Ylid definition

Path 1 may be important if the ylid cannot exchange with a protonic solvent and a p-hydrogen atom is present. This path has not been definitely observed in the presence of hydroxylic solvents (even in the "dry state) and is most often observed when organolithium reagents are used as the base. A syw-elimination cannot be taken as proof that this path is operating, for cis E-2 reactions are also possible. 

This is obviously a Wittig reaction and we should expect a Z-alkene as the ylid is not stabilized by further conjugation. The evidence is plain the signals at 5.10 and 5.35 are the alkene hydrogens and the coupling constant between them is 10 Hz. This is definitely a Z-alkene. 

Even thiophene itself will react with carbenes, at sulfur, to produce isolable thiophenium ylids, and in these the sulfur is definitely tetrahedral." The rearrangement of thiophenium bis(methoxycarbonyl)methylide to the 2-sub-stituted thiophene provides a rationalisation for the long known" reaction of thiophene with ethyl diazoacetate, which produces what appears to be the product of carbene addition to the 2,3-double bond, but which can now be viewed as being produced via initial attack at sulfur followed by S — C-2 rearrangement, then collapse to the cyclopropane. Acid catalyses conversion of the cyclopropanated compound into a thiophene-3-acetic ester." 2,5-Dichlorothiophenium bis(methoxycarbonyl)methylide has been used as an efficient source of the carbene simply heating it in an alkene results in the transfer to the alkene." ... 

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