79999-67-0Relevant academic research and scientific papers
'Thiobenzophenone S-Methylide" (=(Diphenylmethylidenesulfonio)methanide), and C,C Multiple Bonds: Cycloadditions and Dipolarophilic Reactivities
Huisgen, Rolf,Li, Xingya,Giera, Henry,Langhals, Elke
, p. 981 - 999 (2007/10/03)
Thiobenzophenone and diazomethane afford thiadiazoline 1 at -78 deg C. By elimination of N2 from 1 at -45 deg C (t1/2 ca. 1 h), (diphenylmethylidenesulfonio)methanide (2), which cannot be isolated but is interceptible by dipolarophiles, is set free. The nucleophilic 1,3-dipole 2 undergoes cycloadditions with electrophilic C,C multiple bonds; the structures of 16 cycloadducts were elucidated. One-step and two-step cycloaddition pathways are discussed in the light of the steric course observed for (E)/(Z)-isomeric ethylene derivatives. Competition experimetns with pairs of dipolarophiles at -45 deg C and HPLC analysis of the adducts provided relative rate constants of 26 dipolarophiles, involving 2 CC, 13 C=C, 9 C=S, and 2 N=N bonds. In accordance with Sustmann's reactivity model of concerted cycloadditions, 2 shows the highest selectivity of all known 1,3-dipoles, i. e., the largest spread of rate constants (krel = 1 for methyl propiolate and 33 x 106 for TCNE). As a consequence of low LU energies, thiones are very active dipolarophiles, and fluorene-9-thione (krel = 79 x 106) stands at the top.
