Das elektronenreiche Olefin 1 reagiert niit den Acyliso-und Acylisothiocyanaten 4a-f zu den Dipolen 6a-f. Diese addieren Perchlorsaure unter Bildung der Imidazolinium-perchlorate 8a-f. Mit Methyljodid werden die ,,Isocyanat-Dipsle" 6a und b am Stickstoff (9a, b), die ,,lsothiocyanat-Dipole" 6c-f dagegen am Schwefel methyliert (10a-d), ebenso wie der aus 1 und Schwefelkohlenstoff erhaltene Dipol (11 + 12). Hydrolysereaktionen mit 6a, 8b, 8d und 10b lieferten den ,,C02-Dipo16' 13. Die Dipole 6a-f sind charakterisiert durch (3 + 2)-Cycloadditionen mit Diacylacetylenen (14,18a-h) und Isocyanaten (15a, b, 19a-g ) ; bei der Umsetzung von 6b mit Chlorsulfonylisocyanat findet nur N-Acylierung zu 17 statt. Die Dipolbildung aus 1 und Acyliso-bzw. Acylisothiocyanaten wird limitiert durch Redoxreaktionen, bei denen u. a. die 2,2'-Biimidazolindiium-Salze 20 entstehen.Stable Dipoles from the Reaction of 1,1',3,3'-Tetraphenyl-2,2'-biimidazolidinylidenes with Acyl Isocyanates or Acyl kothiocyanatesThe electron-rich olefine 1 reacts with the acyl isocyanates and acyl isothiocyanates 4a-f to give the dipoles 6a -f. These add perchloric acid to form the imidazolinium perchlorates 8a-f. With methyl iodide the ,,isocyanate-dipoles" 6a and b are methylated at the nitrogen atom (9a, b), whereas the ,,isothiocyanate-dipoles" 6c -f are methylated at the sulfur atom (10a-d) as is the dipole obtained from 1 and carbon disulfide (11 + 12). Hydrolysis reactions with 6a, 8b, 8d and 10b yielded the ,,Con-dipole" 13. The dipoles 6a-f are characterized by (3 + 2)-cycloadditions with diacylacetylenes (14, 18a-h) and isocyanates (15a, b, 19a-g); in the reaction of 6b with chlorosulfonyl isocyanate only N-acylation to 17 takes dace. The dipole formation from 1 and acyl isocyanates or acyl isothiocyanates is limited by redox reactions in which, among other products, the 2,2'-biimidazolindiium salts 20 are formed.Die Reaktionen elektronenreicher Olefine mit Elektrophilen wurden uberwiegend am 1,1',3,3'-Tetraphenyl-2,2'-biimidazolidinyIiden (1) untersucht ; sie sind im allgemeinen von einer Spaltung der C=C-Bindung begleitet 1). In diesem Zusammenhang wurde von uns das Verhalten von 1 gegenuber Heterocumulenen bearbeitet. Wahrend Ketene stabile Dipole vom Typ 3 (X = 0, CR2 statt NR) liefertenz), reagierten Alkyl-1)
Reactions of Bis-[l,3-diaryl-imidazolidinyEidenes-(2)1 with Iso-, Isothio-or Isoselenocyanates1)Bis-[1,3-diaryl-imidazolidinylidenes-(2)] (la-c) react with isocyanates in a ratio of 1 : 4 to give 2,4-dioxo-1,3,6,9-tetraaza-spiro[4,4]nonanes (3a-i). As shown in the case of 3f and g, acyl-azides may also be used for this reaction because they rearrange to isocyanates under the reaction conditions; 2-acylimino-l,3-diphenyl-imidazolidines (6a and b) are formed then as byproducts. The reaction of the electron-rich olefine l a with aryl-azides leads to the triazenes l l a or b without loss of nitrogen. Isothio-or isoselenocyanates also undergo a 4 : 1-reaction with l a to give the spiroheterocycles 13a-j. A dipole intermediate 16 could be isolated from 1 a and p-nitrophenyl isocyanate. Analogous 2 : 1-reactions (21 a and b) are found with carbamoyl-isothiocyanates.
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