Synergic nucleophilic and electrophilic properties of carbenes. Synthesis of carbazoles, azafluorenes, .delta.-carbolines, and pyrido- and pyrimido[2,1-a]isoindoles by carbene rearrangement. Tracer studies of the mechanisms and an analysis of the carbon-13 NMR spectra of azafluorenes

Synthesis of two novel pyridine annulated pyrrolidine nitroxides

“…6, 125.3, 138.8, 147.6, 156.8, 161.15, 161.28. These 1H NMR data were in agreement with those reported previously by Mayor and Wentrup (Mayor and Wentrup, 1975).…”

“…Mp 74-76 °C (lit. 75-76 °C) (Mayor and Wentrup, 1975); 1H NMR (400 MHz, CDCl 3 ) δ 7.94-7.96 (dd, J = 1.2 and 4.8 Hz, 1H), 9.24 (d, J =5.2 Hz, 1H), 9.38 (d, J = 0.8 Hz, 1H); 13C NMR (100 MHz, CDCl 3 ) δ 118. 6, 125.3, 138.8, 147.6, 156.8, 161.15, 161.28.…”

Domino Reaction Sequence for the Synthesis of [2.2.2]Diazabicycloalkenes and Base-Promoted Cycloreversion to 2-Pyridone Alkaloids

“…Additionally, only a limited number of methods have been exploited for the synthesis of 1-azafluorene structures. 14,15 …”

3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles

“…We have previously reported strong evidence for the ring expansion of a 2-pyrimidinylcarbene 39 to a diazacycloheptatetraene 40 and subsequent ring contraction to a 3-pyridylnitrene 41 , which undergoes cyclization to afford the pyridoindole (4-azacarbazole) 42 (Scheme 10) [29]. …”

“…The alternative ring expansion/ring contraction/recyclization to the pyrimidoisoindole 43 also takes place [29]. The formation of 42 is important, as it demonstrates that 2-pyrimidinylcarbenes can rearrange to 3-pyridylnitrenes, whereas 4-pyrimidinylcarbenes do not necessarily rearrange to 3-pyridylnitrenes (see 55 below).…”