Palladium-Catalyzed Synthesis of Heterocyclic Ring Systems by Combination of Regioselective C–C with Twofold C–N Couplings

Abstract

The combination of regioselective palladium-catalyzed C–C with twofold C–N couplings allows for the synthesis of a variety of heterocyclic ring systems. Starting materials include thiophenes and benzothiophenes, pyrroles and indoles, furans and benzofurans, pyridines, quinolines and quinoxalines, complex heterocyclic systems and benzophenone derivatives. The products are in many cases complex polyheterocyclic systems, which are not readily available by other methods or, in a number of cases, were not described in the literature before. They are of pharmacological relevance or interesting in the field of material science. Products include thieno[3,2-b:4,5-b′]diindoles, thieno[3,2-b]indoles, thieno[3,4-b]indoles, 5,10-dihydroindolo[3,2-b]indoles, furo[3,2-b:4,5-b′]diindoles, benzo[4,5]furo[3,2-b]indoles, 5,7-dihydropyrido[3,2-b:5,6-b′]diindoles, 5,7-dihydropyrido[2,3-b:6,5-b´]diindoles, α-, β-, γ- and δ-carbolines, indolo[3,2-b]quinolines, indolo[2,3-b]quinolines, indolo[3,2-c]quinolines, indoloquinoxalines, pyrido[2′,1′:2,3]imidazo[4,5-b]indoles, thiadiazolo[2′,3′:2,3]imidazo[4,5-b]indoles, benzo[b]carbazolediones, acridones and thieno[3,2-b]quinolones.Contents1 Introduction2 Thiophenes and Benzothiophenes3 Pyrroles and Indoles4 Furans and Benzofurans5 Pyridines6 Quinolines and Quinoxalines7 Complex Heterocyclic Systems8 2,3-Dibromonaphthoquinone9 Benzophenone Derivatives10 Conclusions

Adventures in CH-Arylation Chemistry

“…In 2005, my co-workers and I started to develop regioselective Pd-catalyzed coupling reactions of polyhalogenated heterocycles 6 and of bis(triflates). 7 Later, this work was extended by combination with twofold Buchwald-Hartwig reactions, 8 domino CN-coupling / hydroamination, 9 and cycloisomerization reactions. 10 In this context, I also became more and more interested in the synthesis of new heterocyclic core structures and their optical, electrochemical and electronic properties.…”

Fe/S cluster catalyzed cascade cyclization of N,S-1,6-enynes for the synthesis of thieno[3,4-b]indoles

“…20 Traditionally thienoindole derivatives are prepared by cross-coupling reaction and further cyclization of pre-functionalized thiophene or indole rings (Scheme 2a). 21 In 2018, Yu's group reported an elemental sulfur-enabled selective cleavage of the unstrained C–C bonds of N , S -1,6-enynes via a sulfur incorporation cyclization process to afford thiophene-fused N -heterocycles. 22 Unlike the above reaction, herein, we reported a radical cascade cyclization strategy to afford 4 H -thieno[3,4- b ]indoles catalysed by Fe/S cluster (Scheme 2b) and reacted with base, some elemental sulfur acted as an oxidant.…”

Synthesis of Nitrogen Heterocycles by Domino C–N Coupling/Hydroamination Reactions

“…Initially, we focused on the development of regioselective cross-coupling reactions of polyhalogenated heterocycles, 5 and then on cyclization reactions based on twofold Buchwald-Hartwig reactions. 6…”