`Thiobenzophenone S-Methylide' (=(Diphenylmethylidenesulfonio)methanide), and C.C Multiple Bonds: Cycloadditions and Dipolarophilic Reactivities

摘要: Thiobenzophenone and diazomethane afford thiadiazoline 1 at −78°. By elimination of N2 from −45° (t1/2ca. 1 h), (diphenylmethylidenesulfonio)methanide (2), which cannot be isolated but is interceptible by dipolarophiles, set free. The nucleophilic 1,3-dipole 2 undergoes cycloadditions with electrophilic C,C multiple bonds; the structures 16 cycloadducts were elucidated. One-step two-step cycloaddition pathways are discussed in light steric course observed for (E)/(Z)-isomeric ethylene derivatives. Competition experiments pairs dipolarophiles HPLC analysis adducts provided relative rate constants 26 involving C≡C, 13 C=C, 9 C=S, N=N bonds. In accordance Sustmann`s reactivity model concerted cycloadditions, shows highest selectivity all known 1,3-dipoles, i.e., largest spread (krel=1 methyl propiolate 33×106 TCNE). As a consequence low LU energies, thiones very active fluorene-9-thione (krel=79×106) stands top.