Syntheses and15N NMR Spectra of Iminodiaziridines - Ring-Expansions of 1-Aryl-3-iminodiaziridines to 1H- and 3aH-Benzimidazoles, 2H-Indazoles, and 5H-Dibenzo[d,f][1,3]diazepines

Autor: Klaus Banert, Helmut Quast, Manfred Hagedorn, Gottfried Philipp, Karl-Heinz Ross, Harald Hahn
Rok vydání: 2009
Předmět:
Zdroj: European Journal of Organic Chemistry. 2009:3940-3952
ISSN: 1099-0690
1434-193X
DOI: 10.1002/ejoc.200900350
Popis: Iminodiaziridines are synthesized by (i) 1,3-dehydrochlorination with potassium tert-butoxide of N-chloroguanidines, generated in situ from N,N′,N″-substituted guanidines with tert-butyl hypochlorite, and (ii) base-mediated 1,3-elimination of sulfuric acid from N,N′,N″-substituted hydroxyguanidine O-sulfonic acids. At elevated temperatures, (alkylimino)diaziridines undergo valence isomerization by 1,3-shift, [2+1] cycloelimination to afford isocyanides and diazenes, and ring-opening elimination to yield alkylideneguanidines. N′-Aryl-N-hydroxyguanidine O-sulfonic acids furnish (N-arylimino)diaziridines, but no 1-aryl-3-iminodiaziridines, instead giving rearranged isomers. Precursors containing perdeuterated tert-butyl groups give rearranged products that show complete scrambling. This indicates that 1-aryl-3-iminodiaziridines are intermediates that undergo very rapid degenerate valence isomerization. Provided that the ortho-aryl positions are substituted, high yields of (arylimino)diaziridines are obtained, along with 2-imino-2,3-dihydro-3aH-benzimidazoles. Otherwise, 2-amino-1H-benzimidazoles and strongly fluorescent 3-amino-2H-indazoles, originating from rearrangements of the elusive 1-aryl-3-iminodiaziridines, predominate. N′,N″-Diaryl-N-hydroxyguanidine O-sulfonic acids give only rearranged products: a 2-amino-1H-benzimidazole and a 6-amino-5H-dibenzo[d,f][1.3]diazepine if aryl = phenyl, or a 2-imino-2,3-dihydro-3aH-benzimidazole if aryl = mesityl. 3aH-Benzimidazoles slowly dimerize through Diels–Alder reactions. 15N NMR signals were assigned to the syn and anti ring nitrogen atoms of iminodiaziridines with the help of a combination of homonuclear NOE and HN-HMBC or HN-gHMBC experiments. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Databáze: OpenAIRE
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