Carbene, IV. Dimethylsulfonio‐methanide aus Diazoverbindungen auf photochemischem Wege

Abstract

Die Bestrahlung der diacylierten Diazomethane la-n, 5a-j und l l a -f in Dimethylsulfid liefert Carbene, die mit dem Losungsmittel zu entsprechenden Dimethylsulfonio-methaniden (3a-n, 6a-j und 12a-f) reagieren; die Wolff-Umlagerung der Carbene wird weitgehend unterdriickt. Als Nebenreaktion findet man reduktive Eliminierung des Diazostickstoffs unter Bildung diacylierter Methane (4, 7 und 13). Die IR-Spektren der Sulfonio-methanide zeigen, da8 fur die Delokalisierung des Elektroneniiberschusses am Methanid-Kohlenstoff vor allem die Carbonylgruppen verantwortlich sind ; die S 0 2 -und PO-Reste zeigen einen wesentlich geringeren EinfluS. Carbenes, I V ) . -Dimethylsulfoniomethanides from Diazo Compounds by Photochemical ReactionThe photolysis of the diacylated diazomethanes la-n, 5a-j, and l l a -f in dimethyl sulfide yields carbenes, which form the corresponding dimethylsulfoniomethanides (3a-n, 6a-j, and 12a-f) by reaction with the solvent; the Wolff-rearrangement can be largely suppressed. The reductive elemination of the diazo nitrogen with formation of diacylated methanes (4, 7, and 13) is found to be a side reaction. The IR-spectra of the sulfoniomethanides show that above all the carbonyl groups take part in the delocalization of the electron excess on the methanide carbon; the SOz-and the PO-groups show an substantially smaller effect.

Catalytic and direct methyl sulfonylation of alkenes and alkynes using a methyl sulfonyl radical generated from a DMSO, dioxygen and copper system

“…Using radical scavenger reagent TEMPO, the desired reaction was completely suppressed and only a small amount of β-keto diethyl phosphonate was obtained (Scheme 2 (c)). Subjecting the β-keto diethyl phosphonate instead of the aryl 15 alkene to our reaction conditions did not lead to the desired product, indicating that β-keto diethyl phosphonate is not the intermediate of this reaction. On the basis of these results, we may conclude that a DMSO/•OH radical process is most likely involved in our reaction system.…”

“…Dimethyl sulfoxide (DMSO) has been used widely as solvent in organic synthesis due to its rather low cost, relative stability and 15 low toxicity. 1 On the other hand, biologists have used DMSO as a hydroxyl radical scavenger to trap the highly reactive oxygen species present in biological system.…”

“…Copper (I) showed more efficiency in the reaction condition compared to copper (II) catalysts (Table 1, entries 7-8). Simple substituents of phosphite like methyl, ethyl, 15 led to more promising results compared to bulky ones (Table 1, entries 5 and 9-10). The reaction also proceeded well under air as oxidant with 73% yield (Table 1, entry 11).…”

“…For example, the β-keto methyl sulfone could be either alkylated with allyl bromide or diazo transferred with tosyl azide under suitable base conditions (Scheme 4, (1) and (2)). 15 It can also easily be halogenated in a 10 radical process to afford 2-bromo-2-(methylsulfonyl)-1-phenylethanone(Scheme 4, (3)), which is a key intermediate for the synthesis of biological active molecule 2-(methylsulfonyl)-3phenyl-5,6-dihydroimidazo [2,1-b]thiazole. 16 The methyl sulfonyl group could be well tolerated in reduction condition to afford (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) (methylsulfonyl)ethyl)benzene in excellent yield from vinyl methyl sulfone (Scheme 4, (4)).…”

Photochemistry of the diazonium and diazo groups

“…When the sample was irradiated in a n alcoholic solution by a 295 nm light, no e.s.r. Photochemistry of the diazonium and diazo groups -Emission spectrum ----Excitation spectrum 353 250 the conjugated system extends, the peak of the absorption band is shifted to longer wavelengths, but the quantum yield tends t o be lower. On the other hand, upon irradiation by 259 nm light, this sample showed an e.s.r.…”