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A novel Lewis acid catalyzed annulation reaction has been established for the synthesis of benzocyclohepta[b]indoles. This method represents a new annulation strategy to a seven-membered carbocyclic ring system from two 3-(1H-isochromen-1-yl)-1H-indole molecules using Cu(OTf)2 catalyst; moreover, the products, benzocyclohepta[b]indoles, can be used as the rapid mercuric ion colorimetric detection reagents.

A new, general method for the synthesis of spiro[4,5]trienones is described by the intramolecular ipso-halocyclization of 4-(p-unsubstituted-aryl)-1-alkynes. In the presence of halide electrophiles, a variety of 4-(p-unsubstituted-aryl)-1-alkynes underwent the intramolecular ipso-halocyclization with water smoothly, affording the corresponding halo-substituted spiro[4,5]trienones in moderate to good yields. The obtained spiro[4,5]trienones can be applied in constructing the azaquaternary tricyclic skeleton via Pd-catalyzed Heck reaction. Notably, the prepared spiro[4,5]trienones and azaquaternary tricycles are of importance in the areas of pharmaceuticals and agrochemicals. The mechanism of the intramolecular ipso-halocyclization reaction is also discussed according to the (18)O-labeling experiments and DFT calculations.

An iron-mediated tandem annulation strategy has been developed for the synthesis of numerous functional indeno[1,2-c]chromenes and 5H-naphtho[1,2-c]chromenes. This work is the first to disclose an iron-mediated method through sequential electrophilic addition of a ketone to an alkyne and annulation tandem reaction. Importantly, a halide is introduced into the products by a ring-opening process among the annulation of alkynylcyclopropanes, which makes the methodology more attractive for organic synthesis.

Palladium-catalyzed cross-coupling reaction of terminal alkynes with arylboronic acids has been described. In the presence of Pd(OAc)(2) and Ag(2)O, a variety of terminal alkynes, including electron-poor terminal alkynes, smoothly underwent the reaction with numerous boronic acids to afford the corresponding internal alkynes in moderate to good yields. Moreover, this methodology was applied to the synthesis of 1H-isochromenes and diynes. It is noteworthy that the reaction proceeds under ligand-free and relative lower loading Pd conditions, and the maximal TONs (turnover numbers) of the reaction are up to 720,000.

An efficient and reusable Cu2O/PPh3/TBAB (n-Bu4NBr) system for the cross-coupling reactions of aryl and heteroaryl halides with terminal alkynes has been developed. Four types of Cu2O, including bulky Cu2O, cubic Cu2O nanoparticles, octahedral Cu2O nanoparticles, and spherical Cu2O nanoparticles, were examined, and the octahedral Cu2O nanoparticles were found to be the most effective catalyst for the reaction. In the presence of the octahedral Cu2O nanoparticles, PPh3, and TBAB, a variety of aryl and heteroaryl halides were reacted with alkynes including alkynols smoothly in moderate to good yields. Noteworthy is that the Cu2O/PPh3/TBAB system can be recovered and reused several times without loss of any activities.

[reaction: see text] A stable and efficient Pd(OAc)2/DABCO (triethylenediamine) catalytic system for Suzuki-Miyaura cross-coupling reaction has been developed. In the presence of Pd(OAc)2 and DABCO, coupling of aryl halides with arylboronic acids was carried out smoothly to afford good to excellent yields and high turnover numbers (TONs) (the maximal TONs were up to 960,000 for the reaction of 1-iodo-4-nitrobenzene with phenylboronic acid) using PEG-400 as the solvent. Moreover, the Pd(OAc)2/DABCO/PEG-400 system could be recycled and reused five times without any loss of catalytic activity for aryl iodides and bromides.

An efficient method for palladium-catalyzed homocoupling reaction of terminal alkynes in the synthesis of symmetric diynes is presented. The results showed that both Pd(OAc)(2) and CuI played crucial roles in the reaction. In the presence of 2 mol % Pd(OAc)(2), 2 mol % CuI, 3 equiv of Dabco, and air, homocoupling of various terminal alkynes afforded the corresponding symmetrical diynes in moderate to excellent yields, whereas low yields were obtained without either Pd(OAc)(2) or CuI. Moreover, high TONs (turnover numbers; up to 940 000 for the reaction of phenylacetylene) for the homocoupling reaction were observed. Under similar reaction conditions, cross-coupling of 1-iodo-4-nitrobenzene with phenylacetylene was also carried out smoothly in quantitative yield. However, the presence of CuI disfavored the palladium-catalyzed Sonogashira cross-coupling reactions of the less active aryl iodides and bromides. In the presence of 0.01-2 mol % Pd(OAc)(2), a number of aryl iodides and bromides were coupled with terminal alkynes in good to excellent yields. It is noteworthy that this protocol employs mild, efficient, aerobic, copper-free, and ligand-free conditions.

A combination of Cu2O nanoparticles with P(o-tol)3 shows highly catalytic activity for the Stille cross-coupling reaction. A series of copper catalysts and ligands were evaluated, and Cu2O nanoparticles combined with P(o-tol)3 provided the best results. In the presence of Cu2O nanoparticles and P(o-tol)3, a variety of aryl halides including aryl chlorides underwent the Stille reaction with organotins smoothly in moderate to excellent yields using inexpensive TBAB (n-Bu4NBr) as the medium. It is noteworthy that the Cu2O/P(o-tol)3/TBAB system can be recovered and reused at least three times without any loss of catalytic activity among the reactions of aryl iodides and activated aryl bromides.

[reaction: see text] PdCl2(PPh3)2 combined with TBAF under solvent-free conditions provided general and fast Sonogashira cross-coupling reactions of aryl halides with terminal alkynes. In particular, this protocol could be applied to the reactions of deactivated aryl chlorides. In the presence of 3 mol % of PdCl2(PPh3)2 and 3 equiv of TBAF, a number of ArX species (X = I, Br, Cl) were coupled with alkynes to afford the corresponding products in moderate to excellent yields under copper-, amine-, and solvent-free conditions.

A general and selective palladium-catalyzed carbonylation of terminal alkynes method for the synthesis of (Z)-3-haloacrylates is presented. In the presence of a catalytic amount of PdX2 and 5 equiv of CuX2 (X = Cl and Br), terminal alkynes were carbonylated to afford the corresponding (Z)-3-haloacrylates exclusively in moderate to good yields. The results showed that the effect of solvent had a fundamental influence on the chemoselectivity and stereoselectivity of the palladium-catalyzed carbonylation reaction.