RESUMO
Chiral hemicyanine fluorophores are afforded in three steps only from Tröger bases via α-imino carbene additions, an original aminal deprotection and Cu(II)-mediated oxidation. The stable benzodiazepinoindolium salts are readily isolated and present (chir)optical properties that can be fine-tuned by late-stage cross-coupling functionalization. The hemicyanine character of dyes was rationalized using first principles.
RESUMO
Polycyclic indoline-benzodiazepines can be accessed through the intermolecular reaction of Tröger bases with N-sulfonyl-1,2,3-triazoles. Under RhII catalysis, α-imino carbenes are generated and a subsequent cascade of [1,2]-Stevens, Friedel-Crafts, Grob, and aminal formation reactions yield the polycyclic heterocycles as single isomers (d.r.>49:1, four stereocenters including two bridgehead Nâ atoms). Further ring expansion by insertion of a second α-imino carbene leads to elaborated polycyclic 9-membered-ring triazonanes.
Assuntos
Benzodiazepinas/síntese química , Indóis/síntese química , Compostos Policíclicos/síntese química , Benzodiazepinas/química , Catálise , Iminas/química , Indóis/química , Metano/análogos & derivados , Metano/química , Modelos Moleculares , Compostos Policíclicos/química , Ródio/química , Estereoisomerismo , Triazóis/químicaRESUMO
In the context of Tröger base chemistry, regio- and stereoselective Csp3 -H azidation reactions are reported. Azide functional groups are introduced at either one or the two benzylic positions selectively. Mild conditions and good yields are afforded by the combination of TMSN3 and iodosobenzene PhIO. The process occurs with high enantiospecificity (es 96-99 %) and-interestingly and importantly-via bridgehead iminium intermediates as shown by mechanistic and in-silico studies. Finally, mono- and bistriazole derivatives were prepared in high yields and enantiospecificity by using copper-catalyzed alkyne azide cycloaddition (CuAAC) reactions; some of the products were used as anion-binding organocatalysts for the tritylation of amines and alcohols.
