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Elucidate the reaction mechanism of the thermal ring contraction of dibenz[b,f]azepine radicals and establish efficient routes to unsubstituted and substituted pyrrolo[3,2,1-jk]carbazoles.

August 12, 2008The Journal of Organic Chemistry

Thermal Ring Contraction of Dibenz[b,f]azepin-5-yl Radicals: New Routes to Pyrrolo[3,2,1-jk]carbazoles

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Elucidate the reaction mechanism of the thermal ring contraction of dibenz[b,f]azepine radicals and establish efficient routes to unsubstituted and substituted pyrrolo[3,2,1-jk]carbazoles.
Subjected N-allyl- and N-benzyldibenz[b,f]azepines to flash vacuum pyrolysis (FVP) across a temperature range of 750 °C to 950 °C.
Generated 2-(indol-1-yl)phenyl radical intermediates via independent pathways, using 1-(2-nitrophenyl)indole as an alternative precursor to validate the proposed mechanism.
Functionalized parent pyrrolo[3,2,1-jk]carbazoles via electrophilic substitution reactions to synthesize 4-substituted derivatives.
Flash vacuum pyrolysis produced pyrrolo[3,2,1-jk]carbazole as the predominant product through dibenzazepin-1-yl radical formation, followed by transannular attack and cyclization.
An optimized two-step synthetic pathway starting from indole and using 1-(2-nitrophenyl)indole as a radical generator afforded pyrrolo[3,2,1-jk]carbazole in 54% overall yield.
Synthetic protocols provided the first reported library of substituted pyrrolo[3,2,1-jk]carbazoles, including diverse 4-substituted analogues via electrophilic reactions.

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Implication

Experimental study demonstrates thermal ring contraction of dibenzazepines to access pyrrolocarbazoles, indicating a viable radical cascade for synthesizing complex polycyclic heterocycles.

Cite This Study

Crawford et al. (2008) studied this question.

synapsesocial.com/papers/6a75d2101eaff9cba9161b67 https://doi.org/10.1021/jo800637u

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Implication

Experimental study demonstrates thermal ring contraction of dibenzazepines to access pyrrolocarbazoles, indicating a viable radical cascade for synthesizing complex polycyclic heterocycles.

Thermal Ring Contraction of Dibenz[b,f]azepin-5-yl Radicals: New Routes to Pyrrolo[3,2,1-jk]carbazoles

Key Points

Discussion

Implication

Cite This Study

Thermal Ring Contraction of Dibenz[b,f]azepin-5-yl Radicals: New Routes to Pyrrolo[3,2,1-jk]carbazoles

Key Points

Discussion

Implication

Cite This Study

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