Furoquinoline scaffolds are one of the important heterocycles and their analogues are found not only in nature 1 but also in pharmacological and biological materials, whose properties include anti-inflammatory, 2 TLR8 (Toll-like receptor-8) agonistic, 3 anti-cancerous, 4 a protein inhibitory, 5 and antimicrobial activity. 6 Owing to their diverse biological activities, there have been great efforts to extract 7 or synthesize furoquinolines, i.e., [3 + 2] cyclization reaction for furo [2,3-b]quinolines, 8 [4 + 2] cycloaddition of imines with enol ethers, 9 and a three component reaction of 4-hydroxyquinolin-2(1H)-one, aromatic aldehyde and isonitrile, and so on. 10 Recently we have paid much attentions to develop green and practical synthetic methods for synthesizing various furoheterocycles 1-6 as shown in Scheme 1. 11 The isomeric 2-substituted furopyridines such as furo[3,2b]-, furo[2,3-b]-, and furo[3,2-c]pyridine were synthesized starting from o-halohydroxypyridines and terminal alkynes catalyzed by commercial Pd/C under copper-and ligandfree conditions. Also we were able to show diversification of our protocol to make 2,3-disubstituted furoquinolines, 5 and 6, by Suzuki and Heck reactions, respectively. 11a As a part of our continuing organometallic studies on diversification of nitrogen-containing biologically active heterocycles, we attempted to synthesize furo[2,3-b]-and furo[3,2-c]quinolines starting from o-halohydroxyquinolines and terminal alkynes with heterogeneous Pd(OAc) 2 catalyst, which was supported by nanosized pore carbon ball. The best reaction condition was obtained under CNB-Pd(OAc) 2

We have developed a one-step synthesis of benzofurans from o-iodophenol and various terminal alkynes, by using Pd catalyst supported on nano-sized carbon balls (NCB) under copper-and ligand free conditions. This recyclable catalyst could be reused more than 5 times in the same heteroannulation reaction. The results have demonstrated that diverse 2-substituted benzofurans with tolerant functional groups can be prepared simply and conveniently under these conditions.

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Title compounds are synthesized starting from o‐halohydroxyquinolines [(I) or (IV), resp.] and terminal alkynes (II) with Pd(OAc)2 supported by nanosized pore carbon balls as catalyst.

Tetracyclic 5-azaindole analogues were prepared by palladium-catalyzed sequential annulation of benzylidene(3-iodopyridinyl-4-yl)amine and 1-aryl substituted internal alkynes under Pd(OAc) 2 , n-Bu4NCl, and Et 3 N at 120 °C. The synthetic procedure showed possible diversification of tetracyclic 5-azaindole analogues by varying the 1-aryl substituent in internal alkynes.