Addition of Diazomethane to Phosphonodithioformates and Reactions of Phosphonylated Thiocarbonyl S‐Methylides.

Abstract

The reaction of phosphonodithioformates 14 with diazomethane at -60°C yielded 2,5-dihydro-1,3,4-thiadiazoles 15 as unstable intermediates. Their structure was evidenced by the base-catalyzed elimination of methylsulfane leading to 1,3,4-thiadiazole-2-phosphonates. At ca. -35°C, thermal decomposition of 15 by N2-elimination led to reactive thiocarbonyl S-methylides 17. In the absence of trapping reagents, these 1,3-dipoles undergo a head-to-head dimerization leading to 1,4-dithianes 18. An intermediate zwitterionic dimer 19 was detected by 31P NMR spectroscopy. The initially formed thiocarbonyl S-methylide 17 as well as an open-chain zwitterionic dimer 20 was intercepted by methanol. Stable interception products were also obtained with S-and N-nucleophiles.

A new approach to 2,2-disubstituted 1-(methylsulfanyl)vinyl phosphonates via an intermediate thiocarbonyl ylide

“…11 On the other hand, it is well established that tetrasubstituted thiocarbonyl ylides do not dimerize but form thiiranes as products of a 1,3-dipolar electrocyclization. 14,15 Based on these results, we decided to test the reactivity of methyl (diethylphosphoryl)dithioformate 6 towards disubstituted diazomethanes 7 with the aim of obtaining the corresponding thiiranes, which by elimination of sulfur could be converted to the corresponding 1-(methylsulfanyl)vinyl phosphonates 8 (Scheme 2).…”

New Thiocarbonyl Ylides Derived from 3,3‐Dichloro‐2,2,4,4‐tetramethylcyclobutanethione; Generation and Reactions.

“…Depending on the substitution pattern, the reaction with morpholine leads to aromatic 1,3,4-thiadiazoles by elimination [16] (see also [17]) or to morpholin-4-carbaldehydhydrazones by a ring opening process and subsequent condensation with the amine [18]. The reaction of 3a with excess of morpholine or piperidine at room temperature occurred smoothly to give the expected products 25 (Scheme 7).…”

Dimerization reactions of aryl selenophen-2-yl-substituted thiocarbonylS-methanides as diradical processes: a computational study

“…In the case of polar groups, such as sulfonyl or phosphonyl moieties, the dimerization leads to five-membered 1,3-dithiolane derivatives 4 (sulfoniumylides) [7–8]. Diaryl-substituted thiocarbonyl S -methanides 1 react in the absence of a dipolarophile, with no exception, via a head-to-head dimerization yielding sterically crowded 1,4-dithianes of type 5 [9–10].…”