Synthesis of 2,2′-bis(1-(2-aryl)-1 H -pyrazol-4-yl)-3,3,3′,3′-tetramethyl-3 H ,3′ H -5,5′-biindoles and 2,7-bis(1-(3-aryl)-1 H - pyrazol-4-yl)-1,1,6,6-tetramethyl-1,6-dihydroindolo[7,6-g ]indoles

2,2′-(Biphenyl-4,4′-diyl)bis(hydrazinium) chloride and 2,2′-(naphthalene-1,5-diyl)bis (hydrazinium) chloride were converted via Fischer syntheses with 3-methylbutan-2-one into bisindolenines, 2,2′,3,3,3′,3′-hexamethyl-3 H ,3′ H -5,5′-biindole 10 and 2,3,3,7,8,8-hexamethyl-3 H ,8 H -indolo[7,6-g ]indole 14 , respectively. Exposure of the bisindolenines to the Vilsmeier reagent produced tetraformyl compounds 11 and 15 , which reacted with hydrazine and arylhydrazines to give the corresponding pyrazoles 12 and 16 in excellent yields.


Scheme 1
The malondialdehydes 2,5 reacted with hydrazine or arylhydrazines to produce substituted pyrazoles 3,6. 1,3,4We have now been able to show that the principles embodied in these transformations can be incorporated into bisindolenine systems, and thus have prepared several more complex pyrazoles.

Scheme 2
For the mechanism of formation of the aminomethylene malondialdehydes, we suggested that a small equilibrium concentration of an enamine tautomer 7 is successively C-substituted and thus, before hydrolysis during work-up, species 8 is present (Scheme 3).We propose that a comparable mechanism operates in the work described herein.
Each of the bisindolenines 10, 14 was now reacted with the Vilsmeier reagent in yields of 90% and 85%, respectively, and tetraformyl compounds 11, 15 were obtained (Schemes 4 and 5).The structures of the aminomethylene malondialdehydes rests on the observation of two twohydrogen singlets at δ 9.79 and δ 9.83 for 11 and δ 9.83 and δ 9.87 for 15 corresponding to aldehyde protons.Absorptions at 3136 cm -1 and 3130 cm -1 for 11 and 15, respectively, were evidence for the presence of N-H bonds, further confirmed by 1 H NMR two-hydrogen signals for the N-hydrogens appearing at δ 13.64 (11) and δ 14.35 (15), respectively.As in our previous work, 1,3 the aminomethylene malondialdehydes reacted with hydrazine and various arylhydrazines to give pyrazoles, with migration of the double bond to reform the imine unit (Schemes 4 and 5).For pyrazoles 12a-f, the newly formed five-membered heterocyclic ring protons resonated in the range δ 8.35-9.37 and for the pyrazoles 16a-e in the range δ 8.50-9.38.

Conclusions
We have been able to show that the principles embodied in transformations of simple indolenines via Vilsmeier formylations can be incorporated into more complex bisindolenine systems and thus have prepared several pyrazoles in excellent yields.

Experimental Section
General.Melting points were recorded on a Philip Harris C4954718 apparatus. 1H and 13 C NMR spectra were recorded on a Bruker Avance AQS 300 MHz spectrometer, at 300 MHz and 75 MHz respectively.Chemical shifts δ are in parts per million (ppm) measured in CDCl3 and DMSO-d6 as solvents and relative to TMS as the internal standard.Infrared spectra were recorded on a Thermonicolet-Nexus 670 FT-IR instrument.High resolution mass spectra were recorded on an Agilent Technology (HP), MS Model: 5973 Network Mass, selective Detector Ion source: Electron Impact (EI) 70 eV, ion source temperature: 230 ºC Analyzer: quadrupole, and relative abundances of fragments are quoted in parentheses after the m/z values.

General procedure for synthesis of (12a-f)
A mixture of the tetraformyl compound 11 (0.117 mmol) and the hydrazine or aryl hydrazine (0.23 mmol) in absolute ethanol (5 mL) was heated with stirring at reflux for 6-8 h.After cooling and concentrating the solution, the resulting crystals were collected by filtration and recrystallized from EtOH to give the corresponding pyrazoles.

General procedure for synthesis of (16a-e)
A mixture of the tetraformyl compound 15 (0.2 mmol) and the hydrazine or aryl hydrazines (0.4 mmol) in absolute ethanol (10 mL) was heated with stirring at reflux for 10-12 h.After cooling and concentrating the solution, the resulting crystals were collected by filtration and recrystallized from EtOH to give the corresponding pyrazoles.