltellurium Derivatives from a Reaction with Isopropylmagnesium Chloride and X‐ray Crystal Structures of Various Pyridyl Ditellurides

“…[1,2] Compared to alkyl-and aryltellurium compounds, [3,4] the use of pyridyltellurium derivatives in organic synthesis has been relatively less studied. This may primarily be due to the lack of a convenient and efficient synthesis of these compounds.…”

One-pot synthesis of aryl butyl tellurides from tellurium tetrachloride and activated aromatics through a solventless step

“…The butyl tellurium group is positioned in para to the more activating group and, in the case of telluride 2g, the product obtained was the b isomer. As mentioned before [5], phenyl n-propyl telluride is an efficient source of phenyllithium. In this way, the compounds presented in (Scheme 1) could be source of para-substituted aryl lithiums (Scheme 2), which are prepared mainly by lithium-halogen exchange [11].…”

“…Most of the synthetic methods developed are based on transformations using vinylic tellurides [4]. Several years ago, Sonoda and coworkers [5] reported the transformation of phenyl n-propyl telluride into phenyllithium. Recently we found that aromatic tellurides can directly generate aryl cyanocuprates through reaction with easily prepared dilithium diorgano cyanocuprates [6].…”