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. 2021 Jul 16;23(14):5294-5298.
doi: 10.1021/acs.orglett.1c01376. Epub 2021 Jun 2.

Visible-Light Driven Selective C-N Bond Scission in anti-Bimane-Like Derivatives

Nejc Petek  1 , Helena Brodnik  1 , Uroš Grošelj  1 , Jurij Svete  1 , Franc Požgan  1 , Bogdan Štefane  1
Affiliations

Visible-Light Driven Selective C-N Bond Scission in anti-Bimane-Like Derivatives

Nejc Petek et al. Org Lett. .

Abstract

In the present study, we report the photochemical transformation of pyrazolo[1,2-a]pyrazolone substrates that reach an excited state upon irradiation with visible light to initiate the homolytic C-N bond cleavage process that yields the corresponding N1-substituted pyrazoles. Moreover, chemoselective heterolytic C-N bond cleavage is possible in the pyrazolo[1,2-a]pyrazole core in the presence of bromomalonate.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Ring Scission of Pyrazolo[1,2-a]pyrazoles
Scheme 2
Scheme 2. C1–N8 and C5–N4 Bond Cleavage of Pyrazolo[1,2-a]pyrazoles
Hydrogens are omitted for clarity. 1 (0.5 mmol), DCM (2.5 mL), LED400nm, 25 °C, under N2 for 24–48 h.
Scheme 3
Scheme 3. C7–N8 Bond Cleavage of Pyrazolo[1,2-a]pyrazoles
Gram scale yield. 1 (0.5 mmol), diethyl bromomalonate (2.0 equiv), 2,6-lutidine (1.5 equiv), DCM (2.5 mL), N2, 18 h.
Scheme 4
Scheme 4. C5–N4 Bond Cleavage of Pyrazolo[1,2-a]pyrazoles
Degassed Me2CO (H2O, 10 equiv). MeOH (anhydrous, degassed, 2.5 mL). THF (anhydrous, degassed, 2.5 mL). [i] H2 (2 bar), 10% Pd(C), 6 h. 1 (0.5 mmol), diethyl bromomalonate (2.0 equiv), DCM (anhydrous, degassed, 2.5 mL), N2, 18 h, HNu (2.0 equiv).
Scheme 5
Scheme 5. Mechanistic Insight
See this image and copyright information in PMC

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