MESOIONIC THIOCARBONYL YLIDES

New Thiocarbonyl Ylides derived from 3,3-Dichloro-2,2,4,4-tetramethylcyclobutanethione; Generation and reactions

The reaction of 3,3-dichloro-2,2,4,4-tetramethylcyclobutanethione (1) with diazo compounds yielded spirocyclic 2,5-dihydro-1,3,4-thiadiazoles 3, which decomposed at ca. 45°C to give the corresponding thiocarbonyl ylide of type 4. In the absence of trapping agents, these thiocarbonyl ylides underwent a 1,3-dipolar electrocyclization to yield spirocyclic thiiranes 5. On the other hand, the thioca...

Selenophen - 2 - yl - substituted thiocarbonyl ylides – at the borderline of dipolar and biradical reactivity

The reactions of aryl (selenophen-2-yl) thioketones with CH2N2 occur with spontaneous elimination of N2, even at low temperature (-65°), to give regioselectively sterically crowded 4,4,5,5tetrasubstituted 1,3-dithiolanes and/or a novel type of twelve-membered dithia-diselena heterocycles as dimers of the transient thiocarbonyl S-methanides. The ratio of these products depends on the type of sub...

Mesoionic sydnone derivatives: An overview

Mesoionic compounds are dipolar five or six membered heterocyclic compounds in which both the negative and the positive charge are delocalized, for which a totally covalent structure cannot be written, and which cannot be represented satisfactorily by any one polar structure. The most important member of the mesoionic category of compounds is the sydnone ring system. Sydnones are mesoionic comp...

Carbenes stabilized by ylides: pushing the limits.

Novel Asymmetrical Dianionic Polyimido-Sulfur(IV)-Ylides

Sulfurdiimides RN=S=NR react in donating solvents with two equivalents of lithiumalkyls to give the dimeric C,N-dilithium-methylenediimidosulfite solvent adducts [(Et2O)Li2{H2CS(NSiMe3)(NBu)}]2 (1) and [(thf)Li2{H8C4S(NBu)2}]2 (2). Firstly, addition of a lithiumalkyl to sulfurdiimide gives the diimidosulfinates [RS(NR )2] (1: R = Me, R = tBu, SiMe3; 2: R = nBu; R = tBu) while in a second step t...